The creative process in engineering Teaching innovation to engineering students

Stéphanie Buisine (LINEACT-CESI) & Samira Bourgeois-Bougrine (LATI-Univ. Paris Descartes)

To face innovation challenges of the 21 st century, many companies rely on their engineers to fuel the creative process and set out the roadmap of future technological innovation. Creativity has therefore become a requisite skill for engineers and a part of their basic training. However, there are many ways to implement engineers' creativity and innovation process according to different epistemological approaches. Contrasting philosophies, in particular positivist and constructivist worldviews, determine different design reasoning models and business strategies [START_REF] Liem | Toward prospective reasoning in design: an essay on relationships among designers' reasoning, business strategies, and innovation[END_REF]. Positivism refers to a scientific and structured method focusing on identifying the causes influencing outcomes. It is an analytical, problem-centred approach that invests high on the fuzzy front-end of innovation and leads to a waterfall sequential process in which creativity takes centre stage. Herbert [START_REF] Simon | The structure of ill-structured problems[END_REF] seminal research contributed to shape this sequential engineering process based on three major steps: problem setting, (creative) problem solving, and evaluation of solutions. This view gave rise to many sequential design practices, like the General Design Theory [START_REF] Yoshikawa | Design Theory for CAD/CAM Integration[END_REF][START_REF] Tomiyama | Design methodologies: Industrial and educational applications[END_REF] and industrial engineering processes organized as a series of stages and gates [START_REF] Aoussat | The new product design -A transverse approach[END_REF][START_REF] Pahl | Engineering design -A systematic approach[END_REF][START_REF] Cooper | Stage-gate systems: A new tool for managing new products[END_REF].

In contrast, constructivism is associated with postmodernism and rejects absolute truth. It considers that reality is a social construct depending on the context: it is a solutionfocused approach in which the problem is iteratively co-constructed with the solution [START_REF] Visser | La conception : de la résolution de problèmes à la construction de représentations[END_REF]. This worldview leads to circular rather than sequential design process, with creative thinking throughout the project. This approach is implemented in many recent design trends, such as information technology [START_REF] Boehm | A spiral model of software development and enhancement[END_REF], user-centred design (ISO 13407, 1999), agile software development [START_REF] Beck | Manifesto for agile software development: agilemanifesto[END_REF], design thinking [START_REF] Cross | Design Thinking: Understanding how designers think and work[END_REF], or lean startup [START_REF] Ries | The Lean Startup: How today's entrepreneurs use continuous innovation to create radically successful businesses[END_REF]. Basically, both positivism and constructivism may produce successful outcomes: choosing a process may depend on the project, on the nature of the product to be designed, and most importantly on corporate culture. Some researchers use an evolutionary metaphor to characterize different business styles and corporate strategies [START_REF] Picq | Un paléoanthropologue dans l'entreprise[END_REF]: K-type companies are analogous to species that follow a qualitative humanlike reproduction strategy (few descendants; high investment in gestation and education; high success rate). In contrast, r-type companies use a quantitative and opportunistic strategy similar to dandelion-like reproduction (many seeds disseminated; low investment; low success rate). K-type approach may be read as positivist engineering with high investment on the fuzzy front-end, waterfall process, convergence, few new product but high success rate. This kind of strategy can be found in large groups and in the traditional industrial sector. Conversely, the r-type strategy corresponds to constructivist engineering with lower temporal and financial budget, iterative or circular process, divergence, many ideas but high risk of failure, like in startup companies. In natural ecosystems, K-type strategy tends to outperform r-type strategy when the competition increases [START_REF] Picq | Un paléoanthropologue dans l'entreprise[END_REF]. This is why a successful r-type startup company with a constructivist approach may progressively turn its strategy into K-type positivist approach when growing and gaining investment capacities.

The innovation process is structured by basic methodologies to be selected and arranged in a customized way (sequential, iterative…) for each project. For clarity's sake, we present these methodologies below as a sequential process divided into the four stages of the New Product Design process [START_REF] Aoussat | The new product design -A transverse approach[END_REF], knowing that each method can be extracted and used independently or integrated into a constructivist process as well:

• The first stage of the New Product Design process, Translation of needs, aims to define functional specifications of the future product to design. This stage involves methods and tools allowing the team to understand better the users, the market, and competitors' products. They include surveys, technological watch, trends analysis, field observations and user studies. Some communication tools exist to share the results of these studies, for example product mappings and inspiration boards to illustrate the state of the art and capture design trends [START_REF] Bouchard | Anticipation and integration of trends in design and engineering design[END_REF], or Personas to represent archetypes of customer segments [START_REF] Pruitt | The Persona lifecycle: Keeping people in mind throughout product design[END_REF]. The data collected is finally synthesized through value/function analysis, which results in a list of functional specifications, associated with key performance indicators and target values to be achieved by the future product.

• The second stage, Interpretation of needs, draws on the results of the first stage to search for new concepts and new solutions that will meet function specifications and key performance indicators. This is the main creative stage of the process. To conduct it successfully, the engineer's toolbox includes basic creativity techniques such as Brainstorming [START_REF] Osborn | Applied Imagination[END_REF] and its declinations brain purge, analogies, or problem reversals [START_REF] Van Gundy | 101 activities for teaching creativity and problem solving[END_REF], mind-mapping [START_REF] Buzan | The Mind Map Book[END_REF], etc. Engineers are used to conducting collective creativity sessions in order to maximize divergent thinking through multidisciplinary team and, when possible, integration of users in the session.

The creative phase results in a pool of ideas and concepts that are then sorted and ranked using multi-criteria matrices which include the key performance indicators from function specification. More specific and convergent creativity methods, such as those from the TRIZ framework [START_REF] Altshuller | And suddenly the inventor appeared[END_REF][START_REF] Savransky | Engineering of creativity: Introduction to TRIZ methodology of Inventive Problem Solving[END_REF], can also be used to model technical/physical problems and find inventive solutions. The second stage ends when a satisfactory concept is selected by the project team to serve as a basis for the new product. In constructivist process, several different leads from the creative phase(s) might be explored in the project.

• The third stage, Product definition, is dedicated to detailed design and materialization of the concept: product architecture, which is sometimes modelled using SADT (Structured Analysis and Design Technique) and/or FAST diagrams (Function Analysis System Technique), choice of technical components and materials, mock-up design, product-process link, Computer-Assisted Design, etc. Intermediate user tests can be conducted on representations of the product concept (3D picture, high-or lowfidelity mock-up, storyboard…). Finally, the product solution, the associated processes and production means can be assessed through FMECA (Failure Mode, Effects, and Critically Analysis).

• The final stage, Product validation, aims to validate product design by (1) building an industrially reproducible prototype and (2) having it user-tested. In a constructivist process, the industrially reproducible prototype is not required and user-tests are preferably conducted on low-fidelity mock-up or minimum viable products [START_REF] Ries | The Lean Startup: How today's entrepreneurs use continuous innovation to create radically successful businesses[END_REF].

The aim of this chapter is to provide insight on what methods engineering students should be trained to aim, how they should be used in the creative process, and the subsequent impact on their creativity in the context of simulated or real innovation projects. We present three pedagogical experiments conducted in three different schools of engineering.

Study 1

The first study took place in a generalist engineering school in Paris (Arts et Métiers ParisTech). The participants were students who were introduced to the above-mentioned New Product Design process [START_REF] Aoussat | The new product design -A transverse approach[END_REF] and the related methodological blocks through a 150-hour class entitled "Product Engineering".

Method

Participants

The sample included 27 students in their final year of engineering studies (4 females, 23 males, age = 23 years ± 1). They were rewarded course credits for their participation.

Procedure

The participants engaged in an innovation exercise that they had to perform individually outside of class hours over an 8-week period. To validate the exercise, they had to dedicate 10 working sessions to this project. The goal was to imagine a kitchen for a minivan with the following requirements: Enable cooking, storage of water, dishes, fresh food; be adaptable to most minivans with no modification of the vehicule; occupy no more than 30% of the trunk; be installed in less than 15 min; weight less than 20 kg; comply with security standards, etc.

The participants were provided with a blank booklet to track their process: for each session they had to fill in a self-report of the stage(s) of the creative process addressed (Table 1) and an open-ended section to describe the methods used and the intermediate ideas and productions. This methodology of repeated measures was previously tested in research on emotions [START_REF] Diener | The personality structure of affect[END_REF][START_REF] Vansteelandt | The co-occurrence of emotions in daily life: A multilevel approach[END_REF][START_REF] Zelenski | The distribution of basic emotions in everyday life: A state and trait perspective from experience sampling data[END_REF]. At the end of the project, the participants were instructed to provide:

• Six different idea sheets corresponding to 6 kitchen layouts: 2 for short-term implementation (< 1 year), 2 for medium-term (between 1 and 10 years) and 2 for long-term implementation (>10 years). • The booklet retracing their process (creative stages, methods used and intermediate productions).

Evaluation of creative performance

A multidisciplinary jury of five teachers from the school, all specialized in innovation, evaluated independently the 162 layouts for a functional kitchen produced by the 27 students on a 7-point Likert-type scale (1: not at all creative to 7: very creative). The judges received the layouts to be evaluated in random shuffled order, with no information about the students and no access to booklets. Inter-judge agreement was .80 (Cronbach's alpha), which is very satisfactory.

In addition, in-depth analysis of the 162 kitchen layouts was conducted according to 4 criteria: originality or uniqueness, flexibility or variety, elaboration and integration of technology. An original kitchen concept was unique, surprising, different from the obvious and commonplace. The focus was on the uniqueness of the concept (e.g. proposed by only one student). Flexibility or variety refers to the number of different kitchen concepts proposed (e.g. at least two different concepts among the six designed kitchen). Elaboration measures the amount of detail associated with each kitchen idea. Elaboration has more to do with focusing on each solution/idea and developing it further and adding details. Integrated technologies included green energy, smart or connected kitchens… The booklets were analysed as well in order to assess the creative process stages and the methods used by the participants.

Results

Output and creative performance

All students managed to produce six layouts for an integrated kitchen. The booklet analysis revealed that the most common aspects considered by students were the reduction of cost and size of the kitchens, the spatial position inside the car, the modalities of use (outside and/or inside the car, while driving), the modularity (functional units as basis of design), practicality (easy to store, deploy and to carry) and technology integration (energy production, water and waste recycling…). The most creative students came up with original unique concepts of kitchens, different from a classic home kitchen, which could allow new experience for the user such as all-weather kitchen, inflatable or ecological kitchen, remote control food cooking using smartphone, dehydrated food, magnetic levitating modular kitchen, smart or connected kitchen e.g. touch screen, electronic recipes, automated food preparation according the weather and the journey information as well as the available ingredients…

The layouts produced were more or less creative according to the assessment made by jury members. The average jury creativity mark was 4±1.6 with a maximum of 6.2 and a minimum of 2 (1: not at all creative to 7: very creative). To investigate the inter-individual differences, the sample was divided in two groups, C+ and C-, respectively above or below the average (4 ± 1.6). Fourteen students obtained a creativity mark above the average (named C+) and thirteen below the average (named C-). The participants were attributed an alphanumeric code according to their rank: S1 for the student with the highest average jury mark (6.2 ± .8) and S27 for the lowest score (2 ± 1.4).

Creative stages

The booklet completed over the 10 sessions revealed the "path" followed by each student to complete the task and solve the problem. The differences between C+ and C-were observed mainly during the last five sessions: C+ were more likely to have "Illuminate, evaluate, associate, experiment and implement" whereas C-continued to "Question, converge, and consider constraints". C+ students used creativity tools up to the very end (7 uses of creative tools in the last session in C+ group vs. 1 use in C-group). The analysis of free comments in the booklets suggested also that some C+ students sought to "summarize" design constraints in some key limitations and seemed to disregard several other constraints. They showed a flexible and even a bold attitude towards the constraints: they did not hesitate to criticize, reinterpret, reformulate and even circumvent some constraints. In contrast, Cstudents were continually preoccupied by constraints such as the size of the trunk, the weight and the volume of the kitchen, energy issues, etc. More importantly, they generated new constraints in addition to the initial specifications and tried to find solutions that were feasible within these constraints.

Creativity and engineering methods

The analysis of the open self-report part in the booklet, in which the participants recorded their progress, shed light on the development and creativity techniques used during the creative process. A total of 13 tools were applied by students to solve problems and generate ideas, including: individual and collective brainstorming, brain purge, problem reversal, mind mapping, analogies, TRIZ, FMECA, Personas, FAST diagram, SADT, and APTE framework for value and function analysis.

C+ students employed on average 4.2 tools in their process (± 1.6; min = 2; max = 7) whereas C-used only 2.2 tools on average (± 1.9; min = 1; max = 6). Personas, mind mapping, brain purge and problem reversal were employed by few students, all of whom were among the most creative (C+). Brain purge is a creativity tool that helps participants empty themselves of their preconceived ideas or any idea they hold dear. This technique was used only once at the beginning of creativity process by a female student (S1) who received the highest creativity mark (6.2 on average). The purge started by a brief documentation on existing kitchens in small flats, boats, camper van etc.; then she wrote down the specifications as well as a drawing of the classical kitchen to avoid absolutely reproducing a classic idea. Indeed, her six alternatives layouts had little in common with the classical kitchen. Four of them were unique, highly original, diverse and included state-of-the-art technologies. It is worth mentioning that S1 applied frequently tools such as mind mapping, brainstorming, personas and analogies during the 10 sessions. The quality of execution and output of these techniques showed high standards and allowed the student to experience stimulating divergent thinking. Interestingly, S1 did not use any of the analytical rational techniques such as value / function analysis.

The Persona technique included narratives about different emotional customer experiences and scenarios of use that helped the students to develop some empathy with target customers such as: explorer in Arctic regions or Amazonian forest, nature lovers (ecological kitchen), tradition seekers, elegant and purist design adepts, or technological geeks. Surprisingly, some students did not fully develop the personas; others did not integrate the output of these creative sessions or failed to produce elaborate details into their final layouts. This could be linked probably to an insufficient training or a lack of trust in the benefits of this user centred design technique.

Value / function analysis was the third most frequently used technique during the early stages of the creative process (the three first sessions). It consisted mainly of reformulating the initial specifications: no new ideas were generated but students felt they gained a better understanding of the problem and declared they were ready to get started. However, among the 11 students who applied function analysis, 8 (73%) did not come up with any unique or original idea. FAST diagrams, which display functions in a logical sequence and prioritize them, were used by only one student (S25) during the 4 th , 5 th and 6 th sessions. The creative performance of this student was in the bottom three (average creativity mark: 2.2 ± 1.3) despite a very structured approach and the use of a total of 6 engineering methods.

Discussion

This study provides several insights on the relation between engineering methods, how / when they are used in the process and the subsequent creative performance. The main features of the creative process of C+ students were: their reduced attention to constraints, their use of creative/diverging tools until the very end of the project (constructivist process), and their reflexion on user needs through personas.

We observed that students who both alleviated technical constraints and adopted users' viewpoints produced the most creative outcomes. This result should be read in conjunction with recent analyses of corporate innovation strategies worldwide, in particular the 2014 study Global Innovation 1000 [START_REF] Jaruzelski | Proven paths to innovation success[END_REF]. It shows that three basic strategies can be found in innovative companies: Technology-driver (whose priority is to develop products of superior technological value), Market-reader (which focuses on creating value through incremental innovation and customization of products), and Need-seeker (which aims to find unstated customer needs of the future, and to be the first to address them). Although the three strategies all possess their own success stories, a long-term analysis shows clearly that Need-seeker outperforms the two other strategies in terms of financial return on investment [START_REF] Jaruzelski | Proven paths to innovation success[END_REF]. In line with this global trend, our results suggest that focusing more on users and less on technical constraints leads to more creativity, and that engineering students should be trained to do so. This way of managing innovation projects is not obvious, particularly in France. Indeed, the Technology-driver model remains dominant in France (60% of innovative companies; [START_REF] Péladeau | L'innovation dans les entreprises en France[END_REF] and Need-seeker model struggles to emerge (17%). In contrast, Silicon Valley firms are the most likely to follow a Need-seeker model in the world (46%). Innovation analysts recommend therefore developing the Need-seeker strategy in France in order to stimulate innovation and thereby economic growth [START_REF] Péladeau | L'innovation dans les entreprises en France[END_REF]. In this respect, the Persona method is a convenient, low-cost approach to support engineers' empathy with users, but the benefits might be even stronger if engineers were used to integrating real users in the innovation process, through e.g. interviews, field observations or user tests. Our sample students were actually taught these methods in the Product Engineering class, but they did not use them in this project. We drew on this set of results to build a new training program for teaching innovation to engineering students, with the following characteristics:

• We decided not to integrate value/function analysis in the innovation process, in order to avoid too much focus on technical constraints and on evaluation criteria. • We integrated field and user studies as mandatory steps, with dedicated sessions planned in the program. • We designed the program in order to foster a constructivist process including several rounds of analysis, creativity and design throughout the pedagogical project. • As corporate innovation projects are always conducted in teams, we decided also to make students work in groups rather than individually. Study 2 reports on the implementation of this second training program.

Study 2

This study took place in another general engineering school in Paris (Ecole d'Ingénieurs du CESI), which is known for its innovative pedagogy: this school is class-free and learning relies exclusively on active pedagogy through projects. The participants were students who had chosen the "Innovation" specialty for their final year and engaged in a 210hour innovation program including 175 hours of group project and 35 hours of personal work.

Method

Participants

The sample included 30 students in their final year of engineering studies (9 females, 21 males, age = 24.3 years ± 1.6). Their participation validated partly a semester of their engineering curriculum.

Procedure

Five groups of 6 students were composed on the basis of an initial deliverable in which the students had to describe their motivation for the Innovation program and list examples of products they would like to study, to improve or to create. The groups were composed by the experimenter and attributed five different projects (one project for each group) in accordance with students' interests. The sample projects included 2 assignments provided by partner companies, 2 entrepreneurial projects provided by students, and a fictitious project provided by the experimenter on the basis of the group members' interests. The projects were focused on different products (3 goods, 2 services) and therefore had different specific goals but they all consisted in starting with a concept and making it become a concrete reality at the end of the project. This required refining the response to users needs and expectations, refining the concept, positioning strategically the product with comparison to existing ones on the market, elaborating a detailed design, and developing a business plan. The groups had 5 full-time weeks (i.e. 175 hours) to achieve their project. They were guided through an innovation process (Table 2), had to produce daily deliverables and were provided with mentorship from several experts. Table 7.2: The methodological steps imposed along the 5 weeks.

Feedback on creative performance

Twelve experts from the school and from partner institutions participated in the mentoring committee that met three times during the project. The experts represented different specialties such as technological innovation, user-centered innovation, industrial design, finances and strategy. The experts gave qualitative feedback on each project and delivered customized advice to each group.

Students were also invited to give an individual feedback on their experience as apprentice innovators. At the end of the project, they had to self-assess the contribution of each methodological step on their creative performance (on Likert-type scale from 1: not important at all to 7: very important), and to indicate what had been most striking to them in this pedagogical project (open-ended question).

Results

The five projects were very different from one another but all groups managed to gain one or several supporters within the experts' committee. For example, one group proved very flexible in the solutions imagined and also achieved a high degree of elaboration. Another group produced a very original business model. A third group combined existing technologies to provide a new solution to unmet societal need, etc. All groups' productions were acknowledged as creative and attested by a Soleau envelope (proof of invention) submitted to the French National Industrial Property Institute. Moreover, one of the projects resulted in a patent application, currently in progress, and another one resulted in a startup creation. Experts' opinions were nonetheless much contrasted, some of them being more receptive to technological innovation, some to business plans, and some to response to user needs.

Regarding students' opinions of which methods were pivotal to their creative performance, the results show that training on creativity methods was ranked first, then mentorship, group composition, and user studies. Likert-type scale from 1: not important at all to 7: very important.

Discussion

Our results did not enable us to distinguish between the 5 projects in terms of creative performance, because each project had its own specificities, strengths and weaknesses, and got support from at least one expert from the mentoring committee. The overall constructivist process seemed natural to students and none of them reported any redundancy between e.g. the 5 iterative creative steps organized throughout the project. Some of them even suggested that the business plan, which was introduced in the fourth week, should have been initiated from the very beginning of the project.

Students judged creativity methods as central to their performance and 21 students out of 30 cited them as one of the most striking learning outcomes of the program. They were actually introduced to basics of the following methods: brainstorming, mind-mapping, visual projection, Kent & Rosanoff list, problem reversal, analogy, trends, and discovery matrix. Informal comments collected during the project suggested that brainstorming and problem reversals were the most widely-used techniques and that each group also had its own favourite techniques in addition to these musts. For instance Kent & Rosanoff list, which consists in forcing unnatural associations on a bissociative principle (see also [START_REF] Desmesnards | Mettre en oeuvre la technique des rencontres inattendues: La bisociation[END_REF], was highly appreciated by some groups and found unfruitful by other groups.

Mentorship was also reported as very relevant to students' creative performance. In this respect, we think that collegial sessions were particularly formative for students: during mentoring committees, up to 7 experts were gathered around the table and openly discussed with each group for an hour. This enabled the experts to deliver detailed advice to the students and also to discuss among themselves and confront their complementary views. Therefore, students had the opportunity to understand that there was neither a unique approach to innovation nor straightforward answers to their doubts and questions.

Group composition obtained the same importance score as mentorship to account for creative performance. In the open-ended section of the questionnaire, many students commented on this effect with highly positive terms, explaining that they had experienced powerful group cohesion during the project. It was a striking experience for 13 students out of 30. Some of them underlined that they had learned to work better in a group and take advantage of their differences. Although students in this school were already used to working in groups, they had never experienced such a long (5 weeks, full time) collaboration. We may point out that both group composition and project assignment were imposed by the experimenter on the basis of a 1-page deliverable produced by the students. Although unusual and risky, this procedure seemed effective, as attested by students' evaluations and by further indirect evidence: on the first day (project launch) when we circulated group composition and project assignment to the students, we allowed one permutation by group, but observed that only 3 students out of 30 actually changed groups. Likewise, after 2 weeks and a half of group work (mid-term project review), we offered a new opportunity to change groups and once again only 3 of them decided to change groups, which suggests that the majority of students were satisfied with their group.

Finally, user studies were the fourth method acknowledged as important for creativity. In this respect, we achieved our goal of promoting user integration in engineers' innovation process. Three days of the training program were dedicated to field studies and students had a special authorization to "get out of the building" on those days. They could observe uses, meet potential end-users of their products and interview them, get feedback on their concepts and better capture user needs and expectations. However, we would describe the results obtained as a Market-reader rather than a Need-seeker process. Students could indeed greatly improve and refine their concepts, but they did not generate disruptive ideas from user studies (or, at most, only one group did). In contrast, the Need-seeker approach is assumed to turn into radical innovation, make future needs arise and generate undreamed of concepts. Examples of companies known for their Need-seeker strategy include Apple, Tesla or Procter & Gamble (Jaruselski et al., 2014) -we suspect that our students did not live up to these prestigious references. This is why we decided to further improve the previous innovation process and guide students through a stronger Need-seeker-like approach.

Need-seeking represents today the pinnacle of innovation and is often attributed to geniuses or visionaries; hence there are relatively few known methods for structuring it. The Lead-User method [START_REF] Franke | Finding commercially attractive user innovations: A test of Lead-User theory[END_REF][START_REF] Hippel | Democratizing innovation[END_REF]) may be the most effective one to date: by definition, lead users are precursors, and are at the leading edge of important trends in the market. Involving lead users in an innovation project may grant access to needs that will later be experienced by many users and therefore may open successful innovation opportunities, as in companies like as 3M. However, this method seems hardly applicable in a 5-week pedagogical project because lead users are difficult to find and may require up to several months to be identified [START_REF] Hippel | Democratizing innovation[END_REF] before being eventually integrated into the innovation process. In contrast, the low-cost Persona method used by some participants in Study 1 enabled them to generate creative ideas because it involved "extreme" (although fictitious) users, for example explorers in Arctic regions or the Amazonian forest. We decided to elaborate an intermediate Need-seeker method between the Lead-User and Personas that would involve "extreme" users, although not as unique as lead users and not as fictitious as Personas. Study 3 reports on the testing of this original method with a new population of engineering students.

Study 3

This study took place in an engineering school specializing in biology and biotechnology oriented towards the pharmaceutical, cosmetic, food and environmental industries (Ecole de Biologie Industrielle). The participants were students who had chosen the "Engineering design" option for their final year. The present study was conducted as part of a 9-hour "User-Centered Innovation" class in this option. Given its limited timeframe, the pedagogical project focused on the Need-seeker step only and did not address the whole innovation process.

Method

Participants

The sample included 55 students in their final year of engineering studies (50 females, 5 males, age = 23 years ± 1). Their participation contributed to the validation of their option.

Procedure

Students composed six groups of 9 to 10 members and each group chose an existing product as the starting point of its project. Most of the students in this school are experts in and passionate about cosmetics and strive to pursue careers in this industry. Therefore most of the groups chose a cosmetic product (e.g. nail polish, eye liner, powder foundation), which offered incidentally a very nice challenge to this experiment. The goal of the project turned into finding out new unmet needs related to existing products from a hyper-competitive market with intensive innovation activity.

The Need-seeker method elaborated for this project was inspired by Universal Design [START_REF] Vanderheiden | Design for people with functional limitations resulting from disability, aging and circumstance[END_REF][START_REF] Vanderheiden | Universal Design of consumer products: current industry practice and perceptions[END_REF][START_REF] Buisine | La conception universelle, inclusive[END_REF]. In many aspects, universal design meets usability principles (ISO 9241-210, 2010;[START_REF] Nielsen | Usability Engineering[END_REF] but generalizes the approach to all users (be they young, old, disabled, tall, small…) and not only to target users of a given product (sometimes corresponding to very narrow market segments). In line with this principle, our method named "Off-target user" consists mainly in testing a product outside of the target user population. We hypothesized that focusing on users with special needs would feed the much-vaunted Need-seeker strategy by renewing the view we take on a product, revealing latent needs that are not expressed by target users, and highlighting new original needs. For example, if we study children needs (e.g. beginner readers, narrower vocabulary, shorter stature, weaker force…) while designing a product for adults, this may result in a more intuitive product, with higher usability for adults, elderly people, disabled, foreigners who speak less well the language, etc. The same reasoning applies to senior needs (i.e. viewing and hearing disorders, lower dexterity, memory disorders, etc.), which are likely to help us design more intuitive products for able-bodied users.

The pedagogical projects were therefore aimed to identify unmet, latent or unknown needs related to the products of interest. The groups had to conduct user tests with 5 target users and 5 off-target users, confront the needs identified in the two conditions and select an innovation challenge for this product for the next 10 years.

The course of the project was designed as follows: students attended a 4-hour class introducing them to user-centered innovation, Need-seeker strategy and finally the original Off-target-user method to implement. Then they had two hours for (1) composing the groups, (2) choosing their product of interest and (3) setting out their protocol for target and off-target user tests. They had subsequently 2 weeks to conduct the tests outside of class hours, analyze and synthesize the data. The final 3-hour class was dedicated to project defense.

Results

Instead of reporting each group's findings, we describe in this section the detailed results of the group that worked on nail polish. We chose this group because it exceeded the initial instructions and conducted a more complete need-seeking process, with a brain purge creativity session, technology watch and market research in addition to the methods required in the exercise. For this reason, their project gives a wider picture of the contribution of offtarget user testing for need seeking. Also, this group published its study [START_REF] Mear | Application de méthodes d'innovation centrée utilisateurs au secteur cosmétique[END_REF].

The initial brain purge was conducted with group members only, which was a very homogeneous group of 10 women, aged 21 to 24 years, with the same training background, all nail polish users (and some of them expert users). The brain purge was dedicated to finding ideas for improving existing products. The main improvement avenues that were identified were e.g. avoiding formula drips, improving application accuracy and reducing drying time. Technology watch enabled them to find original application techniquesincluding nail art techniques -as well as innovations in the formula (extra-fast dry, thermoresponsive, anti-aging, long-lasting, nail foundation, etc.). Market research confirmed that the domain was very dynamic, with sales in constant growth since 2006 and more than 10 million bottles sold each year. The group also conducted a survey on a sample of 23 women aged 10 to 74 years indicating that the first nail polish application occurs at 18 years old on average (6 to 30 years old) and may continue throughout lifetime.

Target user tests were conducted with 5 women aged 18 to 68 years, who were expert to casual users of nail polish. Off-target user tests were conducted with 2 children and 3 men aged 4 to 56 years, non-users of nail polish. They were invited to paint their fingernails of the two hands and think aloud throughout the task. Afterwards they had to perform an autoconfrontation [START_REF] Mollo | Auto-and allo-confrontation as tools for reflective activities[END_REF]) and provide further comments on their nail polish experience while watching the video recording of their activity. They were finally interviewed about avenues and/or suggestions for improvement of nail polish products.

Most of needs reported by target users concerned the formula (viscosity, dry time, smell, easiness to remove). They complained generally about the long time required to paint fingernails. They did not comment much on the devices, just mentioned that the brush used for the test was not flexible enough and too small. On the contrary, off-target users made a lot of comments on the devices: bottle plug difficult to screw and unscrew (in particular with fingernails freshly painted), brush difficult to handle (in particular with fingernails freshly painted), bottle difficult to hold, etc. Also they mentioned the difficulty to paint their fingernails of the dominant hand (with their non-dominant hand) and to paint the thumb because its orientation is different from the other fingers. These needs are so obvious that target users did not mention them. We think that these are nonetheless actual needs, and may improve target users' experience if they were met. Indeed, target users interviewed in this study were still 60% dissatisfied and 80% found nail polish application difficult (this reached 100% of off-target users).

Discussion

This study suggests that testing a product with off-target users could be a smart way of highlighting basic and unmet needs as the starting point of a Need-seeker innovation project. The other groups participating in this study obtained similar results with different products (two other cosmetic products, but also two types of food packaging and a hair straightener). Finding off-target users for cosmetic products and the hair straightener was particularly easy because the students could involve men in their sample. For food packaging all human beings are potential target users, but in this case the students involved "extreme", or non-standard users: they conducted their tests with children and elderly users, with the same effectiveness in identifying unmet needs with comparison to middle-aged users. Other valuable extreme users could be found in people with perceptive, motor or cognitive impairments, but they may be more difficult to find in such short pedagogical projects.

The main advantage of involving off-target or extreme users was to highlight unmet although obvious needs. Leading engineers to (re-)discover them is likely to stimulate their creativity and result in new, original and hopefully more usable devices. We speculate that this could be the creative process that was followed in information technology to achieve the highly usable devices we have today: questioning and re-examining the fundamentals of interaction to create more usable interfaces. Famous companies like Apple have built their reputation on this kind of achievements despite sometimes lower technological capacities of their product with regard to their competitors. Data collected by the groups in this study suggested also that off-target and extreme users showed less cognitive fixations on existing products and generated more divergent (uncensored, fanciful, ambitious) ideas to improve existing products. However, the timeframe of this pedagogical project did not enable the students to use the study outcomes and engage properly in a constructivist creative process. This could be the aim of a future experiment.

In any case, we consider that our goal was met to provide students with a simple method likely to support a Need-seeker innovation strategy, an approach that is currently insufficiently developed in many companies [START_REF] Péladeau | L'innovation dans les entreprises en France[END_REF]. Moreover, according to informal comments of the students, Off-target-user method enabled them to see the product through users' eyes instead of engineers' eyes, which is an achievement in itself.

General conclusion

In this chapter we reported on three pedagogical experiments related to teaching innovation to engineering students. The first study was an attempt to analyze systematically the relations between reasoning processes, engineering tools and creativity. For this purpose we elaborated quite an artificial situation, with a single project addressed in parallel by 27 students, using individual procedures and many traceability constraints (imposed number of sessions, self-reports, booklet to complete, etc.). This was the price to be paid for gaining reliable insights and an understanding of how to design effective pedagogical programs.

The second study was partly designed on the basis of these insights and implemented more realistic situations, with real projects conducted in groups, during working hours -a situation analogous to what students might experience in their (future) professional life. The methodological counterpart was that the five projects turned out to be impossible to compare in terms of creative performance. This study was nonetheless informative as to how the process and the methods were experienced by students, and evidenced further limitations about how they take advantage of user studies to innovate.

The third study enabled us to beta-test the Off-target-user method, which is usable by students and likely to help them to see what Need-seeking is like. The results were very encouraging and call for further study: the method now has to be integrated into a full-length innovation process in order to assess its impact on creativity and innovation.

The "best-of" pedagogical innovation process drawing on this set of results would have the following characteristics:

• A full-constructivist process concerning all dimensions throughout the project (analysis, creativity, evaluation, business plan…) -the sequential waterfall process may become relevant when students get experienced; • An initial Need-seeker approach fed with Off-target / extreme users and/or Personas and/or Lead users; • Field studies as mandatory steps;

• Not too much focus on constraints and function analysis -although important for routine design, they may be counterproductive in innovation; • Mentorship, for example in the form of collegial sessions; • Group work, and ideally multidisciplinary group work -this is a major limitation of the pedagogical experiments presented in this chapter to have entrusted innovation projects to too homogeneous groups in which engineers were among themselves.

In addition to promoting multidisciplinarity, we believe that two main directions should be investigated to further leverage engineers' creativity: the first one consists of developing new creativity methods and tools (see e.g. [START_REF] Guegan | Design and evaluation of inventive avatars for creativity and innovation[END_REF][START_REF] Jaco | Trains of thought on the tabletop: Visualizing association of ideas improves creativity[END_REF][START_REF] Schmitt | Dynamic tabletop interfaces for increasing creativity[END_REF]; the second one relies on orienting engineers' creativity in relevant and original directions through prospective methods (e.g. [START_REF] Nelson | Anticipating the use of future things: Towards a framework for prospective use analysis in innovation design projects[END_REF][START_REF] Nelson | Generating prospective scenarios of use in innovation projects[END_REF]Barré et al., 2014aBarré et al., , 2014b)), and particularly Need-seeker ones, as exemplified in this chapter.

Fig. 7

 7 Fig. 7.1: Subjective evaluation of the impact of methodological steps on students' creativity.Likert-type scale from 1: not important at all to 7: very important.

Table 7 .

 7 1: The thirteen stages considered in the booklet.

Acknowledgements

Study 1 was partly funded by ANR-CREAPRO project. We are very grateful to the experts who participated in study 1 and study 2 and of course to the 112 engineering students from 3 different schools who composed our sympathetic experimental population.


Dominique Morlet

Jérémie Mattout

Catherine Fischer

M.D.Ph.D Jacques Luauté

M.D.Ph.D Frédéric Dailler

M.D Perrine Ruby

Ph.D Nathalie André-Obadia

Infraclinical detection of voluntary attention in coma and post-coma patients using electrophysiology

Keywords: Coma, consciousness disorders, outcome, electroencephalography, event related potentials, active paradigm Highlights

Objectives

Early functional evaluation and prognosis of patients with disorders of consciousness is a major challenge that clinical assessments alone cannot solve. Objective measures of brain activity could help resolve this uncertainty. We used electroencephalogram at bedside to detect voluntary attention with a paradigm previously validated in healthy subjects.

Methods

Using auditory-oddball sequences, our approach rests on detecting known attentional modulations of Event Related Potentials that reflect compliance with verbal instructions. Sixtyeight unresponsive patients were tested in their first year after coma onset (37 coma and 31 first year post-coma patients). Their evolution 6 months after the test was considered.

Results

Fourteen of the 68 patients, showed a positive response. Nine were in a coma and 5 in a minimally conscious state (MCS). Except for one who died early, all responders evolved to exit-MCS within 6 months (93%), while 35 (65%) among non-responders only.

Conclusions

Among those patients for whom the outcome is highly uncertain, 21% responded positively to this simple but cognitively demanding test. Strikingly, some coma patients were among responders.

Significance

The proposed paradigm revealed cognitive-motor dissociation in some coma patients. This ability to sustain attention on demand predicted awakening within 6 months and represents an immediately useful information for relatives and caregivers.

Introduction

Faced with a person with disorder of consciousness (DoC) after brain injury, the most natural questions that immediately arise are: does he/she perceive anything? Will he/she wake up? These questions directly speak to decisions regarding the withdrawal of life-sustaining therapies. However, answering them remains very challenging.

The last decade has seen a huge change in the way we view these patients. We owe this change to several neuroimaging studies using fMRI, to a lesser extend EEG, which enabled some of these patients to provide an overt and reproducible answer to verbal instructions [START_REF] Bardin | Dissociations between behavioural and functional magnetic resonance imaging-based evaluations of cognitive function after brain injury[END_REF][START_REF] Bekinschtein | Neural signature of the conscious processing of auditory regularities[END_REF][START_REF] Cruse | Detecting awareness in the vegetative state: electroencephalographic evidence for attempted movements to command[END_REF][START_REF] Monti | Willful modulation of brain activity in disorders of consciousness[END_REF][START_REF] Owen | Detecting awareness in the vegetative state[END_REF][START_REF] Perrin | Brain response to one's own name in vegetative state, minimally conscious state, and locked-in syndrome[END_REF]. Nearly 20% of chronic unresponsive patients proved able to produce specific and reliable patterns of neural activity, on demand. This opened a new era of research, urging the community to assess the acute phase of brain injury, when prognosis is most uncertain, and to rather use EEG given fMRI's lack of portability and high cost [START_REF] Owen | The Search for Consciousness[END_REF].

A recent study used EEG in the ICU, and found a dissociation between the absence of behavioral response to motor commands and the evidence of brain activation in EEG responses to these commands, in 15% of the patients [START_REF] Claassen | Detection of Brain Activation in Unresponsive Patients with Acute Brain Injury[END_REF]. Interestingly, this study showed a difference in functional outcomes at 12 months between patients with and without cognitive-motor dissociation.

Beyond the need to replicate those findings, one key question that remains unresolved pertains to actual and future level of awareness of these patients and their ability to communicate.

In the current study, we used EEG at bedside to assess covert cognition in different groups defined on a clinical basis: coma patients who, by definition, are believed to be fully unconscious, but also patients showing post-coma disorders of consciousness either in a Vegetative State (VS) or in a Minimally Conscious State (MCS), the latter being the more likely to provide some brain response to any verbal command. We employed an original task-based auditory oddball paradigm that, in healthy subjects, proved to be highly sensitive, at the individual level, to reveal voluntary sustained attention in response to specific instructions [START_REF] Morlet | The auditory oddball paradigm revised to improve bedside detection of consciousness in behaviorally unresponsive patients[END_REF]. Importantly, we also assessed the prognostic value of this active EEG test in terms of awakening that we defined as the exit MCS (e-MCS) stage of the coma recovery scale revised (CRS-R) and functional outcome (using the Glasgow Outcome Scale-Extended (GOS-E) level 3 or higher), 6 months after testing.

According to the known definitions of the various post-coma clinical states, we did not expect to find responders to this active test among either VS or MCS-patients. In contrast, we expected that some MCS+ patients would possibly show a significant positive answer. In coma patients, the aim was to openly investigate whether any patient could reveal a strong cognitive-motor dissociation 1 by positively answering to this test.

We specifically addressed the following questions:

1 -Do DoC patients respond to this active test in a manner consistent with their clinical diagnosis at the time of recording? Since a positive response to the active test requires a voluntary and sustained response to a verbal command, we expected Coma but also VS and MCS-patients to be non-responders, while some MCS+ patients might respond positively.

2 -What is the prognostic value of this test for both responders and non-responders?

For the active test to be valuable in terms of prognosis, it needs to show predictive value, at least for responders or non-responders. In particular, we would expect a valuable positive test to predict awakening (e-MCS) or a functional improvement (GOS-E greater than 2).

1 Cognitive-Motor Dissociation (CMD) refers to "... the sharp dissociation of a retained but unrecognized (covert) cognitive capacity in some severely brain-injured patients with non-purposeful or absent behavioral responses" as initially defined in [START_REF] Schiff | Cognitive Motor Dissociation Following Severe Brain Injuries[END_REF], and recently discussed in [START_REF] Schnakers | What names for covert awareness? A systematic review[END_REF].

Methods

Patients

In the Lyon Neurological Hospital (France), a neurophysiological assessment is typically requested for intensive care patients with delayed awakening, or for patients discharged from intensive care but with DoC status difficult to determine clinically. This assessment always begins with an EEG, and the recording of somatosensory evoked potentials (SEPs), brainstem and middle latency auditory evoked potentials (AEPs). In case of preservation of at least one sensory cortical response type, this evaluation is completed by passive mismatch negativity (MMN) to deviant auditory stimuli and Novelty P3 to the own name [START_REF] Fischer | Novelty P3 elicited by the subject's own name in comatose patients[END_REF].

In 2009, we added an active EEG test to these passive event-related potentials (ERPs). In between 2009 and 2015, we recorded 84 patients. We excluded 3 patients due to technical issues during data recording, and 4 others whose clinical course at 6 months was unknown. Of the remaining 77 patients, we focus on the 68 who were tested within one year of coma onset (see supplemental Figure S1).

Among the 68 included patients, 37 had not opened their eyes from coma onset (coma patients)

and 31 could open their eyes but had not recovered full consciousness (post-coma DoC). The latter were classified as in a vegetative state (VS) or a minimally conscious state lower (MCS-) or upper (MCS+), as shown in Table 1.

All patients were recorded after a 48 hours sedative treatment break (see Supplemental Digital Content for full details). This retrospective study, entitled "Contribution to the wakefulness prognosis of an active EEG test detecting sustained attention abilities in coma patients or chronic patients with disorder of consciousness (DoC)" was approved by the ethics committee of the Lyon University Hospital on 22/01/2020 (IRB N°20-08) and is in accordance with the 1975 Declaration of Helsinki.

Since based on anonymized clinical and neurophysiological data collected during coma and post-coma disorders of consciousness, informed consent was waived by our institutional review board.

Clinical Assessment

Clinical evaluation at the time of the test and clinical outcome at 6 months were assessed by a clinician that did not participate to the ERP data analysis.

At the time of the test, the Glasgow Coma Scale (GCS) was assessed in coma patients. In postcoma patients, the Coma Recovery Scale Revised (CRS-R) was assessed.

The clinical outcome was assessed six months after recording using the CRS-R and the Glasgow Outcome Scale Extended (GOS-E), described in supplemental materials. When a patient awoke and then died from independent reason within 6 months, the score obtained at awakening was retained.

Data acquisition

Auditory stimuli were delivered binaurally through inserted earphones at an intensity of 65 dB HL using Presentation software (Neurobehavioral Systems). A classic auditory two-tone oddball paradigm with frequency deviants was presented in 3 consecutive attention conditions: passive, diverted and focused attention. The instructions in conditions 2 and 3 of the active paradigm were included in the stimulation protocol and delivered binaurally through earphones.

Potentials were recorded continuously from seven scalp electrodes (Fz, Cz, Pz, F3, F4 and the two mastoids). The reference electrode was placed on the tip of the nose and the ground electrode on the forehead. One bipolar EOG derivation was recorded from 2 electrodes placed on the supra-orbital and infra-orbital ridges of the right eye. This minimal set of electrodes was selected for bedside recordings, considering topography of the responses observed with 32 scalp electrodes in healthy subjects.

Electrode impedance was kept below 5 k•. The signal was amplified (band-pass 0.3-100 Hz), digitized (sampling frequency 1024 Hz) and stored for off-line analysis, using a Micromed System98 EEG recording system.

Data analysis

The active auditory paradigm was previously validated in 20 healthy subjects [START_REF] Morlet | The auditory oddball paradigm revised to improve bedside detection of consciousness in behaviorally unresponsive patients[END_REF]. Figure 1 depicts the protocol and the results obtained at the group level in this control population. Two main effects of attention manipulation could be detected: 1) an effect of counting (COUNT effect) observed in the difference between responses to deviants and standards in the focused attention condition (a centro-parietal COUNT P3 wave, possibly preceded by a fronto-central COUNT N2 wave); 2) an effect of attention manipulation (FOCvsDIV effect) assessed as the difference between responses to deviants in the focused attention condition and deviants in the diverted attention condition (a centro-parietal FOCvsDIV P3 effect, possibly preceded by a fronto-central FOCvsDIV N2 effect).

ERP components and attention effects were detected individually in each patient using a twostep process. In a first step, objective detection based on point-by-point randomization tests (described below) was performed. In the second step, when the effect of attention was statistically significant, a trained neurologist validated the wave using visual waveform analysis.

ERP pre-processing and averaging:

ERPs were analyzed off-line using the software package for electrophysiology data analysis (ELAN) developed at the DYCOG team of the Lyon Neuroscience Research Center [START_REF] Aguera | ELAN: A Software Package for Analysis and Visualization of MEG, EEG, and LFP Signals[END_REF], and the scientific programming tool Matlab (The MathWorks, Inc., Natick, MA).

A 30-Hz low-pass digital filter (bidirectional Butterworth, 6th order) was applied to the raw data. In each of the 3 conditions we averaged the responses to standards (except those following a deviant) and to deviants for an epoch of 1700 ms including a prestimulus period of 200 ms. Epochs showing peak-to-peak deflections larger than ±100 mV at any scalp electrode were rejected. When rejection rate was larger than 20%, we considered blink rejection followed by new averaging. Blink correction was carried out in epochs showing peak-to-peak deflections of the EOG larger than 125 mV or absolute value of the first derivative of the EOG exceeding 20 mV/ms. For the trials concerned, blink correction of the raw EEG signal used regression with EOG signals following the method proposed by Gratton et al. [START_REF] Gratton | A new method for off-line removal of ocular artifact[END_REF]. In final averaging after blink correction, rejection thresholds could be increased in some patients for exceptionally noisy electrodes, with the objective of a maximum rejection rate of 20%. The ERPs were eventually baseline-corrected by subtracting the mean value of the signal during the 100 ms prior to stimulus onset.

Objective detection of waves and attention effects

Objective detection of waves (COUNT N2 and P3) and attention effects (FOCvsDIV N2 and P3) was performed on the set of accepted baseline-corrected trials, in spatial and temporal windows derived from previous knowledge. The P300 effect of counting (COUNT P3) between the responses to deviants and standards in the focused attention condition and the P300 effect of attention manipulation (FOCvsDIV P3) between the responses to deviants in the focused and in the diverted conditions were detected in the average of Cz and Pz derivations between 250 and 800 ms. The N2 effect of counting (COUNT N2) between the responses to deviants and standards in the focused attention condition and the N2 effect of attention manipulation (FOCvsDIV N2) between the responses to deviants in the focused and in the diverted conditions were detected in the average of Fz and Cz derivations between 100 and 500 ms.

We used permutation tests: at each sampling point, the probability that the 2 conditions are different was estimated from 2000 permutations of samples from the 2 conditions. Like in our previous study in healthy subjects, an effect was detected when at least 20 consecutive points showed a significant difference (unilateral permutation p < .05). This threshold was extrapolated from the recommendations given by [START_REF] Guthrie | Significance testing of difference potentials[END_REF].

In our previous study [START_REF] Morlet | The auditory oddball paradigm revised to improve bedside detection of consciousness in behaviorally unresponsive patients[END_REF], a FOCvsDIV effect was observed in 19 of the 20 aware healthy subjects. It turned out that the only subject showing no FOCvsDIV effect was clearly not sufficiently engaged in the task. He was, however, conscious and showed a significant COUNT effect under the condition of focused attention. Considering this result and the fact that a FOCvsDIV effect was sometimes more difficult to highlight than a COUNT effect in patients' noisy recordings, we considered that a patient with a positive COUNT effect in the condition of oriented attention responded positively to the active paradigm, even if no FOCvsDIV effect could be detected.

Statistical analysis

We computed sensitivity, specificity, positive and negative predictive values of the active paradigm, on the one hand, to dissociate MCS from VS patients as well as to distinguish MCS+ from other MCS-and VS (i.e. no-MCS+) patients and, on the other hand, to predict awakening (e-MCS) vs no awakening (persistent VS or MCS).

Classic Chi-square or Fisher's exact tests (for small samples), as well as odds ratios were used to assess independence between the ability of the patients to perform the active task (positive effects in ERP results) and other parameters like age, gender, the etiology of coma, the behavioral categorization at the time of recording and the outcome at six months.

Results

An effect of attention manipulation (FOCvsDIV) was observed in 9 patients. A significant difference between focused and diverted deviants was observed in 7 patients at the latency of the P3 response (FOCvsDIV P3) and in 2 other patients at the N2 latency (FOCvsDIV N2). For these 9 patients, a COUNT effect could also be detected at similar latencies. Besides, 5 patients with no effect of attention manipulation (no FOCvsDIV effect) showed however a significant P3 (n=4) or N2 (n=1) in the condition of focused attention (COUNT effect). The ERPs of these 14 (21%) responding patients (i.e. showing at least a COUNT effect) are shown in Figure 2.

The full individual characteristics of these 14 responders are provided in Table 2.

In flowchart form, for the 68 patients tested, Figure 3 represents the results of the active test as well as the clinical observations at 6 months as a function of the initial clinical categories.

Consistency of the active test with clinical assessment at the time of recording

Positive responses to the active paradigm were not related to the age or gender of the patient, nor to the cause of coma (Table 3). Regarding the later, there was no significant relationship between the three main etiologies of coma (brain trauma, stroke and anoxia) and the outcome of the active test (! 2 = 1.51, p = 0.47).

Interestingly, we found no significant difference in test responses between coma and post-coma patients (Fisher's Exact Test p = 0.55; Odds-ratio = 1.67 (95% confidence interval: 0.49 -

5.64)).

Contrary to what would be expected based on clinical assessment alone, 9 coma patients proved responding. The 5 other responders were post-coma patients (2 MCS+ and 3 MCSpatients).

In post-coma patients (N = 31), we found a significant relationship between the clinical category (VS, MCS-and MCS+) and the response to the active test (! 2 = 9.80, p=0.002). Precisely, the distinction between VS and MCS (i.e. MCS+ or MCS-) patients was significantly correlated with test outcome (Fisher's exact test p = 0.011; Odds ratio = 0.05 (95% confidence interval: 0.002 -0.99)). This reveals a significant link between the VS/MCS dichotomy and the outcome of the active test. Indeed, no positive response could be established among VS patients, while some MCS patients did respond positively. The correlation between the no-MCS+ (i.e. VS or MCS-) / MCS+ dichotomy and the result of the active test was not significant (Fisher's exact test p = 0.06; Odds ratio = 16.67 (95% confidence interval: 1.14 -243.9)) but showed a tendency which goes the other way in the sense that being in a MCS+ is fairly predictive of a positive response.

Prognostic value of the active test

The outcome at six months after the active test was assessed in each patient both in terms of awakening (being in an e-MCS state or not) and functional dependencies using the GOS-E (a positive evolution corresponding to GOS-E > 2). Table 4 andTable 5 display Over the whole population, we found a strong correlation between the outcome of the active test and both awakening and functional dependency. For these two measures of functional outcome, the active test shows a high specificity and a high positive predictive value. This illustrates the fact that nearly all patients who responded positively to the active test did awake within the 6 months after the time of recording and showed a GOS-E > 2. Conversely, several patients who responded negatively to the tests did awake and showed a GOS-E > 2, hence the poor sensitivity and negative predictive values.

Similar results are obtained when restricting this assessment to post-coma patients. In these patients, responding positively to the active test is highly predictive of both awakening and good functional outcome. For both measures, the test shows a specificity and a positive predictive value of 1. No VS patients responded positively to the active test and only 4 among 17 obtained a GOS-E score greater than 2 after 6 months (3 were e-MCS). Conversely, 2 out of 3 MCS+ patients did respond positively to the test and all three were in an e-MCS after 6 months with a GOS-E score greater than 2. For the whole group of MCS patients as well as for MCSpatients only, the active test shows a specificity and a positive predictive value of 1, for both outcome measures. On the one hand, among the MCS patients who did not progress to e-MCS and a GOS-E score greater than 2, none had shown a positive active test. On the other hand, all MCS patients who succeeded in the active test, awoke and presented a GOS-E score greater than 2 after 6 months. In the MCS and MCS-populations, the active test also shows a significant correlation with the outcome in terms of awakening. This further reflects the fact that most MCS-patients who did not respond positively to the active test (7 out of 8) did not awake after 6 months.

Finally, in the coma population, all patients who succeeded in the active test (N = 9) were e-MCS and presented a GOS-E greater than 2 at 6 months, except for one patient who died early as a consequence of withdrawal of life sustaining treatment initiated independently of this study. This yields a high specificity and a high positive predictive value. However, the correlation between the outcome of the active test and the clinical outcome at 6 months is not significant.

Discussion

Main findings and conclusions

We used a new, recently validated task-based EEG test at bedside. This test rests on voluntary sustained attention and as such, it is cognitively demanding. In healthy subjects, it has been shown to be sensitive at the individual level [START_REF] Morlet | The auditory oddball paradigm revised to improve bedside detection of consciousness in behaviorally unresponsive patients[END_REF]. In this study, we tested patients with disorders of consciousness for less than a year.

Most previous active paradigms investigated a possible discrimination between MCS and VS patients [START_REF] Kondziella | Preserved consciousness in vegetative and minimal conscious states: systematic review and meta-analysis[END_REF], considering that the former are more likely to follow commands. Accordingly, we found no responders among VS patients. A positive response to the test predicted to be MCS rather than VS and a negative response to the test was in favor of MCS-or VS rather than MCS+.

Beyond the population of chronic patients, it is essential to fully evaluate the relevance of such an active EEG test. In the whole population tested here, 14 patients (21%) showed a positive response with a positive predictive value of awakening (e-MCS) at 6 months of 93%. Strikingly, among responders, 10 patients were tested at the ICU within 1 month after coma onset and 9 of them were still in coma. This is of outmost importance as these results do not only fit with previous findings in chronic disorders of consciousness [START_REF] Kondziella | Preserved consciousness in vegetative and minimal conscious states: systematic review and meta-analysis[END_REF]. They further demonstrate that preserved cognitive functions can be found also in coma patients. Our observations are in agreement with those of Claassen and collaborators [START_REF] Claassen | Detection of Brain Activation in Unresponsive Patients with Acute Brain Injury[END_REF] although it is interesting to note that their test was based on the EEG response to a simple order.

Based on fairly complex instructions, our test provides argument for the preservation of higher levels of cognition in these early-recorded patients. These findings suggest that cognition is not only dissociated from overt expression of awareness but also from overt arousal, thus highlighting the limits of behavioral assessments across the whole spectrum of DoC [START_REF] Giacino | Covert Consciousness in the Intensive Care Unit[END_REF].

Importantly, when considering both coma and chronic patients, we found high positive predictive value (0.93) of the active test for awakening (e-MCS). However, the negative predictive value for awakening over the whole patient population was only 0.44. Among reasons for false negative results, a possible aphasia could have prevented the understanding of instructions. A focal lesion of the dominant hemisphere was an exclusion criterion but understanding or attention disorders independent from vigilance disorders cannot be excluded. Some patients could also have been so tired that they could not perform this demanding tasks over time. Finally, one cannot exclude that consciousness, and ability to respond to the task fluctuate within a day or a week in these patients. This is an important reminder that a negative response to such an active test cannot be considered a marker of poor prognosis [START_REF] Kondziella | Preserved consciousness in vegetative and minimal conscious states: systematic review and meta-analysis[END_REF]. Further studies should ideally repeat the test over several days.

Task-based EEG methods that can easily be applied at patient's bedside and improve prognostication of patients with acute brain injuries have great potential. It also raises questions about the differences and complementarities between alternative active EEG paradigms, and about the nature of the cognitive processes they probe [START_REF] Bayne | Are There Islands of Awareness?[END_REF][START_REF] Cecconi | Islands of Awareness or Cortical Complexity?[END_REF][START_REF] Sergent | Multidimensional cognitive evaluation of patients with disorders of consciousness using EEG: A proof of concept study[END_REF].

There is no doubt that such paradigms will develop and expand, which already raises the critical question of how they should be incorporated into clinical practice [START_REF] Giacino | Practice guideline update recommendations summary: Disorders of consciousness: Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology; the American Congress of Rehabilitation Medicine; and the National Institute on Disability, Independent Living, and Rehabilitation Research[END_REF][START_REF] Peterson | Translating the Discovery of Covert Consciousness Into Clinical Practice[END_REF].

Interestingly, the lack of responsiveness of the EEG to auditory and / or nociceptive stimuli does not appear to be a sufficient criterion for not performing an active test, as three responders had an areactive EEG. This could be explained by the fact that visual analysis of EEG reactivity is subject to great inter-rater variability [START_REF] Duez | Large inter-rater variability on EEGreactivity is improved by a novel quantitative method[END_REF] and cannot be considered as an isolated prognosis criterion. Besides, two responders also showed abnormal early evoked potentials (patients 3 and 8). This suggests that these markers, when altered, should not prevent us from performing an active test. One could even extend this conservative reasoning to any (temporary) failure to detect a cortical response with EEG or any other means. Along this line, it has been argued that cortically mediated states, which are probably necessary but not sufficient phenomena for the emergence of consciousness, will more likely be detected as one diversifies the functional explorations [START_REF] Naccache | Minimally conscious state or cortically mediated state?[END_REF]. The proposed test is original, promising and complementary of existing ones, as it is active and cognitively demanding. It can be operated at bedside and proved able to detect covert cognition in patients with disorders of consciousness of various etiologies and at various times after the onset of coma, including short-lived ones.

Cognitively as demanding as the EEG tasks typically used in brain-computer interfaces (BCI), a positive response to this test also inclines to attempt to communicate with these patients using a BCI [START_REF] Luauté | BCI in patients with disorders of consciousness: Clinical perspectives[END_REF].

Limitations of the study

The main limitation of this study comes from its retrospective nature. In particular, we had to rely on the independent clinical evaluations made by medical experts, which it would have been useful to complement with complementary assessments (e.g. a CRS-R in coma patients).

Future, prospective, studies could focus on either the diagnostic or prognostic value, or both, of the proposed active test, but importantly, they would enable a design where homogeneous subpopulations of patients could be thoroughly assessed and compared, possibly in a longitudinal fashion. Ideally, this would be part of a multicentric study so as to enable larger sample sizes. Note that the latter would likely require to develop a fully-automated data analysis, which is challenging but would definitely make a major step towards disseminating this kind of tests. A classic two-tone auditory oddball paradigm with frequency deviants was used. Standard and deviant stimuli were tone-bursts lasting 200 ms, including 20 ms rise-time and 20 ms fall-time.

Figure legends

Pitch was 500 Hz for the standards, 1000 Hz for the deviants. The stimuli were regularly presented every 1010 ms. The deviants appeared randomly with a probability of 0.15. They were preceded by at least 2 standards.

The auditory oddball paradigm is presented in three attention conditions. 1) Mind wandering: a passive situation, without any instruction, 2) Diverted attention: instruction is given to perform a mental imagery task in order to keep attention away from the stimuli, 3) Focused attention: instruction is given to count deviant stimuli (33 deviants in the first block, 30 in the second block and 31 in the third one).

The 3 conditions were always presented in this particular order to the patients in order to limit the risk of inopportune deviant counting during passive listening and mental imagery. The whole recording session lasted about 30 min.

In each condition, expected responses are depicted by the grand average responses of twenty healthy subjects (from Morlet et al. Psychophysiology 2017). Responses to standards (thin lines) and deviants (thick lines) at the three midline electrodes are displayed in each attention condition: in blue for Mind wandering, in green for Diverted attention and in red for Focused attention. In the Focused attention condition, the COUNT effect (large P300 response resulting from voluntary implication in the counting task) is highlighted by significant differences observed at the group level between responses to standards and deviants at each electrode (horizontal grey bars). The rightmost box displays the FOCvsDIV effect: the difference observed between responses to deviants in the FOCused condition (enhanced P300 response) and deviants in the DIVerted condition (reduced P300 response). This effect is highlighted by thick horizontal black bars displaying significant differences at the group level for each electrode (randomization test point by point with correction for multiple temporal tests). For each patient (numbered from 1 to 14 as in Table 2), the responses of interest at electrode Cz are shown:

above the COUNT effect observed in the comparison between responses to standards (red thin line) and deviants (red thick line) in the condition of focused attention below the FOCvsDIV effect observed in the comparison between responses to deviants in the condition of focused attention (red thick line) and in the condition of diverted attention (green thick line).

As in the healthy population, we observed two distinct patterns: a classic P300 effect in centro-parietal regions (over Cz and Pz) and/or a less expected N2 effect in centro-frontal regions (over Fz and Cz) (see Morlet et al. Psychophysiology 2017). A two-step detection process was used at the individual level. First, an objective detection was performed using point-by-point permutation tests on the individual trials. In the second step, when the effect of attention was statistically significant, a trained neurologist validated the wave using visual waveform analysis. *As the GOS-E does not distinguish between VS, MCS-and MCS+, we classified these different states as follows: VS and MCS-were grouped and entered the GOS-E 2 category, whereas MCS+ was classified as GOS-E 3. Indeed, patients are considered in the GOS-E 2 category when they are unable to respond to simple orders, which also defines the distinction between MCS-and MCS+

  Abbreviations:

  the prognostic value of the active test for these two measures of clinical outcome in the different subpopulations.

Figure 1 :

 1 Figure 1: Experimental paradigm and expected responses.

Figure 2 :

 2 Figure 2: Individual tracings of the 14 patients responding positively to the test

Figure 3 :

 3 Figure 3: Distribution of patients responding positively to the active paradigm as a

  For each sub-population: age, gender, distribution of the different etiologies, delay from coma onset and clinical evaluation at the time of EEG recording (assessed using the Glasgow Coma Scale for comatose patients, and the Coma Recovery Scale Revisited for patients with post-

Table 1 : Full description of the set of 68 patients.

 1

					sub-acute or chronicDoC
				VS	MCS-	MCS+
			Coma
				(n = 17)	(n = 11)	(n=3)
			(n = 37)
		Age
			53 ± 4	45 ± 21	41 ± 27	40 ± 6
		mean ± sd (years)
		Gender
			17 (46%)	6 (35%)	3 (27%)	1 (33%)
	Female sex number (%)
	Etiology	Anoxia	9	8	2	0
	nb of patients	Brain traumatism	8	8	4	2
		Stroke	19	1	1	1
		Consequence of neurosurgery	1 1	0	2 2	0
		Other medical diagnosis	0	0	2 3	0
	Delay from coma onset at the time of
		ERP recording
		mean ± sd	12 days ± 8
		range	2 -33 days

Table 4 : Prognosis value of the active test in terms of awakening in the different sub-populations

 4 . A positive evolution corresponded to the e-MCS category at 6 months.

		Sensitivity Specificity	Positive	Negative	Accurac	Fisher's	Odds-ratio
	Active test			predictive	predictive	y	exact test
				value	value
	All (n = 68)	0.30	0.96	0.93	0,44	0,63	F (p=0.005)	12.07
								(1.473 -98.91)
	Coma (n = 37)	0.30	0.90	0.89	0.32	0,38	F (p=0.39;	3.789
							NS)	(0.409 -35.09)
	Post Coma	0.50	1	1	0.81	0,84	F (p=0.001)	43.00
	(n=31)							(2.050 -902.1)
	VS (n = 17)	0	1	NA	0.82	0,82	NA	NA
	MCS (n=14)	0.71	1	1	0.78	0,86	F (p=0.02)	33.00
								(1.305 -834.5)
	MCS-(n = 11)	0.75	1	1	0,88	0,91	F (p=0.02)	35.00
								(1.118 -1096)
	MCS+ (n=3)	0,67	NA	1	0	0,67	NA	NA

Table 5 : Prognosis value of the active test in terms of dependence in the different sub-populations

 5 . A positive evolution corresponded to a GOS-E>2 at 6 months.

		Sensitivity Specificity	Positive	Negative	Accurac	Fisher's	Odds-ratio
	Active test			predictive	predictive	y	Exact test
				value	value
	All (n = 68)	0.33	0.96	0.93	0,50	0,59	F (p=0.005)	13.00
								(1.587 -106.5)
	Coma (n = 37)	0.30	0.90	0.89	0.32	0,46	F (p=0.39;	3.789
							NS)	(0.409 -35.09)
	Post Coma	0.38	1	1	0.69	0,74	F (p=0.008)	23.94
	(n=31)							(1.183 -484.5)
	VS (n = 17)	0	1	NA	0.76	0,76	NA	NA
	MCS (n=14)	0.56	1	1	0.56	0,71	F (p=0.09;	13.44
							NS)	(0.575 -314.5)
	MCS-(n = 11)	0.50	1	1	0,63	0,73	F (p=0.18;	11.00
							NS)	(0.425 -284.5)
	MCS+ (n=3)	0,67	NA	1	0	0,67	NA	NA

Acknowledgements

We are grateful to the medical and technical staff of the ICU, of the post-reanimation department and of the Neurophysiology and Epileptology unit, in the Lyon Neurological Hospital, for their assistance in data acquisition.

This work was performed in the Lyon Neuroscience Research Centre. Data were recorded in the ICU and in the post-

Funding

This work was supported by the Laboratory of Excellence (LABEX) CORTEX (grant numbers ANR-11-LABX-0042; ANR-11-IDEX-007).

Conflict of Interest Statement

None of the authors have potential conflicts of interest to be disclosed. 1 Same patient's numbering as in Figure 2 2 R = reactive EEG, aR = areactive EEG (visual analysis by the neurophysiologist, in response to auditory and nociceptive stimuli) The asterisk for patients 1 and 13 means that the patient awoke (GOS-E = 3) and then died from independent reason less than six months after the onset of coma. ** 1 frontal meningioma surgery and 2 other medical diagnosis 1 A total of 14 patients were able to perform the active test, with at least positive COUNT effect, including 9 coma patients and 5 MCS patients.

2 A total of 54 patients showed neither FOCvsDIV nor COUNT effect, including 28 coma patients, 9 MCS and 17 VS patients.

SUPPLEMENTARY MATERIAL I -Population

The active auditory ERP paradigm was used as part of the global neurophysiological evaluation in patients admitted in our hospital at the acute phase of coma in the absence of clinical sign of awareness 48h after sedative treatment suppression or for ad-hoc evaluation during a chronic disorder of consciousness. Every patient benefited from a first neurophysiological evaluation with EEG, somatosensory evoked potentials (SEPs) and brainstem and middle latency auditory evoked potentials (AEPs). EEG helps assess cortical responsiveness but also enables to treat possible epileptic seizures in coma patients before pursuing with further assessments. AEPs also permit to discard the presence of a major hearing impairment that could jeopardize the measure of auditory ERPs. Metabolic confounders were also treated before recording. In case of preserved somatosensory and auditory cortical responses, this basic evaluation was completed by passive (MMN and novelty P3) and active tests.

Major lesions of the dominant hemisphere, hearing loss or unfamiliarity with french language were exclusion criteria for the active test.

ERPs using the active paradigm were recorded with a large range of delays from coma onset in 84 unresponsive adults (see Figure S1). Three patients were excluded since ERP recordings were not exploitable for technical reasons. Four recorded patients were excluded since they were addressed to our hospital for a short period of 24 to 48h, specifically to perform a clinical and neurophysiological evaluation and we lost sight of them after the recording. Note that none of these lost patients showed a positive result to the active paradigm.

Nine patients were explored after 1 year. None of them had a positive response to the test.

The study focused on the 68 patients recorded before 1 year post-coma and considered a clinical outcome at 6 months of follow-up determined with the Glasgow Outcome Scale Extended (GOS-E) and in terms of awareness level.

Thirty-seven of the 68 patients included in the study were recorded at the acute phase of coma, at least 48 h after a sedative treatment break and at the latest 33 days after coma onset (mean delay from coma onset: 12 +-8 days). The other 31 patients showed post-coma disorders of consciousness: 17 were in a vegetative state, 3 were characterized as MCS+ and 11 as MCS-.

Figure S1: Patients' enrolment

In the total set of 77 patients, initial coma was post-anoxic in 20 cases, post-traumatic in 28 cases, and consecutive to stroke in 24 cases. It followed a neurosurgical brain intervention in 3 cases and another medical pathology in 2 cases.

II -Outcome assessment

Functional outcome at six months after recording was determined using the CRS-R and the Glasgow Outcome Sale Extended (GOS-E) [START_REF] Fayol | Version française de l'entretien structuré pour l'échelle de devenir de Glasgow (GOS)•: recommandations et premières études de validation[END_REF] whose categories are as follows:

1 -Death.