Enikő Ladányi
email: eniko.ladanyi@vumc.org

Ágnes Lukács

Judit Gervain

Does rhythmic priming improve grammatical processing in Hungarian-speaking children with and without Developmental Language Disorder? Running title: Rhythmic priming in Hungarian

Keywords: DLD, SLI, rhythmic priming, grammar, rhythm, morphology 1

 6-year-old Hungarian-speaking children with and without Developmental Language Disorder perform better on a grammar task subsequent to exposure to a regular rhythm vs. an irregular rhythm/silence  The effect of regular rhythm is specific: it improves performance on a grammatical task but not on a word retrieval or a non-linguistic task  Difference between performance following regular vs. irregular rhythm originates from the facilitating effect of the regular rhythm (not the negative effect of the irregular rhythm)

 The results highlight the importance of rhythm in spoken language processing, and point towards a possible intervention tool in language disorders Abstract Research has described several features shared between musical rhythm and speech or language, and experimental studies consistently show associations between performance on tasks in the two domains as well as impaired rhythm processing in children with language disorders. Motivated by these results, in the current study our first aim was to explore whether a short exposure to a regular musical rhythm (i.e., rhythmic priming) can improve subsequent grammatical processing in preschool-aged Hungarian-speaking children with and without Developmental Language Disorder (DLD). Second, we investigated whether rhythmic priming is specific to grammar processing by assessing priming in two additional domains: a linguistic but non-grammatical task (picture naming) and a non-linguistic task (nonverbal Stroop task). Third, to confirm that the rhythmic priming effect originates from the facilitating effect of the regular rhythm and not the negative effect of the control condition, we added a third condition, silence, for all the three tasks. Both groups of children showed better performance on the grammaticality judgment task in the regular compared to both the irregular and the silent conditions but no such effect appeared in the non-grammatical and non-linguistic tasks. These results suggest that 1) rhythmic priming can improve grammatical processing in Hungarian, a language with complex morphosyntax, both in children with and without DLD, 2) the effect is specific to grammar and 3) is a result of the facilitating effect of the regular rhythm. These results could motivate further research about integrating rhythmic priming into traditional speech-language therapy.

Introduction

Speech is inherently rhythmic. This rhythmicity may be central to how we process and comprehend language. Indeed, recent findings suggest that an exposure to musical rhythm may help patients and young children better process spoken language (e. g., Przybylski et al., 2013). These results offer important insights into how we decode speech and language, and open up a promising new avenue of intervention techniques for developmental speech/language disorders. These early findings thus need to be extended and generalized. In this study, we, therefore, ask whether rhythmic priming improves language processing in Hungarian-speaking children with typical and atypical language development and we probe whether this effect is specific to grammar or whether it applies more generally to other cognitive domains.

Rhythmic priming

Neural resources for music and language overlap (e.g., [START_REF] Patel | The evolutionary biology of musical rhythm: was Darwin wrong?[END_REF][START_REF] Marie | Musicians and the metric structure of words[END_REF][START_REF] Kotz | Cortical speech processing unplugged: A timely subcortico-cortical framework[END_REF], and individual differences in rhythm processing have been found to be linked to speech/language skills. Associations have been documented between various measures of musical rhythmic abilities and phonological [START_REF] Moritz | Links between early rhythm skills, musical training, and phonological awareness[END_REF][START_REF] Ozernov-Palchik | Relationships between early literacy and nonlinguistic rhythmic processes in kindergarteners[END_REF][START_REF] Woodruff Carr | Beat synchronization predicts neural speech encoding and reading readiness in preschoolers[END_REF] as well as grammatical [START_REF] Gathercole | Perspectives on the rhythm-grammar link and its implications for typical and atypical language development[END_REF][START_REF] Gordon | Musical rhythm discrimination explains individual differences in grammar skills in children[END_REF][START_REF] Lee | Rhythm and syntax processing in school-age children[END_REF][START_REF] Woodruff Carr | Beat synchronization predicts neural speech encoding and reading readiness in preschoolers[END_REF]

Can shared neural processes between rhythm and language processing be harnessed for therapeutic purposes? Initial findings of restored neural responses on a grammaticality judgment task after presentation of a regular rhythmic prime (i.e., metronome) in Germanspeaking patients with basal ganglia injury [START_REF] Kotz | The basal ganglia are receptive to rhythmic compensation during auditory syntactic processing: ERP patient data[END_REF] and Parkinson disease [START_REF] Kotz | Can rhythmic auditory cuing remediate language-related deficits in arkinson's disease[END_REF]) motivated an intriguing line of studies that are often referred to as rhythmic priming studies.

This work aims to explore whether performance on various linguistic tasks can be improved by a presentation of a rhythmic stimulus with a regular beat immediately before the linguistic task. In the majority of the rhythmic priming studies, participants are exposed to an auditory signal (e.g., sequence of percussion beats) with either a regular or irregular beat/nonrhythmic stimuli before completing a linguistic task. Previous research has found an improved performance on a grammaticality judgment task after presentation of a regular rhythmic prime in French-speaking children with dyslexia (Przybylski et al., 2013) and DLD [START_REF] Bedoin | Temporally Regular Musical Primes Facilitate Subsequent Syntax Processing in Children with Specific Language Impairment[END_REF]Przybylski et al., 2013) as well as in typically developing French-speaking [START_REF] Bedoin | Temporally Regular Musical Primes Facilitate Subsequent Syntax Processing in Children with Specific Language Impairment[END_REF]Fiveash, Bedoin, Lalitte, & Tillmann, 2020;Przybylski et al., 2013) and English-speaking [START_REF] Chern | New evidence of a rhythmic priming effect that enhances grammaticality judgments in children[END_REF] children. The effect was also found in young adults with and without dyslexia who showed a larger ERP response to grammatical violations following regular vs. the irregular primes (Canette et al., 2020).

A few studies also focused on rhythmic priming effects on phonological perception in pseudowords Cason ch n, 2012) and sentences (Cason st sano ch n, 2015). These studies aimed at investigating the degree to which the acoustic structure of musical rhythmic patterns could act as a scaffold for linguistic processing, and therefore used a slightly different priming paradigm from the grammaticality judgment studies as the rhythm of the primes either matched or did not match the prosodic structure of the speech stimuli. Matching primes facilitated phonological processing compared to not matching primes extending the effect of rhythmic priming to phonemic perception.

These results are highly relevant for our understanding of speech and language processing, and they also hold the promise of providing new intervention methods for speech and language disorders. However, this field is still new. The exact nature of the effect and the underlying mechanisms are not fully understood, so further empirical work is necessary to explore and better document them. The aim of the current study is to contribute to a better characterization of the rhythmic priming effect in at least three ways.

First, while several studies tested the effect of rhythmic priming on grammar and phonological processing, we are not aware of any studies exploring the phenomenon in other linguistic domains. Only one study tested the question with non-linguistic tasks [START_REF] Chern | New evidence of a rhythmic priming effect that enhances grammaticality judgments in children[END_REF] finding no effect of rhythmic priming suggesting a domain-specific effect for language.

The non-linguistic tasks used in that study, however, differed considerably from the grammar task in several respects such as the number of blocks, number of trials within the blocks or the way how trials were presented. Exploring and documenting rhythmic priming in other nonlinguistic as well as linguistic but non-grammatical tasks is important for learning more about the origin of the rhythmic priming effect and the therapeutic contexts within which it can be used. One aim of the current study is, therefore, to explore the scope of the effect.

Second, previous work tested rhythmic priming comparing performance following regular primes with performance following either an irregular prime [START_REF] Chern | New evidence of a rhythmic priming effect that enhances grammaticality judgments in children[END_REF]Przybylski et al., 2013) or a non-rhythmic baseline condition [START_REF] Bedoin | Temporally Regular Musical Primes Facilitate Subsequent Syntax Processing in Children with Specific Language Impairment[END_REF]. Although all these studies have shown a rhythmic priming effect, the contribution of the facilitative effect of the regular prime and the negative effect of the irregular prime cannot be disentangled with using two conditions. With a design including only a regular and an irregular condition, it is impossible to determine if the effect appears because regular rhythm facilitates grammar performance or because irregular rhythm has a negative effect. If rhythmic priming appears when comparing performance following a regular rhythm to silence, that suggests that the regular rhythm has a facilitating effect. However, it remains to be determined whether rhythmic priming can be accounted for by only the positive effect of the regular prime, or by the combination of the positive effect of the regular prime and the negative effect of the irregular prime. To answer this question, the current study used a regular, an irregular and a non-rhythmic baseline condition within the same paradigm.

Third, the rhythmic priming effect has so far only been investigated in a few languages (French, English, German), all of which belong to the Indo-European language family and, albeit rhythmically different, have comparable morphosyntactic structure. To test whether rhythmic priming is a language-general phenomenon, it is crucial to test it in languages with various features. In addition, due to its highly complex morphosyntax (see next section), the gap between typically and atypically developing children's grammatical abilities is greater and more readily observable in Hungarian than in morphologically poor languages. Hungarian thus offers an ideal testing ground to explore the magnitude and potential clinical relevance of the rhythmic priming effect.

The importance of investigating rhythmic priming in Hungarian

Hungarian is an agglutinative language belonging to the Uralic/Finno-Ugric language family.

Word order is relatively free, and grammatical relations are mainly expressed by suffixes.

Both verbal and nominal morphology is complex. For instance, verbs agree with the number and person of their subject as well as with the definiteness of the object. Tense and mood are also marked. These features result in a large number of possible forms showing high complexity. For instance, olvashatnád 'you may/could read it') consists of the word stem olvas 'read') the modal suffix -hat and the 2 nd person singular definite verb suffix in present tense and conditional mood (-nád). In addition, both stems and suffixes show strong allophonic variation, e.g., as a result of vowel harmony. Lexical stress in Hungarian is also different from lexical stress in the languages in which rhythmic priming was studied before.

Hungarian has fixed stress on the first syllable of words (Siptár & Törkenczy, 2007), which thus provides a cue to word boundaries and lexical retrieval. The speech rhythm of Hungarian is syllable-timed, similarly to French, but unlike that of English and German.

Previous studies with children tested the effect of rhythmic priming on the processing of suffixes in English and French. These languages have a simpler morphological system than Hungarian. It is possible that exposure to a regular rhythm is sufficient to boost morphological processing in languages with a simple morphology but does not have an effect in morphologically complex languages in which a greater variety of suffixes need to be processed, with sometimes multiple suffixes attached to a stem.

For example, in the [START_REF] Chern | New evidence of a rhythmic priming effect that enhances grammaticality judgments in children[END_REF] study children always had to detect a missing third person singular -s as a number agreement error and a missing past tense -ed as a tense agreement error. English doesn't allow for a greater diversification of the error types. In contrast, in Hungarian, full verbal conjugation paradigms can be found both in the present and the past tense. In addition, the realization of suffixes differs depending on the phonological features of the word stem. To test how the complexity of the Hungarian verb inflection system interacts with rhythmic priming, in the current study we included all six forms of the verb conjugation paradigm both for present and past tense suffixes as well as verbs with different phonological features leading to a high diversity in the phonetic realization of the grammatical errors to be detected.

Developmental Language Disorder

In addition to a better characterization of the rhythmic priming effect in general, we also aim to contribute to the limited amount of research exploring the possibility of integrating rhythmic priming into therapeutic interventions for children with Developmental Language Disorder (DLD). DLD is a developmental disorder formerly known as Specific Language Impairment (SLI) that primarily affects language (with less prominent problems in other domains). Language problems in children with DLD cannot be attributed to obvious impairments in other cognitive domains or perceptual deficits, neurological disorders, emotional or social problems, environmental deprivation or intellectual disability, but the underlying causes of DLD are not well understood yet [START_REF] Bishop | Phase 2 of CATALISE: A multinational and multidisciplinary Delphi consensus study of problems with lang uage development: Terminology[END_REF][START_REF] Leonard | Children with specific language impairment[END_REF].

Traditional accounts suggest a grammar-specific deficit [START_REF] Clahsen | Lexical entries and rules of language: A multidisciplinary study of German inflection[END_REF][START_REF] Gathercole | Perspectives on the rhythm-grammar link and its implications for typical and atypical language development[END_REF][START_REF] Lely | Binding theory and grammatical specific language impairment in children[END_REF][START_REF] Raven | Specific language impairment as a period of optional infinitive[END_REF], while more recent theories also emphasize the role of domain-general problems and their potential contribution to the linguistic problems [START_REF] Gathercole | Perspectives on the rhythm-grammar link and its implications for typical and atypical language development[END_REF][START_REF] Hsu | Grammatical difficulties in children with specific language impairment (SLI): Is learning deficient?[END_REF][START_REF] Leonard | Children with specific language impairment[END_REF][START_REF] Tallal | Defects of non-verbal auditory perception in children with developmental dysphasia[END_REF][START_REF] Ullman | Specific language impairment is not specific to language: The procedural deficit hypothesis[END_REF].

Hungarian-speaking children with DLD show prominent difficulties in morphology.

They make mistakes with case markers (Lukács, Leonard, Kas & Pléh, 2009) and other aspects of verb morphology were also found to be impaired [START_REF] Leonard | Tense and aspect in childhood language impairment: Contributions from Hungarian[END_REF], as were sentence comprehension and production [START_REF] Kas | magyar vonatkoz mell kmondatok meg rt se tipikus s zavart nyelvi fejlő sben [The comprehension of Hungarian relative clauses in typical development and in children with specific language impairment[END_REF]. Impairments were found in the lexical domain as well: vocabulary size was shown to be lower (Vinkler & Pléh, 1995) and word retrieval was less efficient [START_REF] Ladányi | Lexical Conflict Resolution in Children with Specific Language Impairment[END_REF] in children with DLD than in their typically developing peers.

Populations with language impairments often show weaker rhythmic skills compared to typically developing children. The Atypical Rhythm Risk Hypothesis posits that individuals with atypical rhythm are at higher risk for developmental speech/language disorders [START_REF] Ladányi | Is atypical rhythm a risk factor for developmental speech and language disorders?[END_REF]. In particular, several studies have found impaired performance on rhythm-related tasks in children with dyslexia (e.g., [START_REF] Muneaux | Deficits in beat perception and dyslexia: evidence from French[END_REF][START_REF] Overy | Dyslexia and music: Measuring musical timing skills[END_REF] and with DLD [START_REF] Bedoin | Temporally Regular Musical Primes Facilitate Subsequent Syntax Processing in Children with Specific Language Impairment[END_REF][START_REF] Corriveau | Rhythmic motor entrainment in children with speech and language impairments: Tapping to the beat[END_REF][START_REF] Corriveau | Basic Auditory Processing Skills and Specific Language Impairment: A New Look at an Old Hypothesis[END_REF][START_REF] Cumming | Awareness of Rhythm Patterns in Speech and Music in Children with Specific Language Impairments[END_REF]). While it is not known yet if rhythm problems are a cause [START_REF] Goswami | A temporal sampling framework for developmental dyslexia[END_REF] or simply a frequently co-morbid feature of developmental speech and language problems, [START_REF] Ladányi | Is atypical rhythm a risk factor for developmental speech and language disorders?[END_REF] hypothesize that potentially shared biological underpinnings between rhythm and multiple facets of speech-language development, at the genetic and/or neural levels, may account for associations between rhythm and language traits observed in the population.

Regardless of the origin of deficits in DLD, prior work in English and French shows rhythmic priming effects in this population [START_REF] Bedoin | Temporally Regular Musical Primes Facilitate Subsequent Syntax Processing in Children with Specific Language Impairment[END_REF]Przybylski et al., 2013), such that grammatical task performance is enhanced by regular musical primes. If further research including randomized controlled trials reveals that rhythmic priming can facilitate traditional language therapy at least in a subgroup of children with DLD, rhythmic priming could be integrated into the battery of therapeutic interventions, even if mechanisms underlying rhythmic priming are yet to be understood. This approach is in line with evidence-based practice (ASHA, 2005), that is prevalent in speech-language therapy and in medicine in general, emphasizing the efficacy of a treatment. There is an urgent need to improve treatment for children with DLD (NASEM, 2016), as DLD has a relatively high prevalence rate (~7%, Tomblin et al., 1997), and without efficient treatment, these individuals develop life-long academic, economic, social and emotional difficulties (Conti-Ramsden, Durkin, Toseeb, Botting, & Pickles, 2018).

The current study

In the current study, we aim to explore three questions: 1) Does the presentation of a regular rhythm improve grammatical processing in Hungarian preschool-aged children with and without Developmental Language Disorder? 2) Is the rhythmic priming effect specific to grammar, general across language domains or general across cognitive domains? 3) Does the rhythmic effect result from the facilitative effect of regular rhythm, the negative effect of the irregular rhythm or both?

Our first aim is to explore the rhythmic priming effect in Hungarian-speaking children with TD and DLD. Previous studies found a rhythmic priming effect in a few languages (French, English, German) both in individuals with and without language disorders. It is important to document, however, if the effect is present in various languages to explore its generality across languages. Hungarian is a perfect candidate as its morphology and prosody differs considerably from those of previously tested languages. Testing if the effect appears in Hungarian speaking children with DLD, who have particular difficulties with morphology, beyond children with TD is crucial for investigating its potential clinical utility.

Based on our current understanding, rhythmic priming is a phenomenon present across languages. Therefore, we expect that rhythmic priming will facilitate grammar processing in Hungarian. As previous research has shown a rhythmic priming effect not only in TD children but also in children with DLD despite their impaired rhythm processing skills, we do not expect to see a group difference in the rhythmic priming effect.

Our second aim is to explore whether rhythmic priming is domain-general, specific to language or specific to the processing of spoken language. To test the specificity of rhythmic priming to language processing, we included a non-linguistic task (non-verbal Stroop task) to our design complementing the grammaticality judgment task. We aimed to match the procedures of our non-grammatical tasks in every possible respect to the grammaticality judgment task. Furthermore, similarly to [START_REF] Chern | New evidence of a rhythmic priming effect that enhances grammaticality judgments in children[END_REF])'s study we chose a task that requires attentional processes but stimuli do not involve regularities as speech or rhythm does.

In addition to the non-linguistic task, we also included a linguistic but nongrammatical task to our design to examine the possibility that rhythmic priming is not domain-general but is also present in language production beyond language processing.

We do not expect to find a rhythmic priming effect in the non-linguistic control task.

As no studies have tested the effect of rhythmic priming on a linguistic but non-grammatical task yet, it is less clear if rhythmic priming can affect word retrieval. The presence of a rhythmic priming effect in the picture naming paradigm would indicate that the effect appears due to shared processes between rhythm and language in general while a lack of a rhythmic priming would suggest its specificity to grammar or spoken language processing.

Our third aim is to better understand the origin of the rhythmic priming effect by comparing performance in three within-subject conditions: one in which a regular rhythm is used as a prime, one with an irregular rhythm and a baseline condition in which children were not presented with any auditory stimuli. Previous studies compared performance only between two conditions (regular vs. irregular: [START_REF] Chern | New evidence of a rhythmic priming effect that enhances grammaticality judgments in children[END_REF]Przybylski et al., 2013; regular vs. non-rhythmic baseline condition: [START_REF] Bedoin | Temporally Regular Musical Primes Facilitate Subsequent Syntax Processing in Children with Specific Language Impairment[END_REF], which did not allow for a direct comparison of the irregular prime to a non-rhythmic baseline condition. By including three conditions, we expect to better understand whether regular rhythm improves performance, irregular rhythm hinders it or rhythmic priming results from the combination of the positive effect of the regular prime and the negative effect of the irregular prime.

We expect to find better performance following the regular prime than following the irregular prime and the baseline condition. As [START_REF] Bedoin | Temporally Regular Musical Primes Facilitate Subsequent Syntax Processing in Children with Specific Language Impairment[END_REF] discusses, the effect size of the difference between the regular and the irregular condition was larger in Przybylski et al.'s (2013) study than between the regular and the non-rhythmic baseline conditions in their study, suggesting that the irregular prime may have a negative effect on grammatical processing.

Based on this observation, we expect to find weaker performance in the irregular condition than in the baseline condition.

Methods

Participants

Seventeen 5-7-year-old children with DLD and 17 age-and IQ-matched typically developing children participated in the study. Demographic and screening data for the two groups are shown in Table 1. Children were recruited from six different pre-schools in Budapest. As a first step of recruitment, a larger group of children showing language problems was selected by the speech-language therapists of the pre-schools. Children whose parents agreed to participate in the study (n = 50) were screened for DLD by a speech-language therapist using four language tasks (the Hungarian version of the Peabody Picture Vocabulary Test (Csányi, 1974), the Hungarian adaptation of the Test for Reception of Grammar [START_REF] Bishop | Test for Reception of Grammar[END_REF][START_REF] Bishop | TROG-Test for Reception of Grammar handbook[END_REF]Lukács Győri Rózsa, 2012) the teachers in the same pre-schools. Children whose parents agreed to participate in the study completed the non-verbal intelligence task. One TD child matching in IQ (< 5 points of difference in IQ), age (< 3 months difference) and sex was selected for each DLD child. We made every effort to match the groups in parent education level, but this aim could only partially be met, and the educational level of the DLD group is slightly lower than that of the TD group (see Table 1). TD children also completed the screening tasks to make sure that they did not have language impairment. None of the TD children performed below average on the screening tasks. All children were tested with the informed consent of their parents, in accordance with the principles set out in the Declaration of Helsinki and the stipulations of the local Institutional Review Board.

Tasks

Grammaticality judgment task

Stimuli

We created 60 grammatically correct Hungarian sentences. Then we modified these sentences by violating either the number agreement between the verb and the subject or the tense of the verb with respect to the adverb (Table 2). All 6 forms (singular and plural forms, in 1 st , 2 nd , and 3 rd person) of the present and past verb conjugation paradigm were equally represented both in grammatical and ungrammatical sentences. Two lists of sentences were created by combining 30 grammatically correct and 30 grammatically incorrect sentences. We included correct and incorrect versions of the same sentence in different lists, therefore one child couldn't hear both (see examples in Table 2), and lists were randomly assigned to children.

We also made sure that the two lists were matched in their sentence types and vocabulary.

Sentences were recorded by an adult female speaker in a mild child-directed manner.

As regular and irregular primes, we used the same stimuli as several previous studies [START_REF] Bedoin | Temporally Regular Musical Primes Facilitate Subsequent Syntax Processing in Children with Specific Language Impairment[END_REF][START_REF] Chern | New evidence of a rhythmic priming effect that enhances grammaticality judgments in children[END_REF]Przybylski et al., 2013). Both sequences were played on a tam-tam and maracas and contained the same number of tones. The regular prime had a rhythmic structure from which it was relatively easy to extract the meter, while it was more difficult to extract the rhythmic structure from the irregular prime (see a more detailed description of the primes in Przybylski et al., 2013).

Design and Procedure

During the grammaticality judgment task, children were presented with six blocks of ten sentences on which they were asked to make grammaticality judgments (see a summary of the task procedures in Figure 1). Each block was preceded by a 32-second-long prime. Two primes belonged to the regular condition, two belonged to the irregular condition and two primes belonged to the baseline condition, which did not contain any auditory stimuli. Prime conditions followed each other in a pseudo-randomized order with the restriction that two primes from the same condition could not follow each other. A picture of a cat relaxing and listening to music was visually presented on the screen while the prime stimuli were played.

Children were instructed to relax and take some rest during the primes. Children took breaks of different lengths (from a few seconds to a few minutes) before the presentation of the primes. Sentences were presented immediately after the primes with no breaks.

Each block contained five grammatically correct and five grammatically incorrect sentences, which were presented to the child in a randomized order. The type of violation was counterbalanced across blocks.

We created a background story similar to the one used in previous studies [START_REF] Bedoin | Temporally Regular Musical Primes Facilitate Subsequent Syntax Processing in Children with Specific Language Impairment[END_REF][START_REF] Chern | New evidence of a rhythmic priming effect that enhances grammaticality judgments in children[END_REF]Przybylski et al., 2012) to make our task more comprehensible and interesting for young children. Before the task, we introduced them a purple and a green dinosaur. They were informed that the purple dinosaurwhich looked very confident and attentivewas very attentive, so it said everything correctly, while the green dinosaurwhich looked somewhat confusedwas less attentive, and always made mistakes. We presented them with examples of the sentences the dinosaurs produced. As the first part of the practice phase, children heard the same sentence, once in a correct form, once in an incorrect form, and they had to decide which dinosaur produced the sentence. A second practice phase followed, in which children were presented with different correct and incorrect sentences and they had to decide which dinosaur produced the sentence. Children got feedback for each response during the practice phase. After we made sure that children understood the task, we moved on to the test.

We used d' scores to measure grammaticality judgment performance, similarly to previous studies [START_REF] Bedoin | Temporally Regular Musical Primes Facilitate Subsequent Syntax Processing in Children with Specific Language Impairment[END_REF][START_REF] Chern | New evidence of a rhythmic priming effect that enhances grammaticality judgments in children[END_REF]Przybylski et al., 2013). D' is a measure used by signal detection theory that describes the participant's ability to discriminate between two types of stimuli (in the current study between grammatical and ungrammatical stimuli) and was calculated as the difference between the z-transformed hit rate and false alarm rate d' = z hit rate)-z(false alarm rate)).

We presented stimuli and collected data with OpenSesame [START_REF] Mathôt | OpenSesame: An open-source, graphical experiment builder for the social sciences[END_REF] for all the three rhythmic priming tasks.

Picture naming task

Stimuli

Sixty pictures of simple everyday objects that the children likely knew were selected from the picture set used by the norming study of Bates and colleagues (2003). Pictures were grouped into six blocks. The same auditory stimuli were used as primes as in the grammaticality judgment task.

Design and procedure

To make sure that children were familiar with the names of the pictures, they were asked to name all the pictures in a randomized order at a previous testing session.

The structure of the picture naming task was the same as the structure of the grammaticality judgment task. Children were presented with a prime and then named 10 pictures. Children were asked to name pictures as quickly and as accurately as possible.

Pictures were presented in a randomized order within a block and blocks of pictures were randomly assigned to a prime condition. Children's responses were audio-recorded. Naming errors and response times of the correct responses were coded based on the recording. We decided to code naming times off-line for a more accurate measure. Based on our experience with naming studies with young children, automatic measurements detecting the onset of the name are problematic, since children often make false starts, emitting sounds other than the name before actually naming the picture, which activates the voice key. Children also often produce or start to produce names too softly, which fails to activate the voice key. Both of these lead to inaccurate measures (see also [START_REF] Cummings | Phonological code retrieval during picture naming: Influence of consonant class[END_REF]. We excluded incorrect answers and answers with naming times above 5 seconds, since they indicate that the child was inattentive at that trial, and calculated mean naming times for the three conditions. Accuracy was also coded and calculated, but since performance was at ceiling, we did not analyze accuracy data statistically.

Non-verbal Stroop task

Stimuli

For the non-verbal Stroop task, we created arrows appearing on a blank screen. Arrows As primes, we used the same auditory stimuli as in the grammaticality judgment task and the picture naming task.

Design and procedure

The structure of the task was the same as in the grammaticality judgment task and the picture naming task. Children were presented with a prime and then with a block of 20 arrows.

Children were asked to press a button based on the direction of the arrow. Arrows followed each other in a randomized order in each block and associations between arrow blocks and prime conditions were also randomized. The task was preceded by a practice session. We calculated two different measures for the non-verbal Stroop task. First, for testing the effect of rhythmic priming on executive functions, we calculated mean Stroop effects measured by accuracy and reaction times for the three priming conditions. Stroop effects were calculated as the difference between mean reaction times for correct responses/accuracy in the incongruent and baseline conditions. Second, for testing the effect of rhythmic priming on the general performance on the task, accuracy and mean reaction times were calculated with collapsing across Stroop conditions for the three priming conditions. Trials with reaction times under 300 ms-s and above 5000 ms-s were excluded from the analysis as these data resulted from technical errors or inattentiveness of the child, and are not meaningful.

Results

Grammaticality judgment task

Performance on the grammaticality judgment task is shown in Table 3 andFigure There was no significant difference between the irregular and baseline conditions (t(33) = 0.327, p = .779, d = .05). The Group X Rhythm interaction was not significant. To confirm the reliability of the significant effect of rhythm on grammaticality judgment, we also ran a Bayesian repeated measures ANOVA. This analysis also showed that the model with the main effect of rhythm and DLD is the best model of the data. The probability of the observed data was 42594 times greater with this model than the null model.

Since the DLD group showed a weak performance on the grammaticality judgment task, we tested whether d-prime scores on the three conditions significantly differ from chance level (d' = 0) with a one-sample t-test in the TD and DLD groups, separately. We found that while children with TD showed a performance significantly above chance in each condition (baseline: t(16) = 7.012, p < .001, irregular = t(16) = 8.1, p < .001, regular: t(16) = .6.745, p < .001), children with DLD performed above chance only in the regular rhythm condition (baseline: t(16) = .715, p = .485, irregular t(16) = 1.786, p = .093, regular: t(16) = 3.897, p = .001).

As [START_REF] Bedoin | Temporally Regular Musical Primes Facilitate Subsequent Syntax Processing in Children with Specific Language Impairment[END_REF] argue, using silence as the baseline condition runs a risk that the effect of the previous prime persists and affects the performance in the silent baseline condition.

To test this possibility, we grouped the responses of the baseline condition into three categories: (i) baseline block preceded by a regular block, (ii) baseline block preceded by an irregular block and (iii) baseline as the first block in the task. We calculated the mean d' scores for each category. We did not find a significant difference between these cases in a one-way ANOVA (F(2, 64) = 1.452, p = .242; M irregular = 0.97 M regular = 0.78 M first = 2.06). To investigate the possibility that the prime from the previous block only affected the first items of the block, we ran the same analyses only on the first five items from each block but no significant difference appeared between blocks in this analysis either (F(2, 64) = 0.371, p =

.692; M irregular = 1.46 M regular = 0.94 M first = 1.15).

Picture naming task

Mean naming times in the picture naming task are shown in Table 4. Naming times for the correct answers were analyzed in a 2 x 3 ANOVA with Group (DLD vs. TD) as a betweensubject factor and Rhythm (Regular vs. Irregular vs. Baseline) as a within-subject factor. The main effect of Group was marginally significant (F(1, 32) = 4.14, p = .050) reflecting slower naming times in the DLD (M = 1404 ms, SD = 422 ms) than in the TD group (M = 1177 ms, SD = 370 ms). There were no other significant effects or interactions.

Non-verbal Stroop task

Differences in Stroop effects depending on the priming condition were analyzed both measured by accuracy and reaction times as the dependent variable with 2 x 3 ANOVA-s with Group (DLD vs. TD) as a between-subject factor and Rhythm (Regular vs. Irregular vs.

Baseline) as a within-subject factor (see a summary of Stroop scores in Table 5). The interaction between Group and Rhythm was significant in the case of reaction times (F(2, 64) = 4.23, p = .019). Fisher's Least ignificant Difference L D) post-hoc pairwise comparisons showed a significantly smaller Stroop effect in the case of the irregular than in the baseline (t(16) = 2.53, p = .010) and in the regular (t(16) = 2.53, p = .020) condition in the TD group but no significant differences appeared in the DLD group. No other main effects or interactions were significant in the case of Stroop effects measured by reaction times or accuracy rates.

To explore whether rhythm had an effect on task performance in general, independently of the Stroop effect, accuracy and reaction times of correct responses collapsed across Stroop conditions were analyzed with 2 x 3 ANOVA-s with Group (DLD vs. TD) as a betweensubject factor and Rhythm (Regular vs. Irregular vs. Baseline) as a within-subject factor (see a summary of scores in Table 6). No main effects or interactions were found to be significant either for accuracy, or for reaction times.

Discussion

In the current study, we investigated the rhythmic priming effect in Hungarian-speaking 5-7year-old children with and without Developmental Language Disorder. Following exposure to a regular vs. an irregular rhythm or no prime, children showed a rhythmic priming effect, i.e.

better performance, on a grammaticality judgment task, but did not show a rhythmic priming effect on two tasks requiring no grammatical processing: a picture naming task and a nonverbal Stroop task. The results indicate that a rhythm with a regular metrical structure facilitates subsequent grammatical processing in an agglutinating language, a morphosyntactic type not yet explored within this type of paradigm. The presence of the effect did not depend on the presence or absence of DLD. Children with DLD also benefitted from the regular rhythmic prime, suggesting that rhythmic training or the use of rhythmic stimuli during traditional language therapy might facilitate language processing in this atypical group.

Our finding on the presence of the rhythmic priming effect in a grammaticality judgment task in children with and without DLD is in line with previous studies finding better performance when children are exposed to a regular rhythm compared to an irregular one [START_REF] Chern | New evidence of a rhythmic priming effect that enhances grammaticality judgments in children[END_REF]Przybylski et al., 2013) or no rhythm at all [START_REF] Bedoin | Temporally Regular Musical Primes Facilitate Subsequent Syntax Processing in Children with Specific Language Impairment[END_REF]. Our study also extends previous research by showing evidence for a longer effect of priming than previous studies as in the current study, children were presented with 10 sentences after the prime in the grammaticality judgment task that is slightly more than in previous studies in that 6 sentences were presented per block.

Regarding the difference between the baseline and irregular conditions in the grammaticality judgment task, we expected to find a weaker performance in the irregular condition than in the baseline condition based on Bedoin et al.'s (2016) observation of the rhythmic priming effect being stronger when comparing the regular condition to an irregular condition, than when comparing the regular condition to a non-rhythmic baseline. In the current study, we were able to directly compare the irregular and baseline conditions and found no significant difference between them. This suggests that irregular rhythm does not have a negative effect on subsequent grammatical processing. We note, however, that while [START_REF] Bedoin | Temporally Regular Musical Primes Facilitate Subsequent Syntax Processing in Children with Specific Language Impairment[END_REF] used environmental noise as a baseline condition, we used silence; perhaps environmental noise and silence impact performance differently.

Using silence as the baseline condition runs a risk that the effect of the previous prime persists and affects the performance in the baseline condition. To investigate if the effect of the regular and irregular primes persisted until the presentation of the sentences in the baseline condition, we calculated the grammaticality judgment performance in the baseline condition for 1) blocks preceded by a regular block, 2) blocks preceded by an irregular block and 3) blocks presented as the first block in the task. Grammaticality judgment performance did not show a significant difference between these three types of baseline blocks, suggesting that regular/irregular primes did not affect grammaticality judgment performance in subsequent baseline blocks. This pattern of results suggests that the effect of rhythmic stimulation is long enough to affect grammaticality judgments on the ten sentences immediately following the rhythm but fades away by the time the child is presented with the sentences in the subsequent block. Our procedures do not allow us to calculate the exact duration of the effect of the rhythmic stimulation because children took breaks of different lengths between blocks, but these results suggest that priming is not present for more than a few minutes.

The presence of the rhythmic priming effect in the grammaticality judgment task and its absence in the non-verbal Stroop task, a non-linguistic task strongly relying on attentional processes, is in line with previous results [START_REF] Chern | New evidence of a rhythmic priming effect that enhances grammaticality judgments in children[END_REF]. In the current study, the length of the blocks as well as the task procedures were closely matched between the three tasks.

These results suggest that the rhythmic priming effect is specific to speech/language processing or to grammar processing. Note that in the non-verbal Stroop task, children with TD showed a reduced Stroop effect in the irregular condition compared to the baseline or regular conditions. This result could be explained by the fact that the Stroop effect in the irregular condition was negative in seven out of the seventeen children with TD, meaning that it took longer for them to respond to baseline trials than to Stroop trials. Lack of Stroop effects in the irregular condition in some children with TD motivates further research focusing on the effect of rhythmic priming on inhibition, but we believe that this result is not relevant for the main question of the current study, therefore we do not discuss it further.

To our knowledge, our study is the first one exploring the effect of rhythmic priming on word retrieval. The lack of rhythmic priming in the picture naming task suggests that the rhythmic priming effect is not only specific to the language domain but seems to be restricted to language perception or grammar. These results are in line with a recent study [START_REF] Canette | Rhythmic and textural musical sequences differently influence syntax and semantic processing in children[END_REF] testing the effect of a rhythmical music vs. textural sounds on a semantic evocation task in which children were asked to verbalize concepts that were evoked by rhythmic music or sound texture. The study found that children produced more concepts after the textural sounds, suggesting that rhythmic priming did not facilitate semantic evocation. Although picture naming and semantic evocation measure partly different abilities, both involve lexical processes. The lack of rhythmic priming in lexical tasks further confirms that rhythmic priming is specific to grammar or receptive language skills.

The design of the current study did not enable us to decide which aspect of language processinglower-level auditory processing of phonemes and syllables, the processing of higher-level linguistic structures or bothis facilitated by the regular prime, neither to explore the underlying mechanisms. The result that rhythmic priming facilitates phonological processing [START_REF] Cason | Bridging music and speech rhythm: Rhythmic priming and audio-motor training affect speech perception[END_REF][START_REF] Cason | Rhythmic priming enhances the phonological processing of speech[END_REF] supports the role of auditory processing, but future studies need to find out whether improved grammatical processing is accounted for by better auditory processing in itself, or if rhythmic priming facilitates both auditory processing and grammatical processing.

The mechanisms underlying rhythmic priming are also still to be discovered. While musical rhythm and linguistic syntax certainly engage partially separate brain networks, a recent fMRI meta-analysis identified several overlapping brain regions (left IFG, left SMA, and bilateral insula) recruited both by rhythm and syntactic tasks [START_REF] Heard | Shared neural resources of rhythm and syntax: An ALE meta-analysis[END_REF]. Thus, activation of rhythm networks could affect subsequent syntactic processing through these particular brain regions. It is also possible that facilitation of temporal attention during the perception of rhythmic primes affects sequencing during speech perception, leading to more efficient detection of errors (see [START_REF] Bedoin | Temporally Regular Musical Primes Facilitate Subsequent Syntax Processing in Children with Specific Language Impairment[END_REF][START_REF] Kotz | Non-motor basal ganglia functions: a review and proposal for a model of sensory predictability in auditory language perception[END_REF]Przybylski et al., 2013). More broadly, evidence for enhancement of neural processing during rhythmic priming comes from EEG data showing a relationship between entrainment effects during the primes and linguistic targets (Falk, Lanzilotti & Schon, 2017).

It is important to emphasize that a grammaticality judgment task requires strong metalinguistic skills, that makes it a less direct measure of grammatical processing than other measures of grammatical skills (e.g., sentence comprehension tasks in which participants have to choose the picture corresponding to the sentence among multiple options). While good grammatical skills are obviously necessary to detect grammatical errors, they are not sufficient. As language processes are highly automatic, it is possible that one has good grammatical skills and is able to process sentences but is less successful at detecting errors that requires metalinguistic skills and attention to violations. In this case, their performance will show a high hit rate with a relatively high false alarm rate. High false alarm rates played a stronger role in low d'-s than low hit rates, especially in the DLD group, meaning that judging ungrammatical sentences "correct" accounted for more errors than judging grammatical sentences "incorrect". This could mean that metalinguistic skills attentional problems or the usual "yes"-bias commonly found in children also played a role in the performance on the grammaticality judgment task. Future studies in children with DLD will need to investigate the effect of rhythmic priming on grammatical processing using other behavioral tasks that tap into expressive and receptive morpho-syntactic ability, and would also benefit from using EEG to measure on-line grammatical processing, complementing work in adults (Canette et al., 2020;[START_REF] Kotz | The basal ganglia are receptive to rhythmic compensation during auditory syntactic processing: ERP patient data[END_REF][START_REF] Kotz | Can rhythmic auditory cuing remediate language-related deficits in arkinson's disease[END_REF].

  pointed to the left, to the right, up or down and appeared either in the middle of the screen (baseline condition) or in the left, right, top or bottom of the screen either in a congruent position with the direction of the arrow (e.g., an arrow pointing up appears at the top of the screen) or in an incongruent position with the direction of the arrow (e.g., an arrow pointing up appears at the bottom of the screen). Six blocks of 20 trials were created. The number of arrows with a congruent, incongruent and middle position were counterbalanced across blocks as well as the number of arrows pointing to right, left, up and down.

  with Group as a between-subject factor (DLD vs. TD) and Rhythm (Regular vs. Irregular vs. Baseline) as a within-subject factor. The main effect of Group was significant (F(1, 32) = 42.41, p < .001) showing a significantly higher performance in children with TD (mean d' = 1.60, SD = 0.93) than in children with DLD (mean d' = 0.35, SD = 0.71). The main effect of rhythm was also significant (F(1, 32) = 3.15, p = .0496). Fisher's Least ignificant Difference L D) post-hoc pairwise comparisons showed a significantly better performance in the regular (mean d' = 1.23, SD = 1.10) than in the baseline (mean d' = 0.82, SD = 1.06; t(33) = 2.117, p = .025, d = 0.38) and irregular (mean d' = 0.873, SD = 0.91; t(33) = 2.00, p = .047, d = 0.36) conditions.

  Figure 1. Procedures of the grammaticality judgment rhythmic priming task. The grammaticality judgment task consisted of 6 blocks. In each block, first, children were presented with a prime, and then with 10 sentences half of which was grammatical and the other half was ungrammatical.

Table 2 .

 2 Examples of grammatically correct and incorrect sentences in the rhythmic priming grammaticality judgment task Correct version Violation Number agreement A kisbaba alszik az ágyban. 'The baby is sleeping in the bed.' *A kisbaba alszanak az ágyban. 'The baby are sleeping in the bed.'

	Tense	Tegnap este sok fagyit kaptunk.	*Tegnap este sok fagyit kapunk.
		'We got a lot of ice-cream last	'We get a lot of ice-cream last
		evening'	evening'

Table 3a -

 3a b. a) Means and standard deviations of hit rates, false alarm rates in the DLD and TD groups in the three rhythm conditions. b) Means and standard deviations of z-scored hit rates false alarm rates and d' scores in the DLD and TD groups in the three rhythm conditions.

		Hit rate			False alarm rate
		Baseline Irregular Regular	Baseline Irregular Regular
	DLD 0.61	0.63	0.68	0.57	0.52	0.52
		(0.24)	(0.23)	(0.22)	(0.20)	(0.27)	(0.27)
	TD	0.81	0.77	0.77	0.32	0.30	0.25
		(0.14)	(0.16)	(0.17)	(0.20)	(0.14)	(0.21)
		Hit (z-score)		False alarm (z-score)		d'
		Baseline Irregular Regular	Baseline Irregular Regular	Baseline Irregular Regular
	DLD 0.36	0.42	0.63	0.25	0.10	0.01	0.12	0.32	0.62
		(0.83)	(0.80)	(0.85)	(0.65)	(0.80)	(0.83)	(0.76)	(0.73)	(0.88)
	TD	0.97	0.86	0.90	-0.56	-0.57	-0.94	1.53	1.43	1.84
		(0.56)	(0.61)	(0.70)	(0.70)	(0.43)	(0.91)	(0.90)	(0.73)	(1.13)

Table 4 . Mean naming times and standard deviations in milliseconds in the picture naming task

 4

		Baseline	Irregular	Regular
	DLD	1450 (109)	1328 (86)	1435 (114)
	TD	1183 (101)	1156 (91)	1192 (81)

Table 5 . Mean Stroop effects (difference between mean reaction times for the baseline and incongruent conditions) in the non-verbal Stroop tasks. Reaction time data are reported in milliseconds. Mean Stroop effect reaction time Mean Stroop effect accuracy rate

 5

		Baseline	Irregular	Regular	Baseline	Irregular	Regular
	DLD	213 (282)	324 (231)	288 (345)	0.04 (0.13)	0.11 (0.10)	0.07 (0.08)
	TD	307 (240)	91 (277)	286 (283)	0.08 (0.14)	0.08 (0.12)	0.09 (0.17)

Table 6 . Mean reaction times and standard deviations in the non-verbal Stroop task. Reaction time data are reported in milliseconds.

 6

		Mean reaction time		Mean accuracy rate
		Baseline	Irregular	Regular	Baseline	Irregular	Regular
	DLD	1434 (280)	1437 (355)	1455 (329)	0.93 (0.09)	0.93 (0.09)	0.94 (0.07)
	TD	1444 (293)	1431 (296)	1408 (340)	0.96 (0.05)	0.97 (0.05)	0.96 (0.05)

Figures Figure 1.

This study was conducted with the support of the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement No. 641858 (PredictAble project) to J.G and E.L, the ERC Consolidator Grant (773202 ERC-2017-COG 'BabyRhythm'; https://erc.europa.eu/funding/consolidator-grants) to J.G. Á.L. was supported by the Hungarian Academy of Sciences Lendület Program (96233 MTA-BME Lendület Language Acquisition Research Group). E.L. was also supported by funding from the National Institutes of Health: the NIH Common Fund through the Office of NIH Director, and the National Institute on Deafness and Other Communication Disorders, under Award Numbers DP2HD098859 and R01DC016977. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH. The authors declare no conflicts of interest with regard to the funding source for this study.

Special thanks go to the children, their teachers and parents for their kindness and cooperation. We thank Ágnes Kovács for her inevitable help in screening our participants and Lilla Zakariás for her help in recording the stimuli and helpful advices about task procedures. We thank Dr. Reyna Gordon for her invaluable suggestions for the manuscript and huge thanks go to the Music Cognition Lab of Vanderbilt University Medical Center, Nashville for the fruitful discussions and motivating environment.

Research Highlights

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request from Eniko Ladanyi at the following email address: enikoladanyi@gmail.com.

Documenting effects on rhythmic priming in various languages and tasks could also help design ways to use rhythm in general (see also Schön & Tillman, 2015), or rhythmic priming in particular (Bedoin et al., 2017) efficiently in speech-language therapy. Further rhythmic priming studies that manipulate the rhythm and the target task and measure brain activity during both the rhythmic priming stimuli and the presentation of the linguistic stimuli will help researchers to identify the therapeutical contexts within which rhythm training could be used to facilitate language comprehension or production. If future research ends up supporting the benefits of the use of rhythmic stimuli during speech-language therapy, then rhythmic training or presentation of rhythmic stimuli during tasks targeting speech-language skills can eventually be incorporated directly into clinical practice.

Tables


Dr Renato Micelli Lupinacci
email: rmlupinacci@gmail.com

Matthieu Faron

Philippe Bachellier

Alain Sauvanet

Alain Beauchet

Yves-Patrice Le Treut

Mustapha Adham

Jean-Yves Mabrut

Jean-Robert Delpero

François Paye

A Study of the French Surgical Association

Keywords: Acute pancreatitis, pancreatic ductal adenocarcinoma, complications, pancreatic fistula, survival, recurrence

à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

In 2018, a total of 458,918 new cases of pancreatic cancer and 432,242 related deaths were reported throughout the world [START_REF] Huang | Worldwide Burden of, Risk Factors for, and Trends in Pancreatic Cancer[END_REF] and pancreatic ductal adenocarcinoma (PDAC) is the most frequent type of pancreatic cancer 2 . The global age-standardized rates (ASR) of incidence is estimated to be 4.8 per 100,000, with the highest incidence rates observed in Western Europe, North America, and Central and Eastern Europe [START_REF] Huang | Worldwide Burden of, Risk Factors for, and Trends in Pancreatic Cancer[END_REF] . Actual 5-year survival for PDAC is still below 5% with the highest mortality rates observed in Europe and North America [START_REF] Huang | Worldwide Burden of, Risk Factors for, and Trends in Pancreatic Cancer[END_REF]3 .

There are many clinical features associated with PDAC such as weight loss, abdominal pain and jaundice. Acute pancreatitis (AP) is an uncommon initial presentation of PDAC 4,5 . In most patients, the acute inflammatory response and pancreas damage ultimately resolve 6 .

Nevertheless the need to wait for the resolution of AP related inflammation before surgery may be associated with pre-hospital, but also hospital delays in diagnosing and treating patients 7 . Since PDAC is a rapidly progressing disease, an adverse correlation between the delay of treatment initiation and prognosis seems likely 8,9 . Furthermore, although the stimulation of PDAC progression and metastases by the inflammation associated with AP 6,10 remains speculative in humans, animal studies have identified that AP could markedly accelerate pancreatic cancer development 11 .

It is unclear if AP is a potential means for earlier diagnosis of PDAC 12 or, on the contrary, might delay it 4 . Herein, Kimura et al. showed that only the detection of a pancreatic mass enabled the early diagnosis of pancreatic cancer at the onset of acute pancreatitis 13 . Indeed, up to date, the question whether PDAC patients with an inaugural AP have different outcomes from those without, remains unsolved. Thus, the primary aim of our study was to determine whether AP as the main clinical presentation of resected PDAC affects earlyoutcomes and influences survival.

Patients and Methods

Patient selection and data collection

In 2009, the French Surgical Society (Association Française de Chirurgie) asked its members to collect data of all consecutive patients who underwent resection for pancreatic cancer.

Medical records from patients consecutively diagnosed between 2004 and 2008 were entered retrospectively, whereas data from patients operated during 2009 were collected prospectively. A total of 1887 patients underwent pancreatic resection for PDAC in 37 institutions (France, 34; Belgium, 1; Monaco, 1; Switzerland, 1). All patients from each participating center were collected in the study period. A standardized form was created to retrieve information on preoperative, intraoperative and postoperative data. Three experienced pancreatic surgeons (FP, PB, JRD,) reviewed all data sheets before their transfer into the database in order to get a uniform interpretation of the retrospective data [14][15][16] .

Only patients with non-metastatic PDAC were included. Thus, distal bile duct cancers, duodenal and ampullary tumors, benign cystic lesions as well as cystadenocarcinomas and neuroendocrine tumors were excluded. Finally, to ascertain coherence of the population study, we also excluded patients with confirmed history of chronic pancreatitis (N=83). The remaining 1449 patients were included in this study. Thus, we compared patients with acute pancreatitis (AP group) as the first sign of PDAC with those without acute pancreatitis (control group). A subgroup analysis including only pancreatoduodenectomies (PD) (N=1140) was also performed.

Owing to the multicentric and retrospective design, pancreatic resection and pathological analyses were not standardized among centers and therefore could not be described precisely 17 .

Patient's characteristics included demographic data (age, gender, ASA score, body mass index [BMI], presence of preoperative jaundice and biliary stenting, acute pancreatitis as initial manifestation of PDAC). Intraoperative data included type of pancreatic resection, vascular resection, intraoperative transfusion, and prophylatic use of somatostatin analogue.

Postoperative data included in-hospital mortality (in-hospital mortality or death within the first month after patient discharge), complications graded according to Clavien-Dindo classification system 18 . A severe complication was defined as grade III or IV. Grade V was considered as in-hospital mortality and excluded from the study of long-term survival. For patients with multiple complications, the highest grade was considered. Postoperative pancreatic fistula (POPF) was defined in accordance with the guidelines of the international study group of pancreatic surgery (ISGPS) 19 . A clinically relevant POPF (CR-POPF) was defined as grade B or C. Postpancreatectomy hemorrhage and delayed gastric emptying (DGE) were defined according to ISGPS classification 20,21 . Reoperation, length of hospital stay, and adjuvant treatment were also recorded.

Tumors were graded according to the 7th edition of the American Joint Committee on Cancer staging manual 22 . Tumor size was categorized as ≤2 cm, >2 cm but ≤4 cm, and >4 cm in maximal diameter. At the time of this study, a positive margin was defined as tumor present at the resection margin (R1=0 mm).

End points

We compared patients with acute pancreatitis (AP group) as the first sign of PDAC with those without acute pancreatitis (control group) in both the whole population and the subgroup of patients who underwent PD. Primary end point was the presence of severe postoperative complication (defined as Clavien-Dindo ≥IIIA). Secondary end points included intraoperative complications (rate of extended resection and volume of blood transfusion); short-term postoperative results (occurrence of any complication, rate of pancreatic fistula); pathological findings (size of the tumor, number of harvested lymph nodes, and rate of incomplete resection); and long-term results (recurrence rate, disease free survival and overall survival).

In order to adjust the impact of AP for potential confounders, we performed multivariate analysis.

Statistical analysis

Two biostatistician (MF and AB) performed statistical analysis. Quantitative data were expressed as mean ± standard deviation and median, qualitative data as frequency and percentages (if applicable, missing data were not included in the denominator). Comparisons of means were performed using the Student's t-test. Comparisons of frequencies were performed using the Chi square test and the Fisher's exact test as appropriate. Comparison of median was performed using the Mood's Median test. Kaplan-Meier's method was used to calculate PFS and OS estimates. Comparison of OS and PFS were tested with the log-rank test. A p value <0.05 was considered significant. The multivariable analysis was done with a Cox Proportional Hazard model for time to event endpoints (OS, DFS), and binary logistic regression for dichotomous ones (severe postoperative complications, postoperative pancreatic fistula). No variable selection method was used for the variables included in the multivariate analysis. Multivariate analysis included the presence of acute pancreatitis as the initial symptom and clinically pertinent variables with a p-value < 0.3 in univariate analysis. It was performed to identify factors related to severe postoperative complications, grade B/C postoperative pancreatic fistula, disease-free survival and overall survival. Statistical analyses were performed using R software version 3.2.3 (http://www.r-project.org).

Results

Patients' characteristics

Overall, 1449 patients underwent pancreatic resections. There were 764 males (52.7%) and the median age was 64 years. The ASA score was graded ≥ 3 in 210 patients. Jaundice was present in 876 (60%) patients at time of surgery and a biliary stent was inserted preoperatively in 389 (27%) patients. Obesity (BMI > 30 kg/m²) was present in 9% of patients. One hundred fourteen patients (8.5%) developed an inaugural AP before the diagnosis of PDAC. Patients were significantly younger in the AP group (61 ± 10.2 years vs 64.8 ± 11 years; p <0.001), and this difference persisted in the PD subgroup analysis (60.5 ± 10.7 vs 64.8 ± 11.1 years; p<0.001). Jaundiced patients were more frequent in the control group (62% vs 42%, P<0.0001) whereas the proportion of patients who had a biliary stent inserted preoperatively did not differ between groups (27% vs 26%, P=0.78). These results did not vary for the PD subgroup analysis. Patients' demographics are summarized in table 1.

Surgical procedure

1140 patients (78.7%) underwent PD, 228 (15.7%) underwent distal pancreatectomy (DP) and 73 (5%) underwent total pancreatectomy (TP). Venous resection was performed in 395 (27.2%) patients and 33 (2.3%) patients had arterial resection. Associated multi-visceral resection was performed in 133 (9.2%) patients. There were no statistically significant differences between the type of surgical procedure, the rate of extended (vascular and/or visceral) resection and the volume of blood transfusion between groups. Surgical procedures are detailed in table 1.

Primary end-point

Overall, 781 patients (53.9%) developed at least one complication, among whom 317 (21,8%) were classified as Clavien-Dindo ≥ IIIA (severe). In multivariate analysis, only age, male sex, obesity, and the absence of neoadjuvant therapy were associated with severe postoperative complications. Indeed, AP as the initial clinical presentation of PDAC was not related to the occurrence of severe postoperative complications in neither univariate nor multivariate analysis (OR 1.07 [95% CI 0.60 -1.83], p=0.8). Table 2 andtable 3.

Early outcomes (secondary end points)

Forty-seven (3.2%) died during the first 30 days after surgery. No significant differences were observed between the two groups regarding postoperative fistula rate and location (pancreatic, biliary or digestive), complication rate (overall or severe), reoperation rate, readmission and mortality. Distribution of complications is given in table 2. Multivariate analysis of factors related to postoperative grade B/C pancreatic fistula can be found in the supplementary table 1.

Pathological findings

Tumor size was ≤ 4 cm in 796 (59%) patients. Patients with inaugural acute pancreatitis had tumors ≤ 4 cm more frequently than the control group (43.4% vs 35.6%) although it did not reach statistical significance (p=0.07). The number of harvested lymph nodes (LN) was significantly greater in the AP group (21.4

Adjuvant treatment and long-term survival

Table 5 summarizes survival analysis. The median length of follow-up was 22.4 months.

Patients who died in hospital or after discharge on any day within the first 30 days after surgery were excluded from the long-term survival analysis. The median overall survival after surgery was 29.9 months (95% CI 27 -NA) in the AP group and 30.5 months (95% CI 27 -34.4) in the control group (p=0.54). Overall recurrence rate (42% vs 47%, P=0.39) and local recurrence rate (25% vs 29%, P=0.1) did not differ between groups. Multivariate analysis revealed venous resection, N+ patients and no adjuvant treatment to be associated with worst overall survival, as shown on table 6. Indeed, inaugural AP was not associated with survival in multivariate analysis. Figure 1 illustrates overall and disease-free survivals.

Discussion

In this retroprospective study of 1,449 resected PDAC, patients with an initial history of AP before the diagnosis of PDAC were younger. Localization of the tumor inside the pancreas, and the corresponding type of surgery did not differ between AP and control group. The need for multivisceral and/or vascular resection and the volume of intraoperative transfusions were not different. Postoperative morbidity and mortality were comparable. At last, AP before pancreatectomy did not affect disease-free and overall survivals.

AP is reported to be an early and rare symptom of PDAC 23 . In our series, AP represented 8.5% of resected PDAC patients, in accordance with the reported incidence of 1.2% and 13.8% 12,13,[24][25][26] . AP due to PDAC has been reported to be more frequent in females 27 , smokers 28 , and patients with more comorbidities 25,28 . Also, AP patients have been reported to undergo more frequently surgical resection 12 and to be younger 25,27,28 as observed in our series (median age of 61 years vs 65 years). Some authors consider AP to be an early marker of pancreatic cancer 12,26 . As AP is a painful condition, patients are likely to seek medical care, which could lead to a cancer diagnosis at an earlier stage, particularly for distal pancreatic cancers. We observed a tendency towards a smaller size of the tumors in the AP group in accordance with this assumption and it is supported by previous studies 12,25,28,29 . Why most tumors, although obstructive, do not trigger AP but only upstream dilatation of the pancreatic ducts and parenchymal atrophy remains unknown. AP is probably more likely related to the anatomy of the ducts in which the tumor arises. The pancreatic site of the obstructive tumor was not correlated with the risk of acute pancreatitis, since it was comparable in AP and control group.

The natural history of PDAC is overwhelming: i) the progression time from stage T1 to T4 is estimated to be 1 year 8 ; ii) tumors >2 cm develop CT-detectable metastases in a mean period of 3.5 months (range 1.2-8.4 months) 30 , and iii) assuming exponential tumor growth, the speed of tumor cell replication is highest just before treatment initiation 31 . Thus, earlier diagnosis and treatment could contribute to better patient survival 27 . Contrary to others 12,23,25,28,29 , however, we did not find any improvement of DFS or OS in the AP group compared to controls. This comparable survival despite younger age and the tendency towards smaller tumors could result from the inflammation associated with AP. Inflammation might indeed promote PDAC progression and metastasis 6,10 as in animal experimental studies reporting that AP markedly accelerates pancreatic cancer development 11 . On the opposite, it must be emphasized that our survival analysis did not take account the waiting delay frequently induced by the AP prior to surgical resection. Thus, survival from the very first symptom might be improved in the AP group compared to controls, but this remains hypothetical.

Comparison with the published literature is challenging. The studied periods between the onset of an AP episode and the diagnosis of PDAC varies widely, ranging from ten days to two years 5,12,24,25,28 . Information on tumor stage from administrative databases is often missing, and clinical staging of PDAC is particularly difficult when inflammation co-exists 32 .

Finally, tumor stage may be inaccurately determined in patients not undergoing surgery.

To our knowledge, there is no guideline concerning the timing of surgical intervention in patients with PDAC associated pancreatitis. Pancreatic edema and peripancreatic inflammation can render pancreas resection and pancreatic anastomosis hazardous. Li and Tian. 5 suggested that 24 days was the most apposite cutoff for surgery, and showed a significant difference in postoperative morbidity (7.1% vs 44%) and equivalent postoperative survival. In a large Danish study, Kirkegård et al. grouped patients into three groups according to waiting time between AP and pancreatic resection (<4 weeks ; 4-8 weeks ; and ≥8 weeks) and found that waiting time to surgery did not affect survival in patients undergoing surgery for pancreatic cancer 25 . Herein, the wait time paradox and its association of longer delays with better outcomes has already been described [33][34][35] .

The main strengths of our study are the large sample size collected in a short period of time and the histological confirmation of the PDAC obtained in all patients. The multicentric design reflects the common reality in comparison with the experience of highly specialized tertiary centers. The major limitations of this study are its retrospective nature, lack of available data about the severity of AP and the delay between AP and pancreatectomy.

Determine the optimal timing of pancreatic surgery after AP was not the aim of our study but it is clinically relevant and deserves further research. Also, we can not be completely sure that some patients' pancreatitis were not related to biliary stent insertion. The data collection sheet used for this study specifically argued investigators about acute pancreatitis as the initial clinical presentation of PDAC. Therefore, acute pancreatitis following ERCP should not be included. It seems to be the case because both groups have the same frequency of biliary stenting (26.6% vs 27.9%) although jaundice was significantly more frequent in the control group (62.1% vs 42.1%, p<0.001).

Conclusion

In conclusion, in this retrospective multicenter series of 1449 patients with resected PDAC, inaugural AP was a rare event occurring in younger patients. AP as the initial presentation of PDAC was not associated to worst short-term results nor a less favorable survival after curative intent pancreatic resection.

Figure's legend Figure 1 .

 legend1 Figure's legend

table 4 .

 4 vs 19.6; P=0.02) and it was confirmed in the PD subgroup analysis. Number of positive lymph nodes, presence of tumor emboli and surgical margins were not different between groups. Pathological findings are described in detail in

Conflict of interest statement: Authors declare they do not have any conflict of interest related to this manuscript