Thaíssa Meira

Prof. Dr. iur Anna Petrig

Different principles and common legal loopholes governing the deep-seabed, outer space, celestial bodies, and the high seas

Keywords: exploration, global commons, sponsorship, registry, convince exploration, biens communs mondiaux, parrainage, registre, convaincre

The Legal Commons are the areas beyond national jurisdiction, e.g. deep-seabed, the high seas, Antarctica, celestial bodies, and outer space. Neither States nor private actors can claim ownership, sovereignty rights, or appropriation over these lands, seas, and objects. This paper asks what are the different principles and rules governing mineral exploration in outer space and maritime legal commons. For that purpose, it adopts a threefold approach. Firstly, it introduces the legislative history of the different principles that govern these Legal Commons: i.e. the res communes or Freedom and the Common Heritage of Humankind. Secondly, it assesses how these principles are implemented under the rules for mineral exploration in outer space, celestial bodies, and the deep-seabed. Thirdly, it discusses common challenges shared by these regimes, despite their different stage of development, i.e. the problem of sponsorship or registry of convenience.

Introduction

The Legal Commons (the Commons) are the areas beyond national jurisdiction, e.g. the Antarctic, the high seas, deep-seabed, outer space, and celestial bodies. Some of them are regarded as the new frontiers for exploration, and eventual exploitation, of natural resources that are scarce elsewhere on Earth. 1 In 2021, Mars, a documentary produced by the National Geographic, and Look Up, a movie streamed by Netflix, illustrate interest in these new frontiers. In Mars` second season, a parallel is drawn between the exploration for water on the planet Mars and the exploration for oil and gas at sea, namely, in the Arctic high seas. In Look Up's plot, the high-tech industry regards the apocalyptical scenario of an asteroid heating the Earth, as a prospect for harvesting rare minerals needed to manufacture smartphones. What may initially read like a sci-fi cinematographic plot under the context of the search for natural resources of commercial value and use, 2 is actually an ongoing reality. This reality is mainly triggered by technological developments and commercial interests.

To date, there are 31 contracts sponsored by several States, and carried out by public and private actors, are held with the International Seabed Authority (the Authority) 3 for exploration of mineral resources on the deep-seabed across the Pacific, Indian, and Atlantic Oceans. 4 To date, private actors hold 20% of these exploration licenses for the deep-seabed. However, by including the exploration activities licensed under public entities, but in fact carried out by private investment, this figure rises to 29% i.e. 7 out of all contracts for exploration. 5 Two examples of the latter are: NORI (Nauru Ocean Resources Inc.), sponsored by Nauru, but wholly owned by a subsidiary in Canadian, i.e. Deep-Green, and TOMI (Tonga Offshore Mining Limited), sponsored by Tonga, but also owned by Deep-Green. 6 In the outer space, the figures show a similar rising trend of private investment-orientated expeditions, which are replacing the former public investment in outer space expeditions. 7 A 2019 study named some of the national privately funded initiatives for outer space mineral exploration underway, these included: the US-based Planetary Resources Inc, (an asteroid mining company), the US-Luxemburg based Deep Space Industries (technologies for exploring and harvesting outer space minerals) and the Japan-based Ispace Inc.. 8 Within this context of increasing private investment-oriented exploration for mineral resources both in outer space and on the deep-seabed, this paper starts by asking what are the different principles and rules governing mineral exploration in outer space and maritime legal commons. Then, it asks whether these legal frameworks leave loopholes open for this private investment and operation. It does so by drawing a focused comparison between the international treaty-law for mineral exploration on the outer space celestial bodies and the deep-seabed in a threefold approach.

Firstly, it introduces the two principles governing these Commons: the Res Communis or Freedom and the Common Heritage of Humankind, as well as the political and legislative history contexts behind them. Secondly, it assesses the rules applied to the exploration for mineral resources and how these principles are implemented through these rules. Thirdly, it draws out its conclusion by comparing where both legal regimes stand and remarking that, to some extent, they share a common loophole.

Notably, this paper`s scope is restricted to mineral non-living resources on the outer space celestial bodies and the deep-seabed, with brief analogies to the high-seas (Sections 2.1 and 3.1). Hence, draft mineral exploitation (commercial harvesting or extraction), and biological resources beyond national jurisdiction regulations,9 are topics that fall outside this its scope.

Legal Principles 2.1 Res Communis or Freedom Governing the High Seas, Outer Space and Celestial Bodies

Under the general principle of the res communis, the high seas, the outer space, and celestial bodies shall be subjected neither to the sovereignty of any State, nor general to acquiesce apart and States are bound to refrain from any act that might adversely affect their use by another State or their nationals. [START_REF] Brownlie | Principles of Public International Law[END_REF] Within the 1982 United Nations Convention on the Law of the Sea (LOSC), the res communis principle is translated into the Freedom of the High Seas (Freedom). To date, this Freedom applies to all living and non-living resources in the air space, surface and water column beyond the limits of national jurisdiction (the high seas). 11 According to Western interpretation and historical accounts, the Freedom hails back to private activities that dominated exploration and exploitation of the seas in the XVII and XVI centuries, conducted by companies such as the West Indies Companies, thereby, shaping international law, namely Hough Grotius' doctrine of the Mare Liberum. 12 Since then, Freedom was gradually incorporated as customary international law and crystalized under the LOSC.

A decade later, after the exploration of outer space was launched, the 1967 Treaty Principles on Governing Activities of States in Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies (also known as Outer Space Treaty, or simply OST) was adopted. 13 According to which, the outer space and celestial bodies should be accessible and the subject of exploration to all States, without discrimination and irrespective of their economic and scientific development, as if these Commons are 'the province of all mankind. [START_REF]Articles 1, UN General Assembly Resolution[END_REF] Furthermore, none of these Commons are subject to national appropriation by claim of sovereignty or any means of use or occupation or any other mean thereof. 15 The language of the OST derived from the 1963 UN Legal Principles Governing the Activities Governing the Exploration and Use of the Outer Space. [START_REF] Masson-Zwaan | [END_REF] Both texts are considered crystallized customary outer space law on the basis of freedom of use and prohibition of appropriation. [START_REF] Cheng | United Nations Resolutions on Outer Space: 'Instant' Customary International Law?[END_REF] Moreover, the language of the OST led former scholarship to conclude that the regime and principle governing of the outer space and celestial bodies are very similar to those of the high seas, implying that both regimes provide for: free use only for peaceful purpose; and prohibition on sovereignty claims from individuals or States. [START_REF][END_REF] Accordingly, many analogies can be drawn between these Commons. For instance, the exploration and use of the outer space is free to all States without any sort of discrimination, on the basis of equality. 19 This freedom of access to the outer space reads very similar to the freedom of the high seas, in which all States, irrespective of their geographical location (coastal or landlocked), are among other uses, free to navigate, fish, lay down submarine cables and conduct research. 20 There are also similarities regarding control and responsibility. As under the LOSC, Flag-States have exclusive jurisdiction over the ships, and crew thereof that fly their flag on the high seas. 21 Additionally, all ships must be registered under one State-Registry and comply with the national regulations of that Flag-State-together with standards set under international law by the competent international organization. 22 Similarly, to some extent, Spacefaring-States have responsibility and liability for ships, objects and personnel thereof launched by them into the outer space. [START_REF]Articles VII and VIII[END_REF] Furthermore, the OST mirrors the high seas freedom regimes 24 by providing that this freedom to explore the outer space and celestial bodies is not absolute and shall pay due regard to and not interfere with other uses by other State-Parties. 25 Although, the language of the OST mentions "the province of mankind", as a means to accommodate the 77 Group of developing State` interests, at the time of drafting, there is no hint, implementation or further guidance in the OST text as to what this wording means, this leads to obscurity and debates. [START_REF]Also named 'fragmentation and impression[END_REF] Thus, this paper is of the standpoint that the principle of freedom governs access and exploration on the basis of peaceful propose, equity and mutual due regard for other States-Parties activities in the outer space and celestial bodies. Nonetheless, it is generally agreed the res communis category is not a source for precise rules. [START_REF] Crawford | Brownlie's Principles of Public International Law[END_REF] This will be further discussed in section 3.1.

Common Heritage of Humankind (CHH) governing the Area but not de facto to the Moon

When it comes to mineral resource deposits in situ, [START_REF]namely cobalt-rich crusts, manganese nodules, and sulfide manganese. 29 Article 1[END_REF] on the deep-seabed, ocean floor, and subsoil thereof, beyond the limits of national jurisdiction (hereafter the Area 29 ), the regime of freedom is completely over shadowed by the Common Heritage of Humankind (CHH) principle. 30 It is generally agreed that any exploration activity that targets these minerals in situ in the Area, is governed by this principle. 31 Most notably, this principle is an immutable clause under the LOSC, i.e. it is not subject to amendments. 32 As a commentator put it, it is the 'backbone' principle of the LOCS's regime that governs the Area and its mineral resources. 33 The CHH`s legislative history, under the Law of the Sea, dates back to the 1970s, when Maltese ambassador, Arvid Pardo, proposed (in the realm of the UNCLOS III), [START_REF]the round of diplomatic negotiations between 1973 and 1982[END_REF] that the seabed, sea-floor and subsoil thereof, beyond national jurisdiction, should be declared 'common heritage of mankind'. [START_REF] Un General | Malta Report for the Inclusion of a Supplementary Item in the Agenda of the Twenty Second Session[END_REF] Some scholars suggest that, when Pardo developed his CHH legacy (between 1967-1973), he had in mind the idea of the 'province of mankind' under the OST text. [START_REF] With | A Short History of the Ocean Floor[END_REF] After Pardo`s proposal, developing-States and developed States positioned themselves differently according to their interests and exploration capabilities. 37 Accordingly, the developing-State (Group 77) backed the CHH. 38 They regarded it as a tool to gain solid access, benefit-sharing, knowledge, and technology transfer for exploration and eventual exploitation of the of the Area.

On the other hand, developed States, with greater exploration capacities, backed extending the Freedom to the exploration, and eventual exploitation of the Area's mineral resources. [START_REF]Moratorium Resolution UNGA 2574[END_REF] This favored their wealth and technological development on a first-come, first-served basis in relation to mineral exploration in the Area. 40 It was no surprise that after the adoption of the LOSC, the United States (US) did not ratify and in fact was opposed to it -namely to the regime governing the Area. 41 Other industrialized States also remained reluctant to ratify it and waited more than a decade, until the adoption of the 1994 Implementation Agreement on Exploration and Exploitation of Mineral Resources in the Area, to ratify the LOSC. [START_REF]The LOSC is a 'package deal', i.e. when ratifying it the States agree to its full content and text[END_REF] The latter agreement enlightened the operationalization of the regime for minerals in the Area. 43 According to the LOSC, the CHH principle provides that: i.

No State shall claim or exercise sovereignty or sovereign rights over any part of the Area or its (in situ mineral) resources, nor shall natural or judicial persons appropriate any part thereof. 44 ii.

All activities (of protecting, exploring and exploiting for mineral resources) shall be managed by the Authority for the benefit of humankind. 45 iii.

The States sponsoring activities in the Area must make sure that their nationals or persons under their jurisdiction comply with the rules and also those of the International Organization carrying such activities. 46 Commentators have noted that there are many interpretations of the CHH principle, which mainly entail the following: i) non-appropriation and the exclusion of unilateral appropriation; ii) peaceful purpose, iii) benefit-sharing; iv) environmental protection; and v) a common management regime and internationally agreed rules to be set by an intergovernmental organization. [START_REF] Wolfrum | The Principle of Common Heritage of Mankind[END_REF] As to the latter entailment, the Authority is the embodiment of the CHH by its mandate not only to regulate, manage, control and grant license for mineral orientated activities in the Area, but also to perform these functions on behalf of humankind as a whole. 48 The Agreement on Governing Activities of States on the Moon and Other Celestial Bodies (the Moon Agreement), was adopted by the UN General Assembly in 1979. According to it, the Moon and its resources are the common heritage of mankind 49 and its exploration and use is the province of mankind. 50 This agreement was drafted while the negotiations of the UNCLOS III were coming to an end. Thus, it is no coincidence that the principle reads, to some extent similarly to the LOSC and is more matured than the principle of the OST. Overall commonalities include: its use only for peaceful purpose 51 and the prohibition of appropriation. 52 Other than that, the Moon`s CHH principle literally entails that there should be:

i-Access to all states regardless of their scientific and economic capabilities; 53 ii-Due regard for inter-generation equity; 54 iii-Maximum cooperation on bilateral or multilateral levels and through international organization. 55 iv-An In situ inspection system, which applies, on a reciprocity basis, to all manned or unmanned stations, facilities, installations, equipment, vehicles, etc., which contracting parties may establish and/or utilize on the Moon. 56

To date, the Moon Agreement has only 24 ratifications, [START_REF][END_REF] with the recent accession of Oman and Bahrain. [START_REF]Status of International Agreements relating to Activities in Outer Space<[END_REF] Most of the Spacefaring-States, e.g. China, Japan, Russia and the US, did not ratify the Moon Agreement. It is also worth noting that in 2008 the Parties to the Moon Agreement acknowledged that the CHH in the text does not constitute an obstacle to space mining initiatives. [START_REF] Masson-Zwaan | [END_REF] Hence, the OST, with over 130 ratifications, [START_REF]Agreement Governing Activities in the Outer Space and Other Celestial Bodies, UN Treaty Series n. 8843[END_REF] de facto sets the international rules for the exploration of mineral resources in the outer space and celestial bodies. Against this background, this paper assesses the OST instead of drawing further consideration on the Moon Agreement. With the OST and the LOSC in mind, it now assesses how treaty rules on exploration for mineral resources implement these different principles.

Rules Governing Mineral Exploration and Implementation of the Relevant Principles 3.1. In the Outer Space and Celestial Bodies

This section asks how are the principles of non-appropriation and freedom implanted under the rules of OST. To answer, this question it assesses what the duties of State-Parties are under the OST. It also points to where the loopholes that can lead to fragmented national regulation of outer space exploration, and/or the mismanaged private spacefaring investments lie.

The OST allows both public and private actors to have access to explore the outer space and its resources, thus the private sector can explore, side by side with State-Parties. [START_REF][END_REF] Nonetheless, under international law, only States, and international organizations are responsible for their activities in the outer space. 62 Consequently, State-Parties to the OST are not only responsible for the activities of their public entities, but also for private entities incorporated under their territory and carrying out exploration expeditions in the outer space. 63 By way of explanation, if one would like to a private investors accountable for their breach of Outer Space Law, one State has to regulate that responsibility, liability and accountability within its national law. Some scholars arguably read the rationale behind this rule of Article VI of the OST as a means of fostering these national regulations regarding outer space exploration. 64 . Moreover, Registry-States have control and liability for damage over objects (spaceships) and personal (crew) that they launch into space. 65 Clearly, there is no express due diligence duty to regulate such activities under national law mentioned throughout the OST. Accordingly, comments have been made on the jurisdictional 'laconic provision' of the OST. [START_REF] Jennings | The Objects of International Law, Chapter 7 Outer Space[END_REF] In other words, jurisdiction may be hinted at by using the words 'control' and "'authorization' for activities of nationals under their control, objects launched and operations authorized by them, but does not go anyway beyond that by expressly ruling on jurisdiction. 67 Putting it simply, under the OST, there is no express due diligence to domestically regulate.

Questions could also arise as to the extent of this responsibility and what it would mean in the case of joint outer space exploration. Against these questions, in the case of action or omission of nationals controlled by that Spacefaring-State-Party and in case of joint expeditions all States involved should be jointly responsible. 68 As to debated issues of jurisdiction over nationals of a Registry-State visiting the spaceship of another Registry-State, the jurisdiction of the Registry-State of the spaceship to which the crew originally belongs will prevail over the jurisdiction of the other Registry-State where the crew actually was visiting when it breached the law. 69 Most notably, the OST does not set minimum international standards for the national regulation of this activity. In a nutshell, the OST's open-ended language, on responsibility, and liability as well as its jurisdictional gap, leaves room for a States-Parties' discretionary interpretation and application of the rules set therein, which may result in two problematic scenarios. Firstly, it could lead to inconsistent or fragmented national regulations for outer space spacefaring, and mineral exploration -without minimum standards. Secondly, it could lead to spacefaring business being incorporated under the national rules that they regard most favorable to their operations and to explore mineral resources in a mismanaged fashion. Against these scenarios, it is questionable whether the OST leaves room for a Registry of Convince in Outer Space Law as an analogy to the issue of the Flag of Convenience 70 under the Law of the Sea.

Additionally, the OST provides for a State-Parties' to consult in the case of harmful impacts to, or interference with, the environment or other Stated-Parties` activities. [START_REF][END_REF] This duty is again one of general nature and extends only to consultation, i.e. asking an opinion on a certain problem, without implying a follow-up duty to take such opinion into further decision-making consideration. 72 Ultimately, the OST generally attempts to foster cooperation by two means. Firstly, by encouraging States bilaterally to agree to place observers from other State-Parties onboard their expedition spaceship. 73 Secondly, through unilaterally notifying the UN Secretary General, the general public and international scientific community of the nature, conduct, location and outcomes and information related to the exploration, 74 which the UN Secretary General shall then disseminate. 75 It is also arguable whether private actors engaged in space exploration would be willing to make public the data that could result in their economic profit and even the coordinates of their resources to their competitors.

In the Area

It is questionable how does the Authority implement its mandate to administrate, regulate and grant license for the mineral exploration in the Area on behalf on humankind. This subsection answers this question by summarizing the powers of the Authority, duties of Sponsoring-States and Contractors under the LOSC.

The Authority is an autonomous intergovernmental organization (IGO), with a legal personality and was created under LOSC. It has been operating since 1994. Notably, every State-Party to the LOSC is ipso facto a Party to the Authority. 76 Nonetheless, the Non State-Parties, e.g. the US, can take part, as observers, in discussions at the Authority's Assembly. [START_REF] Harrison | Making of the Law of the Sea: A Study in the Development of International Law[END_REF] The Authority is competent to set the standards for activities in the Area and for compliance with these standards. 78 It also has the power to adopt rules independently from States subsequent to consent, which differentiates the Authority from any other IGO. 79 The Authority rules apply, not only to State-Parties but, most importantly, to investors and to private or third parties (Contractors) carrying out exploration in the Area through means of signing a contract for exploration with the Authority. 80 This set of rules is clearly legally binding. 81 Along, with their rights, duties and accountability, Contractors have standing rights to participate in deep-sea disputes before the International Tribunal for the Law of the Seabed Dispute Chamber. [START_REF]), LOSC; Authority, Regulation for Exploring for Polymetallic Nodules in The Area[END_REF] All these features distinguish this regime from traditional international law systems, where only States and International Organizations are subject to legal personality and have standing rights.

To understand this further, two questions must be asked. Firstly, what is the process for getting a contract? Secondly, how do the standards and rules become binding upon private actors? Any investor, who aims at carrying out exploration in the Area, shall first submit a written plan of work to the Authority, who will assess this plan. 83 In the case that this assessment deliberates in favor of the investor-applicant's intents, then, it will enter into a formal contract with the Authority based on the written plan of work for the exploration of specific minerals, at an specific area and in a specific time frame. 84 The minimum standards of the contract are that the Contractor will carry out its activities following the LOSC, and the rules for exploration of the Authority will be followed. 85 Hence, these rules become binding to any Contractor for exploration, meaning that no State-Party can persistently oppose the rules of the Authority. 86 Notably, the Authority may, at any time, control compliance with the contract and carry out inspections in the exploration licensed-area or installation thereof to monitor compliance. 87 Moreover, under the reporting requirements of the Contracts, the Contractor shall report to the Authority on an annual basis. [START_REF] Lodge | The International Seabed Authority[END_REF] These reports are of a classified nature, but, nonetheless, another monitoring compliance mean.

Additionally, applicants and eventual Contractors shall be nationals or effectually controlled by a Sponsoring-State-Party. 89 As the case law puts it: 'First, [Contractors] must either be nationals of a State-Party to the [LOSC] or effectively controlled by it or its nationals.' 90 'Second, they must be sponsored by such States.' 91 The Sponsoring-States have the responsibility to ensure, within their legal systems, that a Contractor shall carry out exploration in the Area in conformity with the terms of its contract and its duties under the LOSC. 92 Furthermore, this 'responsibility to ensure' establishes a mechanism through which the rules of the LOSC concerning exploration in the Area, although being treaty law and, thus, binding apply only to the subjects of international law (States and IGO) that have accepted them, and becomes effective for Sponsored-Contractors, who find their legal basis in domestic or national law. 93 To put it simply, this duty is to ensure that the Contractor is held liable under the Sponsoring-State's national private contractual law.

Nonetheless, in case of damage, a Sponsoring State shall not be liable for damage caused by any failure of a Contractor sponsored by it, if that State-Party has adopted laws and have taken administrative measures which are within the framework of its legal system and are reasonably appropriate for securing compliance by persons under its jurisdiction. 94 Hence, Sponsoring-States-Parties have the due diligence obligation to ensure that national rules control private or national actors engaged in exploration activities in the Area. 95 Furthermore, the Sponsoring-States have the duty to assist the Authority in its task of controlling exploration in the Area for the purpose of ensuring compliance with LOSC. 96 In summary, the aim of the sponsorship requirement is to ensure that duties that are binding on States-Parties are fulfilled by entities that are subjects of domestic legal systems. 97 Moreover, the benefit-sharing and the parallel system are other means of implementing the CHH principle. According to the reserved areas under the parallel system, each licensed area has to be large enough to be shared between the Contractor and developing States or the Enterprise. 98 The Enterprise is an operational body of the Authority that is not yet under operation and will not be until regulations for exploitation are set in stone. 99 Nonetheless, under this parcel system's reserved areas, many developing States (China, Cook Island, Kiribati, Nauru, Singapore and Tonga) have taken advantage of it to conduct their exploration activities in shared areas with exploration Contractors. 100 However, these reserved areas, under the parallel system, hide the major loophole of this regime as already noted by case law and scholarship. In summary, it has been acknowledged that private actors are the ones carrying out exploration in reserved areas: 85% of activities thereof are held by businesses which in turn are primarily owned by corporations based or incorporated in developing States (Section 1). 101 Due to this trend, scholars have asked, 'What are the implication of this [trend] to the achievement of the [CHH]?' 102

Case law has warned that applying different responsibilities to developing and developed States could lead to the problem of States of Convenience with unharmonious environmental, safety and CHH standards. 103 Case law has also noted that the regime poses no barrier to Western companies operating through, and sponsored by, developing States, with regulatory but no economic control over these companies. 104 Similarly, scholarship has noted that gaps in the deep-seabed mining regime, i.e. an effective nationality test within the parallel system context, could lead to the risk that private actors continue to route their investments through subsidiaries in developing States until the quota of reserved areas is entirely depleted. 105 Hence, these concerns show that, despite the developments of the CHH under the Law of the Sea, it is not completely immune to the issues of State of Convenience.

Another mean of implementing benefit-sharing under the CHH principle is under the duty to transfer technology. 106 According to which, the Contractors shall inform the Authority: i) in the written plan of work with a general description of the equipment and methods to be adopted for exploration, and other relevant non-proprietary information about the characteristics of such technology and information as to where such technology is available: and when any ii) further substantial technological change or innovation is introduced in the review process of exploration. 107 The Authority shall also acquire technology and scientific knowledge from exploration in the Area and promote and encourage the transfer to developing States of such technology and scientific knowledge so that all States-Parties benefit therefrom. 108 Ultimately, the Authority can implement its CHH mandate through the right to call for an "environmental emergency order". In the case that a Contractor foresees a harmful impact of its activity on the environment, it shall notify the Authority, other Constrictors, and ships navigating in the vicinity of its licensed area. 109 Against that notification the Authority's Council can issue emergency orders, which may include orders for the suspension or adjustment of operations, to prevent serious harm to the marine environment arising out of exploration in the Area. 110 In the case of an emergency order of that nature being issued, the Sponsoring-State shall take all necessary measures to ensure that the Contractor provides a guarantee of financial and technical capability to comply promptly with the order or to assure that the Authority's Council that they can take such emergency measures. 111 Otherwise, this could result in liability of the Sponsoring-State under international law. 112

Conclusion

Two principles govern the Commons. The first is the res communis or freedom which applies to the outer space, celestial bodies and the high seas. The second is the CHH, which governs activities, including exploration, in strictu senso related to mineral resources in situ in the Area. Historically, the OST mirrors the High Seas Freedom; the CHH may have had its seeds in the language of the OST, and the Moon Agreement, to some extent, mirrors the CHH principle as governing the Area. However, the CHH principle has matured through debate, implementation agreements, and under the further development of the Law of the Sea. Additionally, the term 'province of mankind', in the OST text, was rapidly adopted without considering its means of implementation or developing it under Outer Space Law. As scholarship put it, the CHH principle has been limited outside the deep-seabed context. 113 In summary, both principles depart from the idea of free and equitable access without appropriation, but what differentiates the CHH from the res communis, is mainly that the first sets a regime for common administration 114 -under international rules legally binding upon public and private investment. The res communis leaves the Commons for free access and allows the discretionary power of the Flag-or Spacefaring-State to control the activities and to enforce the law, which paves the way to de facto inequalities given the advanced technologies and higher revenues to explore and access remote spaces this. 115 The CHH rules in favour of solidarity and cooperation, distributive justice, benefit-sharing, and integration of all States irrespective of their degree of scientific and technological development. 116 On the one hand, the CHH principle under the Law of the Sea is distilled into four central elements: i) common management; ii) no unilateral exploration or exploitation; iii) benefit sharing; and iv) marine environment protection. 117 This translates into 'technology transfer', 'parallel system' and 'benefit-sharing' in the LOSC. Furthermore, the Authority can implement the CHH through means of: conducting reviews of plans of works and contracts; inspecting and monitoring exploration activities; most notably, it has the power to issue an environmental emergency order and prevent or control the harmful impacts or mismanaged conduct of the exploration activity in the Area. Notably, rules and case law, under the Law of the Sea, regarding exploration for mineral resources, makes it clear that the rules and international minimum standards set thereof apply to private and public actors engaged in this exploration activity. Accordingly, scholarship has concluded that this regime, under the LOSC that governs the Area 'sets the most ambitious and comprehensive regime ever devised to govern any global common'. 118 It has been noted that the main objectives of the CHH aim to ensure that developing States can access and benefit from mineral resource exploration and eventual exploitation, on equal footing with developed States. 119 Nonetheless, under this benefit-sharing, and more precisely under the reserved areas of the parallel system, lies the loophole of the regime. This loophole is evident in the trend of Western corporations to carry out contracts for exploration under subsidiaries incorporated in the territory of developing States and linked to the issues of Sponsorship of Convenience.

On the other hand, Outer Space Law under the OST shows major gaps as regards to: minimum standards, due diligence duties of States to regulate, accountability of private actors, control, compliance and cooperation. Most notably, when the OST was drafted, private investment-orientated space exploration was remote. However, this is not the exception anymore rather it is the rule. Hence, this gap in addressing private actors in the outer space needs serious consideration. 120 Consequently, international Outer Space Law stands today where the Law of the Sea stood a hundred years ago: in a legal vacuum outside law enforcement's reach. It is susceptible to the interests of the industries and is largely dominated by private companies, investors, or businesses (e.g. merchant, submarine and cables) and therefore following contractual law. 121 These legal gaps and private investment trends could entail concerning three scenarios. Firstly, the increase the inequality gap between Traditional Spacefaring and Non-Spacefaring States. Secondly, the fragmented or inconsistent national laws on spacefaring. Ultimately, these legal gaps could create room for private actors to explore resources thereof in a miss-managed fashion without legal consequence. 119 Ferrjolo, 'The Common Heritage of Mankind in International Law' (n 47) 120 Cheng (n 7) 622, 634. 121 As from the Law of the Sea perspective see: Hacken With Adersen, 'A Short History of the Ocean Floor', in Telesetsky, Anastasia, and Keyuan Zou. Marine Scientific Research, New Marine Technologies and the Law of the Sea (Brill, 2021), 75-76.

The ISA is combining efforts to finalize drafting the Exploitation Regulations for Mineral Resources in the Area by 2024 and negotiations under the LOCS Implementation Agreement on the Utilization and Conservation of Biodiversity Beyond National Jurisdiction are also under way and might be met until 2024.


domain: info scco

text:
Ph Bolon

Simplified Model of Intercomprehension

The feeling expressed by participants at UNITA meetings is that intercomprehension is effective in 2person discussions, but that larger groups prefer to communicate in English. A simple model can explain this observation. The choice of language depends on the number of participants, their command of the language and the complexity of the discussion.

Context:

Intercomprehension is the process that enables two people (or more) of different mother tongues to communicate, each in his or her native language. This process is promoted within UNITA, one of the 44 alliances participating in the European Universities initiative of the European Commission. The native language of the participants is not English. During a discussion, the alternative to intercomprehension is to switch to English, common language within scientific and academic communities.

Assumptions:

• the understanding process is independent from one participant to another (even if they have the same nationality); • the number of concepts that can be exchanged is finite; • the element of discussion is regarded as successful if all the participants understood which concept was emitted by the speaker; • misunderstanding consists in understanding a concept different from the one expressed by the speaker; • the probability of misunderstanding is the same for all participants. It is uniformly distributed across all the erroneous concepts; • the probability of misunderstanding between English and non-English languages is proportional to the probability of misunderstanding between non-English languages. The proportionality coefficient, denoted λ and which could be called 'understanding ratio', is less than 1; • the probability of understanding is a decreasing linear function of the complexity of the discussion; • the complexity of the discussion ranges from 0 (very very simple) to 1 (excessively complex).

notations:

• P: number of participants;

• c: complexity of the discussion;

• N: number of concepts in the element of discussion;

• P IC : probability of communication success in the intercomprehension mode;

• P EN : probability of communication success in English.

Without loss of generality, the speaker is participant #1, having native language L1. L2 to LP are the native languages of the other participants.

meeting in intercomprehension mode

The block-diagram of the discussion is given in Figure 1.

Fig. 1: Block-diagram of intercomprehension mode

The probability of communication success is:

Eq. 1 L1 L 2 Lp L P P IC 1 c - [ ] P 1 - =
It is a decreasing function of the complexity and the number of participants.

meeting in English

The block-diagram of the discussion is modified as shown in Figure 2. Speakers have to translate concepts from their native language into English. Listeners translate form English into their native language..

Fig. 2: Block-diagram of English mode

The probability of communication success is:

Eq. 2

The second term of the right hand side corresponds to a paradoxal success by means of the compensatiion of translation failures. In realistic situations, this term can be neglected.

experimental results

Let P = 2 to 10; Let λ = 0.75;

Let us define the intercomprehension efficiency gain by: .

Fig. 3: Iintercomprehension efficiency gain as a function of the number of participants and of the discussion complexity

L1 L 2 Lp L P En P EN 1 λc - [ ] P λc [ ] P N 1 - [ ] P 1 - --------------------------- + = G P IC P EN - = #participants Gain % complexity Gain % complexity P=2 P=3 P=4 5
Figure 3 shows that for lower numbers of participants and reasonable discussion complexities, the intercomprehension efficiency gain is positive, meaning that using natives languages is more efficient than switching to English.

It can be shown that, for any complexity level, there is a maximum number of participants for which intercomprehension is the best solution.

Conversely, for a given number of participants, there is a complexity threshold under which intercomprehension is the best mode. Threshold values depend on parameter λ.

conclusion

The concept of discussion complexity and its impact on the probability of successful communication should be refined. Nevertheless, though the communication model is simplistic, it allows to justify the feeling expressed by participants at international meetings and the interest of intercomprehension studies.

Appendix 1: Participant number threshold

For any complexity level c and understanding ratio λ, there exists a threshold P0 such that, if the number of participants P is less or equal to P0, then the interncomprehension mode is more efficient.

Eq. 3 with denoting the floor function.

Figure 4 shows that the participant number threshold is an increasing function of the understanding ratio and a decreasing function of the discussion complexity -------------------------------------------------------= P threshold complexity understanding ratio λ

Fig

  Fig. 4: Participant number threshold


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Physiologie

VERTICALITY PERCEPTION BIAS IN PARKINSON'S DISEASE: A SYSTEMATIC REVIEW AND META-ANALYSIS THÈSE

AVERTISSEMENT

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 [START_REF] Mittelstaedt | Somatic versus Vestibular Gravity Reception in Man[END_REF]. Each of these perceptive modalities provides different but complementary information about the sense of verticality.

VV depends on the interaction of visual and vestibular sensory information systems, permitting, via the vision, to determine the alignment of verticality without reference point for true verticality [START_REF] Bronstein | The Interaction of Otolith and Proprioceptive Information in the Perception of Verticality. The Effects of Labyrinthine and CNS Disease[END_REF][START_REF] Fetter | Assessing Vestibular Function: Which Tests, When?[END_REF]. HV depends on the proprioceptive pathway as processed through articular sensors to inform individuals of their correct position in space [START_REF] Tribukait | The Subjective Visual Horizontal for Different Body Tilts in the Roll Plane: Characterization of Normal Subjects[END_REF]. PV assesses mainly the somaesthetic graviceptive contribution to the sense of verticality, who enables an individual to determine the position of his whole body comparing to the true vertical.

Altered verticality perception in PD was found by multiples studies during these last years ( These inconclusive findings may be related to the different methodological approaches, with various protocols and ways to estimate outcomes. We conducted a systematic review and meta-analysis to estimate first the prevalence and the amplitude of verticality perception biases in PD but also to synthesize knowledge of the methodologies used in order to propose recommendations for better standardization.

METHODOLOGY

We are preparing a PROSPERO registration, for the present review.

Search strategy

The Preferred Reporting Items for Systematic review and Meta-Analysis (PRISMA) protocols (www.prisma-statement.org) were followed to perform the review.

We Only articles written in English were selected.

The reference lists of studies retrieved were reviewed to identify additional studies. We did not include grey literature (i.e., conference abstracts, unpublished studies, or reports). Full texts were uploaded from bibliographic databases or directly asked to the authors.

Studies selection process

Two reviewers (AT and CP) independently screened each record (title and abstract) of articles retrieved from the search. Disagreements were resolved by consensus or involvement of a third reviewer when necessary (DP). A study was considered as meeting the inclusion criteria for the review if: it was 1) an observational study as cross-sectional or case-control study, 2) which analyzes the perception of the verticality in visual and/or postural and/or haptic modalities in baseline condition (neutral background and standard position setting), 3) in PD individuals. We excluded other parkinsonian syndromes. We did not set any sample size minimum.

Quality assessment

We assessed the risk of bias in the included studies using The Newcastle-Ottawa Scale (NOS), constructed for assessing the Quality of Nonrandomized Studies in Meta-Analysis. This scale, constituted of 8 items, addressed three categories: the selection (4 items), the comparability (1 item) and the exposure (3 items). Each item is awarded by a maximum of one point. For the comparability, a maximum of two points can be given. A total of points from 0 (lowest quality) to 9 (highest quality) can be attributed. We used the NOS assessed for case control studies. Two review authors (AT and CP) independently applied the scale to each included study, and recorded supporting information and justifications for judgements of risk of bias for each domain (scores and some concerns). Any discrepancies in judgements of risk of bias or justifications for judgements were resolved by discussion to reach consensus between the two review authors. Following McPheeters et al and Hartling et al, we have retained for the analysis only articles for which the NOS score was superior or equal to 6.

Data extraction

Data extraction was performed independently in duplicate by the two same reviewers (AT and CP), on the full texts of studies selected, by use of a predefined data collection file. Data extracted included:

-Characteristics of the publication: authors, year, journal, and country.

-Characteristics of the participants: number, age, sex, disease duration; the presence of a control group and its characteristics (number, age, sex), the MDS-UPDRS III score during the ON-phase (and when it was mentioned, during the OFF-phase), and when the standard UPDRS III was used, conversions to the MDS UPDRS were made following Goetz et al. ( 2012).

-Characteristics of the disease: the presence of deep brain stimulation, the medication and LEDD when it was possible, the presence of postural abnormalities (Pisa syndrome, camptocormia, retropulsion).

-Characteristics of verticality perception assessments: modality (visual/postural/haptic), paradigm; the characteristics of the test stimulus (the type, the length when applicable for visual or haptic modalities, the magnitude of the initial tilt), plane (frontal/sagittal); the presence or not of time limit; the participant postural setting (position [sitting/ standing], postural installation [free (head and trunk), partially maintained (head or trunk)/maintained (head and trunk)]; the type of task (adjustment/orientation judgment); the response modality (verbal/manual/remote control…); the number of trials, and the number and type of experimental conditions; -Characteristics of outcome measures: the nature (orientation/ uncertainty), the signed or absolute values, the convention adopted for signed values, the normative values.

-The frequency and magnitude of verticality biases, our primary outcome.

Statistical analysis

The primary outcomes were the estimation of the frequency verticality biases and the estimation of the magnitude of these biases in PD. We used random-effects meta-analysis to generate all pooled results

(with 95% confidence intervals [CIs]). The extent of heterogeneity across studies was assessed with the I² statistic: I² 0% to 50% was considered low, 50% to 75% moderate, and >75% high heterogeneity (Higgins, 2003). P values were two-sided, and P < 0.05 was considered statistically significant. All statistical analyses were performed with STATA 15.1 (StataCorp, College Station, TX, USA).

Other data collected were used for descriptive analyses.

RESULTS

Figure 1 presents the flow diagram of the study, resuming all the steps of the selection process.

A total of 874 articles were identified through our database search. Ten were added after being identified through other sources such as references analyze. After title and abstract screening, twenty remained. Up to December 1 st 2021, 17 articles met inclusion criteria after full text review, and were identified as dealing with verticality perception in PD patients, whatever the modality of verticality perception. Except for two older studies, all had been published since 1996 with a marked increase over the past ten years, reaching 3 articles in 2018.

Quality of the selected studies

Table 1 contains the detailed scores at each item and the final scores of quality assessment. One study did not reach quality score cut off of 6 points over 9. Finally, we included a total of 17 studies investigating the verticality perception in PD. Their mean quality, following the NOS, was medium with an average (SD) of 7.4 (1.14). Two studies obtained the maximal score of 9, eight had a score of 8, six had a score of 7, and one had a score of 6.

Population characteristics

Characteristics of verticality perception assessments

Verticality perception modalities

Among the 17 selected studies, 14 investigated the VV, 4 the PV, and 2 the HV. Logically, VV and HV were measured in the frontal plane in all the studies. PV was measured in the frontal plane in 3 of

Type of paradigm

For the VV perception, myriad protocols have been used, 6 used a computerized device whereas 8 used a mechanical device with variable paradigms. In all studies studying HV, participants were instructed to move a physical rod to the direction of the vertical, without vision..

Patient postural setting

In 13/17 studies, patients were in a sitting position, while in 3/17 they were in erect posture. This information is missing in one study [START_REF] Pawlitzki | Spatial Orientation and Postural Control in Patients with Parkinson's Disease[END_REF].

The individual postural setting was variable. In 8 studies, the position of head and trunk were free, with only the instructions to stand upright. In 4 others, head or trunk were restrained by a harness or a belt. As mentioned above, in two studies (Mikami et

Task

Except for one study (Barnett-cowan et al, 2010), verticality perception, whatever the modality, was always assessed by asking PD patients to adjust the stimulus or the body to the vertical. This procedure may be assimilated to the method of adjustment: the patient is asked to control and adjust the orientation of a stimulus or its body until it feels vertical. In 6 studies, PD patients performed the task without time limit, and two of them added time limit. This information was missing in 9 studies

(

Number of trials

This parameter was very variable between studies, with rare justifications for the number of adjustments used to assess verticality perception (Piscicelli 2021). For VV perception, the number of trials varied from 3 to 21, with a tendency for 8 trials. It is more difficult to do this analysis for the other modalities, given the low number of studies and the number of missing data.

The counterweighing of the leftward and rightward initial tilt in order to reduce the effect of the starting position of the stimulus on verticality perception estimates were described and performed in

Ranges of normality

The normal value differed between all of the studies, ranging 0° to 4.6 °. Three studies did not mention this values [START_REF] Bronstein | Visually and Posturally Mediated Tilt Illusion in Parkinson's Disease and in Labyrinthine Defective Subjects[END_REF] ; Barnett-cowan et al, 2010 ; [START_REF] Mikami | Subjective Postural Vertical in Parkinson's Disease with Lateral Trunk Flexion[END_REF]. All these data are synthetized in the table 3.

Magnitude of biases in verticality perception

Given the low number of studies dealing on PV (n=4) and HV (n=2) perception, we performed random-effects meta-analysis only to generate pooled prevalence of VV biases in PD.

Five studies [START_REF] Danta | Judgment of the Visual Vertical and Horizontal in Patients with Parkinsonism[END_REF]

DISCUSSION

This is the first systematic review of verticality perception in PD. We examined 17 studies published from 1960 to December 2021 gathering 618 individuals,. The majority of the researches were published between 2010 and 2020, highlighting increasing interest for this topic. The first main purpose was to estimate the frequency and the magnitude of verticality perception biases in PD for the different assessment modalities: visual, haptic and postural. Secondly, we aimed to synthetize knowledges on assessment methodology in these different studies in order to propose recommendations of a more standardized assessment method. From the three modalities of verticality perception assessment, only the VV was statistically analyzed through the meta-analysis, due to a lack of studies treating HV (n=2) and PV (n=4).

Frequency and magnitude of VV biases in PD

2021).

A first mechanism would imply that VV would be secondary to the PS, i.e. to the body geometry. A second mechanism would imply that VV would be the cause to the PS. Indeed in individuals with a deformed body geometry, vertical estimates may be aligned with the head or with the trunk tilt according to the availability of intact vestibular or somaesthetic information (Anastasopoulos 1997a, Anastasopoulos 1997b, Piscicelli 2016) or perceptive styles [START_REF] Guerraz | Head Orientation Involvement in Assessment of the Subjective Vertical during Whole Body Tilt[END_REF]).

In other cases, at least in some patients, a net bias in the internal model of verticality would induce a marked tilt of verticality perception that is transmodal, bearing both on several modalities of verticality perception as PV and VV and congruent in direction and magnitude with the head and trunk tilts.

These hypotheses strengthen the importance to assess the verticality perception in several modalities for a better understanding of the PS pathogenesis. Our systematic review revealed that verticality perception assessment in PD was mainly limited to the visual modality. Future studies will have to bridge this gap, as others methodological limitations.

Heterogeneity of methodological approaches and suggestions for standardization

The other aim of this systematic review was to help clinicians and researchers establish guidelines for a more homogeneous use of the verticality perception in research and clinical practices.

Fourteen articles assessed VV perception in PD, reporting data for 500 individuals. A majority of these studies were issued from the last 20 years, reflecting the growing interest in the topic. Because of the great variability in the study designs, paradigms for VV assessment and settings, we could only do a meta-analysis of a restricted number of studies. Thus, future studies need follow a standardized protocol which could permit to better synthetize the VV value in future reviews.

Because of the varied study designs, patient characteristics, paradigms for VV assessment, settings and reported outcome measures, we proposed a qualitative synthesis of the data collected and provided ways to standardize protocols in order to limit measurement errors and harmonize the results interpretation.

In their study published in 2016, Piscicelli and Pérennou recommended the electronic assessment procedure to analyze VV bias after the stroke, whose avoids measurement bias due to operator intervention. This assessment should be preferred also in PD. Also, patient postural setting, is a critical question for PD individuals patients given their frequent postural abnormalities, especially lateral trunk inclination, which may compromise their ability to sit on their own, and induce the well-known impact of body tilt on verticality perception. [START_REF] Guerraz | Head Orientation Involvement in Assessment of the Subjective Vertical during Whole Body Tilt[END_REF][START_REF] Barra | Humans Use Internal Models to Construct and Update a Sense of Verticality[END_REF]. Maintaining the trunk upright with an adjustable chinrest is a primordial criterion to correctly analyse the results of VV orientation. Indeed, it was found that measuring VV without any body maintenance is valid only for subjects presenting adequate balance abilities [START_REF] Piscicelli | Maintaining Trunk and Head Upright Optimizes Visual Vertical Measurement After Stroke[END_REF]). The verbal modality response seems to be the better choice to assess PD individuals who have motor and or cognitive disorders which can alter the reliability of the assessments using a manual modality response. Moreover, as for stroke, VV perception should be assessed with an even number of trials to account for the effect of the starting position of the line on the VV measure [START_REF] Baccini | The Assessment of Subjective Visual Vertical: Comparison of Two Psychophysical Paradigms and Age-Related Performance[END_REF]. Under these conditions, the orientation of the VV should be highly reliable criterion that may be used both in research and clinical practice. The ranges of normality issue, is also critical and should be addressed. In a previous systematic review on VV perception after stroke [START_REF] Piscicelli | Maintaining Trunk and Head Upright Optimizes Visual Vertical Measurement After Stroke[END_REF], it has been shown that, despite the variability in protocols, the ranges of normality only slightly differed between studies.

The consensual values to consider VV orientation as normal could be between -2.5° and 2.5° and for

VV uncertainty ≤ 3°.

The lack of studies on haptic or postural modalities constrains such a qualitative analysis on methodological approaches and makes impossible to formulate suggestions for standardization.

However, there is a real necessity to a rigorous and standardized measurement of verticality perception in order to harmonize practices, improve the understanding of postural abnormalities pathogenesis in PD and maybe to guide the emergence of rehabilitation programs specifically dedicated to the sense of verticality in PD.

Study limitations

Our systematic review presents some study limitations.

CONCLUSION

This is the first systematic review on verticality perception in PD, conducted on 17 studies gathering 618 individuals. We show that VV is frequently biased, but with a weak to mild magnitude. Because the VV mainly investigates the vestibular graviception, these findings might mean that the vestibular information processing is frequently impaired in PD, but with a moderate asymmetry between left and right basal ganglia. Moreover, directional concordances between VV biases and PD sides or PS tilts were few analyzed. But, when it was, the sides of VV biases and the PS tilts were in majority concordant. All together, these findings suggest the coexistence of two mechanisms: in some cases,

VV biases seem to be the consequence of the PS on the perception of the vertical, altered by trunk deformity or misorientation with respect to gravity. In some others, VV biases might cause the PS, as in stroke where lateropulsion is explained by the impaired verticality representation. In the future, studies will have to test several modalities of verticality perception, especially VV and PV, on large series, scrutinize concordances in sides of tilts, for body and verticality estimates, and harmonize the practices.

TABLES AND FIGURES

Figure1 Flowchart 11

Reports

  systematically searched the literature published up from 1960 to December, 1 st , 2021 in the databases MEDLINE, and COCHRANE CLINICAL TRIALS. A sensitive search was carried out in Pubmed and COCHRANE using the following strategy: (((Parkinson disease) OR parkinsonism) OR Pisa syndrome) AND ((((((verticality perception) OR verticality representation) OR verticality) OR visual vertical) OR postural vertical) OR haptic vertical) OR gravity).

  2014), due to a lack of Hoehn and Yahr stage in the papers. The two older papers could not mention the UPDRS, who was not yet establish in this period. The Postural Instability and Gait Disorders were mentioned in only one article (Huh et al 2018), the others using different tools. Characteristics of the disease Medication was not systematically mentioned. Fourteen of the 17 articles assessed verticality perception during the ON phase, and only four articles asked the patients to complete the task in OFF phase. Only one article investigating verticality perception bias with patients who underwent deep brain stimulation, and one when the patients benefited a chemosurgery. Postural abnormalities were detailed in five studies (Scocco et al, 2014; Gandor et al, 2016; Huh et al 2018; Mikami et al, 2020; Piscicelli et al, 2021), corresponding to 106 PD individuals, with mainly lateral trunk flexion (LTF), camptocormia, front trunk flexion and lateral or front neck flexion. These data were missing for twelve studies. No article treated the dystonic or dyskinetic trunk. Few articles investigating the concordance between verticality perception bias and the postural disorders in PD patients with Pisa syndrome, using, as a control group, patients with PD but without Pisa syndrome (Gandor et al, 2016; Huh et al, 2018; Mikami et al, 2020).

4

  papers (Proctor et al, 1964; Mikami et al, 2020; Piscicelli et al, 2021), and in the sagittal plane in one paper (Mikami et al, 2018).

  For the PV perception, one study used the wheel test[START_REF] Piscicelli | Contribution of Basal Ganglia to the Sense of Upright: A Double-Blind Within-Person Randomized Trial of Subthalamic Stimulation in Parkinson's Disease with Pisa Syndrome[END_REF] specifically dedicated to the assessment of postural perception of the verticality and validated in others pathologies as stroke[START_REF] Pérennou | Lateropulsion, Pushing and Verticality Perception in Hemisphere Stroke: A Causal Relationship?[END_REF], another used a tilting chair[START_REF] Proctor | JUDGMENT OF VISUAL AND POSTURAL VERTICAL BY PARKINSONIAN PATIENTS[END_REF]. It is important to mention that two studies assessed what they called a "postural vertical", without using apparatus but by measuring the angle between the vertical line and the postural position recognized by the individual patient as the vertical position[START_REF] Mikami | Forward Flexion of Trunk in Parkinson's Disease Patients Is Affected by Subjective Vertical Position[END_REF][START_REF] Mikami | Subjective Postural Vertical in Parkinson's Disease with Lateral Trunk Flexion[END_REF]. This was not a "vertical postural" because such assessment required active body orientation (action) and perception.

  al, 2017; Mikami et al 2020), PD patients were asked to actively orient its body to the vertical in the position at which they displayed maximal lateral trunk flexion. In 3 studies (Khattab et al, 2012; Gandor et al, 2016; Pawlitzki et al, 2018), the instructions of positioning were not specified, and in one article (Barnett-cowan et al, 2010), no instruction or control were provided. Only one study restrained both the trunk and the head (Piscicelli et al, 2021).

  seven papers (Proctor et al, 1964; Azulay et al, 2002; Barnett-cowan et al, 2010; Scocco et al,2014; José Luvizutto et al, 2020; Mikami et al, 2020; Piscicelli et al, 2021) separated their trials in left-side trials and right-side trials. Type of outcome measures Verticality perception was mainly estimated by the orientation criterion, which reflects the direction perceived as vertical by individuals. This criterion also called "verticality perception" (Pereira et al, 2014; Schindlbeck et al, 2017; Huh et al, 2018; Mori et al, 2019; José Luvizutto et al, 2020), "orientation perception" (Barnett-Cowan et al, 2010; Scocco et al, 2014), "spatial orientation" (Pawlitzki et al, 2018) or "vertical estimate" (Piscicelli et al, 2021), is usually calculated by averaging results (deviations from gravitational vertical of the verticality perceived) from the number of trials performed by the patient. Five articles evaluated the incertitude (Schindlbeck et al, 2017; Piscicelli et al, 2021; Danta et Hilton, 1975 Mikami et al 2020, Mikami et al 2017) but only 3 articles (Schindlbeck et al, 2017; Piscicelli et al, 2021; Danta et Hilton, 1975) calculated it, the mean of which was 1.4° (range 0.4-2.4).

(

  Reichert et al, 1982; Pastor et al, 1993 ; Nakamura et al, 1994 ; Nakamura et al, 1995 ; Pollak et al, 2009; Barnett-Cowan et al, 2010) This finding might mean that the deficit in vestibular integration, even if it is frequent, could be moderately asymmetric between left and right basal ganglia. Many studies have looked at whether this disorder is more central or peripheral in origin. Vitale et al found unilateral peripheral vestibular dysfunction, ipsilateral of the LTF and which could explain this latter (Vitale et al, 2011). Reichert et al found a bilateral vestibular defect during caloric tests, which is compatible with a disease of the bilateral peripheral vestibular structures (Reichert et al, 1982). The authors did not exclude any other lesion on the vestibular pathways, in particular central lesions. However, Barnett-Cowan et al found no visual or vestibular disorders in PD patients (Barnett-Cowan et al, 2014). They speculate that the lesions are more likely to be present in the centers of integration of multisensory information. Despite their frequency, VV biases magnitude was weak with a signed VV value measured at 0.2° and an absolute VV magnitude reaching 3.6°. These values are near to the objective vertical gravity (0°) and to the normative values allowing to consider the VV perception as normal ([-2.5°; 2.5°] in signed orientations) (Pérennou et al. 2008; Piscicelli and Pérennou; 2016). Moreover, in comparison to stroke, this amplitude appeared as very small. Indeed, verticality perception biases are frequent and severe after stroke, the most striking human model with a wrong internal model of verticality. Moreover, it has now been clearly established that a biased internal model of verticality is at the origin of postural disorders after stroke (Pérennou 2008; Dai 2021 Neurology a et b). This causal link between verticality perception biases and postural abnormalities has been little studied in PD but findings about the magnitudes of VV biases specifically studied in this present meta-analysis not argued in favor of this hypothesis. Directional concordances of VV biases and PD or PS sides Among the analyzed studies, on verticality perception in PD, only five studies (29.5%) detailed postural abnormalities in the PD individual's sample corresponding to 106 PD individuals, with mainly lateral trunk flexion, camptocormia, front trunk flexion and lateral or front neck flexion. The directional concordances between VV biases and PD sides or trunk tilts were analyzed in 3 studies (18%) (Huh et al, 2018; Piscicelli et al, 2021; Gandor et al, 2016) including 66 individuals with lateral trunk flexion, the vast majority of whom (78%) had VV biases tilted to the ipsilateral side of trunk tilt, while only 22% had contralateral VV biases. Interestingly, these results highly coincided with the directional concordances between VV biases and lateropulsion in post-stroke individuals (Pérennou et al. 2008; Dai et al., 2021). Some authors have discussed the coexistence of two mechanisms to explain this directional concordance between verticality perception biases and postural lateral trunk in PD (Piscicelli et al.

Figure 1 .Figure 2 .Figure 3 .

 123 Figure 1. Flow chart

Anesthésiologie-réanimation et médecine péri-opératoire

	PU-PH	PERENNOU Dominique	Médecine physique et de réadaptation
	PU-PH	PERNOD Gilles	Chirurgie vasculaire ; Médecine vasculaire
	MCF	PINSAULT Nicolas	Sciences de la rééducation et de réadaptation
	PU-PH	PIOLAT Christian	Chirurgie infantile
	PU-PH	PISON Christophe	Pneumologie ; Addictologie
	PU-PH	PLANTAZ Dominique	Pédiatrie
	PU-PH	POIGNARD Pascal	Bactériologie-virologie ; Hygiène hospitalière
	PU-PH émérite	POLACK Benoît	Hématologie ; Transfusion
	PU-PH	POLOSAN Mircea	Psychiatrie d'adultes ; Addictologie
	PU-PH émérite	RAMBEAUD Jean-Jacques	Urologie
	PU-PH	RAY Pierre	Biologie et médecine du développement et de la reproduction ; gynécologie médicale
	PR Ass. Méd.	RECHE Fabian	Chirurgie viscérale et digestive
	MCU-PH	RENDU John	Biochimie et biologie moléculaire
	MCU-PH émérite	RIALLE Vincent	Biostatistiques, informatique médicale et technologies de communication
	PU-PH	RIETHMULLER Didier	Gynécologie-obstétrique ; gynécologie médicale
	PU-PH	RIGHINI Christian	Oto-rhino-laryngologie
	PU-PH émérite	ROMANET Jean Paul	Ophtalmologie
	PU-PH	ROSTAING Lionel	Néphrologie
	PU-PH	ROUSTIT Matthieu	Pharmacologie fondamentale ; pharmacologie clinique ; addictologie
	MCU-PH	ROUX-BUISSON Nathalie	Biochimie et biologie moléculaire
	PR Ass.MG	ROYER DE VERICOURT Guillaume	Médecine Générale
	PU-PH émérite	SARAGAGLIA Dominique	Chirurgie orthopédique et traumatologie
	MCU-PH	SATRE Véronique	Génétique
	PU-PH	SAUDOU Frédéric	Biologie cellulaire
	PU-PH	SCHMERBER Sébastien	Oto-rhino-laryngologie
	PU-PH	SCHWEBEL Carole	Médecine intensive-réanimation
	PU-PH	SCOLAN Virginie	Médecine légale et droit de la santé
	PU-PH	SEIGNEURIN Arnaud	Epidémiologie,
	MCU-PH	PAYSANT François	Médecine légale et droit de la santé
	MCU-PH	PELLETIER Laurent	Biologie cellulaire
	PU-PH	PELLOUX Hervé	Parasitologie et mycologie
	PU-PH	PEPIN Jean-Louis	Physiologie
	PU-PH	PERARD DUMESTRE Chantal	Immunologie

économie de la santé et prévention PU-PH SPEAR Rafaëlle Chirurgie vasculaire ; médecine vasculaire PU-PH émérite STAHL Jean-Paul Maladies infectieuses ; Maladies tropicales

  La maladie de Parkinson (MP) est une cause fréquente d'handicap et est un problème majeur de santé. Sa prévalence et son incidence ont beaucoup augmenté au cours des dernières années. Au-delà des symptômes cardinaux, les troubles posturaux sont fréquents et représentent une source importante d'incapacité. Ils sont souvent résistants aux traitements et leur rééducation reste limitée. Leurs mécanismes sous-jacents restent à clarifier. En plus d'autres mécanismes conduisant à des troubles posturaux dans la MP, la possibilité qu'il existe un biais dans la construction du modèle interne de verticalité a vu le jour récemment. Cela serait en accord avec ce qui a été trouvé dans d'autres altérations cérébrales, tel que l'AVC. Récemment, beaucoup d'études se sont penchées sur la

	Antoine TUOT INTRODUCTION behavior called lateropulsion after hemisphere brain lesion (Pérennou 2008; Dai 2021 a and b), the
	BIAIS DE LA PERCEPTION DE LA VERTICALE DANS LA MALADIE DE PARKINSON : REVUE Parkinson's Disease (PD) is a common condition, which results in accelerated neuronal death of study of the verticality perception in PD is an emerging research.
	DE LA LITTÉRATURE ET MÉTA-ANALYSE. primarily dopaminergic neurons, but the neuropathology involves multiple other motor and non-motor The sense of verticality can be defined as the human ability to explicitly perceive the vertical direction,
	circuits (Bloem et al, 2021). The prevalence is of approximately 6.1 million people worldwide in 2016 to construct and update a mental representation of the vertical, used implicitly or explicitly to orient
	(GBD 2016), and the incidence ranges from 5 in 100 000 to more than 35 in 100 000 new cases yearly, himself (erect posture) or orient his spatial environment (Barra et al., 2013). The conscious experience
	with a clear increase the late decades of life (Simon et al, 2020). For reasons that are not yet fully of being oriented with respect to gravity can be directly tested: healthy people are very accurate in
	understood, the incidence and prevalence of this disease have risen rapidly in the past two decades. aligning their whole body (Postural vertical-PV) or an object by the sigh (Visual vertical-VV) or the
	The global burden of PD, in terms of death and disability, has more than doubled in the past two touch (Haptic vertical-HV) to the physical vertical, showing that they can accurately integrate
	decades. vestibular, visual, somatosensory and interoceptive signals
	One of the most common and most disabling motor complications affecting patients with PD are
	postural abnormalities, regrouping Pisa Syndrome (PS), camptocormia and scoliosis (Doherty et al,
	2011). It represents a major source of disability and falls, reduces quality of life and predicts early
	mortality (Tinazzi et al, 2019 ; Galbusera et al, 2018, Tinazzi et al, 2015). In PD, the
	physiopathological mechanisms of postural disorders remain unclear. Several hypotheses are discussed
	in recent years, which can be classified between peripheral and central hypotheses. Peripheral
	hypotheses refer to the involvement of musculoskeletal system, with myopathy of paraspinal muscles.
	PU-PH Central hypotheses advocate a dysfunction of the basal ganglia and an abnormal integration of sensory STANKE Françoise Pharmacologie fondamentale ; pharmacologie clinique ; addictologie
	MCU-PH	STASIA Marie-José	Biochimie et biologie moléculaire
	PU-PH information. The postural control requires correct body orientation against gravity and relies on STURM Nathalie Anatomie et cytologie pathologiques
	PU-PH PU-PH multisensory integration relying on visual, vestibular, and somaesthetic information. Impaired sensory TAMISIER Renaud Physiologie TERZI Nicolas Médecine intensive-réanimation
	PU-PH PU-PH integration in PD individuals (Almeida et al. 2005; Vaugoyeau et al. 2011; Konczak et al. 2012) could THEVENON Julien Génétique TOFFART Anne-Claire Pneumologie ; Addictologie
	PU-PH therefore favor an alteration of the internal model of verticality leading to lateral body deviation. TONETTI Jérôme Chirurgie orthopédique et traumatologie
	PU-PH	TOUSSAINT Bertrand	Biochimie et biologie moléculaire
	PU-PH PU-PH If the sense of verticality has been extensively and mainly studied after stroke (Yelnik et al. 2002; VALMARY-DEGANO Séverine Anatomie et cytologie pathologiques VANZETTO Gérald Cardiologie
	PU-PH PU-PH Bonan et al. 2006; Saj et al. 2005; Pérennou et al, 2008; Barra et al. 2010; Baier et al. 2012; Piscicelli VUILLEZ Jean-Philippe Biophysique et médecine nucléaire WEIL Georges Epidémiologie, économie de la santé et prévention
	PU-PH et Pérennou, 2017; Piscicelli et al, 2016), allowing to elucidate the mechanism underlying the postural ZAOUI Philippe Néphrologie
	PU-PH émérite	ZARSKI Jean-Pierre	Gastroentérologie ; hépatologie ; addictologie

Résumé:

INTRODUCTION : perception de la verticale dans la MP. L'objectif de cette revue systématique et de cette méta-analyse est de synthétiser les connaissances actuelles sur ce sujet.

METHODOLOGIE :

Nous avons recherché systématiquement dans Medline et Cochrane de 1960 à décembre 2021 en utilisant les termes « maladie de Parkinson », « perception de la verticale » et leurs dérivés. Nous avons suivi les recommandations de PRISMA et de COCHRANE. Les articles éligibles à l'inclusion, ainsi que l'extraction de leurs données et de leur qualité (échelle de Newcastle-Ottawa, NOS) ont été évaluées par deux investigateurs (AT, CP), selon un protocole standardisé. Nous avons analysé la fréquence et l'ampleur des inclinaisons observées dans la perception de la verticale par méta-analyse des modèles à effets aléatoires. Nous avons respecté la définition des inclinaisons de la verticale donnée dans chaque étude. RESULTATS: Nous avons recensé 17 études (618 individus ; âge moyen de 66.3 ans ; 55 % d'hommes ; durée moyenne de la maladie de 8.9 ans), dont la majorité ont été publiées entre 2010 et 2020. Les études avaient un bon score de qualité NOS moyen de 7.4 (écart-type= 1.14). Seule la verticale visuelle (VV) a pu être étudiée au moyen d'une méta-analyse, à cause d'un manque d'études sur la verticale haptique (n=2) et posturale (n=4). Pour la VV, la fréquence combinée des inclinaisons anormales était élevée : 45 % (intervalle de confiance [IC] à 95 % [20; 70], I²=94.5 %) chez tous les patients parkinsoniens, peu importe la gravité ou la durée de la maladie, atteignant 62 % (IC à 95 % [19; 106], I²=92 %) chez les personnes atteintes du syndrome de Pise (SP). Chez toutes les personnes testées, la magnitude combinée des inclinaisons VV était mesurée à 0.2° (IC à 95 % [-0.57; 0.89], I2=0 %) en valeurs signées, et à 3.6° (IC à 95 % [1.83; 5.34], I2=52.2 %) en valeurs non signées. Dans le cas où la VV était anormalement inclinée, la magnitude combinée des inclinaisons était mesurée à 5.3° en valeur absolue (IC à 95 % [3.4; 7.3], I²=52.2 %). Peu d'articles ont étudié la concordance entre les inclinaisons du VV et celle du corps, le cas échéant (SP). Lorsqu'elle est analysée, nous trouvons que 78 % des patients présentaient une inclinaison de VV du même côté que celle du tronc.

CONCLUSION :

Il s'agit de la première revue systématique traitant de la perception de la verticale dans la MP, montrant que la VV est souvent anormalement incliné, mais que sa magnitude est faible. Sachant que la verticale visuelle examine la graviception vestibulaire, ces résultats signifieraient que l'information vestibulaire est souvent altérée dans la MP, et que l'asymétrie entre les ganglions basaux gauche et droit est modérée. Les concordances entre les côtés des inclinaisons de VV et de la MP ou du SP n'ont pas été correctement analysées, et lorsque c'était le cas, cette concordance était proche de celle de l'AVC. Ces résultats indiquent la coexistence de deux mécanismes : une partie des inclinaisons anormales de la VV semblent être la conséquence du SP sur la perception de la verticale, altérée par une déformation du tronc ou une mauvaise perception de la gravité. Dans la majorité des cas, les inclinaisons de la VV reflètent une graviception vestibulaire altérée. A l'avenir, les études devront tester plusieurs modalités de perception de la verticale, en particulier la VV et la PV, sur de plus grandes séries, et examiner les concordances entre les côtés des inclinaisons corporelles et ceux de la perception de la verticale.

Table 2

 2 The mean disease duration was 8.9 (range 4.6 -17.5) years, with a great variation from 5 to almost 18 years.Nine studies used the MDS UPDRS III score to quantify the motor disorders. When the old version of UPDRS-III was used instead of the MDS UPDRS III, we converted into this latter following a conversion formulas (appendix 2). The mean score was 24.6 points (range 14.4-41) in ON phase. However, we could not convert the UPDRS score for two studies[START_REF] Piscicelli | Contribution of Basal Ganglia to the Sense of Upright: A Double-Blind Within-Person Randomized Trial of Subthalamic Stimulation in Parkinson's Disease with Pisa Syndrome[END_REF][START_REF] Scocco | Subjective Visual Vertical in Pisa Syndrome[END_REF]

summarizes the characteristics of the participants. The 17 studies included a total of for 618 patients (range 13 to 90 patients per study), with mean age of 66.3 years (range 54.5 -74.1) , and 55% of males.

  First of all, since 1960, we could only analyze 17 articles. Moreover, the sample size of each study was low (median=38), due to the different selection methods. The measurement procedure requires patients with no or a mild cognitive impairment, although the analyzed articles studied generally patients with advanced PD. On the other hand, we could only analyze VV tilt due of a lack of studies treating the other modalities, ie HV and PV. We know the postural control is a sophisticated processing based in a precise interpretation of the sensory information such as vestibular, visual, or somatosensory. Nevertheless, VV mainly assesses the vestibular and visual contribution to the sense of verticality. Thus, the lack of assessment of verticality perception in other modalities did not allow us to conclude whether the VV biases found in several studies reflects a bias in the internal model of verticality and are not only the consequences of the body geometry deformation. . Finally, few studies studied the concordance between VV tilts and the side where basal ganglia were predominantly altered, as well as the concordance with a body tilt if any (PS).

Table 2 . Sample characteristics of the 17 studies PD

 2 : Parkinsonian disease; PS : Pisa syndrom ; MDS-UPDRS : Movement disorder Society Unified Parkinson's Disease Rating Scale ; H&Y : Hoenh and Yahr ; LEDD : Levodopa Equivalent Delivred Dose ; FTF : Forward Trunk Flexion ; CAMPT : Camptocormia ; NS : non specified. * : study who use the old version of the UPDRS III. ** : chemosurgery.

	Study	Healthy PD	PS	Age		Disease duration	MDS UPDRS III	H&Y	LEDD	MEDICATIO	POSTURAL
										N	ABNORMALITIES
	Proctor et al, 1964	20	0	54.5		4.75	NS	NS	NS	NS**	NS
	Danta et al, 1975	40	NS	60.7±0.9		10.7	NS	NS	NS	NS	NS
	Bronstein et al, 1996 24	NS	68±11		5.4 + 0.7	NS	2.43 (SE 0.51)	250 mg	ON OFF	NS
	Azulay et al, 2002	22	NS	57 ± 14		NS	NS	1 to 3	NS	ON	NS
	Barnett-cowan et al,	13	NS	65.8 ± 11		4.6 ± 3.3	15.7 ±7.2	2.5 (range: 1-2.5) 490	ON OFF	No
	2010
	Khattab et al, 2012	47	0	69.35 ± 7.70 4.71 ± 3.30	15.72 ± 6.90	NS	NS	ON	NS
	Pereira et al, 2014	45	NS	64.5	+/-	9.7 ± 6.8	41	2.5 (CI: 2;3)	NS	ON	NS
				12.3
	Scocco et al,2014	18	8	65.7 ± 6		7.6 ± 5,6	14.4 (8,6)*	NS	747	ON OFF	PISA
	Gandor et al, 2016	0	21	69.5 ± 7		11.4 ± 6	NS	NS	1023 (330-2333)	ON	PISA
	Mikami et al, 2017	15	0	71,9 ±10.1	7.2 ± 5.4	19.2 ± 12.3	2.6 ± 0.7	375.6 ± 114.6	ON	FTF
	Schindlbeck et al,	28	NS	69.2±9.8		6.6 ±5.6	30 (IQR:12)	2	607.5 (±433.5)	ON	NS
	2017
	Huh et al, 2018	0	54	66.4 ± 6.4	7.9 ± 3.4	22.8 ± 5.8	2.2±0.3	593.7±218.	ON	PISA
	Pawlitzki et al, 2018	21	0	68 ± 8.5		7.3 ± 4.4	27.16+/-12.5	2.5 ± 0.5	NS	NS	CAMPT
	Mori et al, 2019	28	NS	72.9± 5.78	NS	34.4 ± 12	2 et 3	655.4 ± 240.3	ON	No
	José Luvizutto et al,	14	NS	65.5 +/-8.9	6.8 +/-2.6	NS	< 3	NS	ON	NS
	2020
	Mikami et al, 2020	NS	5	74.1± 7.6		12.0 ±2.3	15.6±7.8	3.0±0.3	1082.7±416.1	ON	PISA
	Piscicelli et al, 2021	20	18	63.5 [61;67] 17.5 [14;20]	22.8 [17.1;31.1]*	NS	NS	ON OFF	PISA/CAMPT

Table 4 . Prevalence of the verticality perception biases in the 17 studies

 4

	Articles	Prévalence bias (n)	Indice of orientation	Signed value	absolute value	uncertainty	Incertitude value	Value normality
	Proctor et al, 1964	NS	constant error	NS	RBS: 1.09R LBS:	NS	NS	0.57
					1.57L
	Danta et al, 1975	NS	mean	0.1±3.8	2.6	Variance	2.39	<0.1 ± 1.1
	Bronstein et al, 1996	NS	median	-0.2 ± 4.6	Ns	NS	NS	NS
	Azulay et al, 2002	NS	Frame Effect	NS	10.1 ±4.5	NS	NS	5.6± 3.1
	Barnett-Cowan et al,	NS	mean	0.3± 1.3	NS	NS	NS	NS
	2010
	Khattab et al, 2012	NS	mean	NS	0.8 (range: 0.1°-	NS	NS	0.5° (range: 0.0°-4.0°)
					6.6°)
	Pereira et al, 2014	27	mean	-0.8°	3.5° (median) (2.5;	NS	NS	0.2
					4.5)
	Scocco et al, 2014	NS	median	-1.0	NS	NS	NS	0.3 (-0.8; 0.9)
	Gandor et al, 2016	14	absolute mean	NS	4.3° [range: 0.1-	NS	NS	0 +/-2.5°
					17.7],

Forest Plot for the frequencies of the visual vertical biases in the studies analyzing Parkinson disease.

	Study		Frequency of	%
	ID		SVV bias (95% CI)	Weight
	Khattab, et al. 2012		0.09 (0.00, 0.17)	21.25
	Pereira, et al. 2014		0.60 (0.46, 0.74)	20.28
	Gandor, et al. 2016		0.67 (0.47, 0.87)	19.03
	Huh, et al. 2018		0.51 (0.41, 0.61)	20.95
	Piscicelli, et al. 2021		0.39 (0.16, 0.61)	18.48
	Overall (I-squared = 94.5%, p = 0.000)		0.45 (0.20, 0.70)	100.00
	NOTE: Weights are from random effects analysis
	-.869	0 0	.869

Frequency of verticality perception biases

The table [START_REF] Doherty | Postural Deformities in Parkinson's Disease[END_REF] presented for each study the prevalence of verticality perception bias in PD patients.

Globally, 148 of 288 patients (if we take only the studies that present the prevalence) had a verticality perception bias (51.4% of the patients).

Given the low number of studies dealing on PV (n=4) and HV (n=2) perception, we performed random-effects meta-analysis only to generate pooled prevalence of VV biases in PD.

Five studies [START_REF] Khattab | Subjective Visual Vertical Perception and Sense of Smell in Parkinson Disease[END_REF][START_REF] Pereira | Correlation of Impaired Subjective Visual Vertical and Postural Instability in Parkinson's Disease[END_REF][START_REF] Gandor | Subjective Visual Vertical in PD Patients with Lateral Trunk Flexion[END_REF][START_REF] Huh | Pisa Syndrome in Parkinson's Disease: Pathogenic Roles of Verticality Perception Deficits[END_REF][START_REF] Piscicelli | Contribution of Basal Ganglia to the Sense of Upright: A Double-Blind Within-Person Randomized Trial of Subthalamic Stimulation in Parkinson's Disease with Pisa Syndrome[END_REF]), for a total of 221 individuals, analyzed the frequency of SVV bias (Fig 4) regardless of biased side. These biases were frequent: 0.45 (95% CI [0.2; 0.7], I2=94.5%).

We found an outlier [START_REF] Khattab | Subjective Visual Vertical Perception and Sense of Smell in Parkinson Disease[END_REF] in this result, since one study reported very low frequency, which would be attributed to enrolled participants in early stage.

When dropping this study, the pooled frequency was more homogenous, reaching 0.