Disentangling the involvement of primary motor cortex in value-based reinforcement learning and value-based decision making.

When one makes the decision to act in the physical world, the neural activity in primary motor cortex (M1) encodes the competition between potential action choices. Traditional approaches have viewed this activity as reflecting the unfolding of the outcome of a decision process taking place upstream. However, a recently emerging theoretical framework posits that the motor neural structures directly contribute to the decision process. We recently tested this hypothesis (Zenon et al., 2015, Brain Stimulation) by using continuous theta burst stimulation (cTBS) to alter activity in M1 while participants performed a task that required them to select between two fingers in the right hand based on the color of a stimulus (green or red, explicit instruction). Importantly, this finger choice was biased such that, to earn more money, the subjects also had to take into account the shape of the stimulus (circle or square, undisclosed manipulation). So the motor response depended, on the one hand, on a perceptual decision process, interpreting the color of the stimulus according to instructed rules and, on the other hand, on a value-based decision process relying on reinforcement learning. Interestingly, cTBS over M1 modified the extent to which the value-based process influenced the subjects' decisions whereas it had no effect on their ability to make a choice based on perceptual evidence. Importantly, in that study, cTBS was applied at the very beginning of the experiment, before the subjects had learned the task. Hence, we cannot tell from that work whether the effect of M1 cTBS was due to an alteration of value-based reinforcement learning or of value-based decision making, which takes place once learning is complete. Here, we present a study in which we intend to use the same task but with cTBS applied at different times in order to assess the contribution of M1 to the two value-based processes (learning and decision making). More precisely, the experiment will extend over three sessions, each occurring at 24-hours interval. Each experimental session will consist of six blocks, each lasting about 4 minutes. Pilot data suggest that the value-based process begins to effectively shape the subject decisions in the middle of the second session. Given this, cTBS over M1 will be applied either at the beginning of the first session (before learning) or at the beginning of the third session (after learning). This procedure will allow us to disentangle the involvement of M1 in value-based reinforcement learning and value-based decision making

Minimal information for studies of extracellular vesicles 2018 (MISEV2018):a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines

The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points

Effets de la thérapie par ondes de choc dans le traitement de la spasticité après un accident vasculaire cérébral : revue systématique

La spasticité est une complication fréquente après un accident vasculaire cérébral. Les ondes de choc extracorporelles seraient un traitement alternatif, sûr et non invasif des muscles spastiques. Le but de cette revue systématique de la littérature est de déterminer l’effet des ondes de choc sur les muscles spastiques de patients ayant été victimes d’un accident vasculaire cérébral. Quatre bases de données électroniques ont été investiguées (Cochrane, PEDro, Pubmed et Scopus) du 9 novembre 2016 au 13 février 2017, avec les termes «muscle spasticity», «spasticity», «High-Energy shock waves», «shock wave*» et «shockwave*». Six études randomisées contrôlées ont répondu favorablement à la sélection. L’examinateur a pu mettre en évidence à travers leur lecture, un impact bénéfique significatif des ondes de choc sur la spasticité. Les mécanismes impliqués dans la diminution de la spasticité n’ont pas encore été clairement établis, mais il semblerait que les ondes de choc aient davantage un impact sur les propriétés biomécaniques et rhéologiques des muscles que sur la spasticité en elle-même. Aucune recommandation n’existe actuellement, mais il semble déjà évident que l’efficacité thérapeutique est fonction du nombre de sessions ainsi que du délai d’application du traitement après l’apparition de la spasticité, de par leur action sur le muscle lui-même. Des études plus approfondies sont encore nécessaires afin de pouvoir se positionner quant aux mécanismes incriminés et pouvoir élaborer des recommandations claires et optimales.Master [120] en sciences de la motricité, orientation générale, Université catholique de Louvain, 201

Learning stage-dependent effect of M1 disruption on value-based motor decisions.

The present study aimed at characterizing the impact of M1 disruption on the implementation of implicit value information in motor decisions, at both early stages (during reinforcement learning) and late stages (after consolidation) of action value encoding. Fifty subjects performed, over three consecutive days, a task that required them to select between two finger responses according to the color (instruction) and to the shape (implicit, undisclosed rule) of an imperative signal: considering the implicit rule in addition to the instruction allowed subjects to earn more money. We investigated the functional contribution of M1 to the implementation of the implicit rule in subjects' motor decisions. Continuous theta burst stimulation (cTBS) was applied over M1 either on Day 1 or on Day 3, producing a temporary lesion either during reinforcement learning (cTBSLearning group) or after consolidation of the implicit rule, during decision-making (cTBSDecision group), respectively. Interestingly, disrupting M1 activity on Day 1 improved the reliance on the implicit rule, plausibly because M1 cTBS increased dopamine release in the putamen in an indirect way. This finding corroborates the view that cTBS may affect activity in unstimulated areas, such as the basal ganglia. Notably, this effect was short-lasting; it did not persist overnight, suggesting that the functional integrity of M1 during learning is a prerequisite for the consolidation of implicit value information to occur. Besides, cTBS over M1 did not impact the use of the implicit rule when applied on Day 3, although it did so when applied on Day 2 in a recent study where the reliance on the implicit rule declined following cTBS (Derosiere et al., 2017). Overall, these findings indicate that the human M1 is functionally involved in the consolidation and implementation of implicit value information underlying motor decisions. However, M1 contribution seems to vanish as subjects become more experienced in using the implicit value information to make their motor decisions

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Implicit encoding of action values in the human primary motor cortex.

In the present study, we investigated the functional contribution of the human primary motor cortex (M1) to the implicit encoding of action values during motor decisions. In two series of experiments, continuous theta burst stimulation (cTBS) was exploited to alter activity in left M1 while participants performed a decision-making task in which the reward associated with their responses (right hand finger movements) depended on an implicit (undisclosed) value-based rule. In Experiment 1, subjects were provided with two days of practice and cTBS occurred in the middle of Day 2, once the subjects had learned the implicit rule and were ready to use it in the next blocks to choose their responses, as evident in the control group (cTBS over the right somatosensory cortex). In Experiment 2, subjects were given three days of practice and cTBS occurred either at the beginning of Day 1 (before learning) or in the middle of Day 3, while subjects were proficient in using the implicit rule. Interestingly, the implementation of the implicit value-based rule was absent in the group receiving M1 cTBS in the middle of Day 2 (Experiment 1). Oppositely, disrupting M1 before learning (Experiment 2) led to an early and enhanced encoding of the implicit rule during Day 1. Finally, the use of the implicit rule was unaffected when M1 was disrupted in the middle of Day 3 (Experiment 2). Our results suggest that M1 might belong to the brain network underlying the encoding of action values during motor decisions. In Experiment 1, M1 was left undisrupted during learning (until the middle of Day 2) and could have encoded – in concert with other reinforcement learning-related structures such as the basal ganglia or the medial frontal cortex – the implicit value-based rule. A subsequent disruption of M1 in Day 2 might have then perturbed the whole network, impeding the implementation of the learned implicit rule. Of note, when realized in the middle of Day 3 (Experiment 2), M1 cTBS had no impact on the way subjects used the implicit rule; this indicates that the effect of cTBS was dependent on the phase at which it was applied during learning (i.e., more or less labile/stabilized phase of learning). Finally, the disruption of M1 before learning (Experiment 2) might have led to an over-compensation of the aforementioned reinforcement learning-related structures, leading to an increased reliance on the implicit rule from the very beginning of the decision making task

Can modelling the drift of bycaught dolphin stranded carcasses help identify involved fisheries? An exploratory study

Between the 1st of February and the March 31, 2017, 793 stranded cetaceans were found along the French Atlantic coasts. Common dolphins made up 84% of these strandings, and most of these presented evidence of death in fishing gear. The aim of this work is to test an approach that could help identify the fisheries potentially involved in a given stranding event. To do this we examined how the distributions of likely areas of mortality of bycaught dolphins, inferred from carcass drift modelling, coincide with fishing effort statistics of various fleets, generated from the Vessel Monitoring System, in the area over the same dates. Using reverse drift modelling, two main mortality areas were identified. A total of 3690 common dolphins (IC95% [2230; 6900]) were estimated to have died in fishing gear within the Bay of Biscay during this unusual stranding event. There was a positive correlation between the origin of stranded bycaught dolphins and the fishing effort distribution of French midwater pair trawlers, Spanish otter bottom trawlers and French Danish seiners. This co-occurrence highlights a risk and identifies fisheries that require further investigation (through observers or e-monitoring). These fisheries differed in their fishing gear, but two characteristics appear to be shared: they targeted predatory fishes (sea bass and hake) in winter and used high vertical opening gear

Can modelling the drift of bycaught dolphin stranded carcasses help identify involved fisheries? An exploratory study

International audienceBetween the 1st of February and the March 31, 2017, 793 stranded cetaceans were found along the French Atlantic coasts. Common dolphins made up 84% of these strandings, and most of these presented evidence of death in fishing gear. The aim of this work is to test an approach that could help identify the fisheries potentially involved in a given stranding event. To do this we examined how the distributions of likely areas of mortality of bycaught dolphins, inferred from carcass drift modelling, coincide with fishing effort statistics of various fleets, generated from the Vessel Monitoring System, in the area over the same dates. Using reverse drift modelling, two main mortality areas were identified. A total of 3690 common dolphins (IC95% [2230; 6900]) were estimated to have died in fishing gear within the Bay of Biscay during this unusual stranding event. There was a positive correlation between the origin of stranded bycaught dolphins and the fishing effort distribution of French midwater pair trawlers, Spanish otter bottom trawlers and French Danish seiners. This co-occurrence highlights a risk and identifies fisheries that require further investigation (through observers or e-monitoring). These fisheries differed in their fishing gear, but two characteristics appear to be shared: they targeted predatory fishes (sea bass and hake) in winter and used high vertical opening gear