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Supervisor: 橋本 敬, 先端科学技術研究科, 博士

Decision-making is in the service of action regardless of whether the decision concerns perceptual information, goods or memories. Compared to recent advances in the neurobiology of perceptual or value-based decisions, however, the neural bases supporting the sampling of evidence in long-term memory, and the transformation of memory-based decisions into appropriate actions, are still poorly understood. In the present fMRI study, we used multivariate pattern analysis to investigate the temporal dynamics of choice- and action-predictive signals during an item recognition task that manipulated the association between memory choices (old/new) and motor responses (eye/hand) across subjects. Choice-predictive activity was mainly observed in striatal, lateral prefrontal and lateral parietal regions, was sensitive to the amount of decision evidence and showed a rapid increase after stimulus onset, followed by a fast decay. Action-predictive signals were found in primary sensory motor, premotor and occipito–parietal regions, were generally observed at the end of the decision phase and were not modulated by decision evidence. These findings suggest that a memory decision variable, potentially represented in a fronto–striato–parietal network, is not directly transformed into an action plan as often observed in perceptual decisions. Regions exhibiting choice predictive activity, and especially the striatum, however, also showed a second peak of decision-related activity that, unlike pure choice- or action-predictive signals, depended on the particular choice–response association. This second peak of activity in the striatum might represent the neural signature of the transformation of a memory decision into an appropriate motor response based on the specific choice–response association. Electronic supplementary material The online version of this article (10.1007/s00429-020-02124-4) contains supplementary material, which is available to authorized users.

[EN] The use of brain-machine interfaces in people who has suffered a cerebrovascular accident could help the rehabilitation process through the cognitive involvement of the patient. These interfaces translate the brain waves into commands to control the movement of an assistant mechanical device. However, the control of these devices should be more stable and achieve a higher accuracy. This work studies if algorithms, such as Stockwell or Hilbert-Huang transform, can improve the control of these devices, and if a personalization by subject or electrode configuration is desirable. Besides, through the analysis of five volunteers is determined that the motor intention can not be detected only by data acquired previously to the movement using desynchronized/synchronized related events. Therefore, it is needed to extend the time processing to the two seconds after the movement starting., [ES] El uso de interfaces cerebro-máquina en personas que han sufrido un accidente cerebro-vascular puede ayudar en su proceso de rehabilitación mediante la implicación cognitiva del paciente. Dichas interfaces traducen las ondas cerebrales en comandos con el fin de controlar un dispositivo mecánico de movimiento asistido. No obstante, el control de estos dispositivos debería ser más robusto y tener una alta precisión. Este trabajo estudia si algoritmos basados en transformadas como las de Stockwell o Hilbert-Huang pueden mejorar el control de estos dispositivos aumentando su precisión, y si es recomendable llevar a cabo una personalización por sujeto y configuración de electrodos. Mediante el análisis de cinco voluntarios se comprueba además, que no es posible detectar con suficiente robustez la intención motora a partir de la desincronización/sincronización relacionada a eventos motores con únicamente los datos previos al movimiento. Por ello, es preciso extender el tiempo de análisis a los dos segundos posteriores al inicio del movimiento., Este trabajo ha sido realizado en el marco del proyecto Associate - Decodificación y estimulación de actividad cerebral sensorial y motora para permitir potenciación a largo plazo mediante estimulación Hebbiana y estimulación asociativa pareada durante la rehabilitación de la marcha (con referencia DPI2014-58431-C4-2-R), financiado por el Ministerio de Economía y Competitividad (Plan Estatal de I+D+I) y por la Unión Europea a través del Fondo Europeo de Desarrollo Regional - FEDER ((Una manera de hacer Europa)). También queremos agradecer a Neuroelectrics por prestar el equipo Enobio 32 para este estudio.

Motor awareness is the acknowledgment of (i) one's motor state while executing a movement or remaining still and (ii) one's motor abilities. The integrated contribution of different networks involving the parietal cortex, medial and lateral frontal regions, and subcortical structures gives rise to motor awareness. The damage to these structures or their disconnection results in a number of motor awareness disorders, such as the well-known Anosognosia for hemiplegia and apraxia, and the Anarchic Hand Syndrome. The deficit of motor awareness may also be present in other disorders such as Parkinson's and Huntington's diseases, Tics, and Tourette's Syndrome.

Recenti studi hanno evidenziato che le caratteristiche cinematiche di un'azione vengono modulate dall'intenzione motoria con la quale l’azione viene compiuta. In aggiunta, è stato dimostrato che queste variazioni possono essere riconosciute e utilizzate come indicazioni sufficienti per prevedere l’intenzione motoria sottostante l’azione osservata. Tuttavia, un quesito non ancora affrontato è il seguente: la decodifica delle intenzioni degli altri sulla base della loro cinematica dipende unicamente da quanto questa varia attraverso le diverse azioni, o piuttosto è anche influenzata dalla somiglianza tra il repertorio motorio dell’osservatore e quello di un agente intento ad eseguire l’azione? L’obiettivo del presente studio è stato quello di indagare la relazione tra la somiglianza in termini cinematici tra un’azione eseguita/osservata e la capacità di prevedere l’intenzione della stessa azione in assenza di variabili contestuali. A tal scopo, 21 partecipanti sono stati reclutati per due esperimenti che prevedevano un compito di esecuzione di sequenze motorie, seguito da un compito di osservazione e riconoscimento dell’intenzione di un’azione osservata. In primo luogo, ai partecipanti è stato chiesto di eseguire un movimento di raggiungimento e prensione di un cilindro di legno con il fine di posizionarlo in un target in diverse condizioni sperimentali, caratterizzate da un contesto sociale o non sociale. Nel contesto non sociale, i partecipanti dovevano posizionare l'oggetto in una scatola grande o piccola; tale compito richiedeva un diverso livello di accuratezza nell’esecuzione del movimento. Nel contesto sociale, i partecipanti hanno dovuto mettere l'oggetto nelle mani aperte o semi chiuse di un altro individuo. Sono state analizzate le caratteristiche cinematiche di ogni movimento al fine di individuare eventuali variazioni dei parametri cinematici dell’azione in corrispondenza delle 4 condizioni sperimentali. Successivamente lo stesso gruppo di partecipanti è stato reclutato per un secondo esperimento in cui è stato loro chiesto di osservare e prevedere l'intenzione di un attore che eseguiva in un video-clip una delle azioni da loro precedentemente eseguite. Nel video-clip la fase di posizionamento finale del cilindro era visivamente oscurata e veniva richiesto al partecipante di prevedere l'intenzione motoria osservando la sola fase di raggiungimento e prensione dell’oggetto. Prendendo in esame la somiglianza tra i profili cinematici di ciascun partecipante e l'attore sono stati valutati i suoi possibili effetti sull’accuratezza del riconoscimento dell’intenzionalità motoria con la quale l’azione è messa in atto. I risultati del compito di esecuzione hanno dimostrato come i parametri cinematici di entrambi le fasi di raggiungimento e prensione sono stati influenzati dalle dimensioni dell’obiettivo finale del movimento, evidenziando un movimento più accurato (minore elevazione del braccio) e un’apertura delle dita minore nel caso di un target di piccole dimensioni. La presenza di un contesto sociale invece, ha evidenziato un movimento più lento (velocità minore). Ciò è in linea con una più bassa decelerazione del braccio durante l'avvicinamento all'oggetto. Allo stesso tempo, l'accelerazione del braccio era inferiore nei contesti sociale e non sociale, ma limitatamente al confronto con obiettivi di grandi dimensioni. Gli indici di similarità calcolati tra ogni partecipante e l’attore, tra le curve di movimento relative ai parametri cinematici, hanno evidenziato una correlazione significativa con l’accuratezza nel riconoscimento dell’intenzione motoria, risultata al di sopra del caso in tutte le condizioni seppur con risultati migliori durante la discriminazione dell’intenzione sulla base della differente dimensione del target. Tale risultato suggerisce come il riconoscimento dell’intenzione motoria sia un processo visuo-motorio ed evidenzia il ruolo facilitatorio del livello di risonanza motoria tra attore e osservatore nel processo di comprensione dell’azione. Recent studies have shown that the cinematic characteristics of an action are modulated by the motor intention with which the action is performed. In addition, it has been shown that these variations can be recognised and used as sufficient indications to predict the underlying motor intent of the observed action. However, one question not yet addressed is the following: the decoding of the intentions of others on the basis of their kinematics depends solely on how much this varies through the different actions, or rather is also influenced by the similarity between the observer's motor repertoire and that of an agent intent on performing the action? The aim of this study was to investigate the relationship between the kinematic similarity between an performed/observed action and the ability to predict the intention of the same action in the absence of contextual variables. To this end, 21 participants were recruited for two experiments involving a task of performing motor sequences, followed by a task of observing and acknowledging the intention of an observed action. First, participants were asked to perform a movement of reach to grasp a wooden cylinder with the aim of placing it in a target under different experimental conditions, characterized by a social or non-social context. In the non-social context, participants had to place the object in a large or small box; this task required a different level of accuracy in the execution of the movement. In the social context, participants had to put the object in the open or semi-closed hands of another individual. The cinematic characteristics of each movement were analysed in order to identify any changes in the cinematic parameters of the action at the 4 experimental conditions. Subsequently, the same group of participants was recruited for a second experiment in which they were asked to observe and predict the intention of an actor performing one of the actions they had previously performed in a video clip. In the video clip, the final positioning phase of the cylinder was visually obscured and the participant was asked to predict motor intent by observing the only stage of reach and grasp of the object. Looking at the similarity between each participant's kinematic profiles and the actor, its possible effects on the accuracy of the recognition of motor intentionality with which the action is carried out were assessed. The results of the execution task showed that the kinematic parameters of both the reach and grasp phases were influenced by the size of the final goal of the movement, highlighting a more accurate movement (less and a smaller finger opening in the case of a small target). The presence of a social context, on the other hand, showed a slower movement (lower speed). This is in line with a lower deceleration of the arm as it approaches the object. At the same time, the acceleration of the arm was lower in social and non-social contexts limited to comparison with large targets. The similarity indices calculated between each participant and the actor, between the motion curves related to the cinematic parameters, showed a significant correlation with the accuracy in the recognition of motor intent, which was above in all conditions, albeit with better results, during the discrimination of intention on the basis of the different size of the target. This result suggests that the recognition of motor intention is a visuo-motor process and highlights the facilitation alierating role of the level of motor resonance between actor and observer in the process of understanding the action.

In anosognosia for hemiplegia, patients may claim having performed willed actions with the paralyzed limb despite unambiguous evidence to the contrary. Does this false belief of having moved reflect the functioning of the same mechanisms that govern normal motor performance? Here, we examined whether anosognosics show the same temporal constraints known to exist during bimanual movements in healthy subjects. In these paradigms, when participants simultaneously reach for two targets of different difficulties, the motor programs of one hand affect the execution of the other. In detail, the movement time of the hand going to an easy target (i.e., near and large), while the other is going to a difficult target (i.e., far and small), is slowed with respect to unimanual movements (temporal coupling effect). One right-brain-damaged patient with left hemiplegia and anosognosia, six right-brain-damaged patients with left hemiplegia without anosognosia, and twenty healthy subjects were administered such a bimanual task. We recorded the movement times for easy and difficult targets, both in unimanual (one target) and bimanual (two targets) conditions. We found that, as healthy subjects, the anosognosic patient showed coupling effect. In bimanual asymmetric conditions (when one hand went to the easy target and the other went to the difficult target), the movement time of the non-paralyzed hand going to the easy target was slowed by the ‘pretended’ movement of the paralyzed hand going to the difficult target. This effect was not present in patients without anosognosia. We concluded that in anosognosic patients, the illusory movements of the paralyzed hand impose to the non-paralyzed hand the same motor constraints that emerge during the actual movements. Our data also support the view that coupling relies on central operations (i.e., activation of intention/programming system), rather than on online information from the periphery.

Fresh empirical evidence supports the notion that fear of movement-related pain can be acquired through associative learning. In the context of these findings, 2 ideas are appealing, yet uninvestigated. The first is that merely the intention to perform a painful movement acts as a covert conditioned stimulus (CS) inducing defensive fear responses (ie, gaining excitatory properties following Pavlovian acquisition). The second idea is that after extinction, fear of movement-related pain can easily be reinstated after unexpected painful stimuli (ie, reinstatement). In a voluntary differential conditioning movement paradigm with movements as CSs and a painful electrocutaneous stimulus as the unconditioned stimulus (pain-US), 2 groups were included (Experimental/Control). One movement (CS+) was followed by the pain-US and another movement (CS) was not during acquisition, while the CS+ was no longer reinforced during extinction. Next, the Experimental group received 2 reinstating pain-USs, whereas the Control group did not. The CS+ but not the CS evoked fear of movement-related pain in self-reports and eye-blink startles. Intriguingly, the mere intention to perform the painful movement produced higher eye-blink startle responses than the intention to perform the nonpainful movement. We also demonstrated nondifferential reinstatement in the verbal fear ratings in the Experimental group only. Perspective: This study demonstrates that the mere intention to perform a painful movement prior to the actual painful movement itself can come to elicit conditioned fear responses. These results suggest that actual movement may not be necessary to elicit pain-related fear responses, maintaining chronic pain-related fear, avoidance, and disability. (C) 2013 by the American Pain Society

To optimise speed and accuracy of motor behaviour, we can prepare not only the type of movement to be made but also the time at which it will be executed. Previous cued reaction-time paradigms have shown that anticipating the moment in time at which this response will be made (“temporal orienting”) or selectively preparing the motor effector with which an imminent response will be made (motor intention or “motor orienting”) recruits similar regions of left intraparietal sulcus (IPS), raising the possibility that these two preparatory processes are inextricably co-activated. We used a factorial design to independently cue motor and temporal components of response preparation within the same experimental paradigm. By differentially cueing either ocular or manual response systems, rather than spatially lateralised responses within just one of these systems, potential spatial confounds were removed. We demonstrated that temporal and motor orienting were behaviourally dissociable, each capable of improving performance alone. Crucially, fMRI data revealed that temporal orienting activated the left IPS even if the motor effector that would be used to execute the response was unpredictable. Moreover, temporal orienting activated left IPS whether the target required a saccadic or manual response, and whether this response was left- or right-sided, thus confirming the ubiquity of left IPS activation for temporal orienting. Finally, a small region of left IPS was also activated by motor orienting for manual, though not saccadic, responses. Despite their functional independence therefore, temporal orienting and manual motor orienting nevertheless engage partially overlapping regions of left IPS, possibly reflecting their shared ontogenetic roots., Research Highlights ►Anticipating when and how to respond can be functionally and neurally dissociated. ►Temporal orienting (when) engages left IPS for both oculomotor and manual responses. ►Motor orienting (how) engages left IPS only for manual, not oculomotor, responses. ►Manual action circuits may be functionally recycled for anticipating when to respond.

Motion perception is a fundamental feature of the human visual system. As part of our daily life we often have to determine the direction of motion, even in ambiguous situations. These situations force us to rely on exogenous cues, such as other environmental motion, endogenous cues, such as our own actions, or previously learned experiences. In three experiments, we asked participants to report the direction of an ambiguous motion display, manipulating exogenous and endogenous sources of information. Specifically, in all three experments the exogenous information was represented by another motion cue while the endogenous cue was represented respectively by movement execution, movement planning, or a learned association about the motion display. Participants were consistently biased by stable motion cues in the environment when reporting the ambiguous target direction. In the absence of stable exogenous motion information, participants were biased by their motor movements and even the planning of such movements. However, when participants learned a specific association about the target motion, this acquired endogenous knowledge countered exogenous motion cues in biasing participants’ perception. Taken together, our findings demonstrate that we disambiguate ambiguous motion using different sources of exogenous and endogenous cues, and that learned associations may be particularly salient in countering the biasing effects of environmental cues.

In this thesis, I am interested in the functional organization of human cortical sensorimotor system. Somatotopy is the prominent structure of the functional organization in sensory and motor cortex. However, the structure of the functional organization in higher order motor area, such as IPL is little known. Therefore, in the first part, I study the functional organization of human sensory- and motor- related brain regions using fMRI, by guiding healthy subjects to perform simple repetitive movements of different body parts. Our results demonstrate that, 1) motor synergy is the neural basis represented in the motor cortex; and 2) somatotopic organization also exists in IPL but with different structure from that of sensorimotor cortex. Despite continuous criticism on DES, most of our primitive knowledge of the sensorimotor cortex comes from DES studies, and our fMRI result supports the findings of DES. In response to the ongoing debate on DES, in the second study, we review recent evidence to re-establish the confidence on DES. Accumulating evidence indicates that PPC is related to the emergence of motor intention. However, debate on the relation between motor intention and preparation never stops, some claims that motor intention is the byproduct from motor preparation, thus denying the volition of human motor control. Besides this complexity, we design a straightforward behavior experiment, including simple reaction task and Libet task, in order to compare the cognitive process of motor preparation and motor intention. Our result shows that RT from internal motor intention to motor output is equal to the RT from external cue to motor output, thus rejecting the possibility that motor preparation starts in advance of motor intention and doesn't support that motor intention arises from the process of motor intention, Ce travail s'intéresse à l'organisation fonctionnelle du système sensorimoteur. La somatotopie est une caractéristique essentielle de M1, mais l'organisation fonctionnelle des autres aires motrices (PM, SMA, et IPL) n'est pas encore clairement établie. Premièrement, nous avons exploré par IRMf l'organisation fonctionnelle sensorimotrice chez des sujets sains exécutant des mouvements simples. Nos résultats montrent que les représentations motrices sont organisées selon des synergies musculaires et qu'une organisation somatotopique, différente de celle de M1, existe dans l'IPL. Bien qu'elle fasse régulièrement l'objet de critiques, la DES est à la base de la plupart de nos connaissances sur le cortex moteur, que confirme les études en IRMf. Ainsi, en réponse au débat en cours, nous avons passé en revue les arguments récents confortant la confiance que nous pouvons accorder à la DES. Des études récentes concluent à l'implication du PPC dans l'intention motrice, mais le débat reste ouvert sur la relation entre intention et préparation motrices. Certains prétendent que l'intention serait le sous-produit de la préparation motrice, ne laissant aucune place à la volonté dans le contrôle moteur. Pour étudier cette question, nous avons mis en place une expérience comportementale, incluant des tâches de réaction simple et de Libet pour comparer les deux processus cognitifs. Nos résultats montrent que le temps de réaction entre intention interne et réaction motrice est égal à celui séparant commande externe et réaction motrice. Cela contredit donc l'affirmation selon laquelle la préparation motrice précèderait l'intention et donc que l'intention émergerait du processus d'intention motrice

When given a choice between actions that yield the same reward, we tend to prefer the one that requires the least effort. Recent studies have shown that humans are remarkably accurate at evaluating the effort of potential reaching actions and can predict the subtle energetic demand caused by the nonisotropic biomechanical properties of the arm. In the present study, we investigated the time course over which such information is computed and comes to influence decisions. Two independent approaches were used. First, subjects performed a reach decision task in which the time interval for deciding between two candidate reaching actions was varied from 200 to 800 ms. Second, we measured motor-evoked potential (MEPs) to single-pulse transcranial magnetic stimulation (TMS) over the primary motor cortex (M1) to probe the evolving decision at different times after stimulus presentation. Both studies yielded a consistent conclusion: that a prediction of the effort associated with candidate movements is computed very quickly and influences decisions within 200 ms after presentation of the candidate actions. Furthermore, whereas the MEPs measured 150 ms after stimulus presentation were well correlated with the choices that subjects ultimately made, later in the trial the MEP amplitudes were primarily related to the muscular requirements of the chosen movement. This suggests that corticospinal excitability (CSE) initially reflects a competition between candidate actions and later changes to reflect the processes of preparing to implement the winning action choice.

A crucial aspect in the organization of intentional actions is the chaining of single motor acts into well organized motor sequences. In a pioneering experiment was demonstrated that inferior parietal neurons code grasping motor acts differently depending on the final goal of the action where the motor acts were embedded (grasp-to-eat or grasp-to-place). Similar findings have been reported by neurophysiological investigations carried out on the ventral premotor cortex. These results suggest the possible presence of a neural mechanism capable of integrating contextual information used by the monkey to decide which action to perform. Functional results and anatomical connections between the inferior parietal and ventral premotor areas suggest that cortico-cortical projections of different cortical areas can play a crucial role in the selection of inferior parietal and ventral premotor neuronal pools for the organization of intentional actions. The ventrolateral prefrontal cortex appears one of the most plausible candidates to fulfill this function. In fact, several studies evidenced that the ventrolatelateral prefrontal cortex play a role in arranging motor chunks - such as pushing, pulling or turning – into over-trained motor sequences based on learned sensory instructions. The purpose of this study is to clarify, using a controlled behavioral paradigm, the possible contribution of ventrolateral prefrontal neurons to the integration of contextual information for the selection and generation of natural actions.

"Detecting the will to move in patients affected by tremor impairment is necessary for the development of. devices aiming at timely track and limit tremor. Event-related desynchronization (ERD) is a phenomenon leading. to the decrease of EEG power in the alpha band during movement preparation and imagery. The real-time tracking. of such events can give information on motor intention in tremor-affected patients. In this work we propose a. BNCI approach for the real-time detection of motor intention, based on ERD detection, and enhanced by. information on actual movement execution gained from gyroscopes."

In learning models of strategic game play, an agent constructs a valuation (action value) over possible future choices as a function of past actions and rewards. Choices are then stochastic functions of these action values. Our goal is to uncover a neural signal that correlates with the action value posited by behavioral learning models. We measured activity from neurons in the superior colliculus (SC), a midbrain region involved in planning saccadic eye movements, in monkeys while they performed two saccade tasks. In the strategic task, monkeys competed against a computer in a saccade version of the mixed-strategy game “matching-pennies”. In the instructed task, stochastic saccades were elicited through explicit instruction rather than free choices. In both tasks, neuronal activity and behavior were shaped by past actions and rewards with more recent events exerting a larger influence. Further, SC activity predicted upcoming choices during the strategic task and upcoming reaction times during the instructed task. Finally, we found that neuronal activity in both tasks correlated with an established learning model, the Experience Weighted Attraction model of action valuation (Ho, Camerer, and Chong, 2007). Collectively, our results provide evidence that action values hypothesized by learning models are represented in the motor planning regions of the brain in a manner that could be used to select strategic actions.

Although it is well established that parietal cortex is important in processing sensorimotor transformations, less is known about the neuronal dynamics of this process in humans. Using magnetoencephalography, we investigated the dynamics of parietal oscillatory activity during saccade planning in terms of sensory and motor goal processing. In the experiments, a peripheral stimulus was flashed in either the left or right hemifield, followed by a 1.5 s delay period, after which the subject executed a saccade toward (prosaccade) or away from (antisaccade) the stimulus. In response to stimulus presentation, we observed an initial increase in gamma-band power (40–120 Hz) in a region in the posterior parietal cortex contralateral to the direction of the stimulus. This lateralized power enhancement, which was sustained in a more narrow frequency band (85–105 Hz) during the delay period of prosaccades, mapped to the hemisphere contralateral to the direction of the saccade goal during the delay period of antisaccades. These results suggest that neuronal gamma-band synchronization in parietal cortex represents the planned direction of the saccade, not the memorized stimulus location. In the lower-frequency bands, we observed sustained contralateral alpha (7–13 Hz) power suppression after stimulus presentation in parieto-occipital regions. The dynamics of the alpha band was strongly related to the processing of the stimulus and showed only modest selectivity for the goal of the saccade. We conclude that parietal gamma-band synchronization reflects a mechanism to encode the motor goals in the visuomotor processing for saccades.

Experiments in monkeys demonstrated that many parietal and premotor neurons coding a specific motor act (e.g., grasping) show a markedly different activation when this act is part of actions that have different goals (e.g., grasping for eating vs. grasping for placing). Many of these “action-constrained” neurons have mirror properties firing selectively to the observation of the initial motor act of the actions to which they belong motorically. By activating a specific action chain from its very outset, this mechanism allows the observers to have an internal copy of the whole action before its execution, thus enabling them to understand directly the agent's intention. Using electromyographic recordings, we show that a similar chained organization exists in typically developing children, whereas it is impaired in children with autism. We propose that, as a consequence of this functional impairment, high-functioning autistic children may understand the intentions of others cognitively but lack the mechanism for understanding them experientially.

In this paper we present a method for automatic detection of motor intention from in vivo neuronal recordings in monkeys. The analysis relies on a data base of spike trains collected in a series of experiments aiming to study the hand-eye coordination mechanisms in primates. The neural activity is recorded using a multi-electrode system that can monitor up to fourteen neurons at time. In this work we analyze the possibility to “read” the motor intention from the set of simultaneously recorded spike trains, by combining the information from all the available recordings. We show that the information of interest can be successfully extracted from the data, under some constraints. First, we show the analysis of spike trains, segmented according to the behavioral epochs defined by the experiments protocol, and give the discussion of the proposed method performance in extracting the information of interest, i.e. the presence/absence of motor intention. Also, we consider a less ’controlled’ analysis of entire spike trains, without segmenting, where the relevant information is more mixed with the side-effect processes, and accordingly, more difficult to recognize.

International audience; Recent advances in the cognitive neuroscience of action have considerably enlarged our understanding of human motor cognition. In particular, the activity of the mirror system, first discovered in the brain of non-human primates, provides an observer with the understanding of a perceived action by means of the motor simulation of the agent's observed movements. This discovery has raised the prospects of a motor theory of social cognition. In humans, social cognition includes the ability to mindread, and many motor theorists of social cognition try to bridge the gap between motor cognition and mindreading by endorsing a simulation account of mindreading. Here, we question the motor theory of social cognition and give reasons for our skepticism.

In everyday life, we constantly act and interact with objects and with others’ people through our body. To properly perform actions, the representations of the dimension of body-parts (metric body representation, BR) and of the space surrounding the body (peripersonal space, PPS) need to be constantly updated. Previous evidence has shown that BR and PPS representation are highly flexible, being modulated by sensorimotor experiences, such as the active use of tools to reach objects in the far space. In this study, we investigate whether the observation of another person using a tool to interact with objects located in the far space is sufficient to influence the plasticity of BR and PPS representation in a similar way to active tool-use. With this aim, two groups of young healthy participants were asked to perform 20 min trainings based on the active use of a tool to retrieve far cubes (active tool-use) and on the first-person observation of an experimenter doing the same tool-use training (observational tool-use). Behavioural tasks adapted from literature were used to evaluate the effects of the active and observational tool-use on BR (body-landmarks localization task-group 1), and PPS (audio-tactile interaction task – group 2). Results show that after active tool-use, participants perceived the length of their arm as longer than at baseline, while no significant differences appear after observation. Similarly, significant modifications in PPS representation, with comparable multisensory facilitation on tactile responses due to near and far sounds, were seen only after active tool-use, while this did not occur after observation. Together these results suggest that a mere observational training could not be sufficient to significantly modulate BR or PPS. The dissociation found in the active and observational tool-use points out differences between action execution and action observation, by suggesting a fundamental role of the motor planning, the motor intention, and the related sensorimotor feedback in driving BR and PPS plasticity.

The complexity of processes occurring in the brain is an intriguing issue not just for scientists and medical doctors, but the humanity in general. The cortex ability to perceive and analyze an enormous amount of information in an instance of time, the parallelism and computational efficiency are among the questions that attract attention. Even a simple, everyday gesture, for example, reaching for a cup of coffee, evokes a flow of signals in the brain. It goes from the primary visual region, that locates the cup on the table, to the primary motor region that sends the precise coordinates to the hand, and the instruction what to do next. The sequence of signal transmission and transformation continues through several regions, sensory, associative and motor ones. In this study, we will focus on the posterior parietal cortex, the region involved in the transformation of visual inputs into the preliminary motor plans. The years of experimental work revealed mechanisms for integration of multimodal signals, coordinate transformations, information representation in multiple coordinate frames, and many other. Still, a single encompassing theory about movement generation in the parietal cortex does not exist, and is a matter of debate. This study contributes to the analysis of motor intention in the 7a parietal region. The motor intention, a high-level cognitive signal, is defined as the preliminary plan for making a movement. From the engineering point of view, encoding of motor parameters in the neural activity is extensively studied within the framework of brain-computer interfaces. The motivation behind these studies is the development of neural prosthesis for the paralyzed persons. The direct cortical prosthesis can significantly improve the lives of paralyzed people, who have lost every other contact with the outside world. Also, this framework opens the possibilities for monitoring the neural processes during the execution of natural movements, and studying the mechanisms behind it. In this work, a method for identification of motor intention from the standard recordings of neural activity, the spike trains, is developed. The data of interest was collected in a series of behavioral experiments involving reaching or saccadic eye movements. The presence and absence of motor intention was monitored in various phases of motion execution, and for different types of movements. All the recordings obtained simultaneously are combined in the same decoding session. Therefore, the analysis is done using the activity of small population of cells (typically 8 to 12 cells). We aim to study the motor intention in a general context which requires using activity of multiple cells. The population size is determined by the experimental procedure. Throughout this study we assume that the motor intention can be red from the spike rates, the assumption supported by the neurophysiological studies. Therefore, all the simultaneously collected spike trains are converted into vectors of spike rates. The results of this study show that motor intention can be decoded from the spike rates. A machine-learning based algorithm is developed to analyze the presence or absence of motor intention in the obtained spike rate vectors. This algorithm, based on standard support vector machines, can distinguish between the segments of recordings that encode motor intention, from those that do not encode it. The goal of the study was to examine the precision of motor intention identification, when the activity of a randomly selected set of cells is analyzed using on such algorithm. Additionally, several relevant parameters were tested. The algorithm precision during different phases of movement execution is tested. Also, the influence of the population size and of the procedure for spike rates computation is examined. The obtained results demonstrated that the motor intention can be extracted from the neural signals with the precision of around 70% for a randomly selected set of cells. For the best groups of cells, this precision was 82%. The motor intention identification was particularly precise during the intervals of preparation and realization of saccadic eye movements. This is in accordance with the known functions of the 7a region, where the majority of cells respond to the eye movements. The algorithm precision is determined by the considered population size. For the bigger population the precision increases. Still, this conclusion holds only on average, since adding one or a couple of randomly selected cells does not have to change the result. Randomly selected cells do not necessary carry the information of interest. The influence of each of the cells, present in one set, is tested in this context. The obtained results indicate redundant coding of motor intention in the parietal cortex. Many cells carry the same information, and some of them can be removed from the set without changing the algorithm precision. Still, removing all of them degrades the result. Finally, the influence of the window size, used to compute spike rates in some of the tests is studied. In general, the precision improves when using bigger windows, the result that is consistent with the literature. Introducing the window for computing spike rates enables automatic identification of motor intention, the method suitable for the brain-computer interface applications. Finally, the analysis of the experimental data is complemented with the study of an appropriately designed model. Modeling the biological processes, in order to reveal additional functionality and test some parameters not accessible through the data, is a widely accepted approach. Still, the development of a model, sufficiently simple for implementation on the standard hardware, sufficiently tractable in the simulations, yet informative enough to capture the main processes of interest, is not straightforward. Our motivation for accepting this approach was to test several parameters that imposed themselves as important in the data analysis step. Due to the nature of the problem itself, the test on an approximative model was the only feasible tactic. The influence of the population size and the window size was assessed in this study. This, additionally, demonstrated the algorithm precision scaling as a function of the number of cells.