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Terrestrial locomotion requires coordinated bilateral activation of limb muscles, with left–right alternation in walking or running, and synchronous activation in hopping or skipping. The neural mechanisms involved in interlimb coordination at birth are well known in different mammalian species, but less so in humans. Here, 46 neonates (of either sex) performed bilateral and unilateral stepping with one leg blocked in different positions. By recording EMG activities of lower-limb muscles, we observed episodes of left–right alternating or synchronous coordination. In most cases, the frequency of EMG oscillations during sequences of consecutive steps was approximately similar between the two sides, but in some cases it was considerably different, with episodes of 2:1 interlimb coordination and episodes of activity deletions on the blocked side. Hip position of the blocked limb significantly affected ipsilateral, but not contralateral, muscle activities. Thus, hip extension backward engaged hip flexor muscle, and hip flexion engaged hip extensors. Moreover, the sudden release of the blocked limb in the posterior position elicited the immediate initiation of the swing phase of the limb, with hip flexion and a burst of an ankle flexor muscle. Extensor muscles showed load responses at midstance. The variable interlimb coordination and its incomplete sensory modulation suggest that the neonatal locomotor networks do not operate in the same manner as in mature locomotion, also because of the limited cortical control at birth. These neonatal mechanisms share many properties with spinal mammalian preparations (i.e., independent pattern generators for each limb, and for flexor and extensor muscles, load, and hip position feedback).

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Recent advances in the performance and evaluation of walking in exoskeletons use various assessments based on kinematic/kinetic measurements. While such variables provide general characteristics of gait performance, only limited conclusions can be made about the neural control strategies. Moreover, some kinematic or kinetic parameters are a consequence of the control implemented on the exoskeleton. Therefore, standard indicators based on kinematic variables have limitations and need to be complemented by performance measures of muscle coordination and control strategy. Knowledge about what happens at the spinal cord output level might also be critical for rehabilitation since an abnormal spatiotemporal integration of activity in specific spinal segments may result in a risk for abnormalities in gait recovery. Here we present the PEPATO software, which is a benchmarking solution to assess changes in the spinal locomotor output during walking in the exoskeleton with respect to reference data on normal walking. In particular, functional and structural changes at the spinal cord level can be mapped into muscle synergies and spinal maps of motoneuron activity. A user-friendly software interface guides the user through several data processing steps leading to a set of performance indicators as output. We present an example of the usage of this software for evaluating walking in an unloading exoskeleton that allows a person to step in simulated reduced (the Moon’s) gravity. By analyzing the EMG activity from lower limb muscles, the algorithms detected several performance indicators demonstrating differential adaptation (shifts in the center of activity, prolonged activation) of specific muscle activation modules and spinal motor pools and increased coactivation of lumbar and sacral segments. The software is integrated at EUROBENCH facilities to benchmark the performance of walking in the exoskeleton from the point of view of changes in the spinal locomotor output.

When does modular control of locomotion emerge during human development? One view is that modularity is not innate, being learnt over several months of experience. Alternatively, the basic motor modules are present at birth, but are subsequently reconfigured due to changing brain-body-environment interactions. One problem in identifying modular structures in stepping infants is the presence of noise. Here, using both simulated and experimental muscle activity data from stepping neonates, infants, preschoolers, and adults, we dissect the influence of noise, and identify modular structures in all individuals, including neonates. Complexity of modularity increases from the neonatal stage to adulthood at multiple levels of the motor infrastructure, from the intrinsic rhythmicity measured at the level of individual muscles activities, to the level of muscle synergies and of bilateral intermuscular network connectivity. Low complexity and high variability of neuromuscular signals attest neonatal immaturity, but they also involve potential benefits for learning locomotor tasks.

In older adults, two different modes of step-to-step transition have been observed: an anticipated mode when the redirection of the centre of mass of the body (COM) begins before double stance and another when the transition begins during double stance. However, the impact of transition mode on gait kinetics and kinematics has not been investigated. Age and step-to-step-transition-related differences in intersegmental coordination and in the COM trajectory during walking were identified. Fifteen young (24.1 ± 0.7 y.o.) and thirty-six older adults (74.5 ± 5.0 y.o.) walked on a treadmill at 1.11 m s−1 and 1.67 m s−1. Lower-limb motion and ground reaction force were recorded. The COM dynamics were evaluated by measuring the pendulum-like exchange of the COM energies. While all young adults and 21 of the older adults used an anticipated transition, 15 older adults presented a non-anticipated transition. Previously documented changes of intersegmental coordination with age were accentuated in older adults with non-anticipated transition (p < 0.001). Moreover, older adults with non-anticipated transition had a smaller pendulum-like energy exchange than older adults with anticipated transition (p = 0.03). The timing of COM redirection is linked to kinematic and mechanic modification of gait and could potentially be used as a quantitative assessment of age-related decline in gait.

A hallmark of human reaching movements is that they are appropriately tuned to the task goal and to the environmental context. This was demonstrated by the way humans flexibly respond to mechanical and visual perturbations that happen during movement. Furthermore, it was previously showed that the properties of goal-directed control can change within a movement, following abrupt changes in the goal structure. Such online adjustment was characterized by a modulation of feedback gains following switches in target shape. However, it remains unknown whether the underlying mechanism merely switches between prespecified policies, or whether it results from continuous and potentially dynamic adjustments. Here, we address this question by investigating participants’ feedback control strategies in presence of various changes in target width during reaching. More specifically, we studied whether the feedback responses to mechanical perturbations were sensitive to the rate of change in target width, which would be inconsistent with the hypothesis of a single, discrete switch. Based on movement kinematics and surface EMG data, we observed a modulation of feedback response clearly dependent on dynamical changes in target width. Together, our results demonstrate a continuous and online transformation of task-related parameters into suitable control policies.

Central sensitization refers to the increased responsiveness of nociceptive neurons in the central nervous system after repeated or sustained peripheral nociceptor activation and is hypothesized to play a key role in the development of chronic pain. A hallmark of central sensitization is an increased sensitivity to noxious mechanical stimuli extending beyond the injured location and referred to as secondary hyperalgesia. Attention could influence the development of central sensitization through its ability to modulate the transmission and processing of nociceptive inputs. Thus, modulating attention could constitute a promising target to prevent central sensitization and the development of chronic pain. It was recently shown that the experimental induction of central sensitization at both forearms of healthy volunteers, using bilateral high-frequency electrocutaneous stimulation (HFS), can be modulated by encouraging participants to selectively focus their attention to one arm, to the detriment of the other arm, resulting in a greater secondary hyperalgesia on the attended arm as compared to the unattended one. Given the potential value of the question being addressed, we conducted a preregistered replication study in a larger independent sample to assess the robustness of the effect, namely the modulatory role of spatial attention on the induction of central sensitization. Using a double-blind within-subject design, we investigated the impact of selective spatial attention on the development of secondary hyperalgesia. Sixty-seven healthy volunteers performed a task that required focusing attention towards one forearm to discriminate innocuous vibrotactile stimuli while HFS was applied on both forearms simultaneously. Our results showed a significant increase in mechanical sensitivity directly and 20 minutes after HFS. However, in contrast to the previous study, we did not find a significant difference in the development of secondary hyperalgesia between the attended

Judging by the breadth of our motor repertoire during daily activities, it is clear that learning different tasks is a hallmark of the human motor system. However, for reaching adaptation to different force fields, the conditions under which this is possible in laboratory settings have remained a challenging question. Previous work has shown that independent movement representations or goals enabled dual adaptation. Considering the importance of force feedback during limb control, here we hypothesised that independent cues delivered by means of background loads could support simultaneous adaptation to various velocity-dependent force fields, for identical kinematic plan and movement goal. We demonstrate in a series of experiments that indeed healthy adults can adapt to opposite force fields, independently of the direction of the background force cue. However, when the cue and force field were in the same direction but differed by heir magnitude, the formation of different motor representations was still observed but the associated mechanism was subject to increased interference. Finally, we highlight that this paradigm allows dissociating trial-by-trial adaptation from online feedback adaptation, as these two mechanisms are associated with different time scales that can be identified reliably and reproduced in a computational model.

BACKGROUND: In Parkinson's disease (PD), neurophysiological abnormalities within the primary motor cortex (M1) have been shown to contribute to bradykinesia, but exact modalities are still uncertain. We propose that such motor slowness could involve alterations in mechanisms underlying movement preparation, especially the suppression of corticospinal excitability-called "preparatory suppression"-which is considered to propel movement execution by increasing motor neural gain in healthy individuals. METHODS: On two consecutive days, 29 PD patients (on and off medication) and 29 matched healthy controls (HCs) underwent transcranial magnetic stimulation over M1, eliciting motor-evoked potentials (MEPs) in targeted hand muscles, while they were either at rest or preparing a left- or right-hand response in an instructed-delay choice reaction time task. Preparatory suppression was assessed by expressing MEP amplitudes during movement preparation relative to rest. RESULTS: Contrary to HCs, PD patients showed a lack of preparatory suppression when the side of the responding hand was analyzed, especially when the latter was the most affected one. This deficit, which did not depend on dopamine medication, increased with disease duration and also tended to correlate with motor impairment, as measured by the Movement Disorder Society Unified Parkinson's Disease Rating Scale, Part III (both total and bradykinesia scores). CONCLUSIONS: Our novel findings indicate that preparatory suppression fades in PD, in parallel with worsening motor symptoms, including bradykinesia. Such results suggest that an alteration in this marker of intact movement preparation could indeed cause motor slowness and support its use in future studies on the relation between M1 alterations and motor impairment in PD. © 2022 International Parkinson and Movement Disorder Society.

Reinforcement feedback can improve motor learning, but the underlying brain mechanisms remain unexplored. Especially, the causal contribution of specific patterns of oscillatory activity within the human striatum is unknown. To address this question, we exploited an innovative, non-invasive deep brain stimulation technique called transcranial temporal interference stimulation (tTIS) during reinforcement motor learning with concurrent neuroimaging, in a randomised, sham-controlled, double-blind study. Striatal tTIS applied at 80Hz, but not at 20Hz, abolished the benefits of reinforcement on motor learning. This effect was related to a selective modulation of neural activity within the striatum. Moreover, 80Hz, but not 20Hz, tTIS increased the neuromodulatory influence of the striatum on frontal areas involved in reinforcement motor learning. These results show for the first time that tTIS can non-invasively and selectively modulate a striatal mechanism involved in reinforcement learning, opening new horizons for the study of causal relationships between deep brain structures and human behaviour.

Psychophysical, motor control, and modeling studies have revealed that sensorimotor reference frame transformations (RFTs) add variability to transformed signals. For perceptual decision-making, this phenomenon could decrease the fidelity of a decision signal's representation or alternatively improve its processing through stochastic facilitation. We investigated these two hypotheses under various sensorimotor RFT constraints. Participants performed a time-limited, forced-choice motion discrimination task under eight combinations of head roll and/or stimulus rotation while responding either with a saccade or button press. This paradigm, together with the use of a decision model, allowed us to parameterize and correlate perceptual decision behavior with eye-, head-, and shoulder-centered sensory and motor reference frames. Misalignments between sensory and motor reference frames produced systematic changes in reaction time and response accuracy. For some conditions, these changes were consistent with a degradation of motion evidence commensurate with a decrease in stimulus strength in our model framework. Differences in participant performance were explained by a continuum of eye-head-shoulder representations of accumulated motion evidence, with an eye-centered bias during saccades and a shoulder-centered bias during button presses. In addition, we observed evidence for stochastic facilitation during head-rolled conditions (i.e., head roll resulted in faster, more accurate decisions in oblique motion for a given stimulus-response misalignment). We show that perceptual decision-making and stochastic RFTs are inseparable within the present context. We show that by simply rolling one's head, perceptual decision-making is altered in a way that is predicted by stochastic RFTs.

Dexterous manipulation of objects heavily relies on the feedback provided by the tactile afferents innervating the fingertips. Previous studies have suggested that humans might take advantage of partial slip, localized loss of grip between the skin and the object, to gauge the stability of a contact and react appropriately when it is compromised, that is, when slippage is about to happen. To test this hypothesis, we asked participants to perform point-to-point movements using a manipulandum. Through optical imaging, the device monitored partial slip at the contact interface, and at the same time, the forces exerted by the fingers. The level of friction of the contact material was changed every five trials. We found that the level of grip force was systematically adjusted to the level of friction, and thus partial slip was limited to an amount similar across friction conditions. We suggest that partial slip is a key signal for dexterous manipulation and that the grip force is regulated to continuously maintain an upper bound on partial slip across friction conditions.

Motor Imagery is a subject of longstanding scientific interest. However, critical details of motor imagery protocols are not always reported in full, hampering direct replication and translation of this work. The present review provides a quantitative assessment of the prevalence of under-reporting in the recent motor imagery literature. Publications from the years 2018–2020 were examined, with 695 meeting the inclusion criteria for further examination. Of these studies, 64% (445/695) did not provide information about the modality of motor imagery (i.e., kinesthetic, visual, or a mixture of both) used in the study. When visual or mixed imagery was specified, the details of the visual perspective to be used (i.e., first person, third person, or combinations of both) were not reported in 24% (25/103) of studies. Further analysis indicated that studies using questionnaires to assess motor imagery reported more information than those that did not. We conclude that studies using motor imagery consistently under-report key details of their protocols, which poses a significant problem for understanding, replicating, and translating motor imagery effects.

Recent work indicates that healthy younger adults can prepare accurate responses faster than their voluntary reaction times would suggest, leaving a seemingly unnecessary delay of 80–100 ms before responding. Here, we examined how the preparation of movements, initiation of movements, and the delay between them are affected by aging. Participants made planar reaching movements in two conditions. The “free reaction time” condition assessed the voluntary reaction times with which participants responded to the appearance of a stimulus. The “forced reaction time” condition assessed the minimum time actually needed to prepare accurate movements by controlling the time allowed for movement preparation. The time taken to both initiate movements in the free reaction time and to prepare movements in the forced response condition increased with age. Notably, the time required to prepare accurate movements was significantly shorter than participants’ self-selected initiation times; however,the delay between movement preparation and initiation remained consistent across the lifespan (~90 ms). These results indicate that the slower reaction times of healthy older adults are not due to an increased hesitancy to respond, but can instead be attributed to changes in their ability to process stimuli and prepare movements accordingly, consistent with age-related changes in brain structure and function.

The management of nonspecific chronic low back pain (NCLBP) is complex because of its multifactorial origin. To investigate NCLBP care by evaluating patients' condition and therapeutic management of health practitioners. A cross-sectional survey was carried out among 92 patients with NCLBP, 30 medical practitioners (MP) and 20 physiotherapists (PT) from four public health institutions in Burkina Faso. Patients completed the Visual Analogue Scale, Roland Morris Disability Questionnaire and Fear-Avoidance Beliefs Questionnaire. Practitioners were asked about therapy and continuing professional training. Pain was moderate to intense for 80% of participants with NCLBP. They were functionally affected and showed fear-avoidance beliefs related to physical and work activities. The majority (97%) of medical practitioners prescribed analgesics and 53% prescribed nonsteroidal anti-inflammatory drugs (NSAIDs). Physiotherapy was the most frequently recommended nonpharmacological treatment. Forty-three per cent of medical practitioners referred to physiotherapy; 20% never did. Physiotherapists practised both passive treatments, such as massage (50%), electrotherapy (55%) and thermotherapy (50%), as well as active treatments, such as general exercises (55%), specific exercises (70%), functional revalidation (50%) and back school (40%). Having had recent continuing professional training and assessing risk factors for chronicity were associated with MPs' and PTs' therapeutic choices. Participants with NCLBP showed fear-avoidance beliefs, correlated with their algo-functional status. Prescribing habits of MPs were drug-based. Treatments by PTs were passive and active. Continuing professional training of healthcare practitioners and assessment of risk factors had a positive impact on therapeutic choices. Our study is an invitation to the health care system to improve the relationship between a patient's NCLBP and therapeutic choices.

When listening to musical rhythm, humans perceive and spontaneously move to a periodic pulse-like meter. It has been proposed that internal representation of a meter is induced by simple rhythms where sounds are arranged in a way that emphasizes a periodic pulse, compared to complex rhythms with a less regular arrangement of sounds. Previous neuroimaging studies revealed a functional sensory-motor network preferentially activated by simple rhythms, suggesting its special role in meter processing. However, meter processing might not solely depend on the complexity of the rhythmic input, but also on context. To test this, we used functional MRI to characterize brain activity of participants as they listened to stimuli where simple and complex rhythmic sequences were presented either continuously or separated by silent gaps (i.e., block design). To achieve high sensitivity, we analyzed the data using a model-free frequency-tagging approach. The whole-brain conventional analysis of the block design revealed activity in the premotor and supplementary motor areas similar for both simple and complex rhythms. Simple rhythms evoked similar activity to complex rhythms as shown by the model-free analysis of both continuous and block designs. This lack of difference was not due to limited sensitivity of the model-free approach, as (i) the same approach yielded powerful results in a control experiment contrasting low-level acoustic features (pitch), (ii) this null result was also confirmed by a conventional analysis. Importantly, these results also aligned well with a behavioral experiment where participants showed uniform response while tapping their finger along with the same simple and complex rhythms. Together, these findings validate the frequency-tagging approach to analyze auditory responses captured with fMRI. Our results also challenge the view that complex rhythms fail to induce internal representation of meter.

hMT+/V5 is a region in the middle occipito-temporal cortex that responds preferentially to visual motion. In case of early visual deprivation, hMT+/V5 enhances its response to moving sounds. Whether hMT+/V5 contains information about motion directions and whether the functional enhancement observed in the blind also involves sound location, remains unsolved. Moreover, the impact of this crossmodal reorganization on the regions typically supporting auditory motion processing, like the human Planum Temporale (hPT), remains equivocal. We used a combined functional and diffusion MRI approach to study the impact of early blindness on the networks supporting spatial hearing. Whole-brain univariate analysis revealed that the anterior portion of hMT+/V5 responded to moving sounds in sighted and blind people, while the posterior portion was selective to moving sounds only in blind people. Multivariate decoding analysis revealed that the presence of motion directions and sound positions information was higher in hMT+/V5 and lower in hPT in the blind group. While both groups showed axis-of-motion organization in hMT+/V5 and hPT, this organization was reduced in the hPT of blind people. Diffusion MRI revealed that the strength of hMT+/V5 – hPT connectivity did not differ between groups, whereas the microstructure of the connections was altered by blindness. Our results suggest that the axis-of-motion organization of hMT+/V5 does not depend on visual experience, but that blindness alters the response properties of occipito-temporal networks supporting spatial hearing in the sighted.

Executive functions are higher-order mental processes that support goal-directed behavior. Among these processes, Inhibition, Updating, and Shifting have been considered core executive domains. In this meta-analysis, we comprehensively investigate the neural networks of these executive domains and we synthesize for the first time the neural convergences and divergences among the most frequently used executive paradigms within those domains. A systematic search yielded 1055 published neuroimaging studies (including 26,191 participants in total). Our study revealed that a fronto-parietal network was shared by the three main domains. Furthermore, we executed conjunction analyses among the paradigms of the same domain to extract the core distinctive components of the main executive domains. This approach showed that Inhibition and Shifting are characterized by a strongly lateralized neural activation in the right and left hemisphere, respectively. In addition, both networks overlapped with the Updating network but not with each other. Remarkably, our study detected heterogeneity among the paradigms from the same domain. More specifically, analysis of Inhibition tasks revealed differing activations for Response Inhibition compared to Interference Control paradigms, suggesting that Inhibition encompasses relatively heterogeneous sub-functions. Shifting analyses revealed a bilateral overlap of the Wisconsin Card Sorting Task with the Updating network, but this pattern was absent for Rule Switching and Dual Task paradigms. Moreover, our Updating meta-analyses revealed the neural signatures associated with the specific modules of the Working Memory model from Baddeley and Hitch. To our knowledge, this is the most comprehensive meta-analysis of executive functions to date. Its paradigm-driven analyses provide a unique contribution to a better understanding of the neural convergences and divergences among executive processes that are relevant for clinical applications, such as

hMT+/V5 is a region in the middle occipito-temporal cortex that responds preferentially to visual motion in sighted people. In case of early visual deprivation, hMT+/V5 enhances its response to moving sounds. Whether hMT+/V5 contains information about motion directions and whether the functional enhancement observed in the blind is motion specific, or also involves sound source location, remains unsolved. Moreover, the impact of this crossmodal reorganization of hMT+/V5 on the regions typically supporting auditory motion processing, like the human Planum Temporale (hPT), remains equivocal. We used a combined functional and diffusion MRI approach and individual in-ear recordings to study the impact of early blindness on the brain networks supporting spatial hearing, in male and female humans. Whole-brain univariate analysis revealed that the anterior portion of hMT+/V5 responded to moving sounds in sighted and blind people, while the posterior portion was selective to moving sounds only in blind participants. Multivariate decoding analysis revealed that the presence of motion directions and sound positions information was higher in hMT+/V5 and lower in hPT in the blind group. While both groups showed axis-of-motion organization in hMT+/V5 and hPT, this organization was reduced in the hPT of blind people. Diffusion MRI revealed that the strength of hMT+/V5 – hPT connectivity did not differ between groups, whereas the microstructure of the connections was altered by blindness. Our results suggest that the axis-of-motion organization of hMT+/V5 does not depend on visual experience, but that blindness alters the response properties of occipito-temporal networks supporting spatial hearing in the sighted.

The combination of transcranial magnetic stimulation (TMS) and electroencephalography (EEG) represents an increasingly popular tool to non-invasively probe cortical excitability in humans. TMS-evoked brain potentials (TEPs) are composed of successive components reflecting the propagation of activity from the site of stimulation, thereby providing information on the state of brain networks. However, TMS also generates peripherally evoked sensory activity which contributes to TEP waveforms and hinders their interpretation.In the present study, we examined whether topographic analysis of TEPs elicited by stimulation of two distinct cortical targets can disentangle confounding signals from the genuine TMS-evoked cortical response. In 20 healthy subjects, TEPs were evoked by stimulation of the left primary motor cortex (M1) and the left angular gyrus (AG). Topographic dissimilarity analysis and microstate analysis were used to identify target-specific TEP components. Furthermore, we explored the contribution of cortico-spinal activation by comparing TEPs elicited by stimulation below and above the threshold to evoke motor responses.We observed topographic dissimilarity between M1 and AG TEPs until approximately 80 ms post-stimulus and identified early TEP components that likely reflect specific TMS-evoked activity. Later components peaking at 100 and 180 ms were similar in both datasets and attributed to sensory-evoked activity. Analysis of sub- and supra-threshold M1 TEPs revealed a component at 17 ms that possibly reflects the cortico-spinal output of the stimulated area. Moreover, supra-threshold M1 activation influenced the topography of almost all later components. Together, our results demonstrate the utility of topographic analysis for the evaluation and interpretation of TMS-evoked EEG responses.

Background The angular gyrus (AG) is involved in numerous cognitive processes, and structural alterations of the AG are reported in many neuropsychiatric diseases. Because abnormal excitability or connectivity of such cortical hubs could precede structural alterations and clinical symptoms, approaches assessing their functional state are needed. The combination of transcranial magnetic stimulation (TMS) with electroencephalography (EEG) can provide such functional readouts by probing how the cortex responds to direct stimulation. Objective To characterize TMS-evoked potentials (TEPs) elicited by AG stimulation, determine optimal stimulation parameters, and identify TEP biomarkers of AG function. Methods In 19 subjects, we recorded AG-TEPs using four TMS orientations and three intensities and compared their spatiotemporal features using topographic dissimilarity and microstate analyses. We also explored the link between AG-TEPs and TMS-evoked muscle activity. Results Early AG TEP components of interest (P25, N45) showed topographic variability dependent on stimulation parameters. The P25 topography was sensitive to TMS orientation and less to intensity, whereas the N45 topography was highly dependent on both coil orientation and intensity. However, TMS-evoked muscular activity was also dependent on coil orientation and the dominant topography of N45 was strongly related to this muscular activity, indicating that the component may reflect somatosensory-evoked responses to this peripheral activation. Conclusions The earliest AG TEP component P25 likely reflects neural processes triggered by direct AG activation and could provide an index of local excitability. N45 must be interpreted with caution as it may mostly reflect peripherally evoked activity. Coil orientation can be optimized to minimize muscular contractions.

The ability of the brain to integrate motion information originating from separate sensory modalities is fundamental to efficiently interact with our dynamic environment. The human occipito-temporal region hMT+/V5 is known to be highly specialized to process visual motion directions. In addition to its role in processing the dominant visual information, it was recently suggested that this region may also engage in crossmodal motion processing from the auditory modality. How multisensory information is represented in this region remains however poorly understood. To further investigate the multisensory nature of hMT+/V5, we characterized single-subject activity with ultra-high field (UHF) fMRI when participants processed horizontal and vertical motion stimuli delivered through vision, audition, or a combination of both modalities simultaneously. Our preliminary results confirmed that in addition to a robust selectivity for visual motion, portion of hMT+/V5 selectively responds to moving sounds. We are now further characterizing the brain activity in the cortical depths using UHF fMRI combined with vascular space occupancy (VASO) recording at high spatial resolution (.75mm isotropic). We hypothesize that hMT+/V5 might encode auditory and visual motion information in separate cortical layers, reflecting the feed-forward versus feed-back nature of how sensory information flows into those regions. This project will shed new lights on how crossmodal information is represented across the depth of the cortical layers of motion selective human brain areas.

The ability of the brain to integrate motion information originating from separate sensory modalities is fundamental to efficiently interact with our dynamic environment. The human occipito-temporal visual region hMT+/V5 and the auditory area Planum Temporale (PT) are known to be highly specialized to process visual and auditory motion directions, respectively. In addition to their role in processing the dominant sensory information, it was recently suggested that these regions may also engage in crossmodal motion processing. How multisensory information is represented in these regions remain however poorly understood. To further investigate the multisensory nature of hMT+/V5 and PT, we characterized single-subject activity with ultra-high field (UHF) fMRI (7T) when participants processed horizontal and vertical motion stimuli delivered through vision, audition, or a combination of both modalities simultaneously. Our preliminary results confirmed that in addition to a robust selectivity for visual motion, portion of hMT+/V5 selectively responds to moving sounds and a portion of PT responds to moving visual stimuli. We are now further characterizing the brain activity in the cortical depths using UHF fMRI combined with vascular space occupancy (VASO) recording at high spatial resolution (.75mm isotropic). We hypothesize that hMT+/V5 and PT might encode auditory and visual motion information in separate cortical layers, reflecting the feed-forward versus feed-back nature of how sensory information flows into those regions. This project will shed new lights on how crossmodal information is represented across the depth of the cortical layers of motion selective human brain areas.

Postpartum abdominal rehabilitation is a strong demand nowadays. However, there is no evidence-based protocol in physiotherapy. While some exercises like Curl-up are decried because of their potential negative effects on the pelvic floor, other (Hypopressive) are strongly encouraged while they have not been proven to be effective. Through the studies in this thesis, we observed that the Curl-up (to lift the trunk slowly until the tip of the scapula is just off) reduces the interrecti distance and strengthens all abdominal muscles without being deleterious to the pelvic floor. In addition, the Diaphragmatic aspiration (Hypopressive exercise) does not reduce the interrecti distance, strengthens specifically the transversus abdominis muscle and protects the pelvic floor. Therefore, we suggest to perform the two exercises. However, based to the inter-individual variations observed, we suggest to adjust the practice of exercises to each postpartum woman considering her specific needs., (MOTR - Sciences de la motricité) -- UCL, 2022

For most children, language acquisition is an early, effortless process considered to result from the interaction between neuroanatomical foundations and the language environment. Past research has emphasized the importance of the quality and quantity of early language exposure for the development of language skills. However, only a limited number of studies have attempted to explore the neural mechanisms underlying the relation between home language exposure and children's language skills. Combining a natural sleep MRI protocol and the Language ENvironment Analysis (LENA) technology in 12-to-24-month-old children, the present study aims at investigating how variations in early language exposure relates to structural neural connectivity in children with or without an elevated risk for oral language disorders. Two-day long naturalistic audio recordings were acquired as a measure of a child's language environment and development. Estimated counts per hour for conversational turns, adult words, and child vocalizations together with qualitative measures of caregivers' responsiveness were extracted as relevant markers for quantitative and qualitative early language exposure. Preliminary results investigating the relation between these ecological measures of a child's early language development and environment and white matter connectivity measured through fractional anisotropy will be presented.

Anticipatory actions require to keep track of elapsed time and inhibitory control. These cognitive functions could be impacted in Parkinson's disease (iPD). To test this hypothesis, a saccadic reaction time task was used where a visual warning stimulus (WS) predicted the occurrence of an imperative one (IS) appearing after a short delay. In the implicit condition, subjects were not informed about the duration of the delay, disfavoring anticipatory behavior but leaving inhibitory control unaltered. In the explicit condition, delay duration was cued. This should favor anticipatory behavior and perhaps alter inhibitory control. This hypothesis was tested in controls (N = 18) and age-matched iPD patients (N = 20; ON and OFF L-DOPA). We found that the latency distribution of saccades before the IS was bimodal. The 1st mode weakly depended on temporal information and was more prominent in iPD. Saccades in this mode were premature and could result of a lack of inhibition. The 2nd mode covaried with cued duration suggesting that these movements were genuine anticipatory saccades. The explicit condition increased the probability of anticipatory saccades before the IS in controls and iPDON but not iPDOFF patients. Furthermore, in iPD patients the probability of sequences of 1st mode premature responses increased. In conclusion, the triggering of a premature saccade or the initiation of a controlled anticipatory one could be conceptualized as the output of two independent stochastic processes. Altered time perception and increased motor impulsivity could alter the balance between these two processes in favor of the latter in iPD, particularly OFF L-Dopa.

Expected surprise, defined as the anticipation of uncertainty associated with the occurrence of a future event, plays a major role in gaze shifting and spatial attention. In the present study, we analyzed its impact on oculomotor behavior. We hypothesized that the occurrence of anticipatory saccades could decrease with increasing expected surprise and that its influence on visually-guided responses could be different given the presence of sensory information and perhaps competitive attentional effects. This hypothesis was tested in humans using a saccadic reaction time task in which a cue indicated the future stimulus position. In the 'no expected surprise' condition, the visual target could appear only at one previously cued location. In other conditions, more likely future positions were cued with increasing expected surprise. Anticipation was more frequent and pupil size was larger in the 'no expected surprise' condition compared with all other conditions, probably due to increased arousal. The latency of visually-guided saccades increased linearly with the logarithm of surprise (following Hick's law) but their maximum velocity repeated the arousal-related pattern. Therefore, expected surprise affects anticipatory and visually-guided responses differently. Moreover, these observations suggest a causal chain linking surprise, attention and saccades that could be disrupted in attentional or impulse control disorders.

Human tactile afferents provide essential feedback for grasp stability during dexterous object manipulation. Interacting forces between an object and the fingers induce slip events that are thought to provide information about grasp stability. To gain insight into this phenomenon, we made a transparent surface slip against a fixed fingerpad while monitoring skin deformation at the contact. Using microneurography, we simultaneously recorded the activity of single tactile afferents innervating the fingertips. This unique combination allowed us to describe how afferents respond to slip events and to relate their responses to surface deformations taking place inside their receptive fields. We found that all afferents were sensitive to slip events, but fast-adapting type I (FA-I) afferents in particular faithfully encoded compressive strain rates resulting from those slips. Given the high density of FA-I afferents in fingerpads, they are well suited to detect incipient slips and to provide essential information for the control of grip force during manipulation.

Humans and other animals are able to adjust their speed-accuracy tradeoff (SAT) at will depending on the urge to act, favoring either cautious or hasty decision policies in different contexts. An emerging view is that SAT regulation relies on influences exerting broad changes on the motor system, tuning its activity up globally when hastiness is at premium. The present study aimed to test this hypothesis. Fifty subjects performed a task involving choices between left and right index fingers, in which incorrect choices led either to a high or to a low penalty in two contexts, inciting them to emphasize either cautious or hasty policies. We applied transcranial magnetic stimulation on multiple motor representations, eliciting motor evoked potentials (MEP) in nine finger and leg muscles. MEP amplitudes allowed us to probe activity changes in the corresponding finger and leg representations, while subjects were deliberating about which index to choose. Our data indicate that hastiness entails a broad amplification of motor activity, though this amplification was limited to the chosen side. On top of this effect, we identified a local suppression of motor activity, surrounding the chosen index representation. Hence, a decision policy favoring speed over accuracy appears to rely on overlapping processes producing a broad (but not global) amplification and a surround suppression of motor activity. The latter effect may help increasing the signal-to-noise ratio of the chosen representation, as supported by single-trial correlation analyses indicating a stronger differentiation of activity changes in finger representations in the hasty context.

Humans perceive and spontaneously move to one or several levels of periodic pulses (a meter, for short) when listening to musical rhythm, even when the sensory input does not provide prominent periodic cues to their temporal location. Here, we review a multi-levelled framework to understanding how external rhythmic inputs are mapped onto internally represented metric pulses. This mapping is studied using an approach to quantify and directly compare representations of metric pulses in signals corresponding to sensory inputs, neural activity and behaviour (typically body movement). Based on this approach, recent empirical evidence can be drawn together into a conceptual framework that unpacks the phenomenon of meter into four levels. Each level highlights specific functional processes that critically enable and shape the mapping from sensory input to internal meter. We discuss the nature, constraints and neural substrates of these processes, starting with fundamental mechanisms investigated in macaque monkeys that enable basic forms of mapping between simple rhythmic stimuli and internally represented metric pulse. We propose that human evolution has gradually built a robust and flexible system upon these fundamental processes, allowing more complex levels of mapping to emerge in musical behaviours. This approach opens promising avenues to understand the many facets of rhythmic behaviours across individuals and species. This article is part of the theme issue 'Synchrony and rhythm interaction: from the brain to behavioural ecology'.

People have a natural and intrinsic ability to coordinate body movements with rhythms surrounding them, known as sensorimotor synchronisation. This can be observed in daily environments, when dancing or singing along with music, or spontaneously walking, talking or applauding in synchrony with one another. However, the neurophysiological mechanisms underlying accurately synchronised movement with selected rhythms in the environment remain unclear. Here we studied real and imagined sensorimotor synchronisation with interleaved auditory and visual rhythms using cortico-muscular coherence (CMC) to better understand the processes underlying the preparation and execution of synchronised movement. Electroencephalography (EEG), electromyography (EMG) from the finger flexors, and continuous force signals were recorded in 20 participants during tapping and imagined tapping with discrete stimulus sequences consisting of alternating auditory beeps and visual flashes. The results show that the synchronisation between cortical and muscular activity in the beta (14-38 Hz) frequency band becomes time-locked to the taps executed in synchrony with the visual and auditory stimuli. Dynamic modulation in CMC also occurred when participants imagined tapping with the visual stimuli, but with lower amplitude and a different temporal profile compared to real tapping. These results suggest that CMC does not only reflect changes related to the production of the synchronised movement, but also to its preparation, which appears heightened under higher attentional demands imposed when synchronising with the visual stimuli. These findings highlight a critical role of beta band neural oscillations in the cortical-muscular coupling underlying sensorimotor synchronisation.

The extent of high-level perceptual processing during sleep remains controversial. In wakefulness, perception of periodicities supports the emergence of high-order representations such as the pulse-like meter perceived while listening to music. Electroencephalography (EEG) frequency-tagged responses elicited at envelope frequencies of musical rhythms have been shown to provide a neural representation of rhythm processing. Specifically, responses at frequencies corresponding to the perceived meter are enhanced over responses at meter-unrelated frequencies. This selective enhancement must rely on higher-level perceptual processes, as it occurs even in irregular (i.e., syncopated) rhythms where meter frequencies are not prominent input features, thus ruling out acoustic confounds. We recorded EEG while presenting a regular (unsyncopated) and an irregular (syncopated) rhythm across sleep stages and wakefulness. Our results show that frequency-tagged responses at meter-related frequencies of the rhythms were selectively enhanced during wakefulness but attenuated across sleep states. Most importantly, this selective attenuation occurred even in response to the irregular rhythm, where meter-related frequencies were not prominent in the stimulus, thus suggesting that neural processes selectively enhancing meter-related frequencies during wakefulness are weakened during rapid eye movement (REM) and further suppressed in non-rapid eye movement (NREM) sleep. These results indicate preserved processing of low-level acoustic properties but limited higher-order processing of auditory rhythms during sleep.

Developmental dyslexia is a reading disorder that features difficulties in perceiving and tracking rhythmic regularities in auditory streams, such as speech and music. Studies on typical healthy participants have shown that power fluctuations of neural oscillations in beta band (15-25 Hz) reflect an essential mechanism for tracking rhythm or entrainment and relate to predictive timing and attentional processes. Here we investigated whether adults with dyslexia have atypical beta power fluctuation. The electroencephalographic activities of individuals with dyslexia (n = 13) and typical control participants (n = 13) were measured while they passively listened to an isochronous tone sequence (2 Hz presentation rate). The time-frequency neural activities generated from auditory cortices were analyzed. The phase of beta power fluctuation at the 2 Hz stimulus presentation rate differed and appeared opposite between individuals with dyslexia and controls. Atypical beta power fluctuation might reflect deficits in perceiving and tracking auditory rhythm in dyslexia. These findings extend our understanding of atypical neural activities for tracking rhythm in dyslexia and could inspire novel methods to objectively measure the benefits of training, and predict potential benefit of auditory rhythmic rehabilitation programs on an individual basis.

Auditory steady-state evoked potentials (SS-EPs) are phase-locked neural responses to periodic stimuli, believed to reflect specific neural generators. As an objective measure, steady-state responses have been used in different clinical settings, including measuring hearing thresholds of normal and hearing-impaired subjects. Recent studies are in favor of recording these responses as a part of the cochlear implant (CI) device-fitting procedure. Considering these potential benefits, the goals of the present study were to assess the feasibility of recording free-field SS-EPs in CI users and to compare their characteristics between CI users and controls. By taking advantage of a recently developed dual-frequency tagging method, we attempted to record subcortical and cortical SS-EPs from adult CI users and controls and measured reliable subcortical and cortical SS-EPs in the control group. Independent component analysis (ICA) was used to remove CI stimulation artifacts, yet subcortical responses of several CIs were heavily contaminated by these artifacts. Consequently, only cortical SS-EPs were compared between groups, which were found to be larger in the controls. The lower cortical SS-EPs' amplitude in CI users might indicate a reduction in neural synchrony evoked by the modulation rate of the auditory input across different neural assemblies in the auditory pathway. The brain topographies of cortical auditory SS-EPs, the time course of cortical responses, and the reconstructed cortical maps were highly similar between groups, confirming their neural origin and possibility to obtain such responses also in CI recipients. As for subcortical SS-EPs, our results highlight a need for sophisticated denoising algorithms to pinpoint and remove artifactual components from the biological response.

During active object manipulation, the finger-object interactions give rise to complex fingertip skin deformations. These deformations are in turn encoded by the local tactile afferents and provide rich and behaviorally relevant information to the central nervous system. Most of the work studying the mechanical response of the finger to dynamic loading has been performed under a passive setup, thereby precisely controlling the kinematics or the dynamics of the loading. However, to identify aspects of the deformations that are relevant to online control during object manipulation, it is desirable to measure the skin response in an active setup. To that end, we developed a device that allows us to monitor finger forces, skin deformations, and kinematics during fine manipulation. We describe the device in detail and test it to precisely describe how the fingertip skin in contact with the object deforms during a simple vertical oscillation task. We show that the level of grip force directly influences the fingerpad skin strains and that the strain rates are substantial during active manipulation (norm up to 100%/s). The developed setup will enable us to causally relate sensory information, i.e. skin deformation, to online control, i.e. grip force adjustment, in future studies.

Vision-based systems for terrain detection are ubiquitous in mobile robotics, while such systems recently emerged for locomotion assistance of disabled people. For instance, wearable devices embedding vision sensors can assist people in navigation; or guide lower-limb prosthesis or exoskeleton controller to retrieve gait patterns being adapted to the executed task (overground walking, stairs, slopes, etc.). In this research, we present a vision-based algorithm achieving the detection of flat ground, steps, and ramps, using a depth camera. The raw point cloud data obtained from the depth camera passes through multiple processing steps to extract environmental features, and then achieves terrain detection by feeding these features into a classification tree. The camera was mounted on a custom-made wearable tool that can be placed on the chest of human users. This contribution reports a pilot validation study with 6 healthy subjects moving in an indoor environment containing a rich set of different types of terrains. Our method can predict the locomotion modes up to three steps in front of the user. Moreover, it is able to perform terrain detection even if the path is partially occluded by another walker. The method accuracy with a cleared path was found to be above 90% for all locomotion modes.

Since its discovery, the concept central sensitization has become increasingly popular. However, in the scientific literature central sensitization is defined and operationalized in many different ways, which seriously hampers scientific progression. The original description of central sensitization that derives from animal studies referred to a phenomenon of increased spinal excitability induced after peripheral noxious input and was thought to mediate increases in pain perception present after injury (i.e. the spread of hyperalgesia and allodynia restricted to a limited number of spinal segments). The exact spinal mechanisms underlying these forms of hyperalgesia and allodynia are yet unknown, although our understanding is rapidly growing, for example. The results of recent studies clearly indicate that hyperalgesia and allodynia do not depend on one single mechanism, but can be triggered by a range of mechanisms. More recent interpretations of central sensitization, in particular those used in the clinical domain, are broader than the original concept; central sensitization refers to a general state of central nervous system hypersensitivity that explains a variety of symptoms, including pain and non-pain symptoms (e.g. increased sensitivity to bright light, sounds and odors). We have recently argued that when central sensitization is interpreted too broadly, the chance of finding evidence of central sensitization increases. Consequently, the presence of central sensitization is established in many patients but also the heterogeneity of underlying processes/mechanisms increases. The biopsychosocial model considers that different interacting processes/mechanisms can contribute to a patient’s clinical presentation. Grouping different processes/mechanisms under the same umbrella (central sensitization) does not seem to contribute to a mechanism-based approach and may not improve – and may even hamper – pain management.

Human modern life entails the need to make many abstract, deliberative decisions such as selecting a career or buying a house. This fact prompted the development of theories suggesting that decisions are made within a cognitive system prior to being relayed to the motor system for outputting the desired action: a serial architecture of sensing, thinking, and finally acting. However, the human brain is the product of a long evolution during which animals had to face challenges very different from our modern-life decisions. Most decisions in the animal realm must be made in real-time to cope with urgent priorities in dynamically changing environments: here, there is no time for carefully thinking before acting. A recent theoretical framework has proposed that for effective behavior in such environments, the brain uses a parallel architecture in which multiple potential actions can be specified simultaneously, and one is selected on the basis of current sensory information. This is called the affordance competition hypothesis. According to this theory, decisions emerge from a consensus arising in a distributed brain network, especially involving sensorimotor structures. In this presentation, I will describe the work I have been conducting for the six last years as a postdoctoral researcher at the Cognition and Actions lab of the Institute of Neuroscience in Brussels (UCL). My current projects aim at better understanding how the human brain computes action-based decisions. A first project focused on the contribution of the primary motor cortex to reinforcement learning and decision-making. A second project explored the cortical correlates of spatial attention and action selection during motor decisions. Finally, a third project investigated the motor cortical signatures of urgency during dynamic decision-making. Altogether, they involved a combination of techniques including continuous theta burst stimulation, single-pulse transcranial magnetic stimulation, electroencep

Young children with bilateral cerebral palsy (BCP) often experience difficulties with gross motor function, manual ability and posture, impacting developing independence in daily life activities, participation and quality of life. Hand Arm Bimanual Intensive Training Including Lower Extremity (HABIT-ILE) is a novel intensive motor intervention integrating upper and lower extremity training that has been developed and tested in older school-aged children with unilateral and BCP. This study aims to compare an adapted preschool version of HABIT-ILE to usual care in a randomised controlled trial. 60 children with BCP aged 2-5 years, Gross Motor Function Classification System (GMFCS) II-IV will be recruited. Children will be stratified by GMFCS and randomised using concealed allocation to either receive Preschool HABIT-ILE or usual care. Preschool HABIT-ILE will be delivered in groups of four to six children, for 3 hours/day for 10 days (total 30 hours). Children receiving Preschool HABIT-ILE be provided a written home programme with the aim of achieving an additional 10 hours of home practice (total dose 40 hours). Outcomes will be assessed at baseline, immediately following intervention and then retention of effects will be tested at 26 weeks. The primary outcome will be the Peabody Developmental Motors Scales-Second Edition to evaluate gross and fine motor skills. Secondary outcomes will be gross motor function (Gross Motor Function Measure-66), bimanual hand performance (Both Hands Assessment), self-care and mobility (Pediatric Evaluation of Disability Inventory-Computer Adapted Test), goal attainment (Canadian Occupational Performance Measure), global performance of daily activities (ACTIVLIM-CP), cognition and adaptive function (Behavior Rating Inventory of Executive Function-Preschool Version), habitual physical activity (ActiGraph GT3X+) and quality of life (Infant Toddler Quality of Life Questionnaire and Child Health Utility Index-9). Analyses will follow stand

Cerebral palsy (CP) is highly prevalent in sub-Saharan Africa, where clinically-based studies have shown a considerable over-representation of the severe bilateral subtype. However, children's access to rehabilitation care is limited by many local factors, notably the lacking of rehabilitation services, insufficient knowledge of caregivers and financial constraints. In such a context there is an urgent need for studies of the evidence-based rehabilitation approach. Here, we describe the protocol of a randomised controlled study to investigate the efficacy of Hand-Arm Bimanual Intensive Therapy Including the Lower Extremities (HABIT-ILE) in young children with bilateral CP in Benin Republic, a representative low and middle-income country of western Africa. Forty children with bilateral CP aged between 24 and 59 months and with level III-IV in the gross motor function classification will be randomised to either a high intensity conventional therapy or HABIT-ILE therapy. Both therapies will be delivered as a day-camp model over 2 weeks to a total of 50 hours (5 hours per day). The assessor-blinded primary outcomes will include the gross motor function measure and both hands assessment. Secondary outcomes will be the adapted version of the ACTIVLIM-CP questionnaire, the Canadian Occupational Performance Measure, and a perception of CP interview form. Children will be assessed at baseline, after intervention and at 6-week follow-up. A 2 (group)×3 (test sessions) repeated analysis of variance will evaluate changes after the interventions. This study has been approved by the ethics committee of the rehabilitation department of the National Teaching Hospital Hubert Koutoukou Maga of Cotonou, Benin (approval decision: N°01-2019/MS/CNHU-HKM/CEI/CUMPR). All participants' parents/caregivers will provide their written informed consent. Data will be managed with confidentiality. PACTR201911894444879.

Neuroimaging studies suggest that the inferior frontal operculum (IFO) is part of a neuronal network involved in facial expression processing, but the causal role of this region in emotional face discrimination remains elusive. We used cathodal (inhibitory) tDCS to test whether right (r-IFO) and left (l-IFO) IFO play a role in discriminating basic facial emotions in healthy volunteers. Specifically, we tested if the two sites are selectively involved in the processing of facial expressions conveying high or low arousal emotions. Based on the Arousal Hypothesis we expected to find a modulation of high and low arousal emotions by cathodal tDCS of the r-IFO and the l-IFO, respectively. First, we validated an Emotional Faces Discrimination Task (EFDT). Then, we targeted the r-IFO and the l-IFO with cathodal tDCS (i.e. the cathode was placed over the right or left IFO, while the anode was placed over the contralateral supraorbital area) during facial emotions discrimination on the EFDT. Non-active (i.e. sham) tDCS was a control condition. Overall, participants manifested the "happy face advantage". Interestingly, tDCS to r-IFO enhanced discrimination of faces expressing anger (a high arousal emotion), whereas, tDCS to l-IFO decreased discrimination of faces expressing sadness (a low arousal emotion). Our findings revealed a differential causal role of r-IFO and l-IFO in the discrimination of specific high and low arousal emotions. Crucially, these results suggest that cathodal tDCS might reduce the neural noise triggered by facial emotions, improving discrimination of high arousal emotions but disrupting discrimination of low arousal emotions. These findings offer new insights for treating clinical population with deficits in processing facial expressions.

Sensory attenuation (i.e., the phenomenon whereby self-produced sensations are perceived as less intense compared to externally occurring ones) is among the neurocognitive processes that help distinguishing ourselves from others. It is thought to be rooted in the motor system (e.g., related to motor intention and prediction), while the role of body awareness, which necessarily accompanies any voluntary movement, in this phenomenon is largely unknown. To fill this gap, here we compared the perceived intensity, somatosensory evoked potentials, and alpha-band desynchronization for self-generated, other-generated, and embodied-fake-hand-generated somatosensory stimuli. We showed that sensory attenuation triggered by the own hand and by the embodied fake hand had the same behavioral and neurophysiological signatures (reduced subjective intensity, reduced of N140 and P200 SEP components and post-stimulus alpha-band desynchronization). Therefore, signals subserving body ownership influenced attenuation of somatosensory stimuli, possibly in a postdictive manner. This indicates that body ownership is crucial for distinguishing the source of the perceived sensations.

Cerebral palsy (CP) is the leading cause of motor disability in children, a family’s predicament. It is widely studied in High-Income Countries where the prevalence of severe cases is declining thanks to the constant development of better prevention and care strategies. Unfortunately, it is still very poorly known in Low and Middle-Income Countries such as in Sub-Saharan Africa where children show poor developmental outcomes and where there is a higher proportion of severe cases and premature deaths. Therefore, this thesis aimed to contribute to the management of CP in Sub-Saharan Africa, typically in Benin in West Africa, with the development of specific assessment tools and intervention strategies., (MOTR - Sciences de la motricité) -- UCL, 2021

A transient absence of vision early in life permanently alters visual motion discrimination abilities in humans. However, how the absence of early visual experience shapes the development of the visual motion network remains unknown. To address this question, we used functional magnetic resonance imaging to characterize the brain response elicited by visual motion in adults born with dense bilateral cataract that were treated early in life. Our results suggest that early cataract-reversal patients (CAT) showed reduced recruitment of the early visual areas while processing motion information when compared to matched controls with typical visual development (CON). The reduced recruitment of the early visual cortex in CAT correlated with the duration of visual deprivation. No alterations were observed in the higher order visual motion area hMT+/V5. Psychophysiological interaction analyses demonstrated reduced interhemispheric connectivity in V1, and reduced connectivity between hMT+/V5 and V1 during visual motion processing. We further investigated the representation of individual motion directions in V1 and hMT+/V5 using multivariate pattern analyses (MVPA). We observed reduced motion direction information in V1, but not in hMT+/V5, in CAT when compared to CON. Furthermore, we observed selective alteration in the resting connectivity profile of V1 in CAT, but not in hMT+/V5. Altogether these results suggest that a brief and transient period of visual deprivation early in life has a region-specific impact on the visual motion network with V1 being permanently affected while hMT+/V5 shows some resilience to deprivation.