Search

Non-human primates, especially rhesus macaques, have been a dominant model to study sensorimotor control of the upper limbs. Indeed, human and macaques have similar hands and homologous neural circuits to mediate manual behavior. However, few studies have systematically and quantitatively compared the manual behaviors of the two species. Such comparison is critical for assessing the validity of using the macaque sensorimotor system as a model of its human counterpart. In this study, we systematically compared the prehensile behaviors of humans and rhesus macaques using an identical experimental setup. We found human and macaque prehension kinematics to be generally similar with a few subtle differences. While the structure of the preshaping postures is similar in humans and macaques, human postures are more object-specific and human joints are less intercorrelated. Conversely, monkeys demonstrate more stereotypical grasping behaviors that are common across all grasp conditions and more variability in their postures across repeated grasps of the same object. Despite these subtle differences in manual behavior between humans and monkeys, our results bolster the use of the macaque model to understand the neural mechanisms of manual dexterity in humans.New and newsworthyMacaques have been a dominant animal model to study the neural mechanisms of human dexterity because they exhibit complex manual behavior. We show that the kinematics of prehension – a critical dexterous behavior – are largely similar in humans and macaques. However, human preshaping postures are more object-specific and the movement of human digits are less correlated with each other. The thumb, index, and wrist are major driver of these interspecies differences.

During conversations, speech prosody provides important clues about the speaker’s communicative intentions. In many languages, a rising vocal pitch at the end of a sentence typically expresses a question function, whereas a falling pitch suggests a statement. Here, the neurophysiological basis of intonation and speech act understanding were investigated with high-density electroencephalography (EEG) to determine whether prosodic features are reflected at the neurophysiological level. Already approximately 100 ms after the sentence-final word differing in prosody, questions, and statements expressed with the same sentences led to different neurophysiological activity recorded in the event-related potential. Interestingly, low-pass filtered sentences and acoustically matched nonvocal musical signals failed to show any neurophysiological dissociations, thus suggesting that the physical intonation alone cannot explain this modulation. Our results show rapid neurophysiological indexes of prosodic communicative information processing that emerge only when pragmatic and lexico-semantic information are fully expressed. The early enhancement of question-related activity compared with statements was due to sources in the articulatory-motor region, which may reflect the richer action knowledge immanent to questions, namely the expectation of the partner action of answering the question. The present findings demonstrate a neurophysiological correlate of prosodic communicative information processing, which enables humans to rapidly detect and understand speaker intentions in linguistic interactions.

Recent studies have revealed an upper bound in motor adaptation, beyond which other learning systems may be recruited. The factors determining this upper bound are poorly understood. The multisensory integration hypothesis states that this limit arises from opposing responses to visual and proprioceptive feedback. As individuals adapt to a visual perturbation, they experience an increasing proprioceptive error in the opposite direction, and the upper bound is the point where these two error signals reach an equilibrium. Assuming that visual and proprioceptive feedback are weighted according to their variability, there should be a correlation between proprioceptive variability and the limits of adaptation. Alternatively, the proprioceptive realignment hypothesis states that the upper bound arises when the (visually biased) sensed hand position realigns with the expected sensed position (target). When a visuo-proprioceptive discrepancy is introduced, the sensed hand position is biased toward the visual cursor, and the adaptive system counteracts this discrepancy by driving the hand away from the target. This hypothesis predicts a correlation between the size of the proprioceptive shift and the upper bound of adaptation. We tested these two hypotheses by considering natural variation in proprioception and motor adaptation across individuals. We observed a modest, yet reliable correlation between the upper bound of adaptation with both proprioceptive measures (variability and shift). Although the results do not clearly favor one hypothesis over the other, they underscore the critical role of proprioception in sensorimotor adaptation. NEW & NOTEWORTHY Although the sensorimotor system uses sensory feedback to remain calibrated, this learning process is constrained, limited by the maximum degree of plasticity. The factors determining this limit remain elusive. Guided by two hypotheses, we show that individual differences in the upper bound of adaptation in response to a visual perturbation can be predicted by the bias and variability in proprioception. These results underscore the critical, but often neglected role of proprioception in human motor learning.

PURPOSE: The sensorimotor system is a subcomponent of the comprehensive motor control system of the body. However, the complex nature of the sensorimotor system, makes it difficult to interpret findings for clinical application. The purpose of this study was to utilize principal component analysis to identify sex differences and relationships between sensorimotor variables during a dynamic perturbation. MATERIALS AND METHODS: Thirty physically-active individuals (15 males and 15 females) were blindfolded and positioned on an isokinetic dynamometer with their knee flexed to 70°. At random, the dynamometer moved rapidly toward knee extension. Subjects were asked to resist the dynamometer as it would randomly and rapidly move toward knee extension. Torque and position values were used to calculate stiffness values. RESULTS: Principal component analysis revealed sex differences in two principal components (PCs): PC2 in female was comprised from higher position, torque and time values (P = 0.038), PC4 in females was comprised from higher active stiffness and lower short-range stiffness values (P = 0.032) compared to males. Torque at the resting position was correlated to the short-range passive stiffness (ρ = 0.539, P = 0.002), time to peak torque (ρ = −0.375, P = 0.003) and reactive stiffness (ρ = 0.526, P = 0.041). CONCLUSIONS: Females had later reaction time and lower short-range passive stiffness and they resisted the dynamometer by their voluntary activation compared to the males thus requiring muscle activation for meaningful response. In addition, the higher resting muscle activities may correlate to short-range passive stiffness and quicker active stiffness.

To validate a simultaneous analysis tool for the brain and cervical cord embedded in the statistical parametric mapping (SPM) framework, we compared trauma‐induced macro‐ and microstructural changes in spinal cord injury (SCI) patients to controls. The findings were compared with results obtained from existing processing tools that assess the brain and spinal cord separately. A probabilistic brain‐spinal cord template (BSC) was generated using a generative semi‐supervised modelling approach. The template was incorporated into the pre‐processing pipeline of voxel‐based morphometry and voxel‐based quantification analyses in SPM. This approach was validated on T1‐weighted scans and multiparameter maps, by assessing trauma‐induced changes in SCI patients relative to controls and comparing the findings with the outcome from existing analytical tools. Consistency of the MRI measures was assessed using intraclass correlation coefficients (ICC). The SPM approach using the BSC template revealed trauma‐induced changes across the sensorimotor system in the cord and brain in SCI patients. These changes were confirmed with established approaches covering brain or cord, separately. The ICC in the brain was high within regions of interest, such as the sensorimotor cortices, corticospinal tracts and thalamus. The simultaneous voxel‐wise analysis of brain and cervical spinal cord was performed in a unique SPM‐based framework incorporating pre‐processing and statistical analysis in the same environment. Validation based on a SCI cohort demonstrated that the new processing approach based on the brain and cord is comparable to available processing tools, while offering the advantage of performing the analysis simultaneously across the neuraxis., This study presents a new approach for the simultaneous analysis of the brain and cervical spinal cord embedded in a unique SPM‐based framework incorporating pre‐processing and statistical analysis in the same environment. The proposed method yielded comparable results to more standard brain‐ or cord‐specific approaches when used to analyse quantitative MRI. It offers a single tool for any MRI studies investigating neurological disease with spinal cord involvement.

Significance The functional advantages of using a stochastically spiking neural network (sSNN) instead of a nonspiking neural network (NS-NN) have remained largely unknown. We developed an architecture which enabled the parametric adjustment of the spikiness (i.e., impulsive dynamics and stochasticity) of the sSNN output and observed that stochastic spikes instantaneously induced the ordered motion of a dynamical system. We demonstrated the benefits of sSNNs using a musculoskeletal bipedal walker and, moreover, showed that the decrease in the spikiness of motor neuron output leads to a reduction in adaptability. Stochastic spikes may aid the adaptation of a biological system to sudden perturbations or environmental changes. Our architecture can easily be connected to the conventional NS-NN and may superimpose the on-site adaptability., Most biological neurons exhibit stochastic and spiking action potentials. However, the benefits of stochastic spikes versus continuous signals other than noise tolerance and energy efficiency remain largely unknown. In this study, we provide an insight into the potential roles of stochastic spikes, which may be beneficial for producing on-site adaptability in biological sensorimotor agents. We developed a platform that enables parametric modulation of the stochastic and discontinuous output of a stochastically spiking neural network (sSNN) to the rate-coded smooth output. This platform was applied to a complex musculoskeletal–neural system of a bipedal walker, and we demonstrated how stochastic spikes may help improve on-site adaptability of a bipedal walker to slippery surfaces or perturbation of random external forces. We further applied our sSNN platform to more general and simple sensorimotor agents and demonstrated four basic functions provided by an sSNN: 1) synchronization to a natural frequency, 2) amplification of the resonant motion in a natural frequency, 3) basin enlargement of the behavioral goal state, and 4) rapid complexity reduction and regular motion pattern formation. We propose that the benefits of sSNNs are not limited to musculoskeletal dynamics. Indeed, a wide range of the stability and adaptability of biological systems may arise from stochastic spiking dynamics.

It is well-accepted that processing observed actions involves at some extent the same neural mechanisms responsible for action execution. More recently, it has been forwarded that also the processing of verbs expressing a specific motor content is subserved by the neural mechanisms allowing individuals to perform the content expressed by that linguistic material. This view is also known as embodiment and contrasts with a more classical approach to language processing that considers it as amodal. In the present study, we used a go/no-go paradigm, in which participants were requested to respond to real words and pictures and refrain from responding when presented stimuli were pseudowords and scrambled images. Real stimuli included pictures depicting hand- and foot-related actions and verbs expressing hand- and foot-related actions. We, therefore, directly compared the modulation of hand motor responses during the observation of actions and the presentation of verbs, expressing actions in the same category. The results have shown that participants gave slower hand motor responses during the observation of hand actions and the processing of hand-related verbs as than observed foot actions and related verbs. These findings support embodiment showing that whatever the modality of presentation (observed action or verb), the modulation of hand motor responses was similar, thus suggesting that processing seen actions and related verbs shares common mechanisms most likely involving the motor system and the underlying motor experience.

When a person observes someone else performing an action, the observer’s sensorimotor cortex activates as if the observer is the one performing the action, a phenomenon known as action simulation. While this process has been well-established for basic (e.g. grasping) and complex (e.g. dancing) actions, it remains unknown if the framework of action simulation is applicable to visual languages such as American Sign Language (ASL). We conducted an EEG experiment with deaf signers and hearing non-signers to compare overall sensorimotor EEG between groups, and to test whether sensorimotor systems are differentially sensitive to signs that are produced with one hand (“1H”) or two hands (“2H”). We predicted greater alpha and beta event-related desynchronization (previously correlated with action simulation) during the perception of 2H ASL signs compared to 1H ASL signs, due to greater demands on sensorimotor processing systems required for producing two-handed actions. We recorded EEG from both groups as they observed videos of ASL signs, half 1H and half 2H. Event-related spectral perturbations (ERSPs) in the alpha and beta ranges were computed for the two conditions at central electrode sites overlying the sensorimotor cortex. Sensorimotor EEG responses in both Hearing and Deaf groups were sensitive to the observed gross motor characteristics of the observed signs. We show for the first time that despite hearing non-signers showing overall more sensorimotor cortex involvement during sign observation, mirroring-related processes are in fact involved when deaf signers observe signs.

Vision in depth is distorted. A similar distortion can be observed for pointing to visual targets in depth. It has been suggested that pointing errors in depth reflect the visual distortion. Alternatively, pointing in depth might be guided by a prior that biases movements toward the natural grasping distance at which object manipulation is usually performed. To dissociate whether pointing is guided by distorted vision only or whether it takes into account a natural grasping distance prior, we adapted pointing movements. Participants received visual feedback about the success of their pointing once the movement was finished. We distorted the feedback to signal either that pointing was not far enough or in separate sessions that pointing was too far. Participants adapted to this artificial error by either extending or shortening their pointing movements. The generalization of pointing adaptation revealed a bias in movement planning that is inconsistent with pointing being guided only by distorted vision but with the involvement of knowledge about the natural grasping distance. Adaptation was strongest for pointing movements to a middle position that corresponds to the natural grasping distance and it was weakest for movements leading away from it. It has been demonstrated that pointing adaptation in depth changes visual perception (Volcic R, Fantoni C, Caudek C, Assad JA, Domini F.

Transcranial random noise stimulation (tRNS) over cortical areas has been shown to acutely improve performance in sensory detection tasks. One explanation for this behavioural effect is stochastic resonance, a mechanism that explains how signal processing in non-linear systems can benefit from added noise. While acute noise benefits of electrical random noise stimulation have been demonstrated at the behavioural level as well as in in vitro preparations of neural tissue, it is currently largely unknown whether similar effects can be shown at the neural population level using neurophysiological readouts of human cortex. Here we hypothesized that acute tRNS will increase the responsiveness of primary motor cortex (M1) when probed with transcranial magnetic stimulation. Neural responsiveness was operationalized via the well-known concept of the resting motor threshold (RMT). We showed that tRNS acutely decreases RMT. This effect was small, but it was consistently replicated across four experiments including different cohorts (total N=81, 46 females, 35 males), two tRNS electrode montages, and different control conditions. Our experiments provide critical neurophysiological evidence that tRNS can acutely generate noise benefits by enhancing the neural population response of human M1.Significance statementA hallmark feature of stochastic resonance is that signal processing can benefit from added noise. This has mainly been demonstrated at the single-cell level in vitro where the neural response to weak input signals can be enhanced by simultaneously applying random noise. Our finding that tRNS acutely increases the excitability of corticomotor circuits extends the principle of noise benefits to the neural population level in human cortex. Our finding is in line with the notion that tRNS might affect cortical processing via the stochastic resonance phenomenon. It suggests that enhancing the response of cortical populations to an external stimulus might be one neurophysiological mechanism mediating performance improvements when tRNS is applied to sensory cortex during perception tasks.

In the early 2000s, a novel non-invasive brain stimulation protocol, the paired associative stimulation (PAS), was introduced, allowing to induce and investigate Hebbian associative plasticity within the humans' motor system, with patterns resembling spike-timing-dependent plasticity properties found in cellular models. Since this evidence, PAS efficacy has been proved in healthy, and to a lesser extent, in clinical populations. Recently, novel 'modified' protocols targeting sensorimotor and crossmodal networks appeared in the literature. In the present work, we have reviewed recent advances using these 'modified' PAS protocols targeting sensory and motor cortical networks. To better categorize them, we propose a novel classification according to the nature of the peripheral and cortical stimulations (i.e., within-system, cross-systems, and cortico-cortical PAS). For each protocol of the categories mentioned above, we describe and discuss their main features, how they have been used to study and promote brain plasticity, and their advantages and disadvantages. Overall, current evidence suggests that these novel non-invasive brain stimulation protocols represent very promising tools to study the plastic properties of humans' sensorimotor and crossmodal networks, both in the healthy and in the damaged central nervous system.

Speech production gives rise to distinct auditory and somatosensory feedback signals which are dynamically integrated to enable online monitoring and error correction, though it remains unclear how the sensorimotor system supports the integration of these multimodal signals. Capitalizing on the parity of sensorimotor processes supporting perception and production, the current study employed the McGurk paradigm to induce multimodal sensory congruence/incongruence. EEG data from a cohort of 39 typical speakers were decomposed with independent component analysis to identify bilateral mu rhythms; indices of sensorimotor activity. Subsequent time-frequency analyses revealed bilateral patterns of event related desynchronization (ERD) across alpha and beta frequency ranges over the time course of perceptual events. Right mu activity was characterized by reduced ERD during all cases of audiovisual incongruence, while left mu activity was attenuated and protracted in McGurk trials eliciting sensory fusion. Results were interpreted to suggest distinct hemispheric contributions, with right hemisphere mu activity supporting a coarse incongruence detection process and left hemisphere mu activity reflecting a more granular level of analysis including phonological identification and incongruence resolution. Findings are also considered in regard to incongruence detection and resolution processes during production.

The phenomenon of sensory attenuation, that is, the perceptual reduction of intensity for self-generated stimuli, is considered a neurocognitive basis for self-other distinction. Corroboratory, such perceptual attenuation has been shown to be dependent on the sense of embodiment, that is, the perceptual incorporation of an object or body part into one’s body representation. In the present study, we tested whether this relationship is transferrable to unilateral upper limb amputees using a prosthesis. Thirteen participants were asked to touch their foot sole with a) their intact hand (self-touch), b) their prosthesis (prosthesis-touch), or c) let it be touched by another person (other-touch). Intensity of touch was assessed with a questionnaire. In addition, prosthesis embodiment was assessed by the recently introduced Prosthesis Embodiment Scale in nine participants. We found that both self-touch as well as prosthesis-touch was characterized by significant perceptual attenuation compared to other-touch, while self- and prosthesis-touch did not differ. By calculating an index reflecting how similar prosthesis-touch was to self- or other touch and correlating this index with perceived prosthesis embodiment, we found that the more embodied the prosthesis was, the more similar was its elicited touch perception to actual self-touch. This association was specific for prosthesis embodiment, since neither prosthesis satisfaction nor prosthesis adjustment showed a similar relationship. These findings are further evidence that perceptually embodied prostheses can be represented as an actual limb by the users’ sensorimotor system, which might have important implications for future prosthetic rehabilitation.

Grasping actions are directed not only toward objects we see but also toward objects we both see and touch (multisensory grasping). In this latter case, the integration of visual and haptic inputs improves movement performance compared to each sense alone. This performance advantage could be due to the integration of all the redundant positional and size cues or to the integration of only a subset of these cues. Here we selectively provided specific cues to tease apart how these different sensory sources contribute to visuo-haptic multisensory grasping. We demonstrate that the availability of the haptic positional cue together with the visual cues is sufficient to achieve the same grasping performance as when all cues are available. These findings provide strong evidence that the human sensorimotor system relies on non-visual sensory inputs and open new perspectives on their role in supporting vision during both development and adulthood.

Motor synergies are neural organizations of a set of redundant motor effectors that interact with one another to compensate for each other’s error and ensure the stabilization of a performance variable. Recent studies have demonstrated that central nervous system synergistically coordinates its numerous motor effectors through Bayesian multi-sensory integration. Deficiency in sensory synergy weakens the synergistic interaction between the motor effectors. Here, we scrutinize the neuromechanical mechanism underlying this phenomenon through spectral analysis and modeling. We validate our model-generated results using experimental data reported in the literature collected from participants performing a finger force production task with and without tactile feedback (manipulated through injection of anesthetic in fingers). Spectral analysis reveals that the error compensation feature of synergies occurs only at low frequencies. Modeling suggests that the neurophysiological structures involving short-latency back-coupling loops similar to the well-known Renshaw cells explain the deterioration of synergy due to sensory deprivation.

International audience; Most of our daily interactions with objects occur in the space immediately surrounding the body, i.e. the peripersonal space. The peripersonal space is characterized by multisensory processing of objects which are coded in terms of potential actions, specifying for instance whether objects are within reach or not. Our recent work suggested a link between exposure to a new force field, which changed the effector dynamics, and the representation of peripersonal space. To better understand the interplay between the plasticity of the motor system and peripersonal space representation, the present study examined whether changing the direction of the force field specifically modified the perception of action boundaries. Participants seated at the centre of an experimental platform estimated visual targets’ reachability before and after adapting upper-limb reaching movements to the Coriolis force generated by either clockwise or counter clockwise rotation of the platform (120°/s). Opposite spatial after-effects were observed, showing that force-field adaptation depends on the direction of the rotation. In contrast, perceived action boundaries shifted leftward following exposure to the new force field, regardless of the direction of the rotation. Overall, these findings support the idea that abrupt exposure to a new force field results in a direction-specific updating of the central sensorimotor representations underlying the control of arm movements. Abrupt exposure to a new force field also results in a nonspecific shift in the perception of action boundaries, which is consistent with a contraction of the peripersonal space. Such effect, which does not appear to be related to state anxiety, could be related to the protective role of the peripersonal space in response to the uncertainty of the sensorimotor system induced by the abrupt modification of the environment.

Standing can be understood as a motor process in addition to the stereotypes of movement described by Janda. Atypical stress during standing leads to overstraining of myofascial structures and to pain. The search for a specific examination possibility with the prospect of individual therapy recommendations was the reason for the development of this score.In this study 80 healthy volunteers were examined for their stance stability by means of established as well as proportionally newly described test procedures. The equally weighted results were combined into a score and its standard values were determined.For the age group 18-44 years old the norm is the completion of 10 out of the total of 13 individual tasks. For the age group 45-59 years old, according to current measurements 8 out of 13 achieved points are the norm. In the age group from the age of 60 years onwards, no reliable statements can so far be made.The age group up to 44 years old provided reliable data. The age group above that shows at least a clear trend. The existing tests and scores are increasingly concerned with the risk of falling and the dexterity in movements and complex tasks. The status as a motor stereotype has not yet been described. After an examination using the Jena standing stability (JESS) score it is possible to make statements about individual therapy priorities.The JESS score is a practicable test to verify the standing stereotype. The extension of the norm group by including further study participants will decide on a stabilization or modification of the current results. The testing of further cohorts will show to what extent these items are sensitive to changes caused by training methods and whether the score can also be used to congruently map clinical changes.HINTERGRUND: Der Stand bzw. das Stehen kann neben den von Janda beschriebenen Bewegungsstereotypen ebenfalls als motorischer Prozess begriffen werden. Atypische Belastungen während des Stehens führen zur Überbeanspruchung myofaszialer Strukturen und zu Schmerz. Die Suche nach einer dezidierten Untersuchungsmöglichkeit mit der Aussicht auf individuelle Therapieempfehlungen, war Anlass für die Erarbeitung dieses Scores.Es wurden 80 gesunde Probanden mittels etablierter sowie anteilig neu beschriebener Testverfahren auf ihre Standstabilität hin untersucht. Die gleichgewichteten Ergebnisse wurden zu einem Score zusammengefasst und dessen Normwerte bestimmt.Für die Altersklasse der 18- bis 44-Jährigen ist die Norm das Erfüllen von 10 der insgesamt 13 Einzelaufgaben. Für die 45- bis 59-Jährigen sind nach aktuellen Messungen 8 von 13 erreichten Punkten die Norm. In der Altersgruppe ab dem 60. Lebensjahr können bisher keine belastbaren Aussagen getroffen werden.Belastbare Daten liefert die Altersgruppe bis 44 Jahre. Die Altersgruppe darüber zeigt zumindest einen deutlichen Trend. Die existierenden Tests bzw. Scores setzten sich verstärkt mit dem Sturzrisiko und der Geschicklichkeit bei Bewegungen und komplexen Aufgaben auseinander. Der Stand als motorischer Stereotyp wurde bisher noch nicht beschrieben. Nach einer Untersuchung mittels Jenaer-Stand-Stabilitäts-Score (JESS-Score) ist es möglich, Aussagen zu individuellen Therapieschwerpunkten zu treffen.Der JESS-Score stellt einen praktikablen Test zur Verifizierung des Standstereotyps dar. Die Erweiterung der Normgruppe durch Einschluss weiterer Studienteilnehmer wird über eine Verstetigung oder Modifikation der aktuellen Ergebnisse entscheiden. Die Testung weiterer Kohorten wird zeigen, inwieweit diese Items sensitiv für Veränderungen durch Trainingsmethoden sind und ob mit dem Score auch klinische Änderungen kongruent abgebildet werden können.

Background When exposed to a novel dynamic perturbation, participants adapt by changing their movements’ dynamics. This adaptation is achieved by constructing an internal representation of the perturbation, which allows for applying forces that compensate for the novel external conditions. To form an internal representation, the sensorimotor system gathers and integrates sensory inputs, including kinesthetic and tactile information about the external load. The relative contribution of the kinesthetic and tactile information in force-field adaptation is poorly understood. Methods In this study, we set out to establish the effect of augmented tactile information on adaptation to force-field. Two groups of participants received a velocity-dependent tangential skin deformation from a custom-built skin-stretch device together with a velocity-dependent force-field from a kinesthetic haptic device. One group experienced a skin deformation in the same direction of the force, and the other in the opposite direction. A third group received only the velocity-dependent force-field. Results We found that adding a skin deformation did not affect the kinematics of the movement during adaptation. However, participants who received skin deformation in the opposite direction adapted their manipulation forces faster and to a greater extent than those who received skin deformation in the same direction of the force. In addition, we found that skin deformation in the same direction to the force-field caused an increase in the applied grip-force per amount of load force, both in response and in anticipation of the stretch, compared to the other two groups. Conclusions Augmented tactile information affects the internal representations for the control of manipulation and grip forces, and these internal representations are likely updated via distinct mechanisms. We discuss the implications of these results for assistive and rehabilitation devices.

In our daily life we often make complex actions comprised of linked movements, such as reaching for a cup of coffee and bringing it to our mouth to drink. Recent work has highlighted the role of such linked movements in the formation of independent motor memories, affecting the learning rate and ability to learn opposing force fields. In these studies, distinct prior movements (lead-in movements) allow adaptation of opposing dynamics on the following movement. Purely visual or purely passive lead-in movements exhibit different angular generalization functions of this motor memory as the lead-in movements are modified, suggesting different neural representations. However, we currently have no understanding of how different movement kinematics (distance, speed or duration) affect this recall process and the formation of independent motor memories. Here we investigate such kinematic generalization for both passive and visual lead-in movements to probe their individual characteristics. After participants adapted to opposing force fields using training lead-in movements, the lead-in kinematics were modified on random trials to test generalization. For both visual and passive modalities, recalled compensation was sensitive to lead-in duration and peak speed, falling off away from the training condition. However, little reduction in force was found with increasing lead-in distance. Interestingly, asymmetric transfer between lead-in movement modalities was also observed, with partial transfer from passive to visual, but very little vice versa. Overall these tuning effects were stronger for passive compared to visual lead-ins demonstrating the difference in these sensory inputs in regulating motor memories. Our results suggest these effects are a consequence of state estimation, with differences across modalities reflecting their different levels of sensory uncertainty arising as a consequence of dissimilar feedback delays.

Little is known about how disrupted vision affects visual reliance during postural control. postural control. Twenty-four physically active adults volunteered to participate in the study. Static postural control was quantified with center of pressure measures during a one-legged balance test with four different visual inputs (eyes-open (EO), high frequency of strobe vision (HSV), low frequency of strobe vision (LSV), and eyes-closed (EC)) and on two different surfaces (firm and foam). Dynamic postural control was calculated by the dynamic postural stability index and the Y-Balance test for three different visual inputs (EO, HSV, and LSV) and the two different surfaces. Romberg ratios (HSV/EO, LSV/EO, and EC/EO) were then calculated and used for statistical analysis to assess visual contribution during postural control. In the results, Romberg ratios were higher when people were on the foam surface than the firm surface in center of pressure total path in medial-lateral and anterior-posterior directions (p < 0.05, both directions). Similarly, Romberg ratios were higher on the foam surface than the firm surface in dynamic stability index in medial-lateral and anterior-posterior directions (p < 0.05, both directions). Stroboscopic glasses could alter visual reliance when the somatosensory system is disturbed by a foam pad during both static and dynamic postural control. Clinicians could use the glasses to manipulate visual reliance during dynamic balance training for patients with musculoskeletal injuries.

The current study aimed to examine postural control performance during a single-leg balance task in elderly individuals with and without a previous history of lateral ankle sprain (LAS). Eighteen adults with a previous history of LAS (mean age = 66 years old) and 12 healthy controls (mean age = 65 years old) were included in the study. Participants performed three trials of a single-leg balance task during an eyes-opened condition for 20-s. Center of pressure (COP) trajectories in the anteroposterior (AP) and mediolateral (ML) directions were collected with a force plate. The following postural control measures were calculated in the AP and ML directions: 1) Sample Entropy (SampEn); 2) Approximate Entropy (ApEn); 3) mean of Time-to-Boundary minima (mean TTB); and 4) COP velocity (COPV). Older-age participants with a history LAS exhibited lower ApEn-AP, SampEn-AP, and SampEn-ML values compared to healthy controls (p 0.05). The information gained from this investigation indicates more rigid postural control patterns, less adaptability, and more difficulty maintaining COP during a single-leg balance task in adults with a previous history of LAS. Our data suggest that there is a need to consider history of musculoskeletal injury when evaluating factors for postural control and fall risk in the elderly. Future investigations are needed to assess the effect of LAS on age-related declines in postural control and discern associations between potential risk factors of fall-related injuries and LAS in an elderly population.

Action perception and action production are assumed to be based on an internal simulation process that involves the sensorimotor system. This system undergoes changes across the life span and is assumed to become less precise with age. In the current study, we investigated how increasing age affects the magnitude of interference in action production during simultaneous action perception. In a task adapted from Brass et al. (Brain Cogn 44(2):124-143, 2000), we asked participants (aged 20-80 years) to respond to a visually presented finger movement and/or symbolic cue by executing a previously defined finger movement. Action production was assessed via participants' reaction times. Results show that participants were slower in trials in which they were asked to ignore an incongruent finger movement compared to trials in which they had to ignore an incongruent symbolic cue. Moreover, advancing age was shown to accentuate this effect. We suggest that the internal simulation of the action becomes less precise with age making the sensorimotor system more susceptible to perturbations such as the interference of a concurrent action perception.

Neural coupling between the central nervous system and the periphery is essential for the neural control of movement. Corticomuscular coherence is a popular linear technique to assess synchronised oscillatory activity in the sensorimotor system. This oscillatory coupling originates from ascending somatosensory feedback and descending motor commands. However, corticomuscular coherence cannot separate this bidirectionality. Furthermore, the sensorimotor system is nonlinear, resulting in cross‐frequency coupling. Cross‐frequency oscillations cannot be assessed nor exploited by linear measures. Here, we emphasise the need of novel coupling measures, which provide directionality and acknowledge nonlinearity, to unveil neural coupling in the sensorimotor system. We highlight recent advances in the field and argue that assessing directionality and nonlinearity of neural coupling will break new ground in the study of the control of movement in healthy and neurologically impaired individuals.

A long-term debate concerns whether the sensorimotor coding carried out during transitive actions observation reflects the low-level movement implementation details or the movement goals. On the contrary, phonemes and emotional facial expressions are intransitive actions that do not fall into this debate. The investigation of phonemes discrimination has proven to be a good model to demonstrate that the sensorimotor system plays a role in understanding actions acoustically presented. In the present study, we adapted the experimental paradigms already used in phonemes discrimination during face posture manipulation, to the discrimination of emotional facial expressions. We submitted participants to a lower or to an upper face posture manipulation during the execution of a four alternative labelling task of pictures randomly taken from four morphed continua between two emotional facial expressions. The results showed that the implementation of low-level movement details influence the discrimination of ambiguous facial expressions differing for a specific involvement of those movement details. These findings indicate that facial expressions discrimination is a good model to test the role of the sensorimotor system in the perception of actions visually presented.

Referential pointing is a characteristically human behavior, which involves moving a finger through space to direct an addressee towards a desired mental state. Planning this type of action requires an interface between sensorimotor and conceptual abilities. A simple interface could supplement spatially-guided motor routines with communicative-ostensive cues. For instance, a pointing finger held still for an extended period of time could aid the addressee’s understanding, without altering the movement’s trajectory. A more complex interface would entail communicative knowledge penetrating the sensorimotor system and directly affecting pointing trajectories. We compare these two possibilities using motion analyses of referential pointing during multi-agent interactions. We observed that communicators produced ostensive cues that were sensitive to the communicative context. Crucially, we also observed pervasive adaptations to the pointing trajectories: they were tailored to the communicative context and to partner-specific information. These findings indicate that human referential pointing is planned and controlled on the basis of partner-specific knowledge, over and above the tagging of motor routines with ostensive cues.

Contains fulltext : 173517.pdf (Publisher’s version ) (Open Access) The current study was designed to examine whether 1-year-old infants relate the perception of others' being touched to their own sensorimotor system, and whether they distinguish between animate and inanimate targets. During electroencephalography (EEG) assessment, infants watched video sequences in which either a human or a non-human target was touched/not touched by another object. Comparisons of sensorimotor alpha activation (7-9 Hz) on centro-parietal electrodes revealed differential cortical reactivity to the touch versus non-touch situations for the human-, but not or the non-human target. Our findings indicate that infants relate others' sensory experiences to their own sensorimotor system. 9 p.

Several studies have suggested both a local and network reorganization of the sensorimotor system following amputation. Transplantation of a new limb results in a new shifting of cortical activity in the local territory of the transplanted limb. However, there is a lack of information about the reversibility of the abnormalities at the network level. The objective of this study was to characterize the functional connectivity changes between the cortical territory of the new hand and two intrinsic network of interest: the sensorimotor network (SMN) and the default mode network (DMN) of one patient whom received bilateral forearm transplants. Using resting-state fMRI these two networks were identified across four different time points, starting four months after the transplantation surgery and during three consecutive years while the patient underwent physical rehabilitation. The topology of the SMN was disrupted at the first acquisition and over the years returned to its canonical pattern. Analysis of the DMN showed the normal topology with no significant changes across acquisitions. Functional connectivity between the missing hand's cortical territory and the SMN increased over time. Accordingly, functional connectivity between the missing hand's cortical territory and the DMN became anticorrelated over time. Our results suggest that after transplantation a new reorganization occurs at the network level, supporting the idea that extreme behavioral changes can affect not only the local rewiring but also the intrinsic network organization in neurologically healthy subjects. Overall this study provides new insight on the complex dynamics of brain organization.

BACKGROUND: Impairments in fine and gross motor function, coordination, and balance early in development are common in autism spectrum disorders (ASDs). It is unclear whether these deficits persist into adulthood, and whether they may be exacerbated by additional motor problems that often emerge in typical aging. METHODS: We assessed motor skills and used resting state functional magnetic resonance imaging (fMRI) to study intrinsic functional connectivity of the sensorimotor network in 40–65 year-old adults with ASDs (n=17) and typically developing matched adults (n=19). RESULTS: Adults with ASDs scored significantly lower on assessments of motor skills compared to an age-matched group of typical control (TC) adults. Additionally, functional connectivity of the sensorimotor system was reduced, and the pattern of connectivity was more heterogeneous in adults with ASDs. A negative correlation between functional connectivity of the motor system and motor skills, however, was only found in the TC group CONCLUSIONS: Findings suggest behavioral impairment and atypical brain organization of the motor system in middle-age adults with ASDs, accompanied by pronounced heterogeneity.

Humans quickly and sophisticatedly correct their movements in response to changes in the world, such as when reaching to a target that abruptly changes its location. The vigor of these movement corrections is time-dependent, increasing if the time left to make the correction decreases, which can be explained by optimal feedback control (OFC) theory as an increase of optimal feedback gains. It is unknown whether corrections for changes in the world are as sophisticated under full-body motion. For successful visually probed motor corrections during full-body motion, not only the motion of the hand relative to the body needs to be taken into account, but also the motion of the hand in the world should be considered, because their relative positions are changing. Here, in two experiments, we show that visuomotor feedback corrections in response to target jumps are more vigorous for faster passive full-body translational acceleration than for slower acceleration, suggesting that vestibular information modulates visuomotor feedback gains. Interestingly, these corrections do not demonstrate the time-dependent characteristics that body-stationary visuomotor feedback gains typically show, such that an optimal feedback control model fell short to explain them. We further show that the vigor of corrections generally decreased over the course of trials within the experiment, suggesting that the sensorimotor system adjusted its gains when learning to integrate the vestibular input into hand motor control. NEW & NOTEWORTHY Vestibular information is used in the control of reaching movements to world-stationary visual targets, while the body moves. Here, we show that vestibular information also modulates the corrective reach responses when the target changes position during the body motion: visuomotor feedback gains increase for faster body acceleration. Our results suggest that vestibular information is integrated into fast visuomotor control of reaching movements.

Two major concerns with respect to task-based motor functional magnetic resonance imaging (fMRI) are inadequate participants' performance as well as intra- and inter-subject variability in execution of the motor action., SCOPUS: ar.j, info:eu-repo/semantics/published

Senses of ownership (this arm belongs to me) and agency (I am controlling this arm) originate from sensorimotor system. External objects can be integrated into the sensorimotor system following long-term use, and recognized as one's own body. We examined how an (un)embodied prosthetic arm modulates whole-body control, and assessed the components of prosthetic embodiment. Nine unilateral upper-limb amputees participated. Four frequently used their prosthetic arm, while the others rarely did. Their postural sway was measured during quiet standing with or without their prosthesis. The frequent users showed greater sway when they removed the prosthesis, while the rare users showed greater sway when they fitted the prosthesis. Frequent users reported greater everyday feelings of postural stabilization by prosthesis and a larger sense of agency over the prosthesis. We suggest that a prosthetic arm maintains or perturbs postural control, depending on the prosthetic embodiment, which involves sense of agency rather than ownership.

Summary Background Kinesiology tape can improve athletic performance; however, due to cutaneous stimulation its application can have an influence on proprioception. Objectives To determine the effects of kinesiology tape on knee proprioception applied to quadriceps, namely in the joint position sense (JPS) and in the threshold to detect passive movement (TTDPM), both immediately after and 24 h after its application. Methods Thirty young healthy participants were randomly divided into experimental and control group. In the experimental group, a kinesiology tape on the quadriceps muscle was applied. The JPS and the TTDPM of the knee was assessed before, immediately after and 24 h after the kinesiology tape intervention. Results No significant differences were found in the assessment made before intervention. The Friedman Test showed that kinesiology tape had no influence on JPS in either group over time (p > 0.05). However, the TTDPM decreased significantly immediately after and 24 h after its application (p

Maladaptive plasticity in the sensorimotor system, following neurological lesions or diseases, plays a central role in the generation and maintenance of neuropathic pain. Repetitive magnetic stimulation of the central and peripheral nervous system has gained relevance as noninvasive approach for neuromodulation and pain relief. Systematic reviews that evaluate the effectiveness and specificity of different protocols of repetitive magnetic stimulation to control neuropathic pain in clinical populations have the potential to improve the therapeutic applicability of this technique.Studies whose primary goal was to evaluate the effectiveness of repetitive magnetic stimulation for the treatment of various types of neuropathic pain published in PubMed until August 2015 have been included in this systematic review.A total of 39 articles fulfilling the inclusion criteria were analyzed of which 37 studies investigated pain modulation using repetitive magnetic stimulation over the motor or non-motor cortices and two studies evaluated pain modulation using repetitive peripheral magnetic stimulation protocols.Repetitive transcranial magnetic stimulation of the primary motor cortex using high frequency stimulation protocols can effectively reduce neuropathic pain, particularly in individuals with pain related to non-cerebral lesions. The application of multiple sessions can lead to long-lasting pain modulation and cumulative effects. Implications for Rehabilitation Maladaptive plasticity plays a central role in sensitization of nociceptive pathways, generation and maintainance of neuropathic pain; Most neuropathic pain conditions are refractory to pharmacological therapies; Repetitive magnetic stimulation of the central and peripheral nervous system has gained relevance as noninvasive approach for neuromodulation and pain relief.

Can playing action video games improve visuomotor control? If so, can these games be used in training people to perform daily visuomotor-control tasks, such as driving? We found that action gamers have better lane-keeping and visuomotor-control skills than do non-action gamers. We then trained non-action gamers with action or nonaction video games. After they played a driving or first-person-shooter video game for 5 or 10 hr, their visuomotor control improved significantly. In contrast, non-action gamers showed no such improvement after they played a nonaction video game. Our model-driven analysis revealed that although different action video games have different effects on the sensorimotor system underlying visuomotor control, action gaming in general improves the responsiveness of the sensorimotor system to input error signals. The findings support a causal link between action gaming (for as little as 5 hr) and enhancement in visuomotor control, and suggest that action video games can be beneficial training tools for driving.

The 28th annual Barrels meeting was held prior to the Society for Neuroscience meeting in October 2015 at the Northwestern University School of Law in Chicago, Illinois. The meeting brought together researchers focused on the rodent sensorimotor system. The meeting focused on modern techniques to decipher cortical circuits, social interactions among rodents, and decision-making. The meeting allowed investigators to share their work via short talks, poster presentations, and a data blitz.

Neural synchrony has been suggested as a mechanism for integrating distributed sensorimotor systems involved in coordinated movement. To test the role of corticomuscular and intermuscular coherence in bimanual coordination, we experimentally manipulated the degree of coordination between hand muscles by varying the sensitivity of the visual feedback to differences in bilateral force. In 16 healthy participants, cortical activity was measured using EEG and muscle activity of the flexor pollicis brevis of both hands using high-density electromyography (HDsEMG). Using the uncontrolled manifold framework, coordination between bilateral forces was quantified by the synergy index R V in the time and frequency domain. Functional connectivity was assessed using corticomuscular coherence between muscle activity and cortical source activity and intermuscular coherence between bilateral EMG activity. The synergy index increased in the high coordination condition. R V was higher in the high coordination condition in frequencies between 0 and 0.5 Hz; for the 0.5- to 2-Hz frequency band, this pattern was inverted. Corticomuscular coherence in the beta band (16–30 Hz) was maximal in the contralateral motor cortex and was reduced in the high coordination condition. In contrast, intermuscular coherence was observed at 5–12 Hz and increased with bimanual coordination. Within-subject comparisons revealed a negative correlation between R V and corticomuscular coherence and a positive correlation between R V and intermuscular coherence. Our findings suggest two distinct neural pathways: 1) corticomuscular coherence reflects direct corticospinal projections involved in controlling individual muscles; and 2) intermuscular coherence reflects diverging pathways involved in the coordination of multiple muscles.

Learning a novel movement requires a new set of kinematics to be represented by the sensorimotor system. This is often accomplished through imitation learning where lower-level sensorimotor processes are suggested to represent the biological motion kinematics associated with an observed movement. Top-down factors have the potential to influence this process based on the social context, attention and salience, and the goal of the movement. In order to further examine the potential interaction between lower-level and top-down processes in imitation learning, the aim of this study was to systematically control the mediating effects during an imitation of biological motion protocol. In this protocol, we used non-human agent models that displayed different novel atypical biological motion kinematics, as well as a control model that displayed constant velocity. Importantly the three models had the same movement amplitude and movement time. Also, the motion kinematics were displayed in the presence, or absence, of end-state-targets. Kinematic analyses showed atypical biological motion kinematics were imitated, and that this performance was different from the constant velocity control condition. Although the imitation of atypical biological motion kinematics was not modulated by the end-state-targets, movement time was more accurate in the absence, compared to the presence, of an end-state-target. The fact that end-state targets modulated movement time accuracy, but not biological motion kinematics, indicates imitation learning involves top-down attentional, and lower-level sensorimotor systems, which operate as complementary processes mediated by the environmental context.

The control of ankle muscle force is an integral component of walking and postural control. Aging impairs the ability to produce force steadily and accurately, which can compromise functional capacity and quality of life. Here, we hypothesized that reduced force control in older adults would be associated with altered cortico-cortical communication within a network comprising the primary motor area (M1), the premotor cortex (PMC), parietal, and prefrontal regions. We examined electroencephalographic (EEG) responses from fifteen younger (20-26 yr) and fifteen older (65-73 yr) participants during a unilateral dorsiflexion force-tracing task. Dynamic Causal Modelling (DCM) and Parametric Empirical Bayes (PEB) were used to investigate how directed connectivity between contralateral M1, PMC, parietal, and prefrontal regions was related to age group and precision in force production. DCM and PEB analyses revealed that the strength of connections between PMC and M1 were related to ankle force precision and differed by age group. For young adults, bidirectional PMC-M1 coupling was negatively related to task performance: stronger backward M1-PMC and forward PMC-M1 coupling was associated with worse force precision. The older group exhibited deviations from this pattern. For the PMC to M1 coupling, there were no age-group differences in coupling strength; however, within the older group, stronger coupling was associated with better performance. For the M1 to PMC coupling, older adults followed the same pattern as young adults - with stronger coupling accompanied by worse performance - but coupling strength was lower than in the young group. Our results suggest that bidirectional M1-PMC communication is related to precision in ankle force production and that this relationship changes with aging. We argue that the observed age-related differences reflect compensatory mechanisms whereby older adults maintain performance in the face of declines in the sensorimotor system.

Voices are a primary source of emotional information in everyday interactions. Being able to process non-verbal vocal emotional cues, namely those embedded in speech prosody, impacts on our behaviour and communication. Extant research has delineated the role of temporal and inferior frontal brain regions for vocal emotional processing. A growing number of studies also suggest the involvement of the motor system, but little is known about such potential involvement. Using resting-state fMRI, we ask if the patterns of motor system intrinsic connectivity play a role in emotional prosody recognition in children. Fifty-five 8-year-old children completed an emotional prosody recognition task and a resting-state scan. Better performance in emotion recognition was predicted by a stronger connectivity between the inferior frontal gyrus (IFG) and motor regions including primary motor, lateral premotor and supplementary motor sites. This is mostly driven by the IFG pars triangularis and cannot be explained by differences in domain-general cognitive abilities. These findings indicate that individual differences in the engagement of sensorimotor systems, and in its coupling with inferior frontal regions, underpin variation in children’s emotional speech perception skills. They suggest that sensorimotor and higher-order evaluative processes interact to aid emotion recognition, and have implications for models of vocal emotional communication. info:eu-repo/semantics/acceptedVersion

BACKGROUND: Relationships between joint position sense and the sensorimotor characteristics such as joint stiffness, time to detect motion, and time to peak torque during a perturbation test have rarely been investigated due to methodological challenges. The purpose of this study was to compare joint position sense and the sensorimotor characteristics in healthy individuals. METHODS: A total of 26 subjects were recruited and completed joint position sense and a perturbation test on isokinetic dynamometer. Joint position sense was assessed by comparison of the absolute angle difference between a reference and replicated position. During the perturbation test, the dynamometer moved the knee flexion angle from 70 to 30 degrees (0 degree represents a full knee extension) at the velocity of 500 degrees per second at random. Subjects were asked to react and pull back the leg as soon as they perceived the movement. Pearson or Spearman’s correlation coefficients were used to assess these relationships (P < 0.05). FINDINGS: Larger joint position sense absolute error values were significantly correlated with higher short-range at 50 milliseconds (r = 0.572, P = 0.002), at 100 milliseconds (ρ = 0.416, P = 0.035), and reactive joint stiffness (r = 0.395, P = 0.046). INTERPRETATION: There was a paradoxical relationship between higher joint stiffness and worsened joint position sense. Potential reasons include sensory weighting within the sensorimotor system and thixotropic properties (after-effects of muscle eccentric contractions to increase stiffness and alter joint position sense).

This study aimed to compare time-to-boundary and sample entropy during a single-leg balance task between individuals with chronic ankle instability (CAI), lateral ankle sprain copers, and healthy controls. Twenty-two participants with CAI, 20 lateral ankle sprain copers, and 24 healthy controls performed a single-leg balance task during an eyes-closed condition. Participants with CAI exhibited lower time-to-boundary values compared with lateral ankle sprain copers and healthy controls. However, we did not find differences in sample entropy variables between cohorts. A decrease in time-to-boundary values in participants with CAI indicated that CAI may constrain the ability of the sensorimotor system to maintain the center of pressure within the boundaries of the base of support. However, the regularity of the center of pressure velocity time series appears not to be altered in the CAI cohort in this study.

Despite the important role of oral texture perception in feeding and nutritional homeostasis, its impairment has not been of particular clinical interest, and no clinical protocol is available to evaluate its acuity. This preliminary study aimed to establish a method to evaluate the acuity of oral texture perception. Because texture perception is regarded as reflecting integrity of the sensorimotor system of the jaw and mouth, we hypothesized that the ability to perceive various aspects of food texture would correlate with each other, and tested our hypothesis in 11 healthy adults. First, we prepared three types of test foods with different dominant textures, each of which comprised a series of stimuli with different ingredient concentrations; we used these test foods in discrimination tests involving pairwise comparison. Tests performed using the up-down staircase method revealed significant correlation among the discrimination thresholds for three test foods, suggesting that acuities of texture perception correlated with each other across different textural attributes. Second, we examined the associations between the acuity of texture perception and some aspects of mechanical sensation of the tongue: tactile and two-point discrimination thresholds, as well as the graininess recognition threshold. The acuity of texture perception of the subjects whose sensitivity was low for at least one of these aspects of mechanical sensation (n = 5) was significantly lower than that exhibited by the other subjects (Wilcoxon rank-sum test, p = 0.0417). We concluded that oral texture perception ability can be evaluated by discrimination tests for specific aspects of texture, using appropriate test foods.

International audience; When performing upper limb reaches, the sensorimotor system can adjust to changes in target location even if the reachinglimb is not visible. To accomplish this task, sensory information about the new target location and the current position of theunseen limb are used to program online corrections. Previous researchers have argued that, prior to the initiation of corrections,somatosensory information from the unseen limb must be transformed into a visual reference frame. However, mostof these previous studies involved movements to visual targets. The purpose of the present study was to determine if visualsensorimotor transformations are also necessary for the online control of movements to somatosensory targets. Participantsperformed reaches towards somatosensory and visual targets without vision of their reaching limb. Target positions wereeither stationary, or perturbed before (~ 450 ms), or after movement onset (~ 100 ms or ~ 200 ms). In response to targetperturbations after movement onset, participants exhibited shorter correction latencies, larger correction magnitudes, andsmaller movement endpoint errors when they reached to somatosensory targets as compared to visual targets. Because referenceframe transformations have been shown to increase both processing time and errors, these results indicate that handposition was not transformed into visual reference frame during online corrections for movements to somatosensory targets.These findings support the idea that different sensorimotor transformations are used for the online control of movementsto somatosensory and visual targets.

Understanding how changes in afferent signal processing may impact the sensorimotor processes is essential for physical therapists whose objective is to actively improve the reorganization of motor function in patients suffering from sensorimotor system disturbance. Because the sensorimotor processes are slowed with the advance in age, we examined whether a single massage session can reactivate the sensorimotor processes of older adult inpatients. Participants were randomly assigned to the experimental (with massage) or control (without massage) groups. Massage was realized on both feet with 7.30 min spent on each foot (Experiment 1), the right foot or the right foot and knee for 10 min (Experiment 2). Body and nonbody mental rotation tasks were used to assess the lower limb motor representation before (pretest), immediately after (Posttest 1) and 24 hr after the massage (Posttest 2). Results showed the positive impact of massage on the body mental rotation task. The activation of the sensorimotor processes can last up to 24 hr depending on the extent of the massaged area. Importantly, the activation of the sensorimotor representation concerned not only the massaged leg but also the contralateral leg. No difference between groups appeared in the nonbody mental rotation task which did not solicit the sensorimotor processes. These results highlighted that peripheral activation via a massage had a specific impact on the sensorimotor processes. Massage is an interesting technique which can help older adult inpatients cope with the slowdown of the signal processing related to advancing age. (PsycINFO Database Record

The mechanoreceptors around the knee are of interest, including those mechanoreceptors related to the anterolateral ligament. Histopathologic evaluations of mechanoreceptors are the first steps in understanding the exact sensorimotor system of the extremities. Many studies have shown these mechanoreceptors, but more electrophysiologic studies are needed to make sense of the reported phenomena. WOS:000489268900031 31604515 Q1

Over the last decade, the application of novel advanced neuroimaging techniques to study congenital brain damage has provided invaluable insights into the mechanisms underlying early neuroplasticity. The concept that is clearly emerging, both from human and nun-human studies, is that functional reorganization in the immature brain is substantially different from that of the more mature, developed brain. This applies to the reorganization of language, the sensorimotor system, and the visual system. The rapid implementation and development of higher order imaging methods will offer increased, currently unavailable knowledge about the specific mechanisms of cerebral plasticity in infancy, which is essential to support the development of early therapeutic interventions aimed at supporting and enhancing functional reorganization during a time of greatest potential brain plasticity.

To accurately estimate the state of the body, the nervous system needs to account for delays between signals from different sensory modalities. To investigate how such delays may be represented in the sensorimotor system, we asked human participants to play a virtual pong game in which the movement of the virtual paddle was delayed with respect to their hand movement. We tested the representation of this new mapping between the hand and the delayed paddle by examining transfer of adaptation to blind reaching and blind tracking tasks. These blind tasks enabled to capture the representation in feedforward mechanisms of movement control. A Time Representation of the delay is an estimation of the actual time lag between hand and paddle movements. A State Representation is a representation of delay using current state variables: the distance between the paddle and the ball originating from the delay may be considered as a spatial shift; the low sensitivity in the response of the paddle may be interpreted as a minifying gain; and the lag may be attributed to a mechanical resistance that influences paddle’s movement. We found that the effects of prolonged exposure to the delayed feedback transferred to blind reaching and tracking tasks and caused participants to exhibit hypermetric movements. These results, together with simulations of our representation models, suggest that delay is not represented based on time, but rather as a spatial gain change in visuomotor mapping.Significance StatementIt is known that the brain copes with sensory feedback delays to control movements, but it is unclear whether it does so using a representation of the actual time lag. We addressed this question by exposing participants to a visuomotor delay during a dynamic game of pong. Following the game, participants exhibited hypermetric reaching and tracking movements that indicate that delay is represented as a visuomotor gain rather than as a temporal shift.

Objectives Significant advances in laryngotracheal reconstruction over the last few decades have revolutionised the management of paediatric patients with complex congenital or acquired airway stenosis. The primary aim of laryngotracheal reconstruction has focused primarily on airway and surgery specific outcomes, often at the expense of voice, as well as swallowing function, which are all intricately related. There is currently a paucity of data on swallowing outcome. The goal of this paper is to review and discuss the existing research on the impact of laryngotracheal on swallowing. Methods Narrative review. Results Successful and safe oral feeding in children requires a highly complex and integrated sensorimotor system for proper timing and coordination, beginning with a well-coordinated suck-swallow-breathe sequence in infancy. Factors to consider include the normal laryngeal anatomy, nutrition as a stimulus and the development of feeding skills on swallowing, the underlying aetiology and other risk factors, LTR procedures and their adjuncts. All these impact on the children's growth. Swallow assessments and rehabilitation is therefore an important part of the post-operative care. Conclusions As airway reconstructive surgeries have improved in airway and surgery specific outcomes, swallowing function is an important secondary outcome that impacts on the children's and their families' life. Management in a multi-disciplinary manner will optimise the outcome and improve their quality of life.

Our sensorimotor system appears to be influenced by the recent history of our movements. Repeating movements toward a particular direction is known to have a dramatic effect on involuntary movements elicited by cortical stimulation-a phenomenon that has been termed use-dependent plasticity. However, analogous effects of repetition on behavior have proven elusive. Here, we show that movement repetition enhances the generation of similar movements in the future by reducing the time required to select and prepare the repeated movement. We further show that this reaction time advantage for repeated movements is attributable to more rapid, but still flexible, preparation of the repeated movement rather than anticipation and covert advance preparation of the previously repeated movement. Our findings demonstrate a powerful and beneficial effect of movement repetition on response preparation, which may represent a behavioral counterpart to use-dependent plasticity effects in primary motor cortex.

International audience; When we make rapid reaching movements, we have to trade speed for accuracy. To do so, the trajectory of our hand is the result of an optimal balance between feed-forward and feed-back control in the face of signal-dependant noise in the sensorimotor system. How far do these principles of trajectory formation still apply after a stroke, for persons with mild to moderate sensorimotor deficits who recovered some reaching ability? Here, we examine the accuracy of fast hand reaching movements with a focus on the information capacity of the sensorimotor system and its relation to trajectory formation in young adults, in persons who had a stroke and in age-matched control participants. We find that persons with stroke follow the same trajectory formation principles, albeit parameterized differently in the face of higher sensorimotor uncertainty. Higher directional errors after a stroke result in less feed-forward control, hence more feed-back loops responsible for segmented movements. As a consequence, movements are globally slower to reach the imposed accuracy, and the information throughput of the sensorimotor system is lower after a stroke. The fact that the most abstract principles of motor control remain after a stroke suggests that clinicians can capitalize on existing theories of motor control and learning to derive principled rehabilitation strategies.