Intermuscular coherence reveals that affective emotional pictures modulate neural control mechanisms during the initiation of arm pointing movements.

Introduction: Several studies in psychology provided compelling evidence that emotions significantly impact motor control. Yet, these evidences mostly rely on behavioral investigations, whereas the underlying neurophysiological processes remain poorly understood. Methods: Using a classical paradigm in motor control, we tested the impact of affective pictures associated with positive, negative or neutral valence on the kinematics and patterns of muscle activations of arm pointing movements performed from a standing position. The hand reaction and movement times were measured and electromyography (EMG) was used to measure the activities from 10 arm, leg and trunk muscles that are involved in the postural maintenance and arm displacement in pointing movements. Intermuscular coherence (IMC) between pairs of muscles was computed to measure changes in patterns of muscle activations related to the emotional stimuli. Results: The hand movement time increased when an emotional picture perceived as unpleasant was presented as compared to when the emotional picture was perceived as pleasant. When an unpleasant emotional picture was presented, beta (ß, 15-35 Hz) and gamma (γ, 35-60 Hz) IMC decreased in the recorded pairs of postural muscles during the initiation of pointing movements. Moreover, a linear relationship between the magnitude of the intermuscular coherence in the pairs of posturo-focal muscles and the hand movement time was found in the unpleasant scenarios. Discussion: These findings reveal that emotional stimuli can significantly affect the content of the motor command sent by the central nervous system to muscles when performing voluntary goal-directed movements.

Enhancement of Anticipatory Postural Adjustments by Virtual Reality in Older Adults with Cognitive and Motor Deficits: A Randomised Trial.

BACKGROUND: Postural activities involved in balance control integrate the anticipatory postural adjustments (APA) that stabilize balance and posture, facilitating arm movements and walking initiation and allowing an optimal coordination between posture and movement. Several studies reported the significant benefits of virtual reality (VR) exercises in frail older adults to decrease the anxiety of falling and to induce improvements in behavioural and cognitive abilities in rehabilitation processes. The aim of this study was thus to test the efficiency of a VR system on the enhancement of the APA period, compared to the use of a Nintendo Wii system. METHODS: Frail older adults (n = 37) were included in this study who were randomized and divided into a VR exercises group (VR group) or a control group using the Nintendo Wii system (CTRL group). Finally, 22 patients were included in the data treatment. APA were studied through muscular activation timings measured with electromyographic activities. The functional reach test, the gait speed, and the time up and go were also evaluated before and after a 3-week training phase. RESULTS AND DISCUSSION: As the main results, the training phase with VR improved the APA and the functional reach test score along the antero-posterior axis. Together, these results highlight the ability of a VR training phase to induce neuromuscular adaptations during the APA period in frail older adults. Then, it underlines the effective transfer from learning carried out during the VR training movements to control balance abilities in a more daily life context.

Geriatric Rehabilitation and COVID-19: a Case Report.

The COVID-19 infection has particularly affected older adults. Clinical observations in this population highlight major respiratory impairment associated with the development or aggravation of the patient's frailty state. Mr. P is a 93-year-old frail patient, hospitalized after a COVID-19 infection. The assessment process of this patient has been supported by an innovative multi-systemic tool developed in view of the COVID-19 clinical consequences and a systemic evaluation of motor functions by the Frail'BESTest. This process allowed a mixed clinical picture associated with significant respiratory distress (linked with acute respiratory distress syndrome) and an evident motor frailty. The care plan was developed accordingly, and four assessments were done in the same manner until Mr. P returned home. This case report allows us to see a holistic COVID-19 clinical picture, showing the different axes of clinical reasoning to enhance the rehabilitation process. Furthermore, this case report illustrates the importance of rehabilitation in the COVID-19 context.

Development and evaluation of an adapted physical activity program in anorexia nervosa inpatients: A pilot study.

BACKGROUND AND CONTEXT: Problematic use of physical activity is frequent in subjects with anorexia nervosa (AN). Although it increases resistance to therapeutic treatment, paradoxically, physical activity in AN can also improve mental and physical health. Based on the literature review we hypothesized that adding an adapted physical activity (APA) program to treatment programs could be more beneficial than a total suppression of physical activities. We designed this open study to evaluate the outcome of AN inpatients after an APA program implementation as well as the perceived effect of APA. METHOD: Forty-one women with AN (17.2 (±2.5) years old, BMI of 16.86 (±2.0)) were included. An eight-session (1 h30/session/week) standardized APA program was delivered and evaluated by structured questionnaires assessing exercise dependence, perceived physical activity, eating disorder (ED) symptoms, body mass index (BMI), along with an interview before and after the APA program. RESULTS: Twenty-nine women complete the PA program and evaluation. BMI and perceived PA score significantly increased, ED and exercise dependence scores significantly decreased (p < .01). Participants appreciated the program. DISCUSSION/CONCLUSION: The inpatient program which included APA program helped AN inpatients in decreasing their ED symptoms and their dependence to PA, without any deleterious effect on BMI. Furthermore, APA was appreciated by participants.

Immediate effects of shoes inducing ankle-destabilization around Henke's axis during challenging walking gaits: Gait kinematics and peroneal muscles activities.

Due to its high frequency of occurrence, as well as possible residual symptoms, proper treatment of lateral ankle sprains (LAS) is important. From a physiological point of view, increasing the quantity of electromyographic (EMG) activity in the peroneal muscles will mechanically improve the functional stability of the ankle joint. The present study investigated the immediate effects of an ankle destabilization device (ADD) specifically designed to induce imbalances along the Henke's axis during 3 challenging walking tasks. As the effects of such a device have to be tested on healthy participants before being implemented in rehabilitation programs, 12 healthy participants performed 3 different types of walking (normal, aligned, and jumping walking) while the EMG activities in four peroneal muscles and the main gait kinematics parameters were recorded. Our results clearly demonstrated that wearing the ADD during these different walking tasks significantly increased EMG activities in the four peroneal muscles (increases from 9 to 33% on average depending on the muscle and the walking condition) while maintaining previous gait kinematic patterns. Our study shows that an ADD coupled with walking or jumping tasks is able to improve neuromuscular activity. It should therefore be useful for ankle rehabilitation therapy and the prevention of LAS.

Embodiment and the origin of interval timing: kinematic and electromyographic data.

Recent evidence suggests that interval timing (the judgment of durations lasting from approximately 500 ms. to a few minutes) is closely coupled to the action control system. We used surface electromyography (EMG) and motion capture technology to explore the emergence of this coupling in 4-, 6-, and 8-month-olds. We engaged infants in an active and socially relevant arm-raising task with seven cycles and response period. In one condition, cycles were slow (every 4 s); in another, they were fast (every 2 s). In the slow condition, we found evidence of time-locked sub-threshold EMG activity even in the absence of any observed overt motor responses at all three ages. This study shows that EMGs can be a more sensitive measure of interval timing in early development than overt behavior.

The Early Indicators of Functional Decrease in Mild Cognitive Impairment.

OBJECTIVES: Motor deficiency is associated with cognitive frailty in patients with Mild Cognitive Impairments (MCI). In this study we aimed to test the integrity in muscle synergies involved in an arm-pointing movement in functionally unimpaired MCI patients. We hypothesized that early motor indicators exist in this population at a preclinical level. METHODS: Electromyographic signals were collected for 11 muscles in 3 groups: Young Adults (YA), Older Adults (OA), and MCI patients. The OA and MCI groups presented the same functional status. Each subject performed 20 arm-pointing movements from a standing position. RESULTS: The main differences were (1) an earlier activation of the left Obliquus internus in MCI compared with OA group, (2) an earlier activation for the MCI compared with both OA and YA. The temporal differences in muscle synergies between MCI and OA groups were linked with executive functions of MCI patients, assessed by the trail making test. Moreover, the results show a delayed activation of the right Biceps Femoris and the right Erector Spinae at l3 in MCI and OA compared with YA. INTERPRETATION: The motor program changes highlighted in our patient MCI group suggest that discrete modifications of the motor command seem to exist even in the absence of functional impairment. Instead of showing an indication of delayed muscle activation in the MCI patients, our results highlight some early activation of several trunk muscles.

Motor activity improves temporal expectancy.

Certain brain areas involved in interval timing are also important in motor activity. This raises the possibility that motor activity might influence interval timing. To test this hypothesis, we assessed interval timing in healthy adults following different types of training. The pre- and post-training tasks consisted of a button press in response to the presentation of a rhythmic visual stimulus. Alterations in temporal expectancy were evaluated by measuring response times. Training consisted of responding to the visual presentation of regularly appearing stimuli by either: (1) pointing with a whole-body movement, (2) pointing only with the arm, (3) imagining pointing with a whole-body movement, (4) simply watching the stimulus presentation, (5) pointing with a whole-body movement in response to a target that appeared at irregular intervals (6) reading a newspaper. Participants performing a motor activity in response to the regular target showed significant improvements in judgment times compared to individuals with no associated motor activity. Individuals who only imagined pointing with a whole-body movement also showed significant improvements. No improvements were observed in the group that trained with a motor response to an irregular stimulus, hence eliminating the explanation that the improved temporal expectations of the other motor training groups was purely due to an improved motor capacity to press the response button. All groups performed a secondary task equally well, hence indicating that our results could not simply be attributed to differences in attention between the groups. Our results show that motor activity, even when it does not play a causal or corrective role, can lead to improved interval timing judgments.

Inter-hemispheric remapping between arm proprioception and vision of the hand is disrupted by single pulse TMS on the left parietal cortex.

Parietal cortical areas are involved in sensori-motor transformations for their respective contralateral hemifield/body. When arms of the subjects are crossed while their gaze is fixed straight ahead, vision of the hand is processed by the hemisphere ipsilateral to the arm position and proprioception of the arm by the contralateral hemisphere. It induces interhemispheric transfer and remapping. Our objective was to investigate whether a single pulse TMS applied to the left parietal cortical area would disturb interhemispheric remapping in a similar case, and would increase a simple reaction time (RT) with respect to a control single pulse TMS applied to the frontal cortical area. Two LED were superimposed and located in front of the subjects on the saggital axis. Subjects were asked to carefully fixate on these LED during each trial. The lighting of the red LED was used as a warning signal. Following the green one was illuminated after a variable delay and served as a go-signal. The hand for the response was determined before the start of each trial. TMS was applied to the left parietal, the left frontal cortical areas, or not applied to the subject. Results revealed that: (1) Irrespective of its location, single pulse TMS induced a non-specific effect similar to a startle reflex and reduced RT substantially (15ms on average) with respect to a control condition without TMS (mean value=153ms). (2) Irrespective of TMS, RT were shorter when the right or the left hand was positioned in the right visual hemi-field (i.e. normal and crossed positions respectively). (3) Finally, RT increased when single pulse TMS was applied to the left parietal area and when hands were crossed irrespective of which hand was used. We concluded that interhemispheric sensori-motor remapping was disrupted by a single pulse TMS that was applied to the left parietal cortex. This effect was also combined with some visual attention directed towards the hand located on the right visual hemi-field.

On-line coordination in complex goal-directed movements: a matter of interactions between several loops.

Motor flexibility is the ability to rapidly modify behavior when unexpected perturbations occur. In goal directed movements, this process may be involved during the motor execution itself, by using on-line motor corrections, or off-line, on a trial-by-trial basis. A consensus has emerged to describe and unify these two dependant processes within the framework of the internal models theory in which the cerebellum is involved in error processing. However, this general framework may be incomplete to describe on-line motor corrections when complex motor coordination is involved in the task. In particular, interaction torques existing between different effectors limit the independence between different controllers that could be considered to control various body parts. In addition, recent findings suggest that different (sub)-cortical loops may be involved during orienting responses to visual stimuli but also during on-line motor corrections following visual perturbations. The way these different loops with different dynamics interact but achieve the same motor goal is an important problem in motor control. The simplest organization may be sequential, as in the well-known stretch reflex. This implies that during on-line corrections, the nervous system may be involved in a distributed fashion and that motor plans and synergies depend both on anatomical and temporal constraints. More particularly, motor plans and synergies may be stored and may differ according to the (sub)-cortical loops involved during the whole on-line correction process. Finally, questions concerning the independence (or not) of these loops remain unanswered. The case of strict independence would mean that between the various corrective loops, (i) error processing and (ii) motor plans/synergies would be different. By contrast, in a situation of dependency, it would probably mean that interactions would link lower (and faster) to upper (and longer) loops by informing these latter of the motor corrections sent by the former, similarly to an efference copy.

Muscular synergies during motor corrections: investigation of the latencies of muscle activities.

To reduce the complexity of muscular control, a small number of muscular activations are combined to produce an infinity of movements. This concept of muscle synergies has been widely investigated, mainly by means of principal component analyses (PCA) in the case of unperturbed movements. However, reaching movements can be altered at any time if the target location is changed during their execution. In this case, PCA does not precisely measure the latencies of muscles activities. We develop here a simple method to investigate how a random target jump toward a single location induced motor corrections in the whole musculature by precisely determining the latencies of muscle activities during a complex pointing movement. Our main result demonstrated that both initiation times together as well as correction times together were strongly correlated for some pairs of muscles, independently of their occurrences during the motor sequence and independently of the location of the muscles at the anatomical level. This study thus provides a simple method to investigate the latencies of muscular activities and the way they are correlated between certain muscles to stress the muscular synergies involved in the movement. It also suggests that the CNS re-programs a new synergy after the target jumps in order to correct the on-going reaching movement. This latter corrective synergy involves the control of more muscles together compared to that used to initiate the movement. At the level of the Primary Motor Cortice (M1), muscles appear to be controlled as a coupled functional system, rather than individually and separately.

Equilibrium constraints do not affect the timing of muscular synergies during the initiation of a whole body reaching movement.

The aim of this study was to determine whether the timing of the muscular synergies was influenced by the reduction of the base of support when we initiate a whole body reaching movement. To answer this question, we performed a principal component analysis on electromyographic activities of 24 muscles recorded on the leg, the trunk, and the arm. Our results demonstrated that during the initiation of the whole body pointing movement, only three principal components accounted for at least 95% of the variance for the overall muscular data, both when the equilibrium constraints were normal and when the base of support was reduced. These principal components were strongly correlated despite the fact that the center of mass forward displacement and the center of pressure backward displacements significantly decreased when the base of support was reduced. It suggests that the central nervous system did not change the overall timing of the muscular synergies when new equilibrium constraints were introduced in the task but was rather able to tune their amplitude as evidenced by the modification of the center of mass and center of pressure displacements.