Perceiving What Is Reachable Depends on Motor Representations: Evidence from a Transcranial Magnetic Stimulation Study

Background: Visually determining what is reachable in peripersonal space requires information about the egocentric location of objects but also information about the possibilities of action with the body, which are context dependent. The aim of the present study was to test the role of motor representations in the visual perception of peripersonal space. Methodology: Seven healthy participants underwent a TMS study while performing a right-left decision (control) task or perceptually judging whether a visual target was reachable or not with their right hand. An actual grasping movement task was also included. Single pulse TMS was delivered 80 % of the trials on the left motor and premotor cortex and on a control site (the temporo-occipital area), at 90 % of the resting motor threshold and at different SOA conditions (50ms, 100ms, 200ms or 300ms). Principal Findings: Results showed a facilitation effect of the TMS on reaction times in all tasks, whatever the site stimulated and until 200ms after stimulus presentation. However, the facilitation effect was on average 34ms lower when stimulating the motor cortex in the perceptual judgement task, especially for stimuli located at the boundary of peripersonal space. Conclusion: This study provides the first evidence that brain motor area participate in the visual determination of what is reachable. We discuss how motor representations may feed the perceptual system with information about possibl

Neural mechanisms involved in the functional linking of motor cortical points

We sought to understand the basic neural processes involved in the functional linking of motor cortical points. We asked which of the two basic neural mechanisms, excitation or inhibition, is required to functionally link motor cortical points. In the ketamine-anaesthetized cat, a microstimulation electrode was positioned at a point (control point) that was identified by the following three characteristics of the EMG responses: the muscle(s) activated at threshold, any additional muscles recruited by supra-threshold stimulation, and their relative latency. A second distinct point (test point) producing activation of a muscle at a different joint was then identified. At this test cortical point the GABAA receptor antagonist bicuculline was ejected iontophoretically, while stimulating the control point near threshold. A combined response was elicited consisting of the response normally elicited at the control point plus that elicited at the test point. Thus, an artificial muscle synergy was produced following disinhibition of the test point. This was never the case when glutamate was ejected at the test point, even when supra-threshold stimuli were used at the control point. Therefore, simply increasing the excitability of a cortical point was not sufficient to release the muscle(s) represented at that point into a muscle synergy. Kynurenate, a broadly acting excitatory amino acid receptor antagonist, ejected at the bicuculline point reversed the effect of bicuculline. This shows that the release phenomenon was mediated synaptically and was not due to spread of the stimulating current. We suggest that release from inhibition may be one of the neural mechanisms involved in functionally linking motor cortical points. This functional linking may be part of the ensemble of motor cortical mechanisms involved in recruitment of muscle synergies

Cross-cultural translation and psychometric validation of the French version of the Fear-Avoidance Components Scale (FACS)

International audienceBackground The Fear-Avoidance Components Scale (FACS) is a reliable and valid instrument widely used to assess fear-avoidance beliefs related to pain and disability. However, there is a scarcity of validated translations of the FACS in different cultural and linguistic contexts, including the French population. This study aimed to translate and validate the French version of the FACS (FACS-Fr/CF), examining its psychometric properties among French-speaking individuals. Methods A cross-cultural translation process–including forward translation, backward translation, expert committee review, and pre-testing–was conducted to develop the FACS-Fr/CF. The translated version was administered to a sample of French-speaking adults (n = 55) with chronic musculoskeletal pain. Internal consistency (including confirmatory analyses of the 2 factors identified in the Serbian version), test-retest reliability and convergent validity were then assessed. Results The FACS-Fr/CF demonstrated high global internal consistency (α = 0.94, 95% CI: 0.91–0.96) as well as high internal consistency of the 2 factors identified in the Serbian version (α = 0.90, 95% CI: 0.86–0.94 and α = 0.90, 95% CI: 0.85–0.94, respectively). Test-retest analysis revealed a moderate (close to high) reliability (ICC = 0.89; 95% CI: 0.82–0.94 and r = 0.89; p <0.005). Convergent validity was supported by significant correlations between the FACS-Fr/CF scores and the Tampa Scale for Kinesiophobia (r = 0.82; p < 0.005), the Pain Catastrophizing Scale (r = 0.72; p < 0.005) and the Hospital Anxiety and Depression Scale (r = 0.66; p < 0.005). Conclusion The present study provides evidence for the cross-cultural translation and psychometric validation of the FACS-Fr/CF. The FACS-Fr/CF exhibits a high internal consistency, a moderate (close to high) test-retest reliability, and good construct validity, suggesting its utility in assessing fear-avoidance beliefs in the French-speaking population. This validated tool can enhance the assessment and understanding of fear-avoidance behaviors and facilitate cross-cultural research in pain-related studies

Effect of the SOA and the site where TMS was delivered on reaction times in the perceptual judgement of what is reachable task.

<p>(a) Data represent absolute reaction times (ms) and standard deviations in for the different SOA conditions (no TMS, 50ms, 100ms, 200ms, 300ms) and the different sites stimulated (occipito-temporal complex, motor cortex, premotor cortex). (b). Data represent relative reaction times (ms) and standard deviations according to the no-TMS condition in the different conditions.</p

Average trajectories for the thumb and index fingers.

<p>Thumb (black circles) and index finger (white circle) trajectories are plotted every 10ms according to the site stimulated (occipito-temporal complex, motor cortex, premotor cortex) in the No-TMS, 50ms-100ms pooled and 200ms–300ms pooled conditions.</p

Kinematic analysis of thumb trajectory.

<p>Data represent the velocity and acceleration of the thumb as a function of the SOA (No-TMS, 50ms–100ms pooled and 200ms–300ms pooled conditions) and for the different sites stimulated (occipito-temporal complex, motor cortex, premotor cortex).</p

Effect of the SOA and the site where TMS was delivered on reaction times in the perceptual judgement of what is reachable task as a function of target location.

<p>Data represent relative reaction times (ms) and standard deviations according to the no-TMS condition for the different SOAs (50ms, 100ms, 200ms, 300ms) and the site where TMS was delivered (motor cortex, contol/premotor area pooled). Upper row: target 1 (near), middle row: target 3 to 5 (intermediary), lower row target 7 (far).</p

A schematic representation of the experimental apparatus and target display in the right-left decision task, the judgement of what is reachable task and the grasping task.

<p>(a) When looking into the apparatus, the bottom part is visible only through optical projection upon the mirror of information coming from the upper part of the apparatus. (b) Targets display in the right-left decision task, the judgement of what is reachable task and the grasping task. (c) Kinogramme of actual grasping movement.</p