Sonie, S. | bioRxiv Science

bioRxiv2026

Distinct SMA beta bursts support the development of anticipatory postural control in children

To produce smooth and coordinated movements, the brain generates anticipatory postural adjustments (APA) - feedforward motor commands that counteract predicted postural disturbances before they occur. Although APA emerge early in life, their maturation extends into early adulthood, yet little is known about the underlying neural mechanisms. Using magnetoencephalography during a naturalistic bimanual load-lifting task, we investigated anticipatory postural control in children aged 7-12 years. In this task, lifting a load from the contralateral postural forearm induces upward elbow rotation, which is anticipatorily counteracted by inhibition of Biceps brachii postural activity, stabilizing forearm posture. Surprisingly, despite greater variability in inhibition timing and less efficient forearm stabilization in children, the mechanism of anticipatory inhibition was consistent with that recently described in adults: it was mediated by transient oscillatory beta bursts (19-24 Hz), associated with reduced supplementary motor area (SMA) excitability indexed by high-gamma (90-130 Hz) power suppression, and preceded by directed influences from lateral prefrontal and ventral premotor cortex. However, burst frequency was lower in children, and an additional APA mechanism was recruited: while 19-24 Hz bursts were linked to immediate SMA suppression and stronger muscle inhibition, higher-frequency bursts (24-29 Hz) were associated with delayed ([~]100 ms) SMA suppression mediated by alpha activity (8 Hz), which attenuated post-inhibition forearm instability. These results reveal that children in middle childhood already engage adult-like neural mechanisms for anticipatory inhibition, while additionally recruiting a compensatory mechanism to counteract postural imprecision, providing new insights into the neural basis of APA maturation and its alteration in neurodevelopmental conditions.

neuroscience↗

bioRxiv2024

Perception/action coupling in children with autism: insights from looking time and pupil dilation measurements

The objective of this study was to characterize, through indices extracted from eye-tracking measurements, the spontaneous distinction of videos of daily actions with a variable perception/action coupling, depending on whether, for the same action, the video was presented in the forward reading direction (strong coupling), or in the backward reading direction (weaker coupling). 17 pairs of videos of daily actions performed by adults were viewed by 36 typically developing children and 28 children with ASD aged 7-18 years. During the exposure phase, they watched two videos of the same action (forward and backward) presented successively, before looking at these two videos in competition, in a second visual preference phase. During the exposure phase, all participants paid similar general attention to each of the videos. We found greater pupillary dilation for backward than forward actions in both groups, but significantly less in the ASD group. In the visual preference phase, both groups showed significantly greater looking times for backward actions over forward ones, with no difference between groups. If TD children perceived the kinematics of the backward videos as violating their expectations given the strong perception/action coupling they had already built over that action, on the contrary, the lower increased in pupil dilation found in ASD children could reflect altered perception/action coupling. This study confirms the validity of looking time and pupil dilation as behavioral and physiological markers that could be used in a 10-mn eye-tracking test to explore perception/action coupling in childhood and in ASD. Lay summaryPeople with ASD often have difficulty understanding the actions of others. The fine understanding of actions requires a coupling between the action we observe, and its representation stored in our memory. This process might be challenged in autism. Here we used a 10-mn eye-tracking test to explore perception/action coupling in ASD. Participants were watching videos of daily actions. Looking time and pupil dilation were measured while participants watched videos of daily actions, and were found to be relevant indexes.

neuroscience↗