Left Hemisphere Dominance for Bilateral Kinematic Encoding in the Human Brain

Abstract

Neurophysiological studies in humans and non-human primates have revealed movement representations in both the contralateral and ipsilateral hemisphere. Inspired by clinical observations, we ask if this bilateral representation differs for the left and right hemispheres. Electrocorticography (ECoG) was recorded in human participants during an instructed-delay reaching task, with movements produced with either the contralateral or ipsilateral arm. Using a cross-validated kinematic encoding model, we found stronger bilateral encoding in the left hemisphere, an effect that was present during preparation and was amplified during execution. Consistent with this asymmetry, we also observed better across-arm generalization in the left hemisphere, indicating similar neural representations for right and left arm movements. Notably, these left hemisphere electrodes were largely located over premotor and parietal regions. The more extensive bilateral encoding in the left hemisphere adds a new perspective to the pervasive neuropsychological finding that the left hemisphere plays a dominant role in praxis.

Handedness Does Not Impact Inhibitory Control, but Movement Execution and Reactive Inhibition Are More under a Left-Hemisphere Control

“…In fact, reactive but not proactive inhibition seems to be computed mainly by the left hemisphere. Our findings are in line with evidence showing a left-hemispheric dominance in some aspects of movement control [82][83][84][85], including inhibition [50].…”

“…However, there is a second, not mutually exclusive, explanation for the better reactive inhibition of the right arm. As stated above, the ipsilateral cortical representation of reaching arm movements is stronger in the left than in the right hemisphere [82]. This means that when the left arm is moved, both hemispheres are active, while when the right arm is moved, just the left hemisphere is active.…”

“…Very importantly, a recent study showed that the ipsilateral cortical representation of reaching arm movements strikingly differs between the left and right hemispheres [82]. Merrick et al [82], using a kinematic encoding model, analyzed six patients' electrocorticographic activity across the two hemispheres. They found that ipsilateral encoding was much stronger in the left than in the right hemisphere.…”