AI Article Synopsis
- The traditional understanding of motor control suggests that movement of limbs on one side of the body is primarily managed by the opposite side of the brain.
- Studies show that damage (or lesions) in one hemisphere typically leads to impairments in the opposite limb, but effects on the same side (ipsilateral) are less clear and could be influenced by the other hemisphere's activity.
- Experiments on monkeys demonstrated that when specific areas in the parietal region of the brain were inactivated, reaching movements were slower in the affected side, confirming that motor control is mainly organized contralaterally, but challenges the idea of whether it's strictly limited to one hemisphere.
Article Abstract
The canonical view of motor control is that distal musculature is controlled primarily by the contralateral cerebral hemisphere; unilateral brain lesions typically affect contralateral but not ipsilateral musculature. Contralateral-only limb deficits following a unilateral lesion suggest but do not prove that control is strictly contralateral: the loss of a contribution of the lesioned hemisphere to the control of the ipsilesional limb could be masked by the intact contralateral drive from the nonlesioned hemisphere. To distinguish between these possibilities, we serially inactivated the parietal reach region, comprising the posterior portion of medial intraparietal area, the anterior portion of V6a, and portions of the lateral occipital parietal area, in each hemisphere of 2 monkeys (23 experimental sessions, 46 injections total) to evaluate parietal reach region's contribution to the contralateral reaching deficits observed following lateralized brain lesions. Following unilateral inactivation, reach reaction times with the contralesional limb were slowed compared with matched blocks of control behavioral data; there was no effect of unilateral inactivation on the reaction time of either ipsilesional limb reaches or saccadic eye movements. Following bilateral inactivation, reaching was slowed in both limbs, with an effect size in each no different from that produced by unilateral inactivation. These findings indicate contralateral organization of reach preparation in posterior parietal cortex. Unilateral brain lesions typically affect contralateral but not ipsilateral musculature. Contralateral-only limb deficits following a unilateral lesion suggest but do not prove that control is strictly contralateral: the loss of a contribution of the lesioned hemisphere to the control of the ipsilesional limb could be masked by the intact contralateral drive from the nonlesioned hemisphere. Unilateral lesions cannot distinguish between contralateral and bilateral control, but bilateral lesions can. Here we show similar movement initiation deficits after combined unilateral and bilateral inactivation of the parietal reach region, indicating contralateral organization of reach preparation.
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| http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8896556 | PMC |
| http://dx.doi.org/10.1523/JNEUROSCI.0232-21.2021 | DOI Listing |
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