SOMATOSENSORY INPUT DRIVES MEMBRANE POTENTIAL DYNAMICS IN MOTOR CORTEX DURING VOLUNTARY LIMB MOVEMENT

How the motor cortex controls movement remains a fundamental question in neuroscience. Although somatosensory input is thought to influence motor cortex activity and the execution of voluntary movements, its role in driving motor cortex activity during voluntary behavior remains unclear.
To address this, we performed whole-cell recordings from motor cortex neurons in mice during self-initiated, voluntary forelimb movements, and assessed the role of somatosensory input by transecting the sensory nerves innervating the forelimb. In the absence of somatosensation, mice were still able to perform forelimb movements, including reaches, but these movements were significantly slower and more prolonged.
Membrane potential recordings showed that cortical state changes were centrally generated, whereas external somatosensory input drives motor cortical activity before movement onset, curtails synaptic input during reaching to a hyperpolarized reversal potential value, and shapes membrane potential dynamics correlated with limb kinematics.
Together, these findings demonstrate that somatosensory inputs play a central role in shaping the motor cortex activity and its control of limb movement.