How does the brain control our movements?
The role of ipsilateral cortical control of the upper limb
We are elucidating the role of ipsilateral motor cortex during unimanual and bimanual movement. In collaboration with Richard Ivry and Robert Knight, we are conducting parallel neurophysiological studies in human and non-human primates. Electrocorticogram, local field potential, and single unit activity neural recordings will be used to analyze neural activity at different levels of integration.
Previous work from our group has demonstrated that distributed activity in primate motor areas reliably represents ipsilateral upper limb kinematics in monkey and human. This information can be decoded by applying linear methods to neural signals at a variety of temporal and spatial scales, and can be successfully incorporated into a closed-loop BMI system. However, the functional contribution of ipsilateral motor cortex to limb movement remains unclear.
We are testing four, possibly overlapping, hypotheses of ipsilateral representation:
- H1) Activity in ipsilateral motor cortex complements activity in the contralateral hemisphere, providing additional control through the engagement of independent ipsilateral motor pathways.
- H2) Movements of one arm induce activity patterns within ipsilateral motor cortex that are related to the mirror-symmetric movement of the other hand.
- H3) Activity in ipsilateral motor cortex reflects the simultaneous, bilateral preparation of unimanual actions.
- H4) Activity in ipsilateral motor cortex includes a representation of motor commands, or states, from the contralateral hemisphere, information that is especially relevant for coordinating bimanual movements.