Abstract
To plan a visually guided movement, the brain must calculate an extrinsic movement vector and then convert this into intrinsic muscle commands for current posture. Where, how and when this happens in the human cortical arm movement planning network remains largely unknown. Here, we use high spatiotemporal resolution magnetoencephalography (MEG) combined with a pro-/anti-wrist pointing task with 3 different forearm postures to investigate this question. First, we then computed cortical source activity in 16 previously identified bilateral cortical areas (Alikhanian, et al., Frontiers in Neuroscience 2013). We then compared pro/anti trials to identify brain areas coding for stimulus direction vs. movement direction. Sensory activity in α / β bands progressed from posterior to anterior cortical areas, culminating in a β-band movement plan in primary motor cortex. During the delay, movement codes then retroactively replaced the sensory code in more posterior areas (Blohm, et al., Cerebral Cortex 2019). We then contrasted oscillatory activity related to opposing wrist postures to find posture coding and test when and where the extrinsic-to-intrinsic transformation occurred. We found a distinct pair of overlapping networks coding for posture (in γ band) vs. posture-specific movement plans (β). Together with previous results showing a yet again different sub-network specifying motor effector and it’s integration (Blohm, et al., J Neurophysiol 2022), we demonstrate that distinct cortical sub-networks carry out different spatiotemporal computations for movement planning.