If the motor cortex and its brainstem counterparts send muscle-like signals to the spinal cord, then mechanisms must exist upstream of this point to translate the signals representing our movement intent into signals commanding muscle activation. We study these mechanisms by comparing the signals recorded simultaneously from two anatomically interconnected regions of the brain. For example, we measure activity from both the primary motor cortex and from the cerebellum, a major source of input to the motor cortex. By studying the similarities and differences between these signals, much as in our comparisons of neuronal and muscle signals, we hope to understand the way in which higher level signals are generated and transformed. Experiments like these, we hope, will provide clues to understanding the nature of the brain's command signals that control limb movement.
Figure shows a model of the coordinated control from multiple, correlated neurons.
In all panels, the data were obtained from simulations using a real RNm signal as an input. Functional connectivity between cerebellum and primary motor cortex in the awake monkey. Kinematic properties of rapid hand movements in a knob turning task. Correlation of primate superior colliculus discharge with activity of shoulder and arm musculature. Primate red nucleus discharge encodes the dynamics of limb muscle activity.