NicholasG. Hatsopoulos’s research while affiliated with University of Chicago and other places

Voluntary movement initiation involves the modulations of large groups of neurons in the primary motor cortex (M1). Yet similar modulations occur during movement planning when no movement occurs. Here, we show that a sequential spatiotemporal pattern of excitability propagates across M1 prior to the movement initiation in one of two oppositely oriented directions along the rostro-caudal axis. Using spatiotemporal patterns of intracortical microstimulation, we find that reaction time increases significantly when stimulation is delivered against, but not with, the natural propagation direction. Functional connections among M1 units emerge at movement that are oriented along the same rostro-caudal axis but not during movement planning. Finally, we show that beta amplitude profiles can more accurately decode muscle activity when they conform to the natural propagating patterns. These findings provide the first causal evidence that large-scale, propagating patterns of cortical excitability are behaviorally relevant and may be a necessary component of movement initiation.

DefinitionNeuromotor prostheses or, more commonly referred to as brain-machine interfaces (BMIs) or brain-computer interfaces (BCIs), refer to systems controlling prosthetic devices via an interface with ensembles of the neurons often from the cortex. Electrical potentials emanating from neurons in the vicinity of an electrode interface are decoded to extract useful control signals for external devices, typically an artificial limb or a robot. Nonelectric potentials such as the metabolic signals are also being used in some BMIs.IntroductionCortically controlled BMIs utilize voluntary modulations of cortical neurons in controlling an external prosthetic device. The system-level architecture of a BMI setup is shown in Fig. 1. Individual neural signals, i.e., action potential spikes, local field potentials, ECoGs, and EEGs, or a combination of these signals, can be used to control a motor prosthesis. Temporal and spectral modulations of these signals are typically mapped (or decoded) to g ...