Cortical activity during motor execution, motor imagery, and imagery-based online feedback

TLDR

Motor imagery is crucial for learning complex motor skills, such as tennis serves and ballet pirouettes. The study aims to identify the neural substrates underlying motor imagery-based learning. Eight subjects’ electrocorticographic recordings during overt action and kinesthetic imagery were analyzed for high- and low-frequency power, and compared with electrocortical stimulation to confirm primary motor areas’ involvement in imagery. Motor imagery elicits a spatially similar cortical activity pattern to actual movement, with about 25% of the magnitude, but when used for online cursor control, the imagery-induced activity can surpass that of overt movement.

Abstract

Imagery of motor movement plays an important role in learning of complex motor skills, from learning to serve in tennis to perfecting a pirouette in ballet. What and where are the neural substrates that underlie motor imagery-based learning? We measured electrocorticographic cortical surface potentials in eight human subjects during overt action and kinesthetic imagery of the same movement, focusing on power in “high frequency” (76–100 Hz) and “low frequency” (8–32 Hz) ranges. We quantitatively establish that the spatial distribution of local neuronal population activity during motor imagery mimics the spatial distribution of activity during actual motor movement. By comparing responses to electrocortical stimulation with imagery-induced cortical surface activity, we demonstrate the role of primary motor areas in movement imagery. The magnitude of imagery-induced cortical activity change was ∼25% of that associated with actual movement. However, when subjects learned to use this imagery to control a computer cursor in a simple feedback task, the imagery-induced activity change was significantly augmented, even exceeding that of overt movement.