Behavioral neurophysiology of the motor cortex

Area of Science:

• Neuroscience
• Motor Control Research

Background:

• Over 20 years of research on the motor cortex in behaving monkeys has significantly advanced understanding of motor control mechanisms.
• The motor cortex plays a crucial role in planning and executing voluntary movements, particularly reaching actions in space.

Purpose of the Study:

• To review and elucidate motor cortical functions related to the specification of movement direction.
• To explain how neural activity in the motor cortex encodes movement direction.

Main Methods:

• Analysis of single-cell activity in the motor cortex of behaving monkeys during reaching tasks.
• Investigation of neural population activity and its relationship to movement direction.

Main Results:

• Motor cortex neurons exhibit broad tuning to movement direction, with maximal activity for a preferred direction and decreasing activity for other directions.
• A population vector, formed by summing individual cell vectors (preferred direction and activity level), accurately represents the intended movement direction.
• This population code is active during reaction time, instructed delay, and memorized delay periods, indicating its role in movement planning and execution.

Conclusions:

• The motor cortex uses a population code, based on broadly tuned cells, to specify movement direction.
• This population vector mechanism provides insights into cognitive processes involved in transforming movement commands, such as mental rotation.