Movement parameters and neural activity in motor cortex and area 5.

The relations of ongoing single-cell activity in the arm area of the motor cortex and area 5 to parameters of evolving arm movements in two-dimensional (2D) space were investigated. A multiple linear regression model was used in which the ongoing impulse activity of cells at time t + tau was expressed as a function of the (X, Y) components of the target direction and of position, velocity, and acceleration of the hand at time t, where tau was a time shift (-200 to +200 msec). Analysis was done on 290 cells in the motor cortex and 207 cells in area 5. The time shift at which the highest coefficient of determination (R2) was observed was determined and the statistical significance of the model tested. The median R2 was 0.581 and 0.530 for motor cortex and area 5, respectively. The median shift at which the highest R2 was observed was -90 and +30 msec for motor cortex and area 5, respectively. For most cells statistically significant relations were observed to all four parameters tested; most prominent were the relations to target direction and least prominent those to acceleration.