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 + τ 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 τ 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 +90 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.