Fig. 2.

Relationship between SD of discharge rate (y-axis) and mean discharge rate (x-axis) during the CHT (top) and the TET (bottom). Data are shown separately for the neurons in the motor cortex (left) and the parietal cortex (right). The best-fit power functions (see Results) for the CHT (dotted line) and the TET (solid line) are shown twice for each cortical area for the sake of comparison. Because each movement direction is treated separately for the discharge rates during the TET, but not for the CHT, there are eight times as many data points for the TET than for the CHT. Larger variability among the data points for the TET is probably attributable to a smaller number of trials contributing to each data point.