Figure 2.
Mean peristimulus time histograms of neural activity aligned on target appearance. A, Examples of neural modulation in nine cells during a 700 ms time window aligned on the time of the target appearance (0 ms). Each panel plots the average firing rate in time of one neuron with respect to the appearance of the target during active movement (dark blue trace), target and cursor observation condition (orange trace), target-only observation condition (red trace), and cursor-only observation condition (cyan trace). B, top, shows the distribution of depth of modulation over all recorded neurons per condition measured as the ratio of the difference between maximum and minimum post-target hit firing rate to the SD of neural activity before target hit. MI population data for monkeys MK and RS are shown in dark and light orange colors, respectively. PMd population data for monkeys MK and RX are shown in light blue and dark blue colors, respectively. The median of each distribution is marked by the notch and a horizontal line in each vertical bar. The lower and upper quartiles of each distribution are marked by the bottom and top of each vertical bar, respectively. The vertical dashed lines above and below the vertical bars represent the full range of the data. B, bottom, shows the similarity in neural activity as measured by correlation coefficient of the modulation profiles during active movement with modulation profiles during the three observation conditions.
