Figure 3. Analysis of peak firing rate and movement selectivity.

a–d) Examples of choice-related cells. In each case mean wide-band spike waveform is at top right and recording location at bottom right. Center panels show spike rasters for all trials, aligned on choice execution (event 5) and separated by chosen direction (contraversive on top, ipsiversive on bottom). Epochs with a significant (p < 0.01) contra/ipsi firing rate difference are indicated by color shading (contraversive = gold, ipsiversive = green). Vertical black lines outline the 100 ms period with the most significant contra/ipsi difference (value of peak directional selectivity t-statistic is shown above the bin). The selectivity index value is shown above the rasters, on the right side. Bottom panels show corresponding peri-event time histograms (PETHs) for contraversive (gold), ipsiversive (green), and all trials (black). Bin size = 30 ms, with 3-point moving average smoothing. Session-wide mean firing rate is indicated by a dotted line. Arrows indicate times at which firing rates began to ramp up towards the peak rate, as detected by change-point analysis (see Methods). Above the histograms, the point of peak firing rate across all PETHs is shown with a vertical tick, and the period of greater than quarter-maximal response (i.e. > (mean rate * 0.75 + peak rate * 0.25) by a horizontal colored bar. Rasters and PETHs for all neurons are included in the database online (Supplementary Fig. 8). e) Comparison of change-point time distributions for the FSI and M1 cell populations. Included are FSI, M1 cells that reached peak firing rate in choice execution-aligned PETHs (few such cells were obtained for MSN, GP, so their distributions are not shown). Note the burst of detected FSI, M1 firing rate increases shortly before the onset of the chosen action.