Figure 4.

A: Response metrics extracted from mean across-trials SDFs included response onset latency, response magnitude, and response duration. (Using conventions from Fig. 3A.)

B-C: Mean (± SEM) response onset latencies relative to movement onset (B) and go-cue (C) for each response type (green: pre-MPTP, magenta: post-MPTP). MPTP administration shifted responses to earlier onset latencies relative to the time of movement onset (B: ** p<0.01). Relative to the time of go-cue presentation (C), mean latencies did not differ comparing whole pre- versus post-MPTP populations, but latency shifts did differ between the two animals (B: †† , p<0.001). Following MPTP, go-cue -to- response latencies were prolonged in animal G (open circles) while they were shortened in animal I (open triangles).

D: Mean response magnitudes were attenuated following MPTP administration. That attenuation was more severe for decrease-type responses and the decrease component of Poly(−/+) type responses. E: Response durations were prolonged following MPTP administration and that prolongation was accentuated in animal G.

F-G: Two potential mechanisms underlie the observed response attenuation and prolongation post-MPTP: F, an increase in the trial-to-trial temporal dispersion (“jitter”) of responses relative to the task event used for alignment. G, a true attenuation and widening of the neuronal response. For both proposed mechanisms, trial-by-trial rasters of simulated spike trains (top) and across-trials mean SDFs of those simulated spike trains (bottom) are shown as they appear when aligned on a task event (left) and aligned on the actual onset of the simulated response (right). Red circles: times of response onset on individual trials. Below each raster, horizontal box plots depict the trial-by-trial distribution of response onsets (IQR).