FIG. 6.

Models that incorporated synaptic afferent responses during DBS exhibited time-locked behavior overall, but also showed inhibition and a substantial degree of response variability across the spatially distributed population. A: averaged somatic responses to GPi-DBS from a population of model GPi neurons under baseline conditions (n = 10) and during HFS (n = 63). Somatic responses to HFS exhibited a time-locked excitatory phase at 1 and 4–5 ms and an overall decrease in firing frequency across the remainder of the interpulse interval. B: the population, however, exhibited nuanced differences in the somatic response to HFS, which depended on the potential distribution around a particular neuron. C: despite the inhibitory and time-locked behavior within the soma, HFS drove efferent activity through the axons with a prominent excitatory peak at 1 ms and a secondary peak from 5 to 6 ms. D: population responses in the axons similarly depended on stimulation amplitude. These simulations were derived from the GPi neuron population shown in Fig. 4A with stimulation applied through contact 1. Bin widths on the PSTH plots were again 0.05 ms and smoothed with a 5-point averaging window.