Figure 4.

Compund synaptic phase-resetting curve of globus pallidus neurons for subthalamic stimulation. (A) The connections between the subthalamic nucleus and globus pallidus neurons in the internal (GPi) and external (GPe) segments. Red indicates excitation; blue is inhibition (B) Post-stimulus histogram of single stimuli with latencies of 1 ms for excitation and 1.5 ms for inhibition, and excitatory and inhibitory current time constants of 2.5 and 6.0 ms respectively. (C) Compound synaptic phase-resetting curves for three stimulus intensities. (D) Stimulus intensity and frequency map of Lyapunov exponenents for the stochastic compound subthalamo-pallidal phase map, based on a baseline firing rate of 60 spikes/s. (E) Stationary probability distributions of firing time relative to DBS stimulation at 114 Hz, for the same threestimulus intensities shown in (C). (F) Steady-state average firing rate during 114 Hz. DBS across the range of stimulus intensities.