Fig. 4.

Sequence of events involved in GPi ERNA generation. A) Subthalamo-pallidal microcircuit, from the perspective of GPi. GPi receives inhibitory input from GPe and excitatory input from the STN. GPi also sends inhibitory projections to the thalamus. GPe receives excitatory input from STN and inhibitory feedback from other GPe neurons. B) Sequence of events after a DBS pulse. i) GPi afferent and efferent are activated by the DBS pulse. ii) 0.5–1.5 ​ms, antidromic input excites GPe. iii) 1.5–3.5 ​ms, GPe recurrent feedback inhibits the GPe and disinhibits the STN. In parallel, the GPe output from step (ii) arrives at GPi and causes inhibition – manifested as P1 in the GPi LFP. vi) 3.5–5.5 ​ms, excitatory drive from the engaged STN drives both GPe and GPi. In parallel, the GPe output from step (iii) arrives at GPi and causes disinhibition – manifested as N1 in the GPi LFP. v) 5.5–8 ​ms, GPe output from step (iv) arrives at GPi and again causes inhibition – manifested as P2 in the GPi LFP.