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. 2019 Nov 5;13:77. doi: 10.3389/fncom.2019.00077

Figure 4.

Figure 4

Increasing the level of GPe-STN inhibition shifts STN to a low-frequency burst firing mode. Behavior of the autonomous STN-GPe network for increasing values of the GPe to STN synaptic conductance. (A) Mean PSD of the somatic membrane voltages of STN (Ai) and GPe (Aii) neurons. (B,C) Representative spike trains and phase vectors for STN (column i, green) and GPe population (column iii, red) for two values of the GPe to STN conductance [scale 0.33; 2.0 in rows (C,D), respectively]. Column ii shows phase vectors of the STN and GPe populations (in green; red, respectively, mean population vectors plotted as thick solid lines and cell vectors as thin transparent lines) reflecting phase locking to the instantaneous GPe phase. (D) Balance of excitation and inhibition in the STN (Di) and GPe (Dii) based on synaptic currents recorded in three neurons. Population firing rate (brown), E/I ratio (purple), and net synaptic current (blue). Shaded areas represent estimated total synaptic current from one pre-synaptic population during a simulation. (E) Population vector length and angle of STN (green) and GPe (red) population. (F) Metrics that characterize bursting in STN neurons: median burst rate, intra-burst firing rate, and coefficient of variation of ISIs across all STN cells.