Figure 5. Waves of activity in a network model of Purkinje cells.

(a) Schematic illustration of the Purkinje cell axon collateral network model (cells numbered starting at the apex of the folium). Each Purkinje cell was connected to the basally-located nearest neighboring five cells (for illustrative purposes, only two connections are shown, and cells have been colored in alternating colors).

(b) Raster plot from network model showing action potentials (individual dots) of Purkinje cells versus time (cells numbered as in (a)). Activation of depolarizing synapses (gray/red border, arrow) triggered waves of activity traveling from the apex to the base of the folium (black arrow).

(c) Activation of hyperpolarizing synapses (gray/blue border, arrow) triggered waves of activity traveling in the opposite direction (black arrow). Note that the connectivity of the two networks in (b) and (c) was identical; only E_GABA differed.

(d - f) Two-dimensional Fourier transformation (2D FFT) contour plots corresponding to the angular spectrum of the raster plots. When the synapse was off (d), the 2D FFT exhibited a flat band in the temporal frequency without structure in the spatial frequency dimension. In contrast, the 2D FFT of the spike trains obtained with depolarizing (e) or hyperpolarizing connections (f) showed peaks corresponding to traveling waves.