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. 2013 Jan 11;8(1):e53854. doi: 10.1371/journal.pone.0053854

Figure 4. Results of simulations in a unit.

Figure 4

(A), (B), and (C) Chaotic synchronization observed in a unit model with Inline graphic PYRs and Inline graphic INs. The values of the parameters are Inline graphic, Inline graphic, Inline graphic, Inline graphic, Inline graphic, Inline graphic, Inline graphic, Inline graphic, Inline graphic, and Inline graphic. (A) Raster plot of spikes of 100 PYRs and 25 INs (randomly chosen). The firing times of neurons have correlations and we call such firing synchronized. (B) Temporal changes in instantaneous firing rates Inline graphic and Inline graphic of the excitatory ensemble Inline graphic and the inhibitory ensemble Inline graphic, respectively, calculated from the firing in Figure A. It is observed that Inline graphic and Inline graphic fluctuate, and it is found that this fluctuation is caused by chaotic dynamics and not by a stochastic one. (C) Trajectory in the (Inline graphic, Inline graphic) plane obtained from the data in Figure B. It is observed that the trajectory has some complex structure. (D) Asynchronous firing observed in this unit. Raster plot of spikes of 100 PYRs and 25 INs (randomly chosen). The number of firing is very few because the firing rates are low. (E) and (F) Chaotic synchronization in a unit with an infinite number of neurons obtained by analysis with Fokker-Planck equations, which corresponds to the results in Figures B and C obtained in a unit with a finite number of neurons. (E) Temporal changes in the instantaneous firing rates Inline graphic and Inline graphic. The results are similar to those in Figure B. (F) Trajectory in the (Inline graphic, Inline graphic) plane. A fine structure of a chaotic attractor is visible.