File:DA Models Fig3 real.jpg

Summary

D1-state and D2-state dynamics in a biophysical model network. A) State space representation of the network dynamics in D1-dominated, balanced, and D2-dominated regimes (only the nullclines are shown). While D1-stimulation leads to a stretching of the PC nullcline, D2-stimulation leads to a contraction. B) Schema of an ‘energy landscape’ corresponding to the three cases in A. Minima of the energy correspond to the fixed point attractors, and the local slopes depend on the derivatives of the underlying system. The graph makes clear that it is much harder to switch between different attractor states in the D1 dominated regime, where the two fixed points are well separated and surrounded by steep slopes, as compared to the D2 dominated regime with shallower slopes and less separation, and thus increased vulnerability to noise-induced shifts between the states. C) Network simulation illustrating how the system spontaneously switches between different attractors (neural representations) in the D2 dominated regime, while robustly maintaining one of the attractors in the D1 dominated regime. Slightly modified from Durstewitz (2007) and reprinted from Durstewitz and Seamans (2008) with permission from Springer Science+Business Media (Copyright 2007) and Elsevier (Copyright 2008), respectively.

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