Figure 1.

The model network is separated into short and long-latency channels. Input to the long-latency channel is delayed by 100 ms with respect to stimulus onset, representing upstream transmission delays to cortex. Each sub-group consists of 100 neurons (except PFC which contains 1000), with all neurons receiving input from 100 of their pre-synaptic afferents. Connectivity patterns are as depicted in I (sparse), II (parallel), and III (all-to-all). In the sparse PFC–STR pathway, afferent to each STR neuron are selected randomly from PFC modulation of STDP in both PFC → STR and SEN → INT pathways (filled circles), as well as post-synaptic facilitation of STR neurons (filled square) is enabled by DA release. DA output therefore controls, and is controlled by, a precisely timed balance of excitatory and inhibitory influences on DA neurons, resulting from DA modulation of synaptic efficacy and neuronal excitability at STR and INT neurons.