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. Author manuscript; available in PMC: 2009 Jul 14.
Published in final edited form as: Neuron. 2008 Oct 23;60(2):215–234. doi: 10.1016/j.neuron.2008.09.034

Figure 4. A Multiple-Module Network Mechanism for Two-Alternative Forced-Choice Tasks.

Figure 4

(A) Schematic model architecture. Neural pools in the cortical network integrate sensory information and also compete against each other. They project to both the superior colliculus (SC) and the caudate nucleus (CD) in the basal ganglia. CD sends inhibitory projection to the substantia nigra pars reticulata (SNr), which through inhibitory synapses connect with movement neurons in the SC. Each population consists of noisy spiking neurons.

(B) A single trial simulation of the model, showing spike trains from single cells and population firing rates of Cxe, SNr and CD, and SCe. A burst of spikes in movement neurons (SCe) is triggered when their synaptic inputs exceed a threshold level, which results from both direct excitation by cortical neurons and disinhibition from SNr via the cortico-striatal projection. Time zero corresponds to stimulus onset.

(C) The ramping slope of Cxe firing rate is inversely related to decision time on a trial-by-trial basis (each data point corresponds to an individual trial). The red curve is 12,000/(decision time).

(D) Performance (percentage of correct choices) and mean response time as a function of the motion coherence c′. Reproduced with permission from Lo and Wang (2006).