Cortico–basal ganglia circuit mechanism for a decision threshold in reaction time tasks

• DOI: 10.1038/nn1722
• Publication Date: 2006-06-11T17:42:59Z
• Authors: Chung-Chuan Lo; Xiao-Jing Wang
• Keywords: Cerebral Cortex; Neurons; Primates; 0301 basic medicine; Behavior, Animal; Decision Making; Action Potentials; Models, Psychological; Basal Ganglia; Functional Laterality; 03 medical and health sciences; Nonlinear Dynamics; Neural Pathways; Reaction Time; Saccades; Animals; Neural Networks, Computer

Growing evidence from primate neurophysiology and modeling indicates that in reaction time tasks, a perceptual choice is made when the firing rate of a selective cortical neural population reaches a threshold. This raises two questions: what is the neural substrate of the threshold and how can it be adaptively tuned according to behavioral demands? Using a biophysically based network model of spiking neurons, we show that local dynamics in the superior colliculus gives rise to an all-or-none burst response that signals threshold crossing in upstream cortical neurons. Furthermore, the threshold level depends only weakly on the efficacy of the cortico-collicular pathway. In contrast, the threshold and the rate of reward harvest are sensitive to, and hence can be optimally tuned by, the strength of cortico-striatal synapses, which are known to be modifiable by dopamine-dependent plasticity. Our model provides a framework to describe the main computational steps in a reaction time task and suggests that separate brain pathways are critical to the detection and adjustment of a decision threshold.