Cortico-basal ganglia circuit mechanism for a decision threshold in reaction time tasks.
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.
Lo
Chung-Chuan
CC
Volen Center for Complex Systems, Brandeis University, Waltham, Massachusetts 02254, USA.
Wang
Xiao-Jing
XJ
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001479:Basal Ganglia / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology; D002540:Cerebral Cortex / Q000166:cytology* / Q000502:physiology; D003657:Decision Making / Q000502:physiology*; D007839:Functional Laterality / Q000502:physiology; D008960:Models, Psychological; D016571:Neural Networks, Computer; D009434:Neural Pathways / Q000502:physiology*; D009474:Neurons / Q000145:classification / Q000502:physiology; D017711:Nonlinear Dynamics; D011323:Primates; D011930:Reaction Time / Q000502:physiology*; D012438:Saccades / Q000502:physiology