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

Nat Neurosci. 2006 Jul;9(7):956-63. doi: 10.1038/nn1722. Epub 2006 Jun 11.


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.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Action Potentials / physiology
  • Animals
  • Basal Ganglia / physiology*
  • Behavior, Animal / physiology
  • Cerebral Cortex / cytology*
  • Cerebral Cortex / physiology
  • Decision Making / physiology*
  • Functional Laterality / physiology
  • Models, Psychological
  • Neural Networks, Computer*
  • Neural Pathways / physiology*
  • Neurons / classification
  • Neurons / physiology
  • Nonlinear Dynamics
  • Primates
  • Reaction Time / physiology*
  • Saccades / physiology