A spiking neural model of strategy shifting in a simple reaction time task

In a simple reaction-time (RT) task with predictable foreperiods, subjects employ two strategies. They either wait until the cue and then respond, or they time the foreperiod and respond when the cue should occur. Evidence for these performance strategies has been detected in rodents, humans, and other primates. A key brain region for implementing these control strategies is the medial prefrontal cortex (mPFC). Neurons in this brain region show changes in firing rates around the start of trials, or fire persistently during the foreperiod of simple RT tasks, and exert control over the motor system by influencing firing rates in the motor cortex during the foreperiod (Narayanan & Laubach, 2006). Here, we describe a neural circuit model based on the known neuroanatomy that reproduces the observed activity patterns in rat mPFC and exhibits adjustments in the behavioral strategy based on the subject’s recent outcomes. A neural circuit based on Singh and Eliasmith, 2006 tracks the behavioral state and the time elapsed in that state. This circuit serves as a top-down controller acting on a neural control system. When the top-down control is not being exerted, the system waits for the cue and responds at cue onset. When the foreperiod can be timed, top-down control forces a response when the cue is predicted to occur. These adjustments can occur at any time and do not require synaptic weight changes.