Fig. 2.

Overview of model. Simulations of sensory neurons and neural recordings are used to define the left and right inputs ΔI_l(t) and ΔI_r(t) to neural integrators. These inputs are modeled by Gaussian [Ornstein-Uhlenbeck (OU)] processes, which capture noise in the encoding of the motion strength by each pool of spiking neurons (see Eqs. 1–3 for definition of input signals). Similar to Mazurek et al. (2003), the activity levels of the left and right integrators E_l(t) and E_r(t) encode accumulated evidence for each alternative. In the reaction time task, E_l(t) and E_r(t) race to thresholds to determine choice on each trial. In the controlled duration task, the choice is made in favor of the integrator with higher activity at the end of the stimulus presentation.