Figure 1.

Computational architecture (middle panels) and representative activation trajectories (right panels) of the race (A), diffusion (B), and LCA (C) models in a motion discrimination task (left panels). Middle panels: black lines with arrowheads represent excitatory connections, and red lines terminating in filled circles correspond to inhibitory connections. Gray circles represent units encoding left (L) and right (R) responses or their difference (R-L). Blue “tears” stand for activation leakage. Right panels: representative activation over time (x-axis) in L (gray) and R (black) units, or a unit encoding their difference of activation (black, part B only). Bounds on activation level, at which a choice is initiated, are indicated by the dashed line signaled with lowercase letter a (or – a, part B only). Vertical cyan line, estimated reaction time for the representative trial. In the race model, the two options race independently toward a common upper decision boundary. In the diffusion model, choice is determined by which boundary is first reached (upper or lower). In the LCA model, the two options compete against each other toward a common response criterion.