Fig. 2.

Structure of a single trial. (A) Stimuli were composed of a series of velocity values where the sampling probability of a given velocity value was given by a normal distribution with mean = 0 and SD = σ. Example base and comparison stimuli are illustrated, resulting from the sampling of the distribution shown above each stimulus, with σ = 55 mm/s (blue) and σ = 110 mm/s (red) and duration 400 ms. (B) Upper trace indicates at far left the time of entry of the rat in the nose poke and at far right the time of withdrawal. Below, key events of the trial are given. Withdrawal latency was measured as elapsed time between the onset of the go cue and withdrawal from the nose poke. (C) Sketches depicting one trial. (Left) The rat places its snout in the stimulus delivery port to initiate the trial and receive stimuli. (Center) Upon hearing the go cue, the rat withdraws. (Right) The rat selects the right reward port. (D) Human participants performed the same discrimination task as rats, holding their fingertip in contact with the tip of a rod attached to the motor (Left). After the base and comparison stimuli were delivered, a go cue appeared on the monitor (Center), and the subject responded by pressing left or right arrow keys on a standard keyboard (Right).