Figure 1. Task and stereotactic location of vlPFC.

(a) Each monkey decided whether a temporal sequence of tone bursts was predominantly ‘low frequency’ or ‘high frequency’ and responded with a rightward or leftward movement, respectively, of the joystick. The monkey could report its choice any time after stimulus onset. (b) Schematics of the auditory stimulus (+100% and 0% coherence stimuli). The auditory stimulus consisted of a sequence of tone bursts (50 ms duration; 10 ms inter-burst interval). Stimulus coherence refers to the percentage of high-frequency bursts (up to +100%) or low-frequency bursts (down to −100%). (c) vlPFC (pink square) is ventral to the posterior aspect of the principal sulcus (PC) and anterior to the arcuate sulcus (AS; Romanski and Goldman-Rakic, 2002). The dotted box indicates the circumference of the recording chamber. Arrows indicate the anterior (A)-posterior (P) axis and the medial (M)-lateral (L) axis.