Specific Contributions of Ventromedial, Anterior Cingulate, and Lateral Prefrontal Cortex for Attentional Selection and Stimulus Valuation
(A) Lateral and medial view of the macaque cortex with color labeled anatomical subdivisions of the fronto-cingulate cortex following area definitions by Barbas and Zikopoulus  (see also Figure S1). (B) Fronto-cingulate subdivisions shown on partially inflated cortex. (C) A flat map representation of the fronto-cingulate cortex shown in panels A and B (obtained by cutting the inflated brain along the bottom and flipping it vertically, see Figure 2A,B), covering areas of ventromedial frontal cortex (areas 32, 25,14), anterior cingulate cortex (area 24) and lateral prefrontal cortex (areas 6, 8, 9, 10, 46). (D) Behavioral paradigm: Monkeys initiated a trial by directing and maintaining their gaze on a centrally presented fixation point. After 0.3 s two grating stimuli appeared drifting within two separate apertures (Stim. Baseline), and their respective colors changed to either red or green 0.4 s later (Col. Cue Onset). Within 0.05 to 0.75 s after this change in color of the grating, the central fixation point changed to either red or green, thereby cueing the monkeys to covertly shift attention towards the location where the color of the grating matched the color of the fixation point (Att. Cue Onset). In order to obtain a liquid reward, the monkeys had to detect a transient clock- or counterclockwise rotation of the cued target grating by making, respectively, up- and downward saccades towards a response target dot. This rotation of the cued target occurred at random times within 0.05–4 s, drawn from a uniform distribution. In half of the trials the distractor, i.e. the grating whose color did not match the color of the fixation point, rotated before the target (not shown). In a given trial, the red or green color of the cued target grating was associated with either a high or low liquid volume. This color-reward association changed every 30 correct trials. (E,F) The proportion of correct trials (E) and saccadic reaction times (F) for detecting the target's rotation, as a function of the time, relative to the attention cue onset, at which the target grating rotated. Red and blue lines correspond to, respectively, the “high-value” and “low-value” conditions. Color shading shows SEM.