Figure 2.

Behavioral monitoring and results. a, Mouth signal: example from the reward cue epoch of the licking signal, monitored by an infrared reflection detector. The black arrow indicates time of cue presentation, and the gray arrow indicates cue offset and reward tone onset. b, Image of monkey's eyes. Video signal was processed and each frame was classified according to the state of the eyes [i.e., open (top) or closed (bottom)]. c, Behavioral results. Top, Licking (average ± SEM) as recorded by an infrared reflection detector directed at the monkey's mouth. The voltage output of the detector was sampled by A/D converter and the y-scale is given in arbitrary A/D units. Bottom, Fraction of trials with eyes closed (average ± SEM) as recorded by computerized video processing. Columns correspond to trial epoch (cue; outcome, food or air puff; no outcome, sound only) aligned to event onset (time = 0). Note the overlap of 0.5 s between the start of the outcome and the no-outcome epochs and the last 0.5 s of the cue epoch. Data were averaged for each session and then across sessions (N, number of recording sessions). Color coding of trial types is given at bottom right (A, aversive; N, neutral; R, reward; the number is the outcome probability). d, Normalized behavioral response. Licking (blue) and blinking (red) response (average ± SEM, number of sessions as in c) in a time window around the behavioral event (cue, 500–0 ms before cue end; outcome and no outcome, 0–500 ms after cue end for blinking response and 500–1000 ms for licking response). The responses are normalized between 0 and 1 [i.e., in each epoch a response (X) is transformed by (X − min)/(max − min), where min and max are the minimal and maximal values of the response in this epoch]. Abscissa, Different behavioral conditions (A, aversive; N, neutral; R, reward; the number is the outcome probability).