Figure 2.

Rhesus macaques forage nearly optimally in a computerized patch-leaving task, and the rising value of leaving a patch is represented by single neurons in the macaque frontal cortex.(a) Monkeys remain in the patch longer as travel time rises, as predicted by the marginal value theorem (MVT). Each dot indicates a single patch-leaving decision (n = 2,834 patch-leaving events). The time at which the monkey chose to leave the patch (y axis) was defined relative to the beginning of foraging in that patch. Travel time was kept constant in a patch (x axis). Data from two monkeys are shown. Behavior (average is traced by the blue line) closely followed the rate-maximizing leaving time (red line), albeit delayed by 0–2 s. (b) Peri-stimulus time histograms (PSTHs) for an example cell in anterior cingulate cortex (ACC). Neurons responded phasically around the time of decision-making saccades and then fell to a baseline level between trials. Time zero indicates end of saccade, indicating choice. Black rectangle indicates the average duration of the trial. The firing rate during the peri-saccadic decision-making period rose with each successive decision to stay in a given patch, across multiple actions unfolding over tens of seconds. Each panel indicates responses selected from one range of patch residence times. (c) Average responses of example neuron occurring in a series of 1-s peri-saccadic epochs. Firing rates increased as time in patch increased. Error bars represent s.e.m. Firing rates peaked with the decision to abandon a patch and move on to the next. Figure after [5], used with permission.