Functional interactions between inferotemporal and prefrontal cortex in a cognitive task.

Monkeys were trained to perform a visual short-term memory task (delayed matching to sample). In some of the animals, cooling probes were implanted over dorsolateral prefrontal cortex, covering sulcus principalis and adjacent areas; microelectrode pedestals were implanted over inferotemporal cortex. Other animals were fitted with converse implants: cooling probes over a portion of the inferotemporal cortical convexity and microelectrode pedestals over prefrontal cortex. In the awake and behaving monkeys, bilateral cooling of either the prefrontal or the inferotemporal region (to 20 degrees C) induced, in the other region, reversible changes of spontaneous and task-related cell discharge. In the two cortices remote cooling induced augmentations and diminutions of cell reaction to the color samples which the animal had to retain for correct performance of the task. The same was true for cell discharge during the delay, the retention period which followed each sample. However, a net effect of remote cooling was, in both cortices, a diminution of color-dependent differences in the reactions and delay-discharge of some cells. Concomitantly, errors of task-performance increased. Cells that as a result of remote cortical cooling showed changes of reaction to the color samples were found more commonly in supragranular than infragranular layers. The results are interpreted as evidence of mutual influences between inferotemporal and prefrontal areas, probably mediated by corticocortical connections. The single-cell data, together with the behavioral data, suggest that those influences are functionally important for visual discrimination and short-term memory.