I have continued study of the behavioral neurophysiology of the prefrontal cortex. Eye movement, single-neuron and behavioral responses were recorded in order to evaluate the relation between neuronal activity in the prefrontal cortex and conscious control of visually-triggered delayed response tasks. Recordings were obtained from the prefrontal and parietal cortex of two different monkeys trained on novel variations of a task requiring delayed execution of memory-guided eye movements and subsequent memory-guided fixation. The recording experiments have shown that some prefrontal neurons are active only during the initial delay period prior to movement in particular directions while other neurons are active only during memory guided fixation at particular locations and not during visual fixation at the same locations. In addition, some of each type of prefrontal neurons are active only during trials involving spatial memory in complete darkness and not during trials requiring visual memory for one of multiple visible targets. Delay period activity specific for spatial-memory trials has been observed, and ocular fixation-related activity has also been found which is selectively present during memory-guided fixation in complete darkness but not during fixation of single or remembered visible targets at the same locations.
