memory functions of the prefrontal cortex

JOURNALOFNEUROPHYSIOLOGY Vol. 6 1, No. 2. February 1989. Printed in U&4. Mnemonic Coding of Visual Space in the Monkey’s Dorsolateral Prefrontal Cortex SHINTARO FUNAHASHI, CHARLES J. BRUCE, AND PATRICIA S. GOLDMAN-RAKIC Section of Neuroanatomy, Yale University School of Medicine, New Haven, Connecticut 06510 SUMMARY AND CONCLUSIONS 1. An oculomotor delayed-response task was used to examine the spatial memory functions of neurons in primate prefrontal cortex. Monkeys were trained to fixate a central spot during a brief presentation (0.5 s) of a peripheral cue and throughout a subsequent delay period (l-6 s), and then, upon the extinction of the fixation target, to make a saccadic eye movement to where the cue had been presented. Cues were usually presented in one of eight different locations separated by 45O. This task thus requires monkeys to direct their gaze to the location of a remembered visual cue, controls the retinal coordinates of the visual cues, controls the monkey’s oculomotor behavior during the delay period, and also allows precise measurement of the timing and direction of the relevant behavioral responses. 2. Recordings were obtained from 288 neurons in the prefrontal cortex within and surrounding the principal sulcus (PS) while monkeys performed this task. An additional 31 neurons in the frontal eye fields (FEF) region within and near the anterior bank of the arcuate sulcus were also studied. 3. Of the 288 PS neurons, 170 exhibited task-related activity during at least one phase of this task and, of these, 87 showed significant excitation or inhibition of activity during the delay period relative to activity during the inter-trial interval. 4. Delay period activity was classified as div~tional for 79{0e601fc7fe3603dc36f9ca2f49ef4cd268b5950ef1bbcf1f795cc00e94cdd119} of these 87 neurons in that significant responses only occurred following cues located over a certain range of visual field directions and were weak or absent for other cue directions. The remaining 2 1{0e601fc7fe3603dc36f9ca2f49ef4cd268b5950ef1bbcf1f795cc00e94cdd119} were omnidirectional, i.e., showed comparable…