Changes in visual recovery functions and unit activity produced by frontal and temporal cortex stimulation.

Previous reports (Dewson et al. 1966; Spinelli and Pribram 1966) described the effects of chronic electrical stimulation and of ablations of the posterior sensory-specific "association" cortex on the recovery of responses evoked by paired flashes and clicks in the primary projection systems. These experiments demonstrated the corticofugal control which the brain can exert over its own input and provided an explanatory mechanism for the effects on behavior of lesions of the posterior "association" cortex. The success of these studies prompted the question whether the same techniques would prove fruitful in analyzing the functions of the frontal "association" cortex. There had been some indication from neurobehavioral experiments that in certain situations the posterior and frontal systems act in opposition to one another (Pribram 1966). Would, therefore, chronic electrical stimulation of the frontal cortex produce an effect on recovery function opposite to that obtained when the posterior cortex is stimulated? A second question raised by the initial studies concerns the validity of the interpretations based upon them. Recordings were obtained with macro-electrodes and inferences were made about an effect on populations of cells whose activities these electrodes were presumably monitoring. More direct evidence of cortical control over neural units in the input systems would be obtained if micro-electrode recordings were made. Finally, the initial stimulation studies con-