Neuronal activity in the brain stem reticular formation during performance of a “go-no go” visual attention task in the monkey

Abstract

We recorded extracellular unit activity in the brain stem and sensorimotor cortex of rhesus monkeys during the performance of a visual discrimination (attention) task. The animals were required to press a transilluminated disk to red stimuli (“go” trials) and withhold pressing to green stimuli (“no go” trials). Correct performance was rewarded with fruit juice. A total of 235 task-related units (170 in and around the mesopontine reticular formation and 65 in the sensorimotor cortex) was studied in four animals. We classified all units as either type I or type II. Type I units showed changes during go trials only; these changes occurred relatively late in the trial, and in relation to some motor aspect of the task. The majority (81%) of the sensorimotor units was type I. Type II units showed changes in relation to both go and no go trials; these changes typically occurred early in the trial, suggesting that these units are related to input or integration processes rather than to motor output. The majority (67%) of the subcortical units in and around the mesopontine reticular formation showed type II activity, suggesting that this system is involved in the central processes underlying attention in visual discrimination tasks.