Reinforcement-related neurons in the primate basal forebrain respond to the learned significance of task events rather than to the hedonic attributes of reward.

The objective of this study was to determine if the responses of basal forebrain neurons are related to the cognitive processes necessary for the performance of behavioural tasks, or to the hedonic attributes of the reinforcers delivered to the monkey as a consequence of task performance. In all cases, it was found that the primary neuronal responses were to visual stimuli that required analysis important for the selection of a behavioural response and not to the delivery of reinforcement per se. Indeed, reinforcement-related neurons that responded only to the delivery of juice or of saline were never encountered. In additional experiments, it was found that abstract visual cues-specific gestures of the experimenter-that signaled the impending delivery of reinforcement were able to activate these neurons. These data are consistent with the view that reinforcement-related basal forebrain neurons influence the sensory and motor processes in the cerebral cortex, providing control signals that optimise the processing of complex sensory stimuli and/or the generation of appropriate behavioural responses.