The temporal structure of motivation: III. Identification and ecological significance of ultradian rhythms of intracranial reinforcement

Abstract

Adult male Sprague-Dawley rats were stereotactically implanted with intracranial electrodes aimed at the anterior medial forebrain bundle, and trained to self-administer intracranial stimulation. Following 3 weeks of continuous access to the self-stimulation contingency, response patterns were recorded on a consecutive minute-by-minute basis for power-spectral analysis. Spectral analysis revealed the existence of significant ultradian rhythms of reward. The functional significance of these rhythms was further explored in a subsequent experiment, in which temporally correlated feeding and self-stimulation patterns were demonstrated. These findings demonstrate a continuous relationship of a biological reward and ICS.