title: Nonlinear temporal integration of brain stimulation reward.
abstract: A good deal is known about psychological factors that contribute to reward value, but very little is known about how reward is computed in the brain. Integration in the circuit for brain stimulation reward may provide a simple model system. Parametric studies have favored the idea that the integration is linear, although a few have suggested that it involves adaptation. However, these studies have generally not focused on relevance to psychological factors such as temporal discounting of reward. To begin to address these issues, I gave rats a choice between a simple train of 2 seconds of stimulation at a uniform frequency and a compound train of 1 second of stimulation at either 50, 150, or 250 Hz immediately followed by 1 second of stimulation at 50, 150, or 250 Hz, for a total of nine compound trains. For each compound train, the frequency of the simple train was varied until a level was found that produced indifference. The order of the frequencies was important, with Hi-Lo compound stimulation having a higher matching frequency than the symmetrical Lo-Hi. Furthermore, there was an interaction between the first and second frequencies, with the second frequency counting less when the first frequency was high. The results could be fit by computational models incorporating the ideas of either (a) adaptation or (b) temporal discounting and a power function psychological scale. These results suggest that integration in the brain stimulation reward system is nonlinear, and involves either adaptation or temporal discounting of reward value.
authors: Department of Neuroscience, Columbia University, New York, NY 10032, USA. rdh1@columbia.edu
authors: Robert D
authors: RD
authors: Hawkins
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D001921:Brain / Q000502:physiology*; D002755:Choice Behavior / Q000502:physiology*; D017711:Nonlinear Dynamics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012201:Reward; D012653:Self Stimulation / Q000502:physiology*; D013997:Time Factors