title: Refractory periods of neurons mediating stimulation-elicited eating and brain stimulation reward: interval scale measurement and tests of a model of neural integration.
abstract: Paired-pulse stimulation methods have been used in many studies to measure the excitability properties of the directly stimulated neurons mediating stimulation-elicited behaviors. In this article those methods are evaluated quantitatively. The most frequently used method, in which rate of behavior is measured as a function of conditioning-test (C-T) interval, is shown to be inadequate since the results obtained depend on the frequency of stimulation. In order to account for this dependence, a physical model of brain stimulation which implies that the effects of frequency and C-T interval should be multiplicative is proposed. In separate experiments, conjoint and functional measurement methods were used to test this model and to measure the refractory periods of neurons mediating stimulation-elicited eating and brain stimulation reward. The results of both experiments strongly supported the multiplicative model for C-T intervals in the refractory period range (.4-2.0 msec) and indicated that the frequency threshold method (Yeomans, 1975, and the present Experiment 2) provides interval scale measurement of refractory period effects. The refractory period curves obtained for neurons mediating stimulation-elicited eating and brain stimulation reward were very similar, rising steeply at C-T intervals from .4 to 1.2 msec and more gradually at intervals from 1.2 msec to 2.0 msec. These curves were also similar to one previously obtained for bar-pressing self-stimulation (Yeomans, 1975). The implications of these similarities are discussed.
mesh_terms: D000818:Animals; D004435:Eating; D004558:Electric Stimulation; D007026:Hypothalamic Area, Lateral / Q000502:physiology*; D008297:Male; D009042:Motivation / Q000502:physiology*; D009431:Neural Conduction; D009474:Neurons / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000502:physiology; D012032:Refractory Period, Electrophysiological; D012653:Self Stimulation / Q000502:physiology*