Neural substrate for brain stimulation reward in the rat: cathodal and anodal strength-duration properties.
The trade-off between current strength and duration of a stimulating pulse was studied for the rewarding and priming effects of brain stimulation reward (BSR). With cathodal pulses, strenght-duration functions for BSR had chronaxies of .8-3 msec. No differences were observed between the results for rewarding and priming effects. With anodal pulses. strength-duration curves were parallel to the cathodal curves at pulse durations of .1-5 msec, but at pulse durations greater than 5 msec the anodal curves showed a greater drop in required current intensity than did the cathodal curves. The parallel portion of the anodal curves was interpreted as due to anode-make excitation, and the drop at longer pulse durations was interpreted as due to anode-break excitation. Cathodal strength-duration functions for the motor effect elicited through the BSR electrodes had chronaxies of .15-.48 msec. Measurements of the latency of the muscle twitch confirmed that anode-make and anode-break excitation occurred, the latter becoming evident at pulse durations as brief as .3-.4 msec. The results provide quantitative characterization of cathodal and anodal strength-duration properties of the neural substrate for BSR and are discussed in terms of their value in guiding electrophysiological investigation of that substrate.
D000818:Animals; D003216:Conditioning, Operant / Q000502:physiology*; D004576:Electromyography; D004594:Electrophysiology; D008297:Male; D008474:Medial Forebrain Bundle / Q000502:physiology*; D009119:Muscle Contraction; D009434:Neural Pathways / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D051381:Rats; D011930:Reaction Time; D012201:Reward; D012653:Self Stimulation / Q000502:physiology*; D009435:Synaptic Transmission; D013997:Time Factors