Measuring the subjective magnitude of brain stimulation reward by titration with rate of reward.
The magnitude of experienced reward as a function of the pulse frequency and current in trains of fixed duration delivered to the medial forebrain bundle of the rat was measured using a new psychophysical method in which the parameters of the brain stimulation reward on one lever are adjusted to offset the effect of changing the rate of reward on a competing lever. Subjective reward magnitude is a steep sigmoidal function of both pulse frequency and current. The growth of reward to its half-maximal level was approximated by a power function with an exponent that varied from 2 to 10. Within a subject, the exponent was the same for both current and pulse frequency, which supports the hypothesis that the magnitude of reward from a train of fixed duration is determined by the rate at which action potentials are generated in the population of reward-relevant axons (the counter hypothesis). This rate is proportional to Current x Pulse Frequency.
Gallistel
C R
CR
Department of Psychology, University of California, Los Angeles 90024-1563.
Leon
M
M
D000818:Animals; D001070:Appetitive Behavior / Q000502:physiology; D001931:Brain Mapping; D004558:Electric Stimulation / Q000379:methods*; D008297:Male; D008474:Medial Forebrain Bundle / Q000502:physiology*; D009042:Motivation; D011601:Psychophysics; D051381:Rats; D011919:Rats, Inbred Strains; D012055:Reinforcement Schedule; D012653:Self Stimulation / Q000502:physiology*; D009435:Synaptic Transmission / Q000502:physiology*