Absolute and relative refractory periods of the substrates for lateral hypothalamic and ventral midbrain self-stimulation

The pulse-pair paradigm was used to behaviorally assess the absolute and relative refractory periods of neurons subserving brain-stimulation reward. The amplitude of the second pulse was either equal to, 41% greater than, or 73% greater than the amplitude of the first pulse. In the equal amplitude condition, recovery from refractoriness began as early as 0.4 msec and did not asymptote until as late as 3.5 msec. A 41% increase in the intensity …