Amygdaloid Self-Stimulation: A Movable Electrode Mapping Study

The distribution of electrical self-stimulation foci within the amygdala (AMY) was mapped using movable electrodes in rats. Each barpress delivered a 0.4-s train of cathodal rectangular pulses of fixed intensity and duration and variable frequency. The rate-frequency function was recorded for successive dorsoventral sites. Self-stimulation was found throughout the AMY, except in the lateral nucleus. Depending on the site, maximum rates varied from 3 to 37 barpresses/min, whereas threshold frequencies varied from 9.2 to 40 pulses/train; no correlation between these two aspects of self-stimulation was found. Most threshold frequencies lay within the range of 10 to 20 pulses/train, which suggests a relatively homogeneous distribution of rewarding efficacy within the positive areas. The lowest threshold estimates are comparable to those usually obtained for pontine and medial forebrain bundle areas, which suggests that the AMY is an important focus for self-stimulation.