Amygdala unit activity during sleep and waking

Unit activity was recorded from the basolateral amygdala of freely moving cats during quiet waking (QW), slow-wave sleep (SWS), and paradoxical sleep (PS), and in response to sensory stimuli. Nichrome wires, 65 μ in diameter, implanted in bundles of ten each, served as the microelectrodes. Most cells in this region discharged at very low rates (< 1 spike/sec) during all states; the majority of cells ( 39 61) discharged at significantly higher rates during SWS than in either PS or QW; and no increase in discharge rate was seen in association with the phasic activity of PS. All of these results are contrary to those generally reported for other brain loci. Cells that discharged at their highest rates during SWS represented a distinctly different class of cells than the faster firing cells that discharged fastest in PS or QW. These slowly firing cells exhibited high-rate bursts in PS, increased discharge rates in association with EEG synchrony observed over the sensorimotor cortex during PS, and selective responsiveness to complex sensory stimuli.