Amygdala unitary activity in the unrestrained cat

Abstract

In cats a micro-electroda base was stereotaxically implanted into the skull. After recovery from surgery, micro-electrodas were hydraulically driven through the base into the amygdala in unanesthetized, unrestrained animals. The effects of tape-recordad sounds (miaow, whistle, click, hiss), touch, light, smoke, reticular stimulation, and the presence of a white rat were tested on the unitary activity of the amygdala. Results were as follows: 1. 1. Most units of the amygdala showed spontaneous firing in the absence of experimental stimulation. 2. 2. In about half of the units tested the firing rate was modified undar the influence of sensory stimulation. 3. 3. Spontaneous sleep reduced the rate of spontaneous firing, dacreased the facilitatory and increased the inhibitory effects of sensory stimulation. 4. 4. Different sensory stimulations could show convergence of effects on the same unit. 5. 5. Each unit usually respondad with its own pattern (facilitation, inhibition, inhibition-facilitation) to different types of sensory stimulation. Reticular excitation would tend to enhance these responses. Also the attention of the animal seemed to play a role in unitary activity. 6. 6. Responses were more readily evoked by the “miaow” stimulus than by other types of sensory stimulation. 7. 7. The presence of a white rat in the cat's cage produced a rather prominent and lasting increase in the rate of unitary firing. 8. 8. Anatomically, the unitary responses were recordad from: (a) anterior, (b) lateral, and (c) medial part of the amygdaloid complex. The anterior area possessed fewer units responding to sensory stimulation than the other two. Facilitatory responses predominated in the lateral, and inhibitory responses in the medial area. Responses to visual stimulation were more numerous in the lateral group. Responses to touch and smoke did not show anatomical preference.