Effects of Temperature on Electroencephalogram of the Caiman.

Summary Cerebrum. An independent fast frequency of 18-24 cycles per second with an amplitude of 10-20 μv was observed intermittently. Restraint in these animals appears to have little effect on the frequency. Hypothermia, 5°;C (3-6°;C) reduced the spontaneous electrical activity close to the isoelectric base line in most animals tested. Hyperthermia, 35°;C (32-36°;C) was characterized by a “delta” wave of 1-3 cycles per second. A “beta” frequency appeared to be superimposed. The trance-like state also revealed a dominant delta frequency of 0.5-2 cycles per second. A “beta” wave with an amplitude of 5-10 μv was seen superimposed on the slow wave (“theta”). The alpha-like wave appeared to be essentially absent under conditions of hypothermia, hyperthermia, and supine (trance-like state) position. Optic lobes. Electroencephalographs from the optic lobes demonstrated a predominant slow wave of 6-8 cycles per second with an amplitude of 5-10 μv. This frequency and amplitude was markedly depressed under hypothermia. The electrical activity appeared to double in amplitude under hyperthermia. While the animal was in a trance-like state, a well-defined slow wave of 5-6 cycles per second was seen as the most significant change recorded from this area of the brain. Cerebellum. Electrical activity as recorded from the cerebellum was most pronounced under hypothermia and in the supine trance-like state; in both states a well-defined “theta” wave of 4-6 cycles per second with an amplitude of 10-15 μv was seen.