EEG CORRELATES OF TONIC IMMOBILITY IN THE OPOSSUM (DIDELPHIS VIRGINIANA)

Five different behavioral states in the opossum were related to five different EEG patterns. The EEG activity during tonic immobility was characterized by low voltage fast activity. Tonic immobility was always preceded by long bursts of both cortical and amygdaloid alpha range EEG activity which characterized an 'awaking-alert-fixating' state of behavior. However, a similar pattern was also seen in 3 opossums in which tonic immobility could not be obtained. The results suggest that alpha range activity may be a necessary but not sufficient condition for the onset of tonic immobility in this animal. (Author)
Pub. in Electroencephalography and Clinical Neurophysiology v18 p709-11 1965 (Copies available only to DDC users).