Changes in brain electrical activity (EEG) of the awake freshwater turtle Trachemys scripta elegans during anoxia

There is evidence that suggests that electrical depression might be an important energy saving mechanism during anoxia. This study investigates in more depth the changes in electrographic (EEG) activity of the awake and behaving anoxia-tolerant turtle Trachemys scripta elegans when the turtle was breathing 100% N2. The drastic depression of electrical activity by 75% shown in response to anoxia suggests that electrical depression may be the major contributor to metabolic depression and conservation of energy necessary for survival of long periods of anoxia. However, adaptative response to anoxia does not simply consist of a mere depression of brain activity. In fact, there seems to be a systematic shutting down of some of the electrical components of the brain in a very structured manner during entry to anoxia. These components are associated with the slowing down activity of the brain and thus reducing its energy utilization. The EEG changes accompanying recovery in air were different from the depressive processes of entry into anoxia. Extended slow wave activity during recovery in air is similar to the activity pattern seen in the emergence phase of hibernating mammals. It is likely that there are important parallels between the electrical patterns of anoxia and those of hibernating mammals.