Neuroimaging of Consciousness

Abstract

Focal temporal lobe seizures often cause loss of consciousness. Whereas -abnormal function of the temporal lobe is expected to cause memory loss, it is unclear why it should impair consciousness. Recent advances in neuroimaging, behavioral, and electrophysiological techniques spanning both human patients and animal models have revealed new and exciting insights into this old -question. Impaired consciousness in temporal epilepsy (TLE) is correlated with large-amplitude slow electroencephalogram (EEG) activity and decreased metabolic activity in the frontal and parietal association cortices, similar to other states of impaired consciousness such as sleep, coma, and deep anesthesia. According to the network inhibition hypothesis, supported by imaging and electrophysiological data, cortical dysfunction during temporal lobe seizures results from inhibition of subcortical arousal structures which are required for maintaining the cortex in an alert and awake state. Advances in our understanding of impaired consciousness in epilepsy will hopefully pave the way toward novel treatments to prevent this profoundly debilitating side effect of seizures.