The electroencephalogram in psychiatry: clinical and research applications.

The main clinical value of the EEG in psychiatry is as a non-invasive tool for the investigation of organic mental syndromes and epilepsy. Predictions that CT scanning would make the EEG redundant have not been fulfilled. Indeed, the 2 instruments complement each other, the EEG being a measure of function and the CT scan a reflection of brain structure. Both are proving useful in the investigation of dementia, providing different but complementary information about the extent and progress of the disease. Quantitative methods of EEG analysis using laboratory computers are now readily available. Significant changes in both the EEG background activity and event related potentials have been clearly demonstrated in the functional psychoses. These are not specific for any diagnostic condition. This implies that they reflect changes caused by the impact of the psychotic mental state on the individual's cognitive processes and level of arousal. The challenge for the future is to develop models of the relationship between the electrical events and underlying cognitive processes. Some progress has been made concerning the ERP changes in selective attention and in phobic disorder. The computerized EEG has a clearly established place in the investigation of drug action, by-passing the blood brain barrier and providing direct access to brain activity. Clearly this work may prove useful in the study of the effects of drug induced change on neurotransmitter systems. The EEG study of all night sleep in patients with functional psychiatric disorders has not lived up to the early expectations of workers in the field. Nevertheless the studies of insomnia and hypnotic drug effects have had valuable practical implications.