Interpretation of abnormal responses to the Quality Extinction Test in schizophrenia.

The Quality Extinction Test (QET) has proved to be valuable for detecting abnormal hemisphere functioning in neurological as well as psychiatric patients. The present and other studies have shown a higher frequency of left side extinction in schizophrenics. This has been attributed either to contralateral parietal malfunction or to ipsilateral frontal abnormality. To evaluate the role of different brain regions in determining tactile extinctions in schizophrenic patients, a population of 70 such subjects were subgrouped according to their QET scores (left, right, left/right, and non-extinguishers) and their neuropsychological task performance profiles were compared. Right extinguishers had QET scores similar to those of non-extinguishers; left/right extinguishers were closer to left extinguishers. Non-extinguishers were the best performers and left extinguishers the poorest, particularly where right hemisphere-dependent tasks were concerned.