The duration of the movement aftereffect as an index of psychiatric illness.

The duration of the movement aftereffect (MAE) has sometimes been used to make inferences about the subject's state (for example, their level of arousal). Some studies are reviewed in which visual aftereffects (including the MAE) were measured in schizophrenia, with inconsistent results. Some relevant psychopharmacological and neurological evidence is considered. It is concluded that: (i) Differences in the clinical status of the schizophrenic subjects and whether they were receiving medication, but not the method used to measure aftereffects, may underlie the interstudy disagreements. (ii) The effect of schizophrenia is to increase MAE duration, and this is not due to some peripheral artefact. (iii) Longer MAEs in the illness could result from enhanced neurally signalled contrast and/or from the increased adaptability of cortical neurons.