Evoked potentials following unilateral ECT. II. The flash evoked potential

The flash evoked potential (VEP) was recorded in 16 depressed patients before, during and for 0.5 h following administration of unilateral ECT. In 14 the recordings were made following right ECT and in 3 following left ECT. One patient was recorded after right- and left-sided treatments administered on separate occasions. While the patients were conscious, responses were averaged with eyes open and eyes closed. During anaesthesia, ictus and post-ictal coma the response to repetitive stimulation through closed eyes was recorded continuously in sequential runs. Consistent latency differences between VEPs with eyes open and closed were established in the runs prior to treatment. In postictal coma there was a marked asymmetry in the response from the two sides. Component P140, in particular, was significantly smaller and later over the side which received ECT. On average, these asymmetries lasted less than 15 min following the treatment. A significant latency increase, common to both hemispheres, was found at the end of the recording session.