Postperceptual effects and P300 latency

BACKGROUND: Structural and functional brain changes have been described in elderly patients with unipolar affective disorder. Changes appear to be more marked in patients with late-onset depression, but the reversibility of such changes after clinical recovery is not known. METHODS: Magnetic resonance imaging, electroencephalography (EEG), and cognitive tests were performed in 23 elderly patients (mean age 66.5 years) clinically recovered from major depression. Twelve had late-onset depression (first episode over 55 years of age); 11 had early onset (first episode before 50 years). EEG and cognitive testing were also performed on 15 control subjects. RESULTS: Patients with late-onset depression had larger third and lateral ventricles, increased ventricular-brain ratio, and greater frequency and severity of subcortical white matter lesions than those with early onset. There was no difference between early- and late-onset patients in EEG and cognitive measures, but compared with controls patients showed significant changes in EEG evoked potentials and increased slow-wave activity, slowed reaction times, and global impairments in cognitive function. CONCLUSIONS: These results suggest that structural changes are greater in patients with late-onset depression, and that EEG and cognitive impairments persist after recovery, regardless of age of onset of depression, and are independent of structural changes.