Neurophysiological Measures of Treatment Efficacy in Late-Onset Depression

Abstract

Neurophysiological correlates of treatment efficacy in late-onset depression were identified by analyzing EEG spectral parameters, the peak latencies of the “late” components of cognitive auditory evoked potentials, and sensorimotor reaction times during antidepressant treatment in two groups of older patients (53‐72 years) with long-lasting psychogenic depressive reactions (ICD-10 F43.21) and endogenous depression (ICD-10 F33.1 and F31.3). The initial severity of depression was associated with EEG signs of decreases in the functional status of the anterior parts of the left hemisphere and increased activation of the right hemisphere (particularly the temporal areas). Improvements in patients’ mental status in response to antidepressant medication were accompanied by decreases in the peak latencies of the “late” components (P2, N2, and P3) of cognitive auditory evoked potentials and acceleration of sensorimotor reactions, and were linked with improvements in EEG measures of the functional status of the posterior areas of the cerebral cortex and increases in inhibitory processes in the right hemisphere (particularly its frontal-central-temporal areas). These data are consistent with views of the systems nature of impairments to brain activity in depression and the predominant involvement of the left hemisphere in regulating positive emotions and of the right hemisphere in regulating negative emotions, including the pathogenesis of depression.