Paper to be presented at the International Congress of Biological Psychiatry in Sydney, Australia, February 9 - 13, 2004.
Event-related brain potentials (ERPs) during auditory and visual word recognition memory tasks in affective disorders
Jürgen Kayser, Craig E. Tenke, Jonathan W. Stewart, Frederic M. Quitkin, Gerard E. Bruder
New York State Psychiatric Institute, New York, USA
Abstract
Despite considerable behavioral evidence of memory impairments in mood disorders, electrophysiological correlates of mnemonic processes have rarely been assessed in depressed patients. Event-related brain potentials (ERPs) can provide a continuous record of normal and abnormal information processing stages during memory-retrieval tasks. The typical ERP finding for healthy adults during explicit memory tasks is the so-called ‘old/new effect,' an enhanced posterior positivity between 300 and 800 ms for repeated items, which is assumed to index conscious recollection. This study compared 30-channel ERPs recorded from right-handed, healthy adults (n = 26) and right-handed, unmedicated outpatients (major depressive disorder or dysthymia, DSM-IV; n = 24) during auditory and visual word recognition memory tasks. Spatially and temporally overlapping ERP components were measured by covariance-based principal components analysis. Confirming previous findings for healthy adults (Kayser et al., in press), the expected old/new effect was observed in both modalities, with a comparable time course peaking between 500 and 600 ms, but having a more anterior scalp topography for visual items. This suggests a common cognitive process associated with separable neural generators in each modality. Moreover, the old/new effect overlapped ERP components with distinct scalp topographies (N2) or peak latencies (P3) for each modality, suggesting that the old/new effect is dissociable from functions commonly ascribed to N2 or P3. The posterior old/new effect was markedly reduced in depressed patients, particularly for auditory items, despite a lack of group differences in ERP component structure or behavioral performance in either modality. However, both groups revealed even earlier condition effects in both modalities for a negative ERP component with N400-like properties (i.e., peaking at 360 ms, posterior midline topography). The combined use of auditory and visual ERP tasks allowed a better description of modality-independent recognition memory processes, which suggests a dysfunction of conscious item retrieval but preserved automatic repetition memory in depression.
Keywords: event-related potentials (ERP), recognition memory, old/new effect, auditory/visual modality, depression
