Scalp- and sLORETA-derived loudness dependence of auditory evoked potentials (LDAEPs) in unmedicated depressed males and females and healthy controls

Objective: As major depressive disorder (MDD) is associated with altered 5-HT activity, we probed intensity-dependent auditory evoked potentials (AEPs) and loudness dependence of the AEP (LDAEP) slopes, shown pre-clinically to be inversely related to 5-HT activity, in MDD. Methods: AEPs and LDAEP slopes were measured in MDD (N = 50; 27 females) and controls (N = 43; 23 females). Correlations between scalp AEPs/LDAEPs and low-resolution electromagnetic tomography (sLORETA)-derived indices were assessed. Results: Smaller scalp intensity-dependent N1 and N1/P2 amplitudes in MDD versus control males and longer P2 latencies in MDD versus control females were found; no LDAEP group differences existed. Females had greater scalp AEPs, steeper N1 and N1/P2 scalp LDAEPs as well as greater intensity-dependent primary auditory cortex activation during the N1 than males. Scalp LDAEPs correlated weak-moderately with sLORETA counterparts. P2 LDAEP-sLORETA correlated negatively with MADRS scores. Female P2 and N1/P2 LDAEP-sLORETA correlated negatively with HAMD-17 and MADRS scores. Conclusions: MDD was not associated with altered LDAEPs. Impaired processing or potentiated inhibition of auditory stimuli was found in MDD males; longer processing existed in MDD females. Inverse relationships between LDAEPs and clinical scores may be related to treatment history, personality and/or MDD features. Significance: MDD was not associated with an altered LDAEP, though subtle AEPs alterations were noted in MDD. Crown Copyright (C) 2012 Published by Elsevier Ireland Ltd. on behalf of International Federation of Clinical Neurophysiology. All rights reserved.