Abstract

Despite the overlap of cortical and limbic structures involved in olfaction, emotion and depression, there has been little study of olfactory function in depressed patients. Nose-referenced 49-channel ERPs were recorded from 25 clinically-depressed and 27 healthy adults (11/11 male) during an odor detection task using pleasant (Citronalva; CIT) and unpleasant (hydrogen sulfide; H₂S) stimuli. High or low odor concentrations or blank air were presented unilaterally by a constant-flow olfactometer (variable ISI 15-21 s). Subjects indicated odor presence via foot pedal. Neuronal generator patterns underlying ERPs were identified and measured by unrestricted Varimax-PCA of reference-free current source densities (CSD). CSD waveforms were characterized across odors by an early sink (315 ms, bilateral centrotemporal, N1) and two distinct sources (500 ms, mid-frontocentral; 765 ms, mid-centroparietal, P2). Whereas N1 sink varied with odor intensity, P2 source varied with odor quality (H₂S > CIT). CSD amplitude and topography were highly correlated with individual ratings of valence (P2) and arousal (N1) as well as detection accuracy (P2). However, CSD waveforms and topographies did not differ between groups. Likewise, patients showed normal odor identification and thresholds (Sniffin' Sticks), and did not differ from controls in behavioral performance for all conditions (76-90% vs. 74-91% correct). Although CSD measures directly reflected valence and arousal properties of pleasant and unpleasant odors, there was no evidence of impaired olfactory/emotional processing in depression. [Supported by NIMH grant MH082393].