Biol Psychiatry 2012; 71:79S. | Psychophysiology Lab

Biol Psychiatry 2012; 71:79S. [Paper presented at the at the 67^th Annual Meeting of the Society of Biological Psychiatry (SOBP) in Philadelphia, PA, May 3 - 5, 2012.]

Olfaction in the psychosis prodrome: electrophysiological and behavioral measures of odor detection

JÃ¼rgen Kayser^1,2, Craig E. Tenke^1,2, Christopher J. Kroppmann¹, Daniel M. Alschuler¹, Shelly Ben David¹, Shiva Fekri¹, Gerard E. Bruder^1,2, Cheryl M. Corcoran^1,2

¹ Division of Cognitive Neuroscience, New York State Psychiatric Institute, New York, NY
² Department of Psychiatry, Columbia University College of Physicians & Surgeons, New York, NY
³ Depression Evaluation Service, New York State Psychiatric Institute, New York, NY
⁴ Department of Psychiatry, University of Pennsylvania, Philadelphia, PA

Abstract

Background: Smell identification deficits (SIDs) are relatively specific to schizophrenia and its negative symptoms, and may have predictive value for conversion to psychosis in high-risk individuals (Corcoran et al., 2005). Moreover, event-related potentials (ERPs) to odors are reduced in schizophrenia. This study examined whether prodromal patients show SIDs and abnormal olfactory N1 and P2 potentials seen in schizophrenia. Methods: 49-channel ERPs were recorded from 21 prodromal and 20 healthy adolescents (13/13 male; age 21.4Â±3.5, range 13-27 years) during an odor detection task using three concentrations (strong, medium, weak) of hydrogen sulfide (H₂S) or blank air presented unilaterally by a constant-flow olfactometer (variable ISI 15-21 s). Subjects indicated odor presence via foot pedal. Neuronal generator patterns underlying olfactory ERPs were identified and measured by unrestricted Varimax-PCA of reference-free current source densities (CSD; spherical spline interpolation). Results: Replicating previous findings (Kayser et al., 2010), CSD waveforms to H₂S stimuli were characterized by an early N1 sink (345 ms, bilateral centrotemporal) and a late P2 source (580 ms, mid-frontocentroparietal). N1 and P2 varied monotonically with odor intensity (strong > medium > weak) and did not differ across groups. Patients and controls also showed comparable odor detection accuracy and had normal odor identification and thresholds (Sniffin' Sticks). Conclusions: Olfactory ERPs directly reflected differences in odor intensity, but there was no evidence of impaired olfactory processing in prodromal patients. Although this contrasts with findings for schizophrenia, it remains to be seen whether olfactory measures may be helpful in predicting conversion to psychosis.

References

Corcoran C, Whitaker A, Coleman E, Fried J, Feldman J, Goudsmit N, Malaspina D (2005). Olfactory deficits, cognition and negative symptoms in early onset psychosis. Schizophr Res 80(2-3):283-293.
Kayser J, Tenke CE, Malaspina D, Kroppmann CJ, Schaller JD, Deptula A, et al (2010). Neuronal generator patterns of olfactory event-related brain potentials in schizophrenia. Psychophysiology 47(6):1075-1086.

Key Words: prodromal patients; olfaction; ERP; schizophrenia; current source density (CSD)

[Supported by NIMH grant MH086125].