Review
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Psychiatr. Jun 22, 2015; 5(2): 210-221
Published online Jun 22, 2015. doi: 10.5498/wjp.v5.i2.210
Olfactory function in psychotic disorders: Insights from neuroimaging studies
Kimberley P Good, Randii Lynn Sullivan
Kimberley P Good, Departments of Psychiatry and Psychology and Neuroscience, Dalhousie University, Halifax NS B3H2E2, Canada
Randii Lynn Sullivan, Department of Social Work, Dalhousie University, Halifax NS B3H2E2, Canada
Author contributions: Both authors contributed to this manuscript.
Supported by In part the Department of Psychiatry Dalhousie University; The Faculty of Medicine at Dalhousie University; The Nova Scotia Health Research Fund; and the Canadian Institutes of Health Research.
Conflict-of-interest: The authors know of no conflicts of interest related to this work.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Kimberley P Good, PhD, Departments of Psychiatry and Psychology and Neuroscience, Dalhousie University, Suite 4064 AJLB, 5909 Veterans Memorial Lane, Halifax NS B3H2E2, Canada. kim.good@dal.ca
Telephone: +1-902-4734250 Fax: +1-902-4733456
Received: December 2, 2014
Peer-review started: December 4, 2014
First decision: January 20, 2015
Revised: February 20, 2015
Accepted: March 16, 2015
Article in press: March 18, 2015
Published online: June 22, 2015
Processing time: 198 Days and 17.3 Hours
Abstract

Olfactory deficits on measures of identification, familiarity, and memory are consistently noted in patients with psychotic disorders relative to age-matched controls. Olfactory intensity ratings, however, appear to remain intact while the data on hedonics and detection threshold are inconsistent. Despite the behavioral abnormalities noted, no specific regional brain hypoactivity has been identified in psychosis patients, for any of the olfactory domains. However, an intriguing finding emerged from this review in that the amygdala and pirifom cortices were not noted to be abnormal in hedonic processing (nor was the amygdala identified abnormal in any study) in psychotic disorders. This finding is in contrast to the literature in healthy individuals, in that this brain region is strongly implicated in olfactory processing (particularly for unpleasant odorants). Secondary olfactory cortex (orbitofrontal cortices, thalamus, and insula) was abnormally activated in the studies examined, particularly for hedonic processing. Further research, using consistent methodology, is required for better understanding the neurobiology of olfactory deficits. The authors suggest taking age and sex differences into consideration and further contrasting olfactory subgroups (impaired vs intact) to better our understanding of the heterogeneity of psychotic disorders.

Keywords: Olfaction; Schizophrenia; Neuroimaging; Functional magnetic resonance imaging; Positron emission tomography; Single photon emission computed tomography

Core tip: Olfactory identification, familiarity, and memory deficits are consistently noted in patients with psychotic disorders relative to age-matched controls. Olfactory intensity ratings remain intact while olfactory hedonics and detection threshold show inconsistent findings. This review found no consistent differences in functional activity in amygdala and pirifom cortices in psychotic patients relative to control subjects. Secondary olfactory cortices were abnormally activated in psychosis patients, however. Further methodologically consistent research is required for better understanding the neurobiology of olfactory deficits in psychotic disorders. The authors recommend examining sex differences contrasting olfactory subgroups (impaired vs intact) in future examinations.