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Unirhinal olfactory identification deficits in young male patients with schizophrenia and related disorders:
Kimberley P Good1, Jeffrey S Martzke, Heather I Milliken
1Department of Psychiatry, Dalhousie University, Suite 4019-5909, Jubilee Road, Halifax, NS B3H 2E2, Canada. kimpgood@is.dal.ca
Abstract:
We have observed discreet subgroups of male patients with psychotic disorders who have unirhinal olfactory identification deficits (microsmia). The purpose of this study was to examine the relationship between left or right nostril microsmia and performance on literalised neuropsychological tests sensitive to lesions in brain areas implicated in the pathogenesis of schizophrenia. Sixty-six male patients diagnosed with schizophrenia or related disorders were assessed with a battery of neuropsychological tests, sensitive to literalised and regional (temporal and frontal lobe) dysfunction. The University of Pennsylvania Smell Identification Test (UPSIT) was administered unirhinally and resultant scores were used to classify patients into olfactory subgroups. Neuropsychological test scores were compared amongst subgroups. A mixed design MANOVA was performed on cognitive domains with olfactory status (right microsmic; RM, n=8, left microsmic; LM, n=20, and normosmic schizophrenic controls; NSzC, n=38) as the between subject factor while hemisphere (left versus right) and domain (executive/fluency versus memory) were within-subject factors. A three-way (olfactory subgroup by hemisphere by region) interaction was observed. Non-verbal memory impairment was observed in the right and left microsmic subgroups. Verbal memory deficits were demonstrated in patients with left nostril microsmia. These results indicate that unirhinal olfactory performance may provide a meaningful manner by which to subtype patients with schizophrenia. Moreover, the data suggest that olfactory deficits in patients with schizophrenia are associated with dysfunction of temporal lobe, rather than frontal lobe abnormalities. The data are consistent with reports linking the right temporal lobe integrity to adequate olfactory processing.
Insights
Unirhinal olfactory deficits (microsmia) may help subtype male patients with schizophrenia. Left nostril microsmia is linked to verbal memory deficits, while both left and right microsmia correlate with non-verbal memory impairment.
Area of Science:
- Neuroscience
- Psychiatry
- Cognitive Science
Background:
- Subgroups of male patients with psychotic disorders exhibit unirhinal olfactory identification deficits (microsmia).
- Schizophrenia pathogenesis is linked to brain areas potentially affected by olfactory dysfunction.
Purpose of the Study:
- To investigate the relationship between left or right nostril microsmia and neuropsychological test performance.
- To explore the association between olfactory deficits and brain region dysfunction in schizophrenia.
Main Methods:
- Sixty-six male patients with schizophrenia or related disorders underwent neuropsychological testing.
- The University of Pennsylvania Smell Identification Test (UPSIT) was used for unirhinal olfactory assessment.
- Patients were classified into olfactory subgroups (right microsmic, left microsmic, normosmic controls) for comparison.
Main Results:
- A significant three-way interaction was observed between olfactory subgroup, hemisphere, and brain region.
- Non-verbal memory impairment was evident in both right and left microsmic subgroups.
- Verbal memory deficits were specifically observed in patients with left nostril microsmia.
Conclusions:
- Unirhinal olfactory performance can serve as a meaningful biomarker for subtyping schizophrenia patients.
- Olfactory deficits in schizophrenia are associated with temporal lobe dysfunction, not frontal lobe abnormalities.
- Findings support the link between right temporal lobe integrity and olfactory processing.