SPECT IMAGING OF ODOR IDENTIFICATION IN SCHIZOPHRENIA

Deficits in olfactory identification, despite normal odor perception, are found in some neuropsychiatric disorders, including schizophrenia. We examined if regional cerebral blood flow (rCBF) differed between s chizophrenia patients and controls during odor identification, hypothe sizing that these brain regions could be relevant to odor identificati on impairments. Eight schizophrenia and eight comparison subjects prov ided a baseline (picture identity matching) and activation (odor ident ification) SPECT scan, obtained using Tc-99m-HMPAO in a low dose/high dose design. Six patients and seven controls had analyzable data. MEDX data saved in ANALYZE format for SPM 95 generated paired t-test stati stical data for display in Talairach space, with rCBF changes given as Z-scores. There was no schizophrenia vs. control group difference in rCBF for the baseline picture-matching test. For odor identification, schizophrenia patients had a hypometabolic right-sided cortical region that included the frontal lobe Broca's area, superior temporal lobe, and supramarginal and angular gyri. Post hoc within-group contrasts of picture-matching vs. odor identification showed that the controls sig nificantly increased rCRF in the right-sided inferior temporal fusifor m gyrus, and bilateral hippocampi and visual association areas for the odor test. The schizophrenia group showed no rCBF differences for pic ture-matching compared to odor identification. Patients showed signifi cant hypometabolism in right-sided cortical areas for odor identificat ion. They also failed to show increased rCBF in the hippocampus and vi sual association area, as seen in controls for odor identification com pared to picture-matching. These regions may be unique to schizophreni a or have broader implications for olfactory memory retrieval. (C) 199 8 Elsevier Science Ireland Ltd.