Olfactory physiological impairment in first-degree relatives of schizophrenia patients.
BACKGROUND
Efforts to characterize genetic vulnerability to schizophrenia are increasingly focused on the identification of endophenotypes--neurobiological abnormalities that are evident in individuals at risk. Behavioral studies have demonstrated olfactory impairments in odor detection and identification in unaffected 1st-degree relatives of schizophrenia patients, suggesting that abnormalities in this simple sensory system may serve as candidate endophenotypes. It is unclear, however, whether these behavioral abnormalities reflect basic olfactory sensory processing deficits or nonspecific disruptions of attention and cognition.


METHODS
Unirhinal chemosensory olfactory evoked potentials were acquired from 14 unaffected 1st-degree relatives of schizophrenia patients and 20 healthy individuals with equivalent age and gender distributions, using 3 different concentrations of hydrogen sulfide. Subjects were also assessed behaviorally for ability to detect and identify odors.


RESULTS
Family members exhibited left nostril olfactory detection impairments and bilateral olfactory identification abnormalities. They had reduced evoked potential response amplitudes for the initial N1 component in the left nostril. The subsequent P2 evoked potential response was reduced bilaterally. The pattern and magnitude of family member deficits were comparable to those previously observed for schizophrenia patients.


CONCLUSIONS
1st-degree relatives of schizophrenia patients exhibit specific neurophysiological impairments in early olfactory sensory processing. The presence of these neurophysiological abnormalities in both schizophrenia patients and their unaffected 1st-degree relatives suggests that these represent genetically mediated vulnerability markers or endophenotypes of the illness.
Turetsky
Bruce I
BI
Neuropsychiatry Division, Department of Psychiatry, University of Pennsylvania School of Medicine, 3400 Spruce Street, Philadelphia, Pennsylvania 19104, USA. turetsky@upenn.edu
Kohler
Christian G
CG
Gur
Raquel E
RE
Moberg
Paul J
PJ
D000328:Adult; D035061:Control Groups; D005071:Evoked Potentials / Q000235:genetics / Q000502:physiology; D005190:Family; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D005819:Genetic Markers; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D008297:Male; D009666:Nose / Q000502:physiology; D009812:Odorants; D000857:Olfaction Disorders / Q000175:diagnosis* / Q000235:genetics / Q000503:physiopathology; D009833:Olfactory Pathways / Q000503:physiopathology; D010641:Phenotype; D012559:Schizophrenia / Q000175:diagnosis* / Q000235:genetics / Q000503:physiopathology; D012565:Schizophrenic Psychology; D012684:Sensory Thresholds / Q000502:physiology; D012903:Smell / Q000502:physiology
D005819:Genetic Markers