Olfactory Deficits

Many patients with schizophrenia exhibit olfactory dysfunctions. They are impaired in their ability to detect odors due to an increased sensitivity threshold for detection. Their ability to identify odors, to discriminate between odors, and their olfactory memory are also significantly impaired. While the basis for this dysfunction is unclear, olfactory processing is mediated by limbic structures that have been implicated in the pathophys-iology of schizophrenia, including the prefrontal cortex, ventromedial temporal lobe, basal forebrain, and diencephalon. The few studies that have examined the neurobiology of the olfactory system in schizophrenia patients have revealed a reduced evoked potential response to olfactory stimuli, a 23 percent decrease in size of the olfactory bulb, and a decrease in synaptophysin expression in the glomerulus of the olfactory bulb, indicating a reduction in synaptic functioning of this structure (Moberg et al., 1999). Neurodevelopment continues throughout life in the olfactory system, rendering it a good site for examining active neurodevelopmental processes in schizophrenia.

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