Olfactory function in psychotic disorders: Insights from neuroimaging studies.

Area of Science:

• Neuroscience
• Psychiatry
• Sensory Systems

Background:

• Patients with psychotic disorders consistently exhibit olfactory deficits in identification, familiarity, and memory compared to controls.
• While olfactory intensity perception appears intact, data on hedonic processing and detection thresholds are inconsistent.
• Previous research has not identified specific regional brain hypoactivity related to olfactory domains in psychosis.

Purpose of the Study:

• To review and synthesize current neurobiological findings on olfactory processing in psychotic disorders.
• To identify brain regions involved in olfactory deficits within this patient population.
• To highlight inconsistencies and suggest future research directions.

Main Methods:

• Systematic review of studies examining olfactory function and neuroimaging in patients with psychotic disorders.
• Analysis of behavioral data (identification, familiarity, memory, intensity, hedonics, detection threshold).
• Examination of neuroimaging findings, focusing on regional brain activity during olfactory tasks.

Main Results:

• No specific regional brain hypoactivity was identified across all olfactory domains in psychosis patients.
• The amygdala and piriform cortex showed no abnormalities in hedonic processing, contrasting with their known role in healthy individuals.
• Secondary olfactory cortex regions, including orbitofrontal cortex, thalamus, and insula, demonstrated abnormal activation, particularly during hedonic processing.

Conclusions:

• Olfactory deficits in psychotic disorders are associated with abnormal activation in secondary olfactory cortical regions, not typically the amygdala.
• Further research with consistent methodologies is crucial for understanding the neurobiology of these olfactory deficits.
• Consideration of age, sex, and olfactory subgroup differences is recommended to address the heterogeneity of psychotic disorders.