Abstract
‘Super smellers‘ are those individuals who show a heightened sense of smell. Data on the structural neuroanatomy of this phenomenon are still missing. A voxel-based morphometry study was conducted in order to compare gray matter volume (GMV) in specific brain regions of the olfactory network (piriform/entorhinal cortex, orbitofrontal cortex, insula, hippocampus) between 25 male ‘super smellers’ and 20 normosmic men. Participants were assigned to these groups based on their scores on a standardized olfactory performance test. Relative to normosmic men, ‘super smellers’ showed increased GMV in the anterior insula and in the hippocampus (dentate gyrus). These regions are crucial for the integration of olfactory information as well as odor learning and odor memory. Moreover, positive correlations between hippocampal volume and olfactory performance were detected in both groups. Future research should elaborate on how much of the observed neuroanatomical pattern of ‘super smellers’ is genetic and how much of it reflects experienced-based GMV increase.
Highlights
Quantitative alterations in olfactory function can include both impairment and enhancement of performance
Brief symptom inventory (BSI) Both groups did not differ with regard to the scores on the Brief Symptom Inventory (BSI) subscales and the total score (GSI; Table 2)
Peaks of increased volume were found in the anterior part of the insula, and in the dentate gyrus
Summary
Quantitative alterations in olfactory function can include both impairment and enhancement of performance. The ability to detect odors can be reduced (hyposmia), it can be lacking for particular odorants despite the preserved ability to smell most other odors (specific anosmia), or it can be absent, which is the case in anosmia (Hummel et al 2017). The causes of these changes are manifold, including sinonasal disease (e.g., sinusitis), infections (e.g., of the respiratory tract), exposure to toxins/drugs, tumors, neurological/neurodegenerative disease (e.g., Parkinson’s disease, dementia) and genetic conditions (congenital); there can be idiopathic causes (without any connection to a medical diagnosis). There is generally no known medical cause of hyperosmia (idiopathic origin; Doty and Bromley 2007)
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