Associations of olfactory function with brain structural and functional outcomes. A systematic review

Area of Science:

• Neuroscience
• Gerontology
• Olfactory Research

Background:

• Olfactory deficits are linked to cognitive and motor decline in aging.
• Olfactory dysfunction is an early sign of neurodegenerative diseases.
• Understanding neural correlates of olfaction is key to unraveling these associations.

Approach:

• Comprehensive review of 33 studies (30 MRI/DTI, 3 fMRI) on brain structure/function and olfaction in older adults.
• Studies included cognitively normal individuals and those with cognitive impairment, including Alzheimer's disease.
• Focused on associations between olfactory function and brain volumes/activity.

Key Points:

• Lower olfactory function associated with reduced volumes in temporal lobe (hippocampus, parahippocampal gyrus, fusiform gyrus).
• Impairment linked to smaller olfactory-related regions (piriform cortex, amygdala, entorhinal cortex).
• Associated with changes in pre/postcentral gyri and globus pallidus, areas vital for motor function and cognition.

Conclusions:

• Olfactory impairment in aging may indicate pathology in brain regions crucial for cognition and motor control.
• These findings highlight olfaction as a potential early indicator for neurodegenerative diseases.
• Longitudinal neuroimaging studies are needed to confirm neurobiological changes and disease progression.