Altered temporal dynamics of intrinsic brain activity in mild cognitive impairment with olfactory dysfunction

Area of Science:

• Neuroscience
• Cognitive Science
• Medical Imaging

Background:

• Odor identification (OI) impairment is a risk factor for Alzheimer's disease (AD) in individuals with mild cognitive impairment (MCI).
• Understanding the neural mechanisms of OI impairment in MCI is crucial for early diagnosis and intervention.
• Dynamic resting-state functional magnetic resonance imaging (rs-fMRI) offers insights into brain network aberrations.

Purpose of the Study:

• To investigate dynamic intrinsic brain activity in MCI patients with and without OI impairment.
• To correlate dynamic neural signatures with cognitive and olfactory function.
• To identify potential neural mediators linking olfactory deficits and cognitive decline in MCI.

Main Methods:

• Analyzed dynamic metrics (dfALFF, dALFF, dDC, dReHo) in 194 participants (97 MCI, 97 healthy controls [HC]).
• Compared MCI with OI impairment (MCI-OII) group against MCI without OI impairment (MCI-NOII) and HC groups.
• Correlated dynamic brain activity metrics with cognitive performance and OI test scores.

Main Results:

• MCI-OII patients exhibited significant cognitive deficits across all domains compared to HC and MCI-NOII groups.
• Elevated variability in dALFF, dfALFF, dDC, and dReHo was observed in brain regions including the fusiform gyrus, insula, precuneus, and cingulate cortex in MCI-OII.
• Dynamic brain activity metrics significantly correlated with olfactory and cognitive scores, with right precuneus dReHo mediating the link between olfactory function and memory recall.

Conclusions:

• MCI patients with OI impairment display widespread disruptions in dynamic brain activity.
• These neural alterations are associated with clinical deficits in cognition and olfaction.
• Dynamic regional homogeneity in the precuneus may play a role in the relationship between olfactory and cognitive decline in MCI.