The Relationship of Modulation Generated in Brain Intrinsic Connectivity Networks by Simple Sensory Stimuli and...

This study aimed to investigate the modulation of simple sensory stimuli on brain intrinsic connectivity networks in the Alzheimer's disease continuum (ADC) using functional magnetic resonance imaging (fMRI).

fMRI and neuropsychological assessment data of 88 cases in ADC were analysed. fMRI data were recorded in a session including blocks of light stimuli flickering at 20 Hz frequency and in the resting state from 21 Alzheimer's disease dementia (ADD), 34 mild cognitive impairment (MCI) and 33 subjective cognitive impairment (SCI). CONN (functional connectivity toolbox) software was used for functional connectivity analyses of fMRI data. Bonferroni correction was applied according to the number of ROIs in functional connectivity analyses and the significance threshold was determined as pFWE <0.0033.

As a result of the analysis of the resting state data, decreased connectivity was detected between the posterior cingulate cortex seed of the default mode network and the temporal and parietal areas in ADD compared to the SCI and MCI groups. Decreased functional connectivity was detected between the anterior insula and anterior cingulate cortex seeds of the salience network and the temporal, frontal and cingulate cortices in ADD compared to the SCI and MCI groups. However, in the data of flickering light stimulation at a frequency of 20 Hz, increased functional connectivity was detected between the right lateral prefrontal cortex seed of the frontoparietal network, which could not be captured with the resting state data, and the precuneus in the MCI group compared to the SCI group.

The increase in connectivity between the frontoparietal network and precuneus may be a compensatory response in the early stages of the disease. In addition, it was thought that fMRI images performed using simple sensory stimuli were more sensitive to cognitive decline in the early stages of the disease compared to resting state data and could have biomarker potential.