# Altered frequency architecture of spontaneous brain activity in asymptomatic carotid stenosis: a wavelet-based resting-state fMRI study

## TL;DR

This study uses wavelet-based fMRI to show how brain activity frequencies change in people with asymptomatic carotid stenosis, affecting cognitive function.

## Contribution

The study introduces a wavelet-based approach to reveal altered cross-frequency coupling in the default mode network in asymptomatic carotid stenosis.

## Key findings

- Healthy controls show a spatial frequency gradient from lower to higher frequencies in the DMN.
- SACS patients show decreased wavelet-ALFF in the anteromedial and posteromedial DMN at different frequencies.
- Abnormal cross-frequency coupling in the DMN is linked to cognitive impairment in SACS patients.

## Abstract

The intrinsic brain activity measured by resting-state fMRI (rs-fMRI) consists of synchronized neural oscillations across a broad range of low frequencies. Although previous studies have linked frequency-specific changes to cognitive function and impairment, the alterations of these frequency-specific spatiotemporal patterns in chronic occlusive cerebrovascular disease remain unclear. In this study, we investigated the cross-frequency structure underlying cognitive impairment in patients with severe asymptomatic carotid stenosis (SACS) using wavelet-transformed amplitude of low-frequency fluctuation (wavelet-ALFF) of rs-fMRI. We found that, in healthy controls, frequency-specific wavelet-ALFF exhibited a spatial distribution from lower to higher frequencies, aligned with the functional hierarchy extending from the default mode network (DMN) to primary somatomotor and subcortical regions. In contrast, SACS patients exhibited frequency-dependent changes, including significantly decreased wavelet-ALFF in the anteromedial DMN at lower frequencies and the posteromedial DMN at higher frequencies. Further spatiotemporal decomposition analysis revealed that SACS patients exhibited abnormal cross-frequency coupling in the DMN. Our findings suggest that frequency-specific changes underlying cognitive impairment in SACS arise from spatiotemporally abnormal cross-frequency interplay within the DMN. These insights may contribute to a better understanding of other major brain diseases.