Functional connectivity
How brain wave power relates to dynamic fMRI connections
Open access · cc by · source: Europe PMC
Fluctuations in brain connectivity measured by fMRI are directly linked to changing patterns of electrical brain waves, with fast waves boosting connection strength and slow waves suppressing it.
How this study connects
Role on claims
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The slow-acting blood oxygen level-dependent signals measured in functional MRI are fundamentally linked to rapid electrophysiological brain wave activity, showing that network dynamics correspond to electrical oscillations.
Evidence for the claim as stated.
Dynamic fluctuations in BOLD functional connectivity are tightly coupled with shifting electrophysiological brain rhythms, where high-frequency gamma bands correlate with stronger network integration and alpha/beta bands reflect reduced connectivity.
Evidence for the claim as stated.
Electrophysiological correlates of dynamic BOLD connectivity alter during state transitions, such as falling asleep, where slow delta waves become positively correlated with frontal network connectivity.
Evidence for the claim as stated.
Discoveries this paper informs or conflicts with
- Autism network differences appeared in function and structure at once — in a sample chosen to be able to show them
This paper conflicts with this development.
Study at a glance
- Design
- Human experiment — Dynamic BOLD connectivity in awake rest plus an independent vigilance-transition group with electrophysiology
- N
- N=28 · 15 awake (10 women, mean age 26.2) and 13 in a vigilance-transition group
- Population
- Healthy adults scanned awake and during vigilance transitions
- Outcome
- Time-varying BOLD functional connectivity and its electrophysiological correlates
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How brain wave power relates to dynamic fMRI connections
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15 awake participants
A total of 15 awake subjects were included in the study (10 female, age 26.2 ± 6), together with an independent group of 13 subjects undergoing vigilance transitions between wakefulness and light sleep or N1 sleep (8 female, age 23.3 ± 3.4).
90 brain regions
As a first step, the average BOLD signal was extracted from each one of the 90 cortical and subcortical regions defined by the AAL template (Tzourio-Mazoyer et al., ) (information on all the regions is provided in Table ).
Key findings
They discovered that high-frequency gamma waves positively correlate with stronger, more integrated BOLD connectivity across the brain, particularly in frontal regions. Conversely, alpha and beta waves negatively correlate with connectivity, reflecting an idling or inhibitory state. In participants falling asleep, slow delta waves positively correlated with frontal connectivity, while alpha power correlated with a more fragmented, less efficient network structure.
Methodology
Researchers recorded brain activity in 15 awake participants and 13 participants transitioning into light sleep using simultaneous EEG and fMRI scans. They measured how functional connectivity between 90 brain regions changed over time using 2-minute sliding windows. They then correlated these functional connectivity changes with fluctuations in the power of different electrical brain wave bands.
Limitations
This study is correlational, meaning it cannot prove that changing electrical brain waves directly cause changes in fMRI network connectivity. The sample sizes are relatively small, with only 15 awake and 13 sleeping participants. Additionally, using 2-minute sliding windows limits the ability to observe rapid, sub-second neural transitions. Lastly, the researchers could not control for spontaneous, unguided thoughts during the resting-state scans.
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