Transcranial photobiomodulation modulates brain signal variability in older adults
Poster No:
83
Submission Type:
Abstract Submission
Authors:
Hong LI1, Ying Han2, HAIJING NIU1
Institutions:
1Beijing Normal University, Beijing, Beijing, 2Xuanwu Hospital of Capital Medical University, Beijing, Beijing
First Author:
Co-Author(s):
Introduction:
Transcranial photobiomodulation (tPBM), as a a safe and noninvasive neuromodulation technique, plays a critical role in preventing normal brain aging and maintaining or improving cognition in older adults. Recently, Hu et al. conducted a study to investigate the effect of tPBM on brain activation during a working memory (WM) task in healthy older adults and found that tPBM resulted in a decrease in brain activation mainly in the right hemisphere. Brain signal variability is the fluctuation of functional brain activity within an individual at different temporal and spatial levels, which allows for adaptation and adjustment to changing internal and external demands. There is a growing body of evidence suggesting that moment-to-moment brain signal variability could be considered an important neuro marker in characterizing healthy aging. However, it is still unknown whether tPBM can modulate brain signal variability and thereby enhance working memory ability in older adults.
Methods:
In this study, 84 healthy adults aged 49-79 (mean ± SD, 64.19 ± 6.22, 60 females) participated in a single-blind, counterbalanced design. Participants first received either a 12-minute active or sham tPBM stimulation targeted on the left dorsolateral prefrontal cortex, followed by a digit n-back working memory task with three loads (n = 1, 2, 3). Functional near-infrared spectroscopy (fNIRS) was used to record the hemodynamic changes of the whole head during the task. The sham session followed the same procedure as the active tPBM session, except that the laser device was turned off after 5 seconds. The active tPBM and sham-controlled sessions were separated by one month. After preprocessing the fNIRS data, the brain signal variability (operationalized as the SD HbO) was estimated by averaging the variability within each block for each WM load. The n-back task performance was evaluated by accuracy (ACC) and mean response time (RT). To extract spatial patterns of brain signal variability associated with task conditions or behavior performance, we used a multivariate Partial Least Squares (PLS) analysis. The task PLS analysis was used to examine the effect of tPBM stimulation on SD HbO for each memory load. Next, we utilized a behavioral PLS analysis to examine the relationship between tPBM-related changes in SD HbO and tPBM-related changes in WM performance.
Results:
A task-PLS model revealed one significant latent variable (LV) (permuted p < 0.001) indicating a decrease in brain signal variability after tPBM compared to the sham-controlled condition, regardless of 1-, 2-, or 3-back condition (Figure 1). This was observed in several regions typical of WM studies, including the bilateral dorsolateral prefrontal cortex (DLPFC), pre-motor cortex and supplementary motor area (PMA), supramarginal gyrus (SMG), visual cortex 3 (V3), frontal eye fields (FEF), and left angular gyrus (AG). No regions showed an increase in variability on tPBM compared to the sham-controlled condition. Additionally, a behavioral PLS analysis was conducted to examine whether the reduction of tPBM-related fNIRS signal variability could predict improved WM performance. Results revealed that the decreased tPBM-related fNIRS signal variability was associated with improved accuracy, as indicated by a single significant LV (permuted p = 0.005, Figure 2). This negative relationship was mainly significant in several regions, including bilateral DLPFC, SMG, AG, V3, left primary somatosensory cortex (PSS), somatosensory association cortex (SAC), right V2, and PMA. However, no significant LV (permuted p = 0.289) was found for the mean RT model.
Conclusions:
In summary, tPBM has been shown to reduce task-related fNIRS signal variability in older adults, and this reduction has been linked to improved WM performance. This suggests that tPBM may reduce the cognitive effort required to complete WM tasks, offering a potential avenue for inducing long-term cognitive improvements in normal aging or age-related conditions.
Brain Stimulation:
Non-Invasive Stimulation Methods Other 1
Learning and Memory:
Working Memory 2
Lifespan Development:
Aging
Modeling and Analysis Methods:
Multivariate Approaches
Novel Imaging Acquisition Methods:
NIRS
Keywords:
Near Infra-Red Spectroscopy (NIRS)
Other - brain signal variability; working memory; transcranial photobiomodulation
1|2Indicates the priority used for review
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