Key result
fNIRS scale-invariance analysis differentiates cognitive load, yielding higher Hurst exponents in 1-back versus 2-back tasks.
Why the study?
It was unknown whether scale invariance measured by the Hurst exponent can be used with functional near-infrared spectroscopy to quantify cognitive load.
Can scale invariance (Hurst exponent) measured by fNIRS quantify cognitive load during working memory tasks?
Observational
Can scale invariance (Hurst exponent) measured by fNIRS quantify cognitive load during working memory tasks?
Scale invariance measured by fNIRS is a promising, portable method for quantifying cognitive load in real-life settings.
May support noninvasive cognitive monitoring; leaves open validation in clinical populations or trials.
Scale invariant neural dynamics are a relatively new but effective means of measuring changes in brain states as a result of varied cognitive load and task difficulty. This study is the first to test whether scale invariance (as measured by the Hurst exponent, H) can be used with functional near-infrared spectroscopy (fNIRS) to quantify cognitive load. We analyzed H extracted from the fNIRS time series while participants completed an N-back working memory task. Consistent with what has been demonstrated in fMRI, the current results showed that scale-invariance analysis significantly differentiated between task and rest periods as calculated from both oxy- (HbO) and deoxy-hemoglobin (HbR) concentration changes. Results from both channel-averaged Hurst and a multivariate partial least squares approach (Task PLS) demonstrated higher H during the 1-back task than the 2-back task. These results were stronger for Hurst derived from HbR than from HbO. As fNIRS is relatively portable and robust to motion-related artifacts, these preliminary results shed light on the promising future of measuring cognitive load in real life settings.
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Kardan et al. (2021) conducted an observational in Cognitive load. N-back working memory task vs. Rest periods and 2-back task was evaluated on Hurst exponent (H) differentiation between task and rest periods, and between task difficulties. Scale-invariance analysis of fNIRS data significantly differentiated between task and rest periods, with higher Hurst exponents observed during the 1-back task compared to the 2-back task.
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