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Evaluation of fNIRS signal components elicited by cognitive and hypercapnic stimuli
Journal article   Open access   Peer reviewed

Evaluation of fNIRS signal components elicited by cognitive and hypercapnic stimuli

Pratusha Reddy, Meltem Izzetoglu, Patricia A Shewokis, Michael Sangobowale, Ramon Diaz-Arrastia and Kurtulus Izzetoglu
Scientific reports, v 11(1), pp 23457-23457
06 Dec 2021
PMID: 34873185
url
https://doi.org/10.1038/s41598-021-02076-7View
Published, Version of Record (VoR)CC BY V4.0 Open

Abstract

Adult Biomarkers - metabolism Brain - physiology Brain Mapping - methods Cerebral Cortex - physiology Cognition - physiology Female Humans Hypercapnia - physiopathology Male Neurosciences Principal Component Analysis Spectroscopy, Near-Infrared - methods Statistics as Topic Wavelet Analysis Young Adult
Functional near infrared spectroscopy (fNIRS) measurements are confounded by signal components originating from multiple physiological causes, whose activities may vary temporally and spatially (across tissue layers, and regions of the cortex). Furthermore, the stimuli can induce evoked effects, which may lead to over or underestimation of the actual effect of interest. Here, we conducted a temporal, spectral, and spatial analysis of fNIRS signals collected during cognitive and hypercapnic stimuli to characterize effects of functional versus systemic responses. We utilized wavelet analysis to discriminate physiological causes and employed long and short source-detector separation (SDS) channels to differentiate tissue layers. Multi-channel measures were analyzed further to distinguish hemispheric differences. The results highlight cardiac, respiratory, myogenic, and very low frequency (VLF) activities within fNIRS signals. Regardless of stimuli, activity within the VLF band had the largest contribution to the overall signal. The systemic activities dominated the measurements from the short SDS channels during cognitive stimulus, but not hypercapnic stimulus. Importantly, results indicate that characteristics of fNIRS signals vary with type of the stimuli administered as cognitive stimulus elicited variable responses between hemispheres in VLF band and task-evoked temporal effect in VLF, myogenic and respiratory bands, while hypercapnic stimulus induced a global response across both hemispheres.

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Neurosciences
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