Abstract
Functional Near-Infrared Spectroscopy (fNIRS) captures activations and inhibitions of cortical areas and implements a viable approach to neuromonitoring in clinical research. Compared to more advanced methods, continuous wave fNIRS (CW-fNIRS) is currently used in clinics for its simplicity in mapping the whole sub-cranial cortex. Conversely, it often lacks hardware reduction of confounding factors, stressing the importance of a correct signal processing. The proposed pipeline includes movement artifact reduction (MAR), bandpass filtering (BPF), and principal component analysis (PCA). Eight MAR algorithms were compared among 23 young adult volunteers under motor-grasping task. Single-subject examples are shown followed by the percentage in energy reduction (ERD%) statistics by single steps and cumulative values. The block average of the hemodynamic response function was compared with generalized linear model fitting. Maps of significant activation/inhibition were illustrated. The mean ERD% of pre-processed signals concerning the initial raw signal energy reached 4%. A tested multichannel MAR variant showed overcorrection on 4-fold more expansive windows. All of the MAR algorithms found similar activations in the contralateral motor area. In conclusion, single channel MAR algorithms are suggested followed by BPF and PCA. The importance of whole cortex mapping for fNIRS integration in clinical applications was also confirmed by our results.
Highlights
For more than two decades, functional Near-Infrared Spectroscopy has become a valuable tool for non-invasively estimating the Hemodynamic Response Function (HRF) and mapping cerebral cortex activations [1]
The results of Functional Near-Infrared Spectroscopy (fNIRS) signal processing are given relevant to the group of 23 healthy young adults (HYA)
The percentage of the signal labelled motion artifacts (MAs) was low in both Hybrid-Movement Artifact Reduction Algorithm (MARA) (1.10–0.90%, median–IQR), which is a single channels (SCs)-method, and SCMARA (0.32–0.42%, median–IQR)
Summary
For more than two decades, functional Near-Infrared Spectroscopy (fNIRS) has become a valuable tool for non-invasively estimating the Hemodynamic Response Function (HRF) and mapping cerebral cortex activations [1]. The phenomenon of HRF had been observed many decades earlier in invasive experiments investigating the fine functional mapping of the exposed cortex. The feature which allows HRF to be accessible to fNIRS and other non-invasive transcranial measurements is the critical variation of perfusion to even modest increments in the local oxygen consumption. This is probably needed to compensate for transport delays from vessels to cells and is driven by powerful neuro-vascular coupling mechanisms [5]. HRF-related signals are powerful, yet indirect markers of neural activity with a fair spatial resolution
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