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Noise reduction in functional near-infrared spectroscopy signals by independent component analysis
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View: Figures


Image of FIG. 1.
FIG. 1.

The proposed ICA method: The original hemodynamic response is reconstructed using independent components (ICs).

Image of FIG. 2.
FIG. 2.

ICA concept: (a) examples of 5 hemodynamic signals (i.e., a hemodynamic response due to neuronal activation, low frequency oscillation #1, respiratory, motion artifact, and low frequency oscillation #2), (b) the power-spectral densities of (a), (c) three signals used in the ICA of http://www.cis.hut.fi/projects/ica/fastica, (d) three identified ICs from (c), and (e) the power-spectral densities of (d) that can be compared with (b), where IC 1, IC 2, and IC 3 are claimed to be the estimated hemodynamic responses , , and , respectively.

Image of FIG. 3.
FIG. 3.

Experimental design: (a) optodes configuration (Fp1 and Fp2 in the International 10-20 System are used as reference points), (b) experimental procedure for arithmetic task.

Image of FIG. 4.
FIG. 4.

Processing scheme.

Image of FIG. 5.
FIG. 5.
Image of FIG. 6.
FIG. 6.

A typical example of raw HbO, HbR, and HbT data (Subject 1, Ch. 12).

Image of FIG. 7.
FIG. 7.

PSDs of typical 4 ICs chosen from Figure 5 (Subject 8).

Image of FIG. 8.
FIG. 8.

HbO comparison (Subject 8): the low-pass-filtered (LPF) signal () at Ch. 15 (dotted), the reconstructed hemodynamic response () using Eq. (7) (solid), and the modeled hemodynamic signal () (the -value between () and () is 37 and that between () and () is 51).

Image of FIG. 9.
FIG. 9.

Comparison of () using (7) (solid) and () using only four ICs with high -values (dotted): The drifting behavior of () during 360-450 s has been removed.

Image of FIG. 10.
FIG. 10.

Comparison of the highest -values of () and (), respectively, for all 8 subjects and their grand averages.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Noise reduction in functional near-infrared spectroscopy signals by independent component analysis