How much do time-domain functional near-infrared spectroscopy (fNIRS) moments improve estimation of brain activity over traditional fNIRS?

Abstract

. Significance Advances in electronics have allowed the recent development of compact, high channel count time domain functional near-infrared spectroscopy (TD-fNIRS) systems. Temporal moment analysis has been proposed for increased brain sensitivity due to the depth selectivity of higher order temporal moments. We propose a general linear model (GLM) incorporating TD moment data and auxiliary physiological measurements, such as short separation channels, to improve the recovery of the HRF. Aims We compare the performance of previously reported multi-distance TD moment techniques to commonly used techniques for continuous wave (CW) fNIRS hemodynamic response function (HRF) recovery, namely block averaging and CW GLM. Additionally, we compare the multi-distance TD moment technique to TD moment GLM. Approach We augmented resting TD-fNIRS moment data (six subjects) with known synthetic HRFs. We then employed block averaging and GLM techniques with “short-separation regression” designed both for CW and TD to recover the HRFs. We calculated the root mean square error (RMSE) and the correlation of the recovered HRF to the ground truth. We compared the performance of equivalent CW and TD techniques with paired t-tests. Results We found that, on average, TD moment HRF recovery improves correlations by 98% and 48% for HbO and HbR respectively, over CW GLM. The improvement on the correlation for TD GLM over TD moment is 12% (HbO) and 27% (HbR). RMSE decreases 56% and 52% (HbO and HbR) for TD moment compared to CW GLM. We found no statistically significant improvement in the RMSE for TD GLM compared to TD moment. Conclusions Properly covariance-scaled TD moment techniques outperform their CW equivalents in both RMSE and correlation in the recovery of the synthetic HRFs. Furthermore, our proposed TD GLM based on moments outperforms regular TD moment analysis, while allowing the incorporation of auxiliary measurements of the confounding physiological signals from the scalp.

Change in brain asymmetry reflects level of acute alcohol intoxication and impacts on inhibitory control

“…To convert the preprocessed DToF moments data to relative changes in oxy-and deoxy-hemoglobin concentrations (HbO and HbR, respectively), we used a sensitivity method described in detail previously 29,[53][54][55] to obtain absorption coefficients at each wavelength. Finally, these coefficients were converted to relative changes in the two chromophores using the extinction coefficients for the two wavelengths and the modified Beer-Lambert law (mBLL) 56 .…”

Acute effects of subanesthetic ketamine on cerebrovascular hemodynamics in humans: A TD-fNIRS neuroimaging study

“…The relative changes in preprocessed moments were then converted to relative changes in absorption coefficients for each wavelength using the sensitivities of the different moments to changes in absorption coefficients (moments Jacobians, i.e. derivative of each moment with respect to a change in absorption coefficient), following the procedure recently described in 40 . To obtain the sensitivities of the different moments, we used a 2-layer medium with a 12-mm superficial layer.…”

“…After the first fNIRS study with psychedelics was conducted in 2019 38 , this study is the second fNIRS neuroimaging study with psychedelics ever and the first fNIRS neuroimaging study with ketamine ever conducted. TD-fNIRS systems have been considered the gold standard for optical neuroimaging-they can retrieve more information than the continuous wave (CW-) systems, and in particular they can achieve absolute measurements and higher sensitivity to deeper tissue layers on the human head 39,40 . With these systems, picosecond pulses of light are emitted into the scalp tissue, and arrival times of single photons are measured at nearby detectors.…”

“…TD-fNIRS systems have been considered the gold standard for optical neuroimaging—they can retrieve more information than the continuous wave (CW-) systems, and in particular they can achieve absolute measurements and higher sensitivity to deeper tissue layers on the human head 39,40 . With these systems, picosecond pulses of light are emitted into the scalp tissue, and arrival times of single photons are measured at nearby detectors.…”

Wearable, high-density fNIRS and diffuse optical tomography technologies: a perspective

“…This technology has great potential to provide improved functional mapping, particularly in terms of quantitation, both within and across individuals. Although significant publications are expected to emerge in the coming months, to date, the demonstration and validation of the flow device, particularly in terms of imaging capability, has been limited 49 …”