Temporal decoupling of oxy- and deoxy-hemoglobin hemodynamic responses detected by functional near-infrared spectroscopy (fNIRS)

Abstract

This study provides experimental evidence that there is temporal decoupling between the hemodynamic responses of oxy-and deoxy-hemoglobin (Hb) as detected by functional nearinfrared spectroscopy (fNIRS). Using 64 spatially distributed optrodes to record motor cortical activities during a free arm movement task (right-left and front-back movements), we detected that the temporal profile of oxy-and deoxy-Hb responses are desynchronized and decoupled (i.e., oxy-and deoxy-Hb levels do not rise and fall at the same time). We correlated four different measures of hemodynamic profiles with the arm movements, namely, oxy-(HbO 2 ) and deoxy-hemoglobin (Hb) and their summation (HbO 2 + Hb) and difference (HbO 2 -Hb) signals. These measures correspond to the changes in oxygen delivery, oxygen extraction, total blood volume delivered, and total oxygenation with specific movement directions, respectively. They revealed different components of the hemodynamic response in a localized neuronal population in the motor cortex. The results suggested that, by using these four measures, oxygen delivery and oxygen extraction can be coupled in one movement direction, but decoupled in another movement direction for the same human subject executing the same movement task. Oxygen delivery and oxygen extraction do not always co-vary together temporally. Thus, using a single measure of oxygen delivery or extraction alone may not be sufficient to determine whether the cortical area is activated or deactivated. Rather, a combination of all four measures of hemodynamic signals that represent temporal coupling and decoupling of oxygen delivery and extraction is needed to differentiate the temporal profiles of neural activation and deactivation. It demonstrated that different hemodynamic measures can reveal temporally decoupled activation/deactivation patterns differentially during the right-left and front-back motor task. Therefore, relying on a single measure of deoxy-Hb may be insufficient to characterize the neural responses without the oxy-Hb measure. Orthogonal arm

Bundled-Optode Method in Functional Near-Infrared Spectroscopy

“…It measures the scattered light through the brain using light-detectors (optodes) positioned 2~4 cm apart from the light-source on the scalp. Typically, the changes of the hemoglobin concentration can be computed, based on the modified Beer-Lambert law (MBLL), according to the known extinction coefficients and differential path-length factor [1–14]. Recently, this technique has been integrated into portable equipment using light emitting diodes, electronic circuits, and wireless transceivers [8,15].…”

Mind over motor mapping: Driver response to changing vehicle dynamics

“…Temporal decoupling of HbO and Hb signals indicates that either metric represents only a portion of the hemodynamic response associated with neural processing (Tam and Zouridakis, 2014). Thus, we report primary results for changes in HbO and include results for Hb in the Supplement for completeness (see Supporting Information, Text and Figure 2).…”

“…The parietal cortex, which has previously been implicated in motor planning (Hanakawa et al, 2008) did not show any differences in activation measured by change in HbO during the straight portion (preparatory to making the lane-change maneuver) under incongruent vs. congruent steering control, although we did note a significant difference in Hb signal in the right superior parietal cortex when comparing incongruent to congruent steering (Supporting Information). Lack of significant results for HbO during the preparatory period may be due to the timing of our experimental design and/or temporal decoupling of HbO and Hb signals during motor planning and motor execution (Tam and Zouridakis, 2014). As mentioned previously, considering both HbO and Hb signals is important in the evolving field of fNIRS research (Tachtsidis and Scholkmann, 2016).…”

“…The X-axis corresponds to T scores for the personality factor listed congruent steering (Supporting Information). Lack of significant resultsfor HbO during the preparatory period may be due to the timing of our experimental design and/or temporal decoupling of HbO and Hb signals during motor planning and motor execution(Tam and Zouridakis, 2014). As mentioned previously, considering both HbO and Hb signals is important in the evolving field of fNIRS research(Tachtsidis and Scholkmann, 2016).…”

Near-Infrared Optical Technologies in Brain-Computer Interface Systems

“…At present, the necessity for more "fine" research on hemodynamic response's features registered in the NIR modality in order to obtain more detailed description of its features from the point of view of physiology is obvious. In [83], experimental confirmation presented that there is a time difference between hemodynamic answers in oxy-and deoxyhemoglobin. Authors revealed that a time profile of hemoglobin-concentration-change curve is desynchronized; i.e., their levels do not fall, and their sum and the difference do not rise simultaneously.…”