Intersubject variability of near-infrared spectroscopy signals during sensorimotor cortex activation

Abstract

We investigate the intersubject signal variability of near-infrared spectroscopy (NIRS), which is commonly used for noninvasive measurement of the product of the optical path length and the concentration change in oxygenated hemoglobin (DeltaC'oxy) and deoxygenated hemoglobin (DeltaC'deoxy) and their sum (DeltaC'total) related to human cortical activation. We do this by measuring sensorimotor cortex activation in 31 healthy adults using 24-measurement-position near-infrared (NIR) topography. A finger-tapping task is used to activate the sensorimotor cortex, and significant changes in the hemisphere contralateral to the tapping hand are assessed as being due to the activation. Of the possible patterns of signal changes, 90% include a positive DeltaC'oxy, 76% included a negative DeltaC'deoxy, and 73% included a positive DeltaC'total. The DeltaC'deoxy and DeltaC'total are less consistent because of a large intersubject variability in DeltaC'deoxy; in some cases there is a positive DeltaC'deoxy. In the cases with no positive DeltaC'oxy in the contralateral hemisphere, there are cases of other possible changes for either or both hemispheres and no cases of no change in any hemoglobin species in either hemisphere. These results suggest that NIR topography is useful for observing brain activity in most cases, although intersubject signal variability still needs to be resolved.

A spatial and temporal comparison of hemodynamic signals measured using optical and functional magnetic resonance imaging during activation in the human primary visual cortex

“…In terms of the optical data, many of the characteristics of the hemodynamic changes in the visual cortex observed in this work are similar to those noted by Sato et al (2005) in their assessment of the inter-subject variability on NIR topography data obtained during sensorimotor activation in humans. These features include the high inter-subject variability of the amplitudes of changes, and changes opposite to "normal" in some subjects, i.e., decreases in [HbO 2 ] and increases in [HHb] during activation.…”

“…However, the majority of these works use near infrared spectroscopy (NIRS) to study the human brain with little spatial resolution beyond the location of the optical probe (Strangman et al, 2003;Toronov et al, 2003b). A relatively small number of papers have performed surface mapping of the functional cerebral hemodynamics, i.e., the locations of the hemodynamic or neuronal changes are projected onto the surface of the head, again with a significant loss of spatial information Sato et al, 2005;Schroeter et al, 2004;Seiyama et al, 2004).…”

Task complexity relates to activation of cortical motor areas during uni- and bimanual performance: A functional NIRS study

“…Individual subjects showed a variable activation pattern during finger-tapping which may be obscured during analysis at the group level. Inter-individuality has been described in previous fNIRS studies of inter-subject (Hiroki et al, 2005, Sato et al, 2005 and inter-session reliability (Plichta et al, 2006, Strangman et al, 2006, Plichta et al, 2007. Subjects in our study were measured only once.…”

Comparison of Cortical Activation During Real Walking and Mental Imagery of Walking - The Possibility of Quickening Walking Rehabilitation by Mental Imaginary of Walking

“…According to previous studies, oxy-Hb is more useful for analysis of cortical activation than deoxy-Hb because of its higher reproducibility (Plichta 2006;Sato 2005), lower inter-subject variability (Sato 2006), and higher correlation with fMRI signals. Therefore, in the present study, oxy-Hb was measured as an indicator of changes in blood volume.…”