Brain Cortical Mapping by Simultaneous Recording of Functional Near Infrared Spectroscopy and Electroencephalograms from the Whole Brain During Right Median Nerve Stimulation

Abstract

To investigate relationships between hemodynamic responses and neural activities in the somatosensory cortices, hemodynamic responses by near infrared spectroscopy (NIRS) and electroencephalograms (EEGs) were recorded simultaneously while subjects received electrical stimulation in the right median nerve. The statistical significance of the hemodynamic responses was evaluated by a general linear model (GLM) with the boxcar design matrix convoluted with Gaussian function. The resulting NIRS and EEGs data were stereotaxically superimposed on the reconstructed brain of each subject. The NIRS data indicated that changes in oxy-hemoglobin concentration increased at the contralateral primary somatosensory (SI) area; responses then spread to the more posterior and ipsilateral somatosensory areas. The EEG data indicated that positive somatosensory evoked potentials peaking at 22 ms latency (P22) were recorded from the contralateral SI area. Comparison of these two sets of data indicated that the distance between the dipoles of P22 and NIRS channels with maximum hemodynamic responses was less than 10 mm, and that the two topographical maps of hemodynamic responses and current source density of P22 were significantly correlated. Furthermore, when onset of the boxcar function was delayed 5-15 s (onset delay), hemodynamic responses in the bilateral parietal association cortices posterior to the SI were more strongly correlated to electrical stimulation. This suggests that GLM analysis with onset delay could reveal the temporal ordering of neural activation in the hierarchical somatosensory pathway, consistent with the neurophysiological data. The present results suggest that simultaneous NIRS and EEG recording is useful for correlating hemodynamic responses to neural activity.

Optimizing the general linear model for functional near-infrared spectroscopy: an adaptive hemodynamic response function approach

“…Similarly, in a simultaneous measurement using fNIRS and EEG, onset and peak delays for Gaussian functions have been adopted for oxy-Hb signal, while deoxy-Hb signal remains to be analyzed. 18 Given this, there is still the need to explore model functions suitable for examining the temporal behaviors of oxy-and deoxy-Hb signals.…”

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“…1,2 Recently, several researchers [3][4][5] have assessed whether NIRS can detect the actual cortical hemodynamic changes associated with neural activation in response to tasks by using NIRS in combination with other methods, such as magnetoencephalography (MEG), transcranial magnetic stimulation (TMS), and electroencephalograms (EEG). Although the results of these studies showed good concordance between NIRS data and those of other modalities, most did not show either short-time or intrinsic (without stimulation) neurohemodynamic processes.…”

Optimal optode montage on electroencephalography/functional near-infrared spectroscopy caps dedicated to study epileptic discharges

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