|| There is increasing interest in the intrinsic activity of the resting brain, especially the activity slower than 0.1Hz (i.e., low-frequency oscillations, or LFOs). To investigate the origin of LFOs observed in functional near-infrared spectroscopy (fNIRS), we recorded multichannel fNIRS and electroencephalography (EEG) from the frontal cortex of 11 healthy young volunteers in the resting state. Electrocardiography (ECG), electro-oculography and respiration were also measured. Synchronous oscillations of oxy-hemoglobin (oxy-Hb) around 1.0Hz were detected in all fNIRS channels, and their frequency was consistent with a peak frequency of ECG, suggesting the changes of cerebral blood flow due to heart beats. In addition, oxy-Hb oscillations around 0.1Hz (i.e., LFOs) appeared in the fNIRS. The channels where LFOs appeared differed among the subjects, and the LFOs appeared or disappeared even in the same fNIRS channels. The appearance of LFOs in fNIRS channels was significantly higher when the LFOs appeared on the EEG in the adjacent EEG electrodes compared to when LFOs did not appear on EEG. The amplitude and coherence (synchronicity) of the LFOs were increased by changing the subjects' position from dorsal to the sitting position in both fNIRS and EEG, and the coherence in particular was increased in the homologous fNIRS channels on the bilateral hemispheres. These results suggest that LFOs of oxy-Hb couple with resting-state EEG activity.
|| 1) Mesquita RC, Franceschini MA, Boas DA : Resting state functional connectivity of the whole head with near-infrared spectroscopy. Biomed Opt Express (2010) 1, 324-336.
2) Obrig H, Neufang M, Wenzel R, Kohl M, Steinbrink J, Einhaupl K, Villringer A : Spontaneous low frequency oscillations of cerebral hemodynamics and metabolism in human adults. Neuroimage (2000) 12, 623-639.
3) Tachtsidis I, Elwell CE, Leung TS, Lee CW, Smith M, Delpy DT : Investigation of cerebral haemodynamics by near-infrared spectroscopy in young healthy volunteers reveals posture-dependent spontaneous oscillations. Physiol Meas (2004) 25, 437-445.
4) Monto S, Palva S, Voipio J, Palva JM : Very slow EEG fluctuations predict the dynamics of stimulus detection and oscillation amplitudes in humans. J Neurosci (2008) 28, 8268-8272.
5) Deco G, Jirsa VK, McIntosh AR : Emerging concepts for the dynamical organization of resting-state activity in the brain. Nat Rev Neurosci (2011) 12, 43-56.
6) Fox MD, Raichle ME : Spontaneous fluctuations in brain activity observed with functional magnetic resonance imaging. Nat Rev Neurosci (2007) 8, 700-711.
7) He BJ, Snyder AZ, Zempel JM, Smyth MD, Raichle ME : Electrophysiological correlates of the brain's intrinsic large-scale functional architecture. Proc Natl Acad Sci U S A (2008) 105, 16039-16044.
8) Pfurtscheller G, Bauernfeind G, Neuper C, Lopes da Silva FH : Does conscious intention to perform a motor act depend on slow prefrontal (de)oxyhemoglobin oscillations in the resting brain? Neurosci Lett (2012) 508, 89-94.
9) Rowley AB, Payne SJ, Tachtsidis I, Ebden MJ, Whiteley JP, Gavaghan DJ, Tarassenko L, Smith M, Elwell CE, Delpy DT : Synchronization between arterial blood pressure and cerebral oxyhaemoglobin concentration investigated by wavelet cross-correlation. Physiol Meas (2007) 28, 161-173.
10) Scheeringa R, Fries P, Petersson KM, Oostenveld R, Grothe I, Norris DG, Hagoort P, Bastiaansen MCM : Neuronal dynamics underlying high- and low-frequency EEG oscillations contribute independently to the human BOLD signal. Neuron (2011) 69, 572-583.
11) Tong Y, Frederick BD : Time lag dependent multimodal processing of concurrent fMRI and near-infrared spectroscopy (NIRS) data suggests a global circulatory origin for low-frequency oscillation signals in human brain. Neuroimage (2010) 53, 553-564.
12) Pfurtscheller G, Daly I, Bauernfeind G, Muller-Putz GR : Coupling between intrinsic prefrontal HbO2 and central EEG beta power oscillations in the resting brain. PLoS One (2012) 7, e43640.
13) Lewis DA, Fish KN, Arion D, Gonzalez-Burgos G : Perisomatic inhibition and cortical circuit dysfunction in schizophrenia. Curr Opin Neurobiol (2011) 21, 866-872.
14) cohere (signal processing toolbox) : ftp://184.108.40.206/MATLAB/jhelp/toolbox/signal/cohere.html（2013年12月閲覧）
15) Wavelet toolbox- MathWorks : www.mathworks.com/tagteam/58032_TT031_Wavelet_Tlbx_Manual.pdf（2013年12月閲覧）
16) Kubo M, Shoshi C, Kitawaki T, Takemoto R, Kinugasa K, Yoshida H, Honda C, Okamoto M : Increase in prefrontal cortex blood flow during the computer version trail making test. Neuropsychobiology (2008) 58, 200-210.
17) Fernandez-Espejo D, Owen AM : Detecting awareness after severe brain injury. Nat Rev Neurosci (2013) 14, 801-809.