Regular papers

Detection of inter-hemispheric functional connectivity in motor cortex with coherence analysis

¹ Department of Radiology and Experimental Imaging Centre, University of Calgary, Calgary, AB, Canada
² Seaman Family MR Research Centre, Calgary, AB, Canada
³ Department of Electrical & Computer Engineering, University of Calgary, Calgary, AB, Canada
⁴ Department of Radiology and Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
⁵ Department of Radiology; Experimental Imaging Centre, and Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada

^* dunnj@ucalgary.ca

Received: 29 June 2012
Revised: 25 September 2012

Abstract

Functional near-infrared spectroscopy (fNIRS) is showing promise as an alternate method to fMRI for studying cortical function. Resting state studies in both methods are showing functional linkages. The strength of functional connections is typically quantified by the level of significance of the temporal synchrony between brain regions, termed resting-state functional connectivity. Coherence analysis of resting state allows for phase insensitive and frequency specific analysis. This paper provides a detailed method for undertaking fNIRS in combination with resting-state coherence analysis. We show that maps of inter-hemispheric resting-state functional connectivity between the motor cortices can be reliably generated, and the frequency responses (to 50 Hz) for both oxy- and deoxyhemoglobin. Frequencies of 0-0.1 Hz provide robust data as have been shown previously. Higher frequencies (up to 5 Hz) also exhibit high coherence. Deoxyhemoglobin also shows high coherence above 10Hz. Coherence is similar during both resting and task activated states. fNIRS allows for mapping cortical function and, in combination with coherence analysis, allows one to study variations in frequency response.