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

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.

Functional Near-Infrared Spectroscopy Reveals Reduced Interhemispheric Cortical Communication after Pediatric Concussion

“…Positioning was based on the standard 10–20 electroencephalogram (EEG) protocol at 40% of the measured distance from nasion to inion. 24 , 44 , 45 Each pad was held in place by a velcro strap placed in the coronal orientation and tightened for comfort. Pads were then connected to one another, and hair was moved out of the way for optimal contact of the optodes with the scalp.…”

“…The calculation of coherence for fNIRS data has been described previously by our group. 24 The source-detector pair exhibiting the greatest change in total Hb and oxy-Hb during the tapping task was chosen as the reference, whose signal during the 300-sec rest period was compared with all other source-detector pairs by coherence analysis. Tomographical maps of coherence within the frequency range of 0.04–0.10 Hz were then computed using software written in MATLAB (The MathWorks).…”

“… 29 , 30 We and others have shown that fNIRS can also be used to measure functional connectivity during the resting state and during tasks. 24 , 31 …”

Reduced Functional Connectivity in Adults with Persistent Post-Concussion Symptoms: A Functional Near-Infrared Spectroscopy Study

“… 16 This method is used to study resting-state networks in functional MRI (fMRI) by monitoring signal oscillations that are caused by changes in deoxyhemoglobin. 17 , 18 Our group, 16 , 19 , 20 and others, 21 have used fNIRS to study hemodynamic oscillations using coherence analysis, which determines the degree of frequency-coupling between two signals, as a marker of regional communication…”

Effects of Working Memory Load on Frontal Connectivity in Children with Autism Spectrum Disorder: an fNIRS study

“…Over the last decade, fNIRS has been used to assess the functional coupling of brain regions, especially the PFC, during performance of a wide variety of tasks. For example, fNIRS has been used to measure functional connectivity between two cortical areas that underlie motor performance (Varshney, Liapounova, Golestani, Goodyear, & Dunn, 2012). It has also been used to measure intrahemispheric and/or interhemispheric connectivity within the dorsolateral PFC and frontal pole during the n-back task in healthy young adults (Fishburn, Norr, Medvedev, & Vaidya, 2014;Sun et al, 2019).…”