Functional connectivity in the prefrontal cortex measured by near-infrared spectroscopy during ultrarapid object recognition

Abstract

Near-infrared spectroscopy (NIRS) is a developing technology for low-cost noninvasive functional brain imaging. With multichannel optical instruments, it becomes possible to measure not only local changes in hemoglobin concentrations but also temporal correlations of those changes in different brain regions which gives an optical analog of functional connectivity traditionally measured by fMRI. We recorded hemodynamic activity during the Go-NoGo task from 11 right-handed subjects with probes placed bilaterally over prefrontal areas. Subjects were detecting animals as targets in natural scenes pressing a mouse button. Data were low-pass filtered<1 Hz and cardiac∕respiration∕superficial layers artifacts were removed using Independent Component Analysis. Fisher's transformed correlations of poststimulus responses (30 s) were averaged over groups of channels unilaterally in each hemisphere (intrahemispheric connectivity) and the corresponding channels between hemispheres (interhemispheric connectivity). The hemodynamic response showed task-related activation (an increase∕decrease in oxygenated∕deoxygenated hemoglobin, respectively) greater in the right versus left hemisphere. Intra- and interhemispheric functional connectivity was also significantly stronger during the task compared to baseline. Functional connectivity between the inferior and the middle frontal regions was significantly stronger in the right hemisphere. Our results demonstrate that optical methods can be used to detect transient changes in functional connectivity during rapid cognitive processes.

Comparison of neural correlates of risk decision making between genders: An exploratory fNIRS study of the Balloon Analogue Risk Task (BART)

“…This approach is often referred to as full width at half maximum (FWHM) and has been often applied to such phenomena as the duration of pulse waveforms, the spectral width of sources used for optical communications, and the spatial resolution of optical images (Gallagher et al, 2007). Several previous publications also utilized and demonstrated such an approach when studying fNIRS-based brain images (Gallagher et al, 2007; http://en.wikipedia.org/wiki/Full_width_at_half_maximum; Medvedev et al, 2011;Wolf et al, 2011). Furthermore, in this study, we experienced negative HbO or HHb values, for which maximal absolute values were used to find FWHM and then to generate corresponding ROIs.…”

“…Indeed, the two approaches (i.e., GLM-based image formation and DOT) are complementary and can be utilized together. The only difference between them is whether image reconstruction is performed; several recent reports have demonstrated such combined approaches (Gallagher et al, 2007;Medvedev et al, 2011;Wolf et al, 2011).…”

“Seeing” electroencephalogram through the skull: imaging prefrontal cortex with fast optical signal

“…Our experimental approach has been described in detail elsewhere, 29 and here we provide a brief description of the methods.…”

“…The slow (hemodynamic) signal was downsampled at 20 Hz, analyzed separately, and presented elsewhere. 29 Here, we present only the fast signal along with the EEG data. The fast optical signal was downsampled at the same sampling rate used for EEG data acquisition (200 Hz).…”

Detecting Bilateral Functional Connectivity in the Prefrontal Cortex During a Stroop Task by Near-Infrared Spectroscopy

“…[9][10][11][12][13] With the developments of multichannel highly sensitive NIRS instruments, it has also become possible to measure temporal correlations of local activity at di®erent brain areas, deriving an optical \functional connectivity". 14 In recent years, there have been some studies that investigated and preliminarily validated the feasibility of NIRS in studying functional connectivity. [15][16][17] However, most of these studies are about resting state functional connectivity (RSFC), which re°ects interactions of spontaneous neuronal activity among di®erent brain regions at the resting state.…”