Simultaneous Optical Tomography (OT) and fMRI with and without Task Activation

Correlation analysis of low-frequency fluctuations in blood-oxygen level dependent (BOLD) fMRI data is known to yield functional connectivity maps. The procedure, also referred to as ‘resting-state connectivity’, does not rely on a specific task performance and has recently been successfully applied to optical tomography (OT) data [1]. One of the limitations of OT is the low spatial resolution. To overcome this limitation, dense probe arrays had been used in the above pioneering study. However, full head coverage is desirable in order to avoid that analysis is constrained to specific networks. Here, we assess whether a sparser topographical sampling still yields results that are comparable to the ‘gold standard’ of resting-state network assessment, i.e. fMRI. In a first step, we used a subset of optical fibers in a typical grid (2-3cm inter-optode distance) covering both motor cortices. Such a grid can be extended to whole head coverage, without overly interfering with the subject’s comfort. We combined OT with concurrent fMRI measurements to cross-validate our resting-state data analysis.