Fig. 2: Multiparametric functional connectivity and group-level correlations (n = 10) between the simultaneously acquired blood oxygen level-dependent (BOLD), oxygenated (HbO), deoxygenated (HbR), and total (HbT) hemoglobin components.
a Group seed-maps derived from BOLD, HbO, HbR, and HbT for seven functional regions positioned in the left hemisphere overlaid onto the structural optoacoustic image that emphasizes major vascular structures. Strong intra- and inter-hemispheric correlations were evident, revealing spatial overlap and distinct anti-correlations. White circles represent the seed regions. S1-t, primary somatosensory area, trunk; S1-ll, primary somatosensory area, lower limb; M1, primary motor cortex; M2, secondary motor cortex; Vis, primary visual area; Ptl, parietal area; Rs, Retrosplenial area. b Distribution of correlation coefficients within the brain for three representative seeds across the various hemodynamic components. c–e Voxel-wise relationship of functional connectivity (FC) (r > 0.1) derived from group seed maps of three representative seeds. The inter-modal correlation differed across the functional regions and hemoglobin components. The highest correlation to BOLD was observed for HbT in S1-t, M1, and Vis seeds, followed by HbO and HbR. f Distribution of linear correlation coefficients (r) between voxel-wise BOLD and HbO/HbR/HbT for the whole range of FC. The distinct colors represent the quartiles of each distribution. g Cross-correlation (CC) analysis of positive connections (n = 128) between BOLD seed maps and HbO, HbR, HbT, indicating higher correlations with HbT (p = 3.298 × 10−4) and HbO (p = 1.115 × 10−5) as compared to HbR. (h) Evaluation of negative connections (n = 128) highlighting stronger correlations between BOLD seed maps and HbT (p = 1.323 × 10−21), HbO (p = 8.129 × 10−17), as compared to HbR, with HbT exhibiting superior correlation compared to HbO (p = 8.384 × 10−8) in negative connections. The central line within the box represents the mean, while the lower and upper box edges denote the 25th and 75th percentiles, respectively. The whiskers extend to the furthest data points within the non-outlier range. (*) p < 0.05, (**) p < 0.01, (***) p < 0.001, paired t test (two-sided).
