Heart–Brain Temporal Coupling as a Candidate Biomarker of Self-Congruency

Figures

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  Figure 1. Schematic illustration of the methods used in this study. fMRI, functional magnetic resonance imaging; HRV, heart rate variability; IBI, inter-beat interval; BOLD, blood-oxygen-level-dependent; CCA, cross-covariance analysis. (A) Self-congruency assessment. Participants estimated their self-congruency using a graphic rating scale. Two cardboards representing their emotional experience and enacted behavior were overlapped, and the degree of overlap was quantified using a proportional metric (see Supplementary Figure S1). (B) Neural dynamics data. Resting-state fMRI was acquired with a repetition time (TR) of 500 ms, corresponding to a sampling frequency of 2 Hz and yielding 720 time points over 6 min. T1-weighted structural images were parcellated into 506 regions of interest based on the Lausanne 2018 symmetric atlas [29]. For each region, the mean BOLD fMRI signal was extracted across 720 time points. (C) Heart rate variability data. Photoplethysmography (PPG) was recorded at 200 Hz throughout the fMRI acquisition. Peak detection and interpolation yielded an IBI time series, from which HRV measures were derived. For analyses requiring temporal alignment with the BOLD signal, the…

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  Figure 2. Associations between self-congruency, HRV metrics, and neural metastability. Self-congruency scores showed a significant positive correlation with low-frequency (LF) HRV measures (top left panel) and a trend-level association with RMSSD (root mean square of successive differences; bottom left panel). No significant associations were observed between self-congruency and high-frequency (HF) HRV measures (top right panel) or neural metastability values (bottom right panel). LF, low frequency; RMSSD, root mean square of successive differences; HF, high frequency.

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  Figure 3. Neural-cardiac relations and their association with self-congruency. Abbreviations: HRV, heart rate variability; IBI, inter-beat interval; BOLD, blood-oxygen-level-dependent signal; FDR, false rate discovery. (A) Neural dynamics variability in relation to HRV. Brain regions in which inter-beat interval (IBI) fluctuations significantly covaried with BOLD activity when the BOLD signal was shifted 1 s prior to the IBI signal are shown for cortical (top) and subcortical (bottom) structures. Subcortical regions are displayed in detail in the lower panel. The color scale represents p-values, and regions surviving a threshold of p < 0.001 (FDR-corrected) are shown. (B) Heart–brain covariance associated with self-congruency. Brain regions in which IBI–neural activity covariance positively correlated with self-congruency scores are displayed. Covariance values correspond to the condition in which the IBI signal was shifted 2.5 s before the BOLD signal. The color scale represents p-values, with regions significant at p < 0.001 (uncorrected).