Changes in Prefrontal fNIRS Activation and Heart Rate Variability During Self-Compassionate Thinking Related to Stressful Memories

The aim of this study was to investigate the effects of self-compassionate thinking (SCT) related to stressful autobiographical memories (SAM) on the prefrontal cortex (PFC) activity and heart rate variability (HRV) parameters in healthy subjects. A naturalistic paradigm was built with two conditions, SAM followed by SCT. We used functional near-infrared spectroscopy (fNIRS) to measure oxy and deoxyhemoglobin concentration changes in 33 healthy adults (men = 10) with a mean age of 33.24 years (SD = 6.85). Two HRV parameters were also measured during both conditions: the standard deviations of the normal-to-normal (SDNN-HRV) and the high-frequency component of heart rate variability (HF-HRV). During the SAM condition, the left dorsolateral PFC (DLPFC) and the frontopolar area showed a significantly increased oxyhemoglobin concentration compared with the control condition (corrected-p < 0.01). During the SCT condition, the frontopolar area showed a significantly increased oxyhemoglobin compared with the control condition (corrected-p < 0.001). A significant increase in time-domain SDNN-HRV (p = 0.002) during SCT compared with the SAM condition was also observed. An association between the frontopolar area fNIRS signal and the HF-HRV during SAM condition was found (corrected-p < 0.05). Our findings suggested that the SAM condition is associated with activity in the left DLPFC and in the frontopolar area, while the SCF is associated with activity in the frontopolar area. The SCT was related to an increase in SDNN-HRV when compared with the SAM condition, and an association between HF-HRV and PFC activity was seen. Our results also suggested that self-compassionate thinking can be an effective emotional regulation strategy. Clinical Trials NCT03737084.