正念维持适应的机制:来自心率变异性自相似的初步证据

Physiological mechanisms of mindfulness:Preliminary evidence from self-similarity of heart rate variability

引入自相似的算法表征功能内稳态的过程,从功能内稳态的角度探讨特质正念与不同过程中心率变异性(Heart rate variability, HRV)自相似的关系,以揭示正念起作用的可能机制。功能内稳态是机体面对内外环境的变化保持自身功能相对稳定的一种能力或素质。研究设置静息态、冷加压任务、冷加压后恢复和正念练习4种不同的条件,并记录被试在这4个环节的HRV指标。结果显示, HRV自相似与特质正念之间存在显著相关,高HRV自相似组在冷加压环节的HRV各指标都比低HRV自相似组高。结果表明,正念维持适应的生理机制可能与功能内稳态有关。

Mindfulness has a considerable contribution to one’s physical and psychological health and his/her ability to adapt to an endlessly changing environment. Researchers have proposed different perspectives in studying the mechanism of mindfulness. However, few of the previous theoretical frameworks are based on the ongoing changes in a dynamic process. In this study, we investigate the relationship between trait mindfulness and the functions of the autonomic nervous system from a “self-similarity” perspective, which represents function- specific homeostasis. The concept of self-similarity refers to the ability of the human body to remain stable when experiencing changes from the internal and external environmental factors In the current study, four conditions （5 min resting, 3 min stressful, 5 min post-stress states, and 5.4 min mindfulness practice） were established to induce different physical and psychological status and to examine the self-similarity levels of the participants. The cold-pressor task, a safe and effective paradigm to induce pain in laboratory settings, was used in this study, which involved 56 undergraduate students. Heart rate variability （HRV） with its time- and frequency-domain measures （SDNN, RMSSD, TP, LF, and HF）, which represent the functions of the autonomic nervous system, were employed to calculate self-similarity. A biofeedback system （emWave Pro Plus） with an ear sensor was used to record the HRV measures consecutively during the four phases.The three main results of the study are as follows. First, one-way repeated analyses of the variance test on HRV measures （SDNN, RMSSD, TP, LF, and HF） yielded significant effects for the conditions. The post hoc test indicated that the HRV under stressful condition was higher than those under conditions of resting state, post-stress state, and mindfulness practice. Hence, the whole function and balance of the autonomic nervous system, HRV measure, and coherence were significantly higher in mindfulness practice than in the resting, stressful, and post-stress states. Second, correlation analysis revealed that the self-similarity level of HRV significantly correlated with trait mindfulness measured by the Mindful Attention Awareness Scale （MAAS）. Third, the 56 participants were divided into two groups according to mean self-similarity level. Measures of HRV （SDNN, RMSSD, TP, LF, and HF） of the high self-similarity group （n = 25） were significantly higher than those of the low self-similarity group （n = 31） only under stressful conditions. However, this was not the case under the other three conditions. The above results indicated that HRV changes according to the changing conditions; moreover, high trait mindfulness and self-similarity can protect organisms from poor adaptation, especially when they encounter stressful conditions. The correlation between mindfulness and self-similarity of HRV measures implies that self-similarity may play a core role in how mindfulness works. The current study is a pilot study conducted with only college students, thus limiting the generalization of our conclusion. Moreover, the participants in our study had no previous experience of mindfulness practice, as their mindfulness level was represented with the MAAS measurement. In the future, we seek to recruit people with mindfulness or meditation practice experiences to explore whether meditation experts would better keep their function-specific homeostasis in different processes than meditation novices would.