Biomarker of Lateralization Index for Stress Calculated from Hemodynamic Responses of fNIRS for Subdividing between Eustress and Distress

While performing various mental stress tasks, we can easily observe differences in brain activations between the stress group and the control group (i.e., non-stress group). Moreover,it is essential to subdivide the stress groups into eustress and distress groups in order to enhance personal cognitive abilities and mental/physical health. However, it is very challenging to subdivide stress group, because of the difficulty to reveal differences in brain activations between two stress groups. In our study, we aim to ascertain the necessity of subdividing two stress groups screened by salivary alpha-amylase (sAA). Furthermore, we develop a potential biomarker to subdivide two stress groups using hemodynamic responses of functional near-infrared spectroscopy (fNIRS). We stimulate two stress groups divided by sAA with an international affective picture system (IAPS) inducing positive or negative emotions and measure hemodynamic responses at the same time. As a result, we have developed a newly designed biomarker, lateralization index for stress (LIS) calculated from hemodynamic responses, resulting in separating the two stress groups. The two stress groups show distinct LIS values in the visually dominant positive session. Therefore, using fNIRS, we, for the first time to the best of our knowledge, figure out that the differences in brain activations among three groups (control vs. eustress vs. distress groups) are distinguishable.

在开展各类心理应激任务时，我们可清晰观测到应激组与对照组（即非应激组）之间的脑激活差异。此外，为改善个体认知能力与身心健康，将应激组进一步划分为良性应激（eustress）组与不良应激（distress）组至关重要。然而，由于难以区分两类应激组之间的脑激活差异，对应激组进行细分颇具挑战。本研究旨在明确通过唾液α-淀粉酶（salivary alpha-amylase, sAA）筛选得到的两类应激组进行细分的必要性。此外，本研究借助功能性近红外光谱（functional near-infrared spectroscopy, fNIRS）的血流动力学响应，开发出一种可用于区分两类应激组的潜在生物标志物。本研究采用国际情感图片系统（international affective picture system, IAPS）诱发被试产生正性或负性情绪，对经sAA划分的两类应激组进行刺激，并同步采集其血流动力学响应数据。最终，本研究基于血流动力学响应开发出一种全新设计的生物标志物——应激偏侧化指数（lateralization index for stress, LIS），可有效区分两类应激组。在视觉主导的正性情绪刺激阶段，两类应激组的LIS值存在显著差异。据此，据我们所知，本研究首次借助fNIRS证实，对照组、良性应激组与不良应激组三者之间的脑激活差异可被有效区分。