## 4 Discussion  
This study identified and compared the activated brain areas and number of voxels in moderate- and high-stress groups using PSS scores under both stress-induced and recovery states. Several brain regions are activated during stress-inducing tasks, including the amygdala, prefrontal cortex, anterior cingulate cortex, insula, and hypothalamus [11]. The amygdala, found to activate during acute and chronic stress, is involved in processing emotional information such as fear and anxiety [11]; the prefrontal cortex, activated during stress-related tasks, is associated with higher-order cognitive processes such as attention, decision making, and self-regulation [11]; the anterior cingulate cortex, involved in emotional  
Figure 3: Comparison of activation voxels between the moderate- and high-stress groups during (**a**) stress-inducing conditions and (**b**) post-stress recovery state. regulation, has been implicated in pain and anxiety perception [11]; the insula, activated during stress-related tasks, is linked to interoception and the processing of visceral sensations [11]; and finally, the hypothalamus region, also activated during stress-related tasks, is found to be involved in the regulation of the stress response [11]. Research on the relationship between stress and brain activation has found that, as stress levels increase, there is often increased activation in regions of the brain associated with the stress response, such as the amygdala, hypothalamus, and prefrontal cortex. Studies using various stressors, including the MIST, have consistently shown increased activation of these brain regions in response to stress [10; 12]. Additionally, research has suggested that the strength of the relationship between stress and brain activation may depend on factors, such as sex, age, and history of stress exposure [13]. Overall, research suggests that changes in brain activation patterns are related to stress and may vary based on individual differences and the type of stressor experienced. In this study, the areas of the brain activated in both the moderate- and high-stress groups when stress was induced were the middle temporal gyrus, superior frontal gyrus, anterior cingulate, inferior frontal gyrus, middle frontal gyrus, and parahippocampal gyrus (PHG) in the left hemisphere and the superior temporal gyrus and middle temporal gyrus in the right hemisphere. When comparing the number of activation voxels, the moderate-stress group showed a greater number of activation voxels than the high-stress group in most areas of the brain, while the reverse was true for the PHG in the limbic lobe, that is, the activation voxel number was greater in the high-stress group compared to the moderate-stress group. Functionally, the PHG engages in memory encoding, retrieval, and spatial navigation. While the PHG may not be the primary region involved in the stress response, one study found increased activation in the PHG during the MIST task compared with a control task, suggesting that it may play a role in the cognitive processing required for this task [10]. In individuals under high stress (compared with those under moderate stress), it is possible that increased activation of the PHG during stress-inducing tasks reflects a heightened emotional response to stress. This could be due to several factors, such as greater levels of stress-related hormones, heightened anxiety or fear, or greater attentional demands on emotional stimuli [4; 14; 15]. Additionally, the PHG is part of a large neural network involved in emotional processing, including the amygdala, prefrontal cortex, and hippocampus [14; 16]. Increased activation of the PHG in individuals under high stress may reflect alterations in the connectivity or functional interactions between these regions, potentially resulting in a greater emotional response to stress. Characteristic activation of the left precuneus was observed only in the high-stress group.