文献表明应激可激活下丘脑一垂体一肾上腺皮质(hypothalamic- pituitary-adrenal, HPA)轴和交感神经系统( sympathetic nervous system, SNS )，导致外周糖皮质激素( glucocorticoid)和儿茶酚胺(catecholamine)递质水平升高。应激可对一记忆功能产生影响，但是应激反应中HPA轴和SNS的激活与记忆不同阶段的关系尚无系统研究。为进一步探讨HPA轴和SNS在应激影响一记忆功能中的作用模式，采用相关研究方法，研究应激对一记忆不同阶段的影响及其与HPA轴和SNS反应的关系。研究包括以下两个部分:
Previous studies demonstrated that stress activated both the hypothalamic-pituitary-adrenal (I:PA) axis and the sympathetic nervous system (SNS),increased the levels of peripheral glucocorticoid and catecholamine. Glucocorticoid and catecholamine secreted during stressful events may affect memory function. To further clarify the roles of HPA axis and SNS in stress-induced changes of memory performance, the present study investigated the effects of passive emotional stress on different memory phases and the relationship with neuroendocrine function.Experiments were divided into two parts.
In the first part, HPA axis (indexed by salivary cortisol level)and SNS (indexed by blood pressure level and heart rate) reactions to negative affective picture stimuli were examined in healthy female college students. Then the effects of negative emotional stress on memory and attention performances and the relationship with HPA axis and SNS responses were investigated. Results are as follows:
1 Negative affective picture stimuli induced negative emotional responses and increased peripheral blood pressure level and salivary cortisol level, suggesting both SNS and HPA functions were activated. These results demonstrate that the negative affective picture stimuli can be used in laboratory as a negative emotional stress model.
2 Negative emotional stimuli increased the recall performance for learn-recall test, in which blood pressure reaction was associated with increased memory performance, suggesting that high SNS activation may facilitate memory performance.Cortisol reaction was associated with decreased memory performance, suggesting stress-induced HPA axis response may impair memory performance.
3 Negative emotional stimuli increased the attention performance, in which blood pressure reaction was associated with increased attention performance,suggesting that high SNS activation may facilitate attention performance. Cortisol reaction was associated with decreased attention performance, suggesting that stress-induced IIPA axis response may impair attention performance.
In the second part, experiments were performed to investigate the effects of negative emotional stimuli on memory encoding, consolidation and retrieval process and the relationships with HPA axis and SNS responses. Results are as follows:
1 .Negative emotional stimuli presented before encoding process increased the memory performance, in which blood pressure reaction was associated with the increased performance, suggesting that high SNS activation may facilitate memory encoding process. HPA axis response seemed not to be associated with memory encoding process.
2. Negative emotional stimuli presented during consolidation process had complex effects on the memory performance. Cortisol reaction was associated with increased memory performance. But high blood pressure reactions were associated with poor memory performances.
3. Negative emotional stimuli presented before retrieval process had no significant effect on memory performance. However, cortisol reaction was associated with decreased memory performance.
In summary, negative affective picture stimuli induced negative emotional responses and activated both SNS and HPA functions. Reactions of HPA axis and SNS induced by negative affective picture stimuli play different roles in the effects of passive emotional stress on memory performance. The high level of SNS activation may increase memory performance of encoding, decrease memory performance of consolidation. Responses of HPA axis induced by negative emotional stimuli may impair memory retrieval process and enhance memory consolidation process.