Douglas Mental Health University Institute, McGill University, Montreal, Quebec, Canada.
Hippocampus. 2010 Feb;20(2):323-34. doi: 10.1002/hipo.20623.
Increased activation of the hypothalamus pituitary adrenal (HPA) axis, marked by increased secretion of cortisol, is a biological marker of psychological stress. It is well established that the hippocampus plays an important role in the regulation of HPA axis activity. The relationship between cortisol (stress-related elevation or exogenous administration) and the hippocampal-related cognitive function is often examined. However, few human studies to date have examined the effect of stress on hippocampal activity and the interactions between stress-induced activation of the HPA axis and hippocampal function during different phases of cognitive function. On the basis of our previous work, we hypothesized that group differences in stress-sensitivity relate to differences in hippocampal-related stress-integration. To test this hypothesis, we conducted a functional MRI study using tasks known to involve the hippocampal formation: novel-picture encoding, psychological stress, and paired-picture recognition. On the basis of their cortisol responses to stress, we divided subjects into stress-responders (increase in cortisol, n = 9) and nonresponders (decrease in cortisol, n = 10). Responders showed higher hippocampal deactivation during the stress task and lower recognition scores due to a larger number of misses. Intriguingly, stress-responders showed significant differences in hippocampal activation already prior to stress, with higher levels of hippocampal activity during the picture encoding. Although effects of both cortisol and hippocampal activation on recognition were present in responders, similar effects were absent in the nonresponder group. Our results indicate that hippocampus plays an important role in adaptive behavioral responses. We hypothesize that states of hippocampal activation prior to stress might reflect states of vigilance or anxiety, which might be important for determining interindividual differences in subsequent stress response and cognitive performance.
下丘脑-垂体-肾上腺 (HPA) 轴的过度激活，表现为皮质醇分泌增加，是心理应激的生物学标志物。众所周知，海马在调节 HPA 轴活性方面起着重要作用。皮质醇（与应激相关的升高或外源性给药）与海马相关认知功能之间的关系经常被研究。然而，迄今为止，很少有人类研究检查应激对海马活动的影响以及 HPA 轴应激激活与认知功能不同阶段之间的海马功能之间的相互作用。基于我们之前的工作，我们假设应激敏感性的组间差异与海马相关应激整合的差异有关。为了验证这一假设，我们使用已知涉及海马结构的任务进行了功能磁共振成像研究：新图片编码、心理应激和成对图片识别。根据他们对应激的皮质醇反应，我们将受试者分为应激反应者（皮质醇增加，n = 9）和非反应者（皮质醇减少，n = 10）。反应者在应激任务中表现出更高的海马去激活，并且由于更多的失误导致识别分数降低。有趣的是，应激反应者在应激之前已经表现出明显的海马激活差异，在图片编码期间海马活动水平更高。尽管皮质醇和海马激活对识别的影响都存在于反应者中，但在非反应者组中不存在类似的影响。我们的结果表明海马在适应性行为反应中起着重要作用。我们假设应激前的海马激活状态可能反映出警觉或焦虑状态，这对于确定随后的应激反应和认知表现的个体间差异可能很重要。
