2.3 Effects on the hippocampus and prefrontal cortex
As you will have seen from Activity 6, the constant barrage of glucocorticoids during chronic stress is deleterious for glucocorticoid receptors, which play a critical role in controlling the stress response. Uncontrolled, high levels of glucocorticoids are also thought to weaken neurons in the hippocampus and the prefrontal cortex, making them more susceptible to damage or death.
Based on what you learned about these brain structures in Activity 6, what would be the psychological effect of:
- a.hippocampal damage?
- b.prefrontal cortex damage, of the kind caused by HPA hyperactivity?
- a.It might affect our ability to retrieve conscious memories of facts or events or the ability to form new ones.
- b.It would become more difficult to make judgements and decisions; to concentrate on a task in hand, and to exert conscious control over behaviour, thoughts or impulses.
There is evidence from brain imaging data that the volume of the hippocampus, and of areas in the prefrontal cortex, is lower in people with depression (Campbell et al., 2004; Drevets et al., 1997). There is also evidence that activity in the prefrontal cortex is reduced in areas that are thought to be implicated in the control of emotions (Drevets, 1998). Via its effects on the hippocampus and the prefrontal cortex, stress may thus cause some of the symptoms of depression, such as difficulties in learning, remembering and concentrating, and the inability to control negative thoughts and emotions (see Lewis Wolpert’s account (Vignette 1) and diagnostic criterion 8 in DSM-IV-TR, described in the related OpenLearn course).
Depression and anxiety often comorbid, so it is not surprising that anxiety too has links to stress – as considered in the next section.