IB Psychology - Meaney et al. (1988)

Aims

To find out what the effect of glucocorticoids is

on memory

Methods

One set of rats were taken away from their

mother and did not experience the normal

grooming that baby rats experienced. These rats

were labeled the "non-handled" rats. The second

set of rats were not taken away from their

mothers. These rats served as a control group

Results

Rats that were not handled secreted more glucocorticoids in response to stress than did handled

rats. At later ages, non-handled rats also showed elevated basal glucocorticoid levels, with the

result that there was a greater cumulative exposure to glucocorticoids in non-handled rats.

Increased exposure to adrenal glucocorticoids can accelerate hippocampal neuron loss and

cognitive impairments in ageing. To test the effect, aged rats were put into a pool of milky water.

In the pool was a platform. Meaney and his team tracked the route of the rats as they sought

out the platform based on the rats' memories of previous attempts to escape the water

Hippocampal cell loss and pronounced spatial memory deficits emerged with age in the non-handled

rats, but were almost absent in the handled rats

Conclusions

- There are several studies that show a link between glucocorticoid levels and the onset of Alzheimer's.

- There are acetylcholine receptor sites in the hippocampus. Loss of hippocampal cells also correlates with lower levels of acetylcholine. This may play a key role in the development of dementia.

- It appears that a rat mother's grooming helps to activate genes which are responsible for the reaction to the stress response. This is an example of epigenetics - the grooming process "turns on" the genes which help the young rat cope with stress - which then leads to a longer and healthier life.

- However, further research has shown that epigenetics is the reason why the hippocampal cell loss happens.

- Since the original study in 1988, Meaney has shown the complex interaction between the hippocampus, glucocorticoids and our genes in the development of dementia

Strengths

- Showed a cause-effect relationship between stress and the effect on memory.

Weaknesses

- Rats were harmed

- Can't fully be generalised to humans

- Even though the cause and effect was established, it did not explain the exact process of what was happening