Animal Models - Cortisol - ERQ

Discuss the value of animal models to understand human behaviour in relation to hormones.

Cortisol

• Steroid hormone secreted by adrenal glands

• Helps control blood sugar levels, regulate metabolism and reduce inflammation

• Assists with immune system functioning

Cortisol in relation to memory

Assists with memory formation

• High levels = poor retrieval of memory

• Slightly elevated cortisol = improved learning and processing of information.

HL ERQ Structure

• Intro - rephrase the Q, state definition of terms, state the problem, two animal studies

• body 1 - Study 1 - A,M,R,C,L

• Body 2 - Study 2 - A,M,R,C,L

• Body 3 - Critical thinking of Animal Models

• Body 4 - Conclusion

Meaney

Animal study that used rats to find out what the effect of glucocorticoids (stress hormones) is on memory

Aim of Meaney

The aim of the study was to investigate the effect of glucocorticoids (stress hormones) on memory in rats

Method of Meaney

• independent samples design

• two condition; handled rats and non-handled rats

• handled rats were seperated from their mothers, lacking normal grooming

• non-handled rats stayed with their mothers so they served as the control group

• once the rats were older, they were placed in milky water with a hidden platform and their paths to find the platform were tracked to measure their spatial memory and hippocampi function

Results of Meaney

the results of this study were that rats that were handled secreted higher levels of glucocorticoids (stress hormone) in response to stress, while the non-handled group showed lower levels of glucocorticoids(stress hormone) which caused minimal hippocampi cell loss and fewer memory deficits.

Conclusion of Meaney

In conclusion, whether the rats were seperated from their mothers or not affected their memory performance because the rats that were seperated secreted higher levels of glucocorticoids (stress hormone) which caused increased hippocampi neuron loss which would cause a loss in memory performance while the rats that were not seperated didn’t show any significant changes in glucocorticoid (stress hormone) level.

Link back for Meaney

Thus, the study shows the relation between cortisol and memory because the rats with more cortisol (glucocorticoids) showed an inhibition in finding the hidden platform which measured spatial memory while the rats with no additional cortisol showed no change.

aim of Sapolsky

The aim of this study was to investigate the effects of prolonged exposure to increased cortisol levels on the structure of neurons in the hippocampus.

method of Sapolsky

• The study used monkeys

• small capsules with cortisol (experimental condition) or cholesterol (control condition) were inserted into the brains of the monkeys

• this allowed the researchers to isolate the effects of cortisol on the brain, specifically the hippocampi neurons

results of Sapolsky

The results showed that cortisol damaged the neurons in the hippocampus of the monkeys because the monkeys with the cortisol capsules showed significant lesions in the hippocampus compared to the monkeys with cholesterol

conclusion of Sapolsky

In conclusion, cortisol might affect memory because the hippocampus of the monkeys with the cortisol capsules showed lesions meaning cortisol might negatively affects the brain’s ability to retrieve and formulate memory.

link back of Sapolsky

therefore, the Sapolsky study has value in that researchers learned that cortisol impacts neurons in the hippocampus, which may affect memory and this might also apply to humans. It follows then that humans with high levels of cortisol may have damage to their hippocampus and possible memory issues

Critical thinking of animal models

Strengths

• Allows for a longitudinal study across whole lifespan

• Can rigorously control environment allowing for less extranious variables

• Human study to support - newcomer

Limitation

• Animals are different to humans in their cognitive levels meaning the results might not be generalised to the human population

hippocampus

• Plays crutial role in memory and navigation, specifically the formation of semantic and spatial memory

• Consolidation of memory

glucocorticoids

steroid hormones that increase the cortisol levels in animals and humans

Rephrase the Q

There is value to using animal models to understand human behaviour in relation to hormones. Specifically we can use animal models to examine the effect of cortisol on memory

hormone

• chemical messenger

• secreted by glands in endocrine system

• released directly to the blood stream

• stimulate parts of the body (physiological responses and brain activity)

• take longer to feel effects compared to neurotransmitters

Animal Models

used in research to understand humans without risk of causing harm to a human during the process, however there are still some ethical considerations that must be followed even with animal studies.

Newcomer

• aimed to investigate whether high levels of the stress hormone cortisol interfere with verbal declarative memory

• The results indicated that high cortisol levels impaired performance in the memory task since the participants who received the highest level of cortisol also showed the worst performance in verbal declarative memory

• these results demonstrate a clear link between levels of cortisol and memory

Longitudinal approach

The study's examination of long-term effects of stress hormone exposure on memory and hippocampal function as the rats aged provided valuable insights into the cumulative impact of stress over time. This longitudinal perspective strengthens the study's ability to explain how early-life stress can influence cognitive decline later in life.

Generalizability to humans

Since the study was conducted on rats, there are limitations in generalizing the findings directly to humans due to differences in brain structure and complexity. While the hippocampus functions similarly, human memory processes are more intricate, making it challenging to extrapolate the results fully.