Biological: Animal Research

cases aim

to investigate the relationship between low levels of MAOA and aggression 

cases procedures

-mice were genetically modified to delete the MAOA gene
-After maturity an intruder test was conducted to simulate an intruder entering the cage (male mice scents)
TRANSGENIC MICE WERE FASTER TO ATTACK THAN NORMAL MICE

cases findings

-with control mice, when the "intruder" was introduced, the mice would sniff and engage with the mouse. in the transgenic mice, the mice adopted a threatening hunched position and would engage in aggressive behavior.

-autopsies of the brains of the mice showed an increase in serotonin, dopamine, and norepinephrine. serotonin levels were six to nine times higher than the control mice.

cases conclusion

-the study showed that the genetic variation led to MAOA-deficient mice that exhibited strong aggressive behavior. 

-researchers concluded that when human males lack MAOA and demonstrate aggressive behavior, the behavior cannot be attributed to social factors.

-instead, MAOA deficiency is a predisposition toward aggressive behavior which may be expressed through interaction with social and environmental factors.

cases critical thinking

Although the research confirms human research, it is still questionable whether an animal model truly reflects the types of aggression that we see in humans.

It is believed that the majority of people who have the MAOA polymorphism do not exhibit aggressive behavior.  This does not mean that the gene does not have this potential effect on human behavior, but it means that there must be a gene x environment interaction for the behavior to occur.

The study is experimental, so a cause-and-effect relationship can be established.  This type of cause-and-effect relationship could not be studied in human participants.

There are ethical concerns about using animals in such a manner, leading to permanent damage (because the mice had to be killed).

rogers & kesner aim

determine the role of acetylcholine in the formation of spatial memory.

rogers & kesner procedures

-Lab experiment

-The rats were either injected in the hippocampus with scopolamine or with a placebo ten minutes before running the maze.

-Encoding of memory was assessed by the average number of errors made on the first five trials of Day 1 compared to the last five trials of Day 1, whereas the average number of errors made on the first five trials of Day 2 compared to the last five trials of Day 1 was used to assess retrieval.

rogers & kesner findings

-the scopolamine group took longer and made more mistakes in the learning of the maze - that is, there was a higher average number of mistakes made on the last five trials on Day 1.

-however, it did not appear to affect the retrieval of memories that had already been created.

rogers & kesner conclusion

-it appears that acetylcholine may play an important role in the consolidation of spatial memories

rogers & kesner critical thinking

• The researchers used a rigorously controlled experiment with a placebo condition to avoid the effect of confounding (extraneous) variables.

• The study can establish a cause-and-effect relationship; however, it is a reductionist approach to understanding memory.  There are several different types of memory and the process of memory consolidation is very complex.

• The research could one day lead to the development of treatments for people suffering from dementia or Alzheimer's disease.

• Biologists believe that animals can serve as models for human physiology and behavior; however, there are questions about the extent to which findings can be generalized to humans.

meaney aim

determine the effect of glucocorticoids (stress hormones) on memory.

meaney procedures

-experiment with independent samples design

-treatment group: Newborn rats were handled daily by the researchers for three weeks - from the day of their birth until the day of weaning.  During this time they were taken away from their mothers for 15 minutes and placed in a plastic container lined with a paper towel. They were then brushed for an intense 15 minutes to simulate the grooming of the mother rat.

-control group: these rats were taken away from their mother but there was no handling by the researchers.

-to test the effect of these elevated rates of stress hormones over their lifetime, two-year-old 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.

meaney findings

The researchers found that high levels of glucocorticoids - stress hormones - in the early life of a rat resulted in changes that affected the rats in old age.  Increased exposure to adrenal glucocorticoids accelerated hippocampal neuron loss and cognitive impairments in aging.

-rats who were not groomed took a much more complicated route, displaying their stress. rats who were groomed took a simple, linear route.

meaney conclusion

it appears that the extra stroking and grooming “turns on” the genes that help rats cope with stress - leading to a longer life.

meaney critical thinking

• It is questionable to what extent we can generalize the findings from rats to human beings.

• When Meaney did his research he did not yet understand the role of epigenetics in explaining the results.

• The study was artificial - lacking ecological validity.

• This research led to new theories of the role of stress on cognitive functioning.

• To measure hippocampal volume in rats, the animals had to be killed.  There are ethical concerns about the killing of animals in research

sapolsky aim

to investigate the role of social hierarchies on stress in baboons and how this relates to humans

sapolsky procedures

-true experiment, longitudinal

-Sapolsky conducted a long-term naturalistic observation of wild baboons in East Africa (primarily the Serengeti) over several decades. He monitored the social structure of troops and collected biological samples (blood) to measure stress hormone levels (cortisol). He also recorded behaviors such as aggression, grooming, and social rank.

sapolsky findings

-the baboons on the lower rungs of the social hierarchy had higher levels of stress and, therefore, more health problems.

-dominant baboons had lower cortisol and better overall health, largely due to greater control and predictability in their lives.

sapolsky conclusion

-social hierarchies directly impact stress levels and health. Lack of control and low social rank are strongly associated with chronic stress.

-These findings parallel human societies, suggesting that social status and perceived control significantly affect physical and mental health.

sapolsky critical thinking

The sample population was wild. This eliminates the effects of laboratory conditions and results in high ecological validity.

As data was gathered using different research methods, this increases the credibility of the data.

There are questions about the validity of generalizations to human hierarchies. In human hierarchies, there is more mobility - that is, people change their position over time. In addition, the stress response in baboons may not be exactly the same as in humans.

Sapolsky argues that hierarchies alone do not explain cortisol levels; under naturalistic conditions, it is impossible to control for extraneous variables. Such studies have low internal validity.  For example, it may be that the stability of the hierarchy is important to consider. If the hierarchy is unstable, then the alpha males have to fight to maintain their position. In this case, the alpha males have very high levels of cortisol - as high as the lowest-ranking males.

Personality may play a role in cortisol levels. In other words, did the baboons that are able to manage stress better rise to the top of the hierarchy? Or does simply being a the top of the hierarchy moderate cortisol levels?  In other words, the research is correlational and suffers from bidirectional ambiguity.

caspi aim

see the role epigenetics play in major depressive disorder (5-HTT gene, which is the serotonin transporter gene)

caspi procedures

-sample assessed for mental health on an every-other-year basis until they were 21.

-divided into three groups based on 5-HTT levels: 2 short alleles, 2 long, 1 short 1 long

-participants were asked to fill out a “stressful life events” questionnaire which asked them about the frequency of events (financial, employment, health, and relationship stressors). they were also assessed for depression.

caspi findings

people who had one or two short alleles demonstrated more symptoms of depression and suicidal ideation in response to stressful life events

caspi conclusion

inheriting the gene for the short allele mutation is not enough to lead to depression, but the gene’s interaction with stressful life events increased one’s likelihood of developing depression

caspi critical thinking

limitations:

-correlational study, so no cause-and-effect relationship

-info was self-reported, those who are more resilient may not recall life events as easily

-results were not able to be replicated, so this study has low reliability

-assumes thats serotonin causes depression