Animal Research (HL) Revision

Rodgers and Kesner (2003) aim

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

Rodgers and Kesner sample

30 rats - had them acclimate to the Hedd-Williams maze by placing food in the corners. Once they were no longer afraid of the maze the experiment could begin

Rodgers and Kesner Procedures

Rats randomly allocated one of two conditions - either injected with Scololamine (acetylcholine antagonist) or a saline solution (control and placebo to ensure that an increase in adrenaline as a result of a placebo is not a confounding variable). Injections made into hippocampus

Encoding of memory was assessed by the average number of errors amde on the first five trials of Day 1 compared to the last five trials on Day 1.

Retrieval was assessed by comparing average number of errors made in last five trials of day 1 compared to first trials on day 2.

Rodgers and Kesner Results

Scopolamine (antagonist) group took longer and made more mistakes in the learning of the maze - more errors made on the last 5 trials on day 1.

It did not appear to affect the retrieval of memories that had already been created.

Rodgers and Kesner conclusion

Acetylcholine may play an important role in memory consolidation

Rodgers and Kesner Strengths and Limitations

Placebo condition - highly controlled
Cause and effect relationship established
Research could lead to develpment of treatment for people with Alzheimers disease

Generalizability to humans
Reductionist approach - possibly oversimplifying the mechanisms associated with memory consolidation

Rozenweig (1972) Aim

To investigate whether changing the level of stimuli in environment would affect the development of neurons in the cerebral cortex

Rozenweig (1972) Sampling

3 male rats from a common litter

Rozenweig Research Methods (1972)

Random assignment, independent samples design, lab experiment

Rozenweig (1972) Procedures

The rats were placed in one of three conditions:
10-12 other rats with lots of different stimulus objects to explore
Three other rats in the cage (control)
Individual cage with no toys or mazes

They spent 30-60 days in their environments before they were killed so researchers could study the brain’s anatomy

Rozenweig (1972) Results

The anatomy in the brain was different in the enriched condition compared to the impoverished condition (isolation). There was an increased thickness and higher weight in the enriched condition.

The researchers believe there was also greater activity in the neurons associated with actetylcholine which is an important neurotransmitter for learning and memory.

Rozenweig (1972) Conclusion

Since brain plasticity is implied to follow the same pattern in humans and rats, the study implies that the human brain is also affected by environmental factors such as stimulation.

Rozenweig (1972) Strengths and Limitations

Limitations:
Unclear variable - social stimulation or toys
Animals - difficult to generalise to humans unless a study done on humans provide the same results
Ethical consideration - undue stress or harm and killed at the end - cost benefit analysis should be done to demonstrate that the goals were worthwhile

Strengths:
Lab experiment - highly controlled lack of confounding variables
Cause and effect relationship established
Replicated many times and results remain constant

Meaney et al (1988) Aim

To investigate the effect of stress hormones on memory

Meaney et al (1988) Sampling

Independent samples design - random assignment

Newborn rats

Meaney et al (1988) Reseach Methods

Lab experiment - IV manipulated

Meaney et al (1988) Procedures

Newborn rats in treatment condition were handled daily by researchers for three weeks from DOB. They were taken away from mothers for 15 minutes and placed in plastic container and brushed for 15 minutes to simulate grooming of mother rat

Rats in control condition were taken away but not handled by researchers.

Two-year old rats were put into pool of milky water and had to find a hidden platform. The route was tracked by researchers as the rats tried to find pathway based off memories of previous attempts to escape

Meaney et al (1988) Results

High levels of stress hormones in the early life of the rat resulted in changes that affected the rats in old age. Increased stress hormones accelerated hippocampal neuron loss

Meaney et al (1988) Conclusion

Extra stroking led to activation of genes that are responsible for coping with stress response (epigenetics). Long term exposure to stress hromones can cause more neurons to admit calcium through membrane which leads to over stimulation and hippocampal cell death. This can affect our ability ot create a memory

Meaney et al (1988) Strengths and Limitations

Strengths:
Research led to new theories of the role of stress on cognitive function.
Cause and effect relationship established

Limitations:
Low generalisability - however new research showing that high levels of stress hormones are present in Alzheimers patients
Lacking ecological validity - artificial
Ethics - rats had to be killed to measure hippocampal volume

Hormones (animal research) Studies to use

Meaney (1988) and Sapolsky

Genetics studies to use

Cases (1995) and Shmelkov

Transgenic Mice

Mice who have been modified at a genetic level to include a transgene - a foreign sequence

Cases (1995) Aim

To investigate the genetic origins of aggression

Cases (1995) Sampling Methods

Genetically modified mice - knockout mice - where the gene that breaks down serotonin into norepinephrine is deleted

Cases et al (1995) Research Methods

Lab Experiment, observations used to investigate behaviour

Cases et al (1995) Procedures

Resident intruder tests were carried out where the researchers would put a mouse in the cage of another mouse.

Brain autopsies also carried out.

Cases (1995) Results

Between days 11 and 16, the transgenic mice showed several signs of low MAOA. Behaviours included frantic running, violent shaking during sleep and biting researcher. They showed aggressive behaviour in adult males

In the control mice, they would sniff them, and engage with them. In transgenic mice, they would engage in aggressive behaviour (true for both male and female inturders).

Cases et al (1995) Conclusion

Genetic variation led to mice that exhibited aggressive behaviour. When human males lack MAOA and demonstrate aggressive behaviour, the behaviour cannot be attributed to social factors.

Cases et al (1995) Strengths and Limitations

Strengths:
Other studies confirm model
Cause and effect relationship established

Limitations:
Generalisability
Majority of people who have this gene don’t exhibit aggressive behaviour, suggesting a gene and environment interaction
Ethical concerns - undue stress or harm, rats killed

Shmelkov (2010) Aim

To investigate the association between genetics and phenotypes linked to OCD.

Shmelkov (2010) Sampling

Knockout mice used - the SLITRK5 gene was replaced with another gene leading to homozygous (2x new gene), heterozygous, and control mice (2x SLITRK5 gene)

Shmelkov (2010) Research methods

Method triangulation - variety of measures used

Lab experiment

Shmelkov (2010) Procedures

Mice put in quadrants and were observed to see how much exploring they did
They were placed in a smaller cage with 20 marbles in sawdust and after 20 minutes they measured how many had been buried - measure of anxiety.

Shmelkov (2010) Results

From 3 months old the homozygous mice developed skin lesions and hair loss due to excessive grooming comapred to healthy other groups.

Heterozygous displayed same behaviours but later in life (7-9 months)

Experimental mice spent less time exploring and buried a greater percentage of the marbles.

Shmelkov (2010) Conclusion

The SLITRK5 gene is important for the healthy development of neural circuits in mice and turning off this gene is associated with anxiety and compulsive behaviour.

Similarites between CNS in mice and humans, one can extrapolate findings and infer that abnormalities relating to this gene may also be linked to compulsive behaviours.

Shmelkov (2010) Strengths and Limitations

Strengths:
True experiment - gene was manipulated so cause and effect can be established.
Ecologically valid for mice
Animal experiments allow for extraneous variables to be highly controlled - e.g handling of mice

Limitations:
OCD in humans also catergorised by excessive thoughts as well as compulsive behaviours. Animal models can only tell us about observable behaviours
Some researchers disagree with the use of burying marbles as a way to measure the anxiety levels.
Mice given an antianxiety drug that reduces marble burying, but has little effect on OCD in humans, questions generalisability

Knockout mouse

Lab mouse that has a gene that has been :knocked out” or deleted by researchers

Cross benefit analysis

Whether goals of the study justify the harm done to animals

Three Rs

Replace
Reduce
Refine

Utalitarianism

The belief that the harm done to small group of animals will be beneficial for the wider population