Animal research studies

Rogers and Kesner (2003)

aim: to determine the role of acetylcholine in the formation of spatial memory

procedure:

• 30 rats

• put in maze and familiarise themselves with it

• randomly allocated two conditions

• con 1- injected with scopolamine

• con 2- saline solution

• ten minutes before maze

• injections directly into hippocampus

• encoding memory asses- average no. of errors made on day one for first 5 trials and last 5 on day one.

• put food in one of the corners for them to find.

findings:

• scopolamine group too longer and more mistakes

• did not affect retrieval of memories that were already created

• acetylcholine plays important role in spatial memories.

Rosenzweig et al (1972)

aim: investigate whether environmental factors such as a rich or impoverished environment would affect the development of neurons in the cerebral cortex.

procedure:

• three male rats

• randomly allocated three enviornments

• control- three rats in cage

• impoverished- each rat in individual cages without toys and maze

• enriched- 10-12 rats in cage with stimulus objects and toys

• all groups had water and food

• 30-60 days in environment

• killed to study brain anatomy

findings:

• anatomy different in EC and IC

• increased thickness and weight of cortex in EC

• EC greater activity in neurone in cerebral cortex associated with the transmission of acetylcholine- important in learning and memory

• follow up- 30 mins a day in enriched environment= same changes in brain as original study

Meaney et al (1988)

aim: determine the effect of glucorticoids (stress hormones) on memory.

procedure:

• independent samples design

• randomly allocated 2 conditions

• treatment group- newborn rats for three weeks from birth to weaning. Taken from mothers of 15 minutes in plastic container with paper towel. Brushed for 15 mins to simulate grooming of mother rat.

• control group- taken from mother and did nothing

• put into pool of milky water.

• tracked the rats route they sought to get to the platform in the pool

findings:

• high levels of glucocorticoids in early life effects rats in old age

• increased exposure to adrenal glucocorticoids accelerated hippocampus neuron loss and cognitive impairments in aging.

• rats taken from mothers at young age has a messier route not as direct.

• neglected rats- hippocampal cell loss and spatial memory deficits

• stroking rat= activation of genes responsible for stress response- epigenetics

• when rat is stressed it releases cortisol that goes to hippocampus binding to glucocorticoid receptor sites, which shuts down fight or flight.

• over stimulation = hippocampal cell death.

Newcomer et al (1999)

aim: investigate if high levels of stress hormone - cortisol- interfere with verbal declarative memory

procedure:

• had clynical interview with physician before to check if they were fit for the experiment

• double-blind

• condition 1- high level cortisol- tablet of 160mg cortisol on each day. Blood levels similar to major stressful events

• condition 2- low level of cortisol- tablet of 40mg cortisol each day. Blood levels of minor surgical procedure.

• condition 3- placebo- control group

• asked to listen and recall paragraph everyday

• did the paragraph before without the dosage and there was no difference

findings:

• high cortisol- impaired memory and worst verbal memory

• no difference between low cortisol and placebo

• con 2 and 3 got better overtime because of practice

Friedman et al (1994)

aim: support the lipostatic theory and investigate what is the feedback mechanism.

procedure:

• OB mouse- genetic mutation leading to hyperplasia- lack of control over eating

• surgically attached OB mouse with a lean mouse so they shared blood supply.

• hypothesis- if hormone that controls wait it should be transferred to OB mouse

• if harmon in OB leading to overeating- lean mouse gain weight

findings:

• OB mouse lost weight

• discovered leptin- hormone that tells us we are done eating- we feel full.

Caspi et al (2003)

aim: examine the role of the 5htt gene in depression

procedure:

• gene is two short= depressions cut of stressful life event

• newzealand 26 year olds

• group 1- short

• group 2- one short one long

• group 3- long

• mutation- short

• stressful life event survey- financial, employment, health, relationships

• assessed for depression

findings:

• one or more short- symptoms of MDD and intrusive thoughts

• strongest with 3 or more events

• inheriting the short gene is not enough but the interaction between short gene and no. of stressful events = depression

Cases et al (1995)

aim: investigate correlation between low levels of MAOA and aggressions

procedure:

• genetically modified male mouse- gene that regulates production of monoamine oxidase A (enzyme that breaks down serotonin and norepinephrine, was knocked out.

• days 11 and 16- signs of low MAOA like frantic running, violent shaking during sleep and biting

• adult males- signs of aggression

• resident-intruder test- mouse put in a cage of another mouse

findings:

• control- sniff other mouse

• transgenic mice- threatening hunched position with both female and male intruder mouse

• autopsies- increase of serotonin, dopamine and norepinephrine

• serotonin 6-9 times higher than control

• MAOA-deficient mice- aggressive behaviour

• aggressive behaviour is due to interaction with MAOA deficiency and social and enviornmental factors.