ROLE OF NEUROTRANSMITTERS IN LEARNING AND MEMORY – Martinez and Kesner (1991) Aim: determining the role of the neurotransmitter acetylcholine on memory Method:
* Rats were trained to go through a maze and get to the end, where they received food * Researcher injected one group of rats with scopolamine (blocks acetylcholine receptor sites thus decreasing available acetylcholine) * Injected second group of rats with physostigmine (blocks the production of cholinesterase – cholinesterase does the ‘clean-up’ of acetylcholine from the synapse and returns the neuron to its ‘resting state’. * Third group (control group) were not given any injections Results:
* Scopolamine group – slower at finding their way round the maze and made more errors than both the control group and physostigmine group. * Physostigmine group – ran through the maze and found the food even more quickly than the control group, and took fewer wrong turns Conclusion: Acetylcholine plays an important role in creating a memory of the maze. * Strengths - research lie in its design and its application; use of an experimental method with a control group made it possible to establish a cause-and-effect relationship between levels of acetylcholine and memory * Limitations – questionable to what extent these findings can be generalised to humans; assumed that memory processes are the same for all animals.
Case study: PHINEAS GAGE
Aim: the most famous study of how brain damage can affect behaviour * Phineas Gage, 25 years old railroad worker, got in a serious accident. While trying to blast through a rocky cliff, an explosion sent a metal pole through his skull. Iron entered Gage’s left cheek, pierced the base of the skull, went through the front of his brain, and exited at high speed through the top of his head. Method/ Results: Balance between his intellectual abilities and his emotional control had been destroyed. * He became highly agitated and disrespectful; impatient and indulgent * He could make plans for his future, but could never follow through on them * Described him as “a child in his intellectual capacity, but with the animal passions of a strong man.” Conclusion:
* Longitudinal study of the damage to his frontal lobe provided evidence that the brain affects personality and social behaviours. * The frontal lobe has a specific function, many behaviours are localised in this area.
IS SCHIZOPHRENIA GENETIC? – Heston (1966)
Aim: whether schizophrenia is genetic of not
* Heston correlated this incidence with the diagnosis of schizophrenia in their biological mothers * If schizophrenia were genetic – adoption would not affect the number or children who were later diagnosed with schizophrenia * Because of biological inheritance – a higher incidence of schizophrenia would be expected among the adopted children of schizophrenic mothers than among adoptees whose mothers did not have a diagnosis of schizophrenia * If nurture were important – adoption would reduce number or children with schizophrenia, and incidence would be approximately the same as among other adoptees. Results:
* Over 10% of adopted children with a family history of schizophrenia were later diagnosed with it. Conclusion: strong evidence that schizophrenia has a genetic component
HOMOSEXUALITY IN TWINS – Baily and Pillard (1991)
Aim: measured how often, when on twin was homosexual, the other one was also homosexual in monozygotic (MZ) twins and dizygotic (DZ) twins. Method:
* Sample of male homosexual probands, all over the age of 18 with a twin * Recruitment was through advertisements placed in homophile publications in several cities in the Midwest and Southwest of the United States * Probands interviewed in person with informed consent
* Questionnaires were sent to the cotwins – five questions regarding sexual orientation were imbedded in over 100 other items about...
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