Intro:
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Neurotransmission is process which neurons transmit info from one neuron to another at synapse for certain bodily functions to
occur
Process begins when an action potential travels to axon terminal of presynaptic neuron, and causes vesicles to fuse with membrane
of synaptic neuron and release neurotransmitters.
Neurotransmitters bind to the receptors on post synaptic nueron to carry on electrical impulse to next neuron.
An example of research on the role of neurotransmission in human behaviour is Martinez and Kesner (1991) + Freed et al (2001)
which supports the argument well that neurotransmission impacts memory.
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A study by Martinez & Kesner tried to determine the role of acetylcholine (ACh) on the encoding of memories.
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The researchers conducted this experiment on rats through a lab experiment.
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The rats were trained to learn a simple maze, and before the memories could be learned well-enough to be transferred from shortterm memory to long-term memory, the rats were divided into 3 groups and injected with drugs.
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Group 1 received an injection with an antagonist called scopolamine, a chemical that binds to the receptors in the brain to prevent
a reaction, leading to a reduction in available ACh. Group 2 received an injection with an agonist called physostigmine, a chemical
that binds to receptors in the brain and causes a reaction, leading to more ACh. Group 3 were injected with a saline solution that
had no effect on acetylcholine, thus it was the control group.
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Afterwards, the researchers measured the rats’ learning and memory by comparing the number of mistakes they made while
completing the maze again. Group 1 showed problems of finding their way through the maze and made more mistakes, whilst
group 2 ran quickly through the maze and made few mistakes, and was fast than the control group. These results supports that ACh
is important in memory since the rats showed different memory capacity depending on ACh level.
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The experimental design allowed rigorous control of confounding variables and allows for cause and effect conclusions based on
the isolation of a variable in three experimental conditions.
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Furthermore, the methodology allows other researchers to replicate findings. The issue with this study is that we are unable to
know the extent to which the findings are generalisable to humans as rats were used. Another issue is the construct validity
because the neurobiology of memory is very complex and the chemicals used in the drugs may affect other factors as well.
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Freed et al (2001) wanted to determine the role of dopamine in parkinsons disease
Dop. = neurotransmitter (that is both excitatory and inhibitory), that regulates motor behaviour, motivation, pleasure and
emotional arousal.
Researchers used a experiment and independent measures design.
Sample= 19 female and 21 male at ages 34 – 75
Participants were randomly assigned to either receive transplant of human embryonic dopamine neurons or sham (placebo)
surgery
Results = 12 months after surgery, only younger patients in the transplantation group reported improvement
No significant improvement - older patients in transplantation group
All other patients reported worsening
Irrespective of age group, PET scans revealed increased growth of dopamine producing cells in the putamen
Evaluation = PET scans offer a good resolution of the brain, but are invasive + expensive so it’s hard to replicate
Gender imbalance in participants, Small sample size = not generalisable to the general population
Deception, unethical as patients are given palcebo
Researcher bias= colours shown on PET scans may mislead researcher, as it may look like specific region is clearly defined when in
fact the activity of the brain is much more distributed than localised
Overall, Strengths
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Some studies used methods which produced quantitative data, which means that it is not subject to interpretation
Limitations
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Reductionists approach
Research is often correlational in nature
Experimental research is reliable, but often highly artificial
Many studies consists of animal research which may not be as generalisable to humans
Neurotransmission can only be studied indirectly
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Research on the role of human behaviour has both its strengths and limitations
High internal validity and reliable results (Kesner)
REsearch on the role of neurotransmission does have potential concerns of ecological validity due to the difficulty of isolating and
operationalizing variables in the complex abstract process of memory