LP 3: Memory and neurotransmission
This lesson focuses on the role of neurotransmission in human behaviour - specifically, on memory.
In keeping with the rest of the content of this mini unit on the biology of memory, acetylcholine will be the primary example given. However, there are other examples of neurotransmission affecting behaviour throughout the course; for example, dopamine and addiction; serotonin and depression; or serotonin and aggression.
It is important that students understand the process of neurotransmission and how this physiological process may actually affect specific behaviours. However, students do not need to understand the complexities of the sodium-potassium pump and action potential.
But before you get started, watch this "Crash Course Psychology" video on the chemical nature of our brain.
The following powerpoint presentation can be used to accompany this lesson.
Teaching the basics
The nervous system plays an important role in human behaviour. The nervous system in an electro-chemical system that has an affect both on our physiology and our psychology. In order to talk about the system, we need to learn something about its structure.
Biologists argue that most behaviour has a electrochemical origin. "Information" travels through the neural networks by stimulating the dendrites of a neuron. The neuron is then polarized, sending an electrical charge to the terminal buttons. The terminal buttons then release neurotransmitters across the synapse. This is known as synaptic transmission. These neurotransmitters attach to the dendrites of another neuron and are the cause of behaviour
Once the action potential has traveled to the end of the neuron, the neurotransmitters are released from the terminal buttons. Each molecule of a neurotransmitter has a specific shape by which it is identified. These molecules fit into receptor sites on the dendritic branches. The neurotransmitters fit into the receptor sites like a lock and key.
Once a neurotransmitter is released into the synaptic gap, the terminal buttons will either release enzymes which "clean up" the synapse, such as acetylcholinesterase (note it ends with erase - thanks, Chemists!) which breaks down acetylcholine in the synapses. - or the terminal buttons will "soak up" the neurotransmitter, a process known as re-uptake.
Here is a good description of this process.
It is important to understand how neurotransmitters work in order to understand drug treatments. Drugs can replicate the shape of the neurotransmitter and then occupy the receptor site on the dendrites. The lock and key concept at work. Sometimes, the neurotransmitter or drug may be excitatory - that is, they activate the neuron - like stepping on a gas pedal. Sometimes the neurotransmitter or drug may be inhibitory - that is, it prevents a neuron from firing - like putting on the brakes.
A fun task to do with students - and to get them out of their seats - is to have them put into groups of six and ask them to do a short skit which shows how neurotranmission works. Five people should be used to act out the process - and one person should describe it to the class.
Research on the role of acetylcholine on memory
Start by showing students the following video. It is very similar to the research done by Rogers & Kesner (2003).
Then have students read the following two studies - Antonova (2011) and Arti (2004). This worksheet asks them to think about the strengths and limitations of the two studies.
Sperling et al (2002) carried out a study of memory consolidation in which the team looked at activity in the hippocampus. In the two placebo conditions, you can see teh activity in the limbic system. In the Lorazepam and Scopolamine conditions - both inhibitors of acetylcholine - you can see less activity in this region.
One of the key problems with the study of neurotransmitters and behaviour is that the research is done indirectly - that is, we cannot measure the levels of neurotransmitters in the brain during a behaviour - whether it be aggression, memory consolidation or sexual arousal. What we can measure is brain activity in the regions known to have a lot of receptor sites for a specific neurotransmitter, or we can block receptor sites and inhibit the neurotransmitter to test its effects.
Key issues with neurotransmission theories
- Research on neurotransmission can only be done indirectly. Reliance on fMRI technology means that the limitations of such techniques are relevant to the evaluation of many studies of neurotransmission.
- One of the key strengths of neurotransmission theories is that they have led to successful treatments for certain behaviours. Successful drug treatments have been developed for psychological disorders.
- There is experimental research that supports the role of neurotransmitters in behaviour. These experiments can be replicated to establish reliability.
- However, many of these studies are on animals. This means that we cannot guarantee that the neurotransmitter plays the same role in human behaviour.
- Much of the research on humans in correlational in nature. This means that we cannot establish a cause and effect relationship. For example, in the case of depression, bidirectional ambiguity is a problem. We do not know if a deficit in dopamine and serotonin causes depression or whether these deficits are a result of depression.
- The argument that neurotransmitters are the cause of behaviour is reductionist. Although a reductionist argument may be good in the study of memory since such arguments could potentially lead to positive strategies for helping people with memory impairment, explaining a complex behaviour like falling in love as a "neurochemical cocktail" could be considered an over simplification of human behaviour.
ATL: Inquiry and neurotransmission
Give students the following headline. (I have linked it to a similar article)
Have students do some research to see if this is actually true. The answer is - it's complicated. Research shows that nicotine - a drug that excites acetylcholine receptor sites - may play a role in protecting against the early states of Alzheimer's disease. However, tobacco seems to have a negative effect on memory in the long-term.