2.3 Explain, using one or more examples, the effects of neurotransmission on human behaviour.

2.3 Explain, using one or more examples, the effects of neurotransmission on human behaviour.

When a nerve impulse reaches the end of the neuron, the neuron fires and neurotransmitters are released into the synaptic gap where they travel to the neuron at the other side of the synaptic gap. If the neurotransmitter is not absorbed it can be re-uptaken, diffused out or destroyed. The neurotransmitter then binds to specific receptors at the other side. If a neurotransmitter is blocked or replaced (e.g. because another chemical interferes) then the messages change. This affects the physiological system, cognition, mood, or behaviour.

Dopamine

Dopamine is a neurotransmitter involved in goal-directed behaviour (motivation) such as pleasure seeking, control of movement, emotional response, and addictive behaviour. Dopamine is released in the brain’s reward system.

Dopamine is released in the brain’s reward system and has been associated with pleasure seeking and addictive behaviour. Addictive drugs or substances increase of dopamine in the reward system. Dopamine can be released by environmental triggers (e.g. the sight of a cigarette package, food, or a gambling machine) because this is associated with pleasure (reward). Nicotine is the psychoactive ingredient in tobacco, which increases the level of dopamine in the brain’s reward circuit causing feels of pleasure or relaxation.

Berridge and Kringelbach (2009)

fMRI scans were used to study brain areas involved in the subjective experience of pleasure. They found that the orbitofrontal cortex was active when people reported feeling pleasure. The researchers concluded that: dopamine and the nucleus accumbens is perhaps rather involved in pleasure seeking. This could explain addictive behaviour. The orbitofrontal cortex and natural opioids (endorphins) are perhaps linked to the subjective experience of pleasure.

Fisher (2004)

This is an evolutionary explanation of behaviour. Dopamine increases desire and reward by triggering the same emotional rush of pleasure when you see or think of the loved one as if you were taking a drug like cocaine. Dopamine can explain the highs of romantic passion (high levels of dopamine) and the lows of rejection (low levels of dopamine).

Acetylcholine (ACh) on memory

Acetylcholine is a neurotransmitter which has been linked to synaptic plasticity in the hippocampus and it seems to play an important role in learning and short-term memory via the cholinergic system (Shinoe et al. 2005). The cholinergic system is a system of nerve cells that uses acetylcholine in transmitting nerve signals. Memory processing and higher cognitive functioning are dependent on the cholinergic system.

Martinez and Kesner (1991)

The aim was to investigate the role of acetylcholine in memory formation. They did experimental studies using rats. They were trained to run through a maze. They were divided into three groups. Group 1 receive injection with scopolamine (blocks ACh receptor sites, reducing available ACh). Group 2 received injection with physostigmine (blocks production of cholinesterase (enzyme) which cleans up ACh from the synapses) leading to more available ACh. Group 3 was the control group.  The results showed that group 1 had problems finding their way through the maze and made more mistakes. Group 2 ran quickly through the maze and made few mistakes. The group was quicker than the control group. The study shows that ACh is important in memory since the rats showed different memory capacity depending on ACh level. Since this was a controlled laboratory experiment, it can be concluded that the level of ACh is one factor that affects memory but the neurobiology of memory is very complex.