(2026 Exams) Brain Neurochemistry Explanation

Q: Olds and Milner (1954)

__Olds and Milner (1954)__ studied the effects of brain neurochemistry in addiction; specifically the effects of dopamine in rats. It could potentially explain the importance of dopamine.

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Smoking Addiction and the Brain Neurochemistry Explanation

Smoking can cause many harmful effects like emphysema or cancer, but people still smoke because of an addiction to a chemical in the cigarette called nicotine.

Cigarettes

For decades now, the harmful effects of smoking have been made known to the public.
- Cancer, bronchitis, and emphysema are all serious diseases caused by smoking.
But people still smoke. Addiction to cigarettes is due to a chemical called nicotine.

Nicotine

Nicotine alters brain neurochemistry.
It triggers the release of dopamine in the brain, which causes higher levels in the brain as well as increased dopamine stimulation on neurons.
Dopamine is a neurotransmitter that creates feelings of relaxation and pleasure.
Once a neurotransmitter has been sent across a synapse to stimulate the next neuron, they are removed from the synapse through a process called reuptake.

Neurotransmitter

Once the neurotransmitters are removed, the feelings associated with that particular neurotransmitter also disappear.
- For example, once dopamine reuptakes, the feelings of relaxation and pleasure diminish.
So for people to regain these feelings, they need more dopamine and consume more of the drug that caused it. In this case, cigarettes.

Dopamine

If people smoke regularly, then people’s bodies regularly expect the dopamine released caused by the nicotine.
The body will also start to reduce the amount of dopamine it releases naturally, so people rely on the nicotine as a source of dopamine.
People need to smoke regularly to maintain a normal level of dopamine.
Smoking behaviour is reinforced because of this biological need. Consequently, an addiction develops.

Withdrawal

It is very hard on the body to quit smoking as people need the levels of dopamine maintained.
When a person quits smoking, their body lacks dopamine, causing unpleasant withdrawal symptoms.
- These symptoms include irritability, anxiety, nausea, and sleep issues.

Olds and Milner (1954)

Olds and Milner (1954) studied the effects of brain neurochemistry in addiction; specifically the effects of dopamine in rats. It could potentially explain the importance of dopamine.

Condition 1

Method:
- Rats had an electrode directly connected to the hypothalamus, which when stimulated, releases dopamine.
- Rats could step on a lever that caused an impulse to be sent to the hypothalamus, thereby releasing dopamine.
Results:
- Rats were found to voluntarily (did not have to be forced) press the lever.

Condition 2

Method:
- Rats with the electrode in place in the hypothalamus had to walk across an area of a cage where a painful electric shock was given in order to press the lever.
Results 2:
- Even with the electric shock, rats chose to walk over to press the lever.

Conclusion

The rats voluntarily chose to press the lever, even if they had to endure a painful shock first, to receive a dosage of dopamine.
This shows the effect of dopamine as being a reward and the fact that it was addictive.

Weaknesses of study

There are several critiques to this study.
The first is that it was unethical. The rats were purposefully hurt to complete the study. Many argue that this is animal cruelty.
Secondly, the study was conducted on rats, not on humans, so the findings cannot necessarily be generalised to humans.

Strengths of study

A strength of the study was that it was a laboratory study, so highly controlled.
This increases the reliability of the results.

Evaluation of the Brain Neurochemistry Explanation of Addiction

The explanation states that addiction is caused by organisms wanting to maintain levels of dopamine (pleasure neurotransmitter) by consuming substances.

Strength - proven

There are three main strengths to this explanation:
Firstly, Olds and Milner (1954) and other researchers have provided evidence of this theory through scientific research.
- They have proven that dopamine plays a role in addiction.

Strength - cause and effect

Secondly, because the studies were done in a laboratory setting, this means that they can be highly controlled.
In these circumstances, extraneous variables are limited and causal relationships can be established.
- For example, maintain dopamine levels in the brain is a cause of addiction.

Strength - Zhang et al. (2012) support

Finally, another study conducted by Zhang et al. (2012) also supported the notion that nicotine plays a part in smoking addiction.
They found that those that had quit smoking had abnormal levels of dopamine after they had quit.
The study was conducted on mice who were given nicotine for several weeks.
They stopped giving them nicotine suddenly and found that dopamine productions were lower than normal.

Weakness - reductionist

There are three weaknesses to the brain neurochemistry explanation.
Firstly, the approach is reductionist.
The explanation tries to pare down addictive behaviour to differences in neurotransmitter levels.
The approach ignores other factors such as learning theory or other psychological factors.

Weakness - genetics

Secondly, the role that genetics plays is also ignored.
A study conducted by Doweiko (2002) examined adoption records.
They found that among 3,000 people, biological children of alcoholics were more likely to become alcoholics themselves.
Even if the children were raised by non-alcoholic adoptive parents, there was little to no effect.
This means there must be a genetic influence to addiction.

Weakness - generalisability

Finally, Zhang (2012) and Olds and Milner (1954) used animals in their studies.
Scientists cannot necessarily generalise these findings to humans.