# Explain why it is difficult for scientists to research the structure and functions of the human brain.

> WJEC A-Level Biology (Wales) — 4.3 Variation and evolution · Explain · 5 marks

## Mark scheme (5 marks)

1. There are billions of neurones (making the brain extremely complex to study)
2. The brain must still be working / patient must be alive to study many functions
3. Ethical issues with studying patients with brain damage because they may not be able to give informed consent
4. Studies are only carried out after damage has occurred so the brain cannot be compared to the healthy brain / before the damage
5. Brain damage rarely causes a single problem / difficult to match which problem is caused by which damaged neurones

## Related

- [Revision notes for WJEC A-Level Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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