At least some content in this article is derived from information featured in Harry Potter: Hogwarts Mystery. Spoilers will be present within the article.
The brain is an organ present in all but the simplest of creatures which exerts control over all other organs in the body. Arthur Weasley considered it reasonable not to trust anything if one could not see where it kept its brain, advice he passed on to his children and repeated to Ginevra Weasley after learned the amount of trust she had devoted to Tom Riddle's diary.
Damage to the brain
There exists a number of means to damage the brain; damage by a direct object passing into it is almost always fatal.
The brain can also suffer damage from non-physical sources that affect its stability. Traumatic experiences, such as the ones endured by Sirius Black and Dobby, can negatively affect the brain, but not irreparably. Other things that can damage one's thinking are exposure to the Mirror of Erised (such as Harry Potter) and the Emerald Potion created by Lord Voldemort (such as Kreacher and Albus Dumbledore).
The brain can be damaged permanently by prolonged exposure to the Unforgivable Curses. When under the Imperius Curse, Bartemius Crouch Senior became delirious for the rest of his life, and when he himself placed his son under the curse, he experienced similar symptoms. When under the Cruciatus Curse for a long time, Alice and Frank Longbottom became permanently insane and spent the rest of their lives in St Mungo's Hospital for Magical Maladies and Injuries. When struck by the Killing Curse, the victim's brain will shut down instantly.
Study of the brain
In a certain room of the Department of Mysteries, there exists a large tank containing a number of brains or brain-like objects. These brains exude thoughts as thin tendrils along their "bodies", and appear to have a certain amount of sentience on their own. They are used by Unspeakables to study human thought.
During the Battle of the Department of Mysteries, Ronald Weasley, under influence of a Death Eater's spell that made him disoriented (possibly the Confundus Charm), used a Summoning Charm on one of these brains. The brain immediately attacked when it touched Ron, wrapping its tentacle-like thoughts around his body and attempting to suffocate him. Though he was eventually able to get free and was treated to by Poppy Pomfrey, he suffered a great deal of damage and had scars from the event that would presumably last the rest of his life.
Behind the scenes
- Harry Potter and the Chamber of Secrets (First mentioned)
- Harry Potter and the Order of the Phoenix (First appearance)
- LEGO Harry Potter: Characters of the Magical World (Mentioned only)
- LEGO Harry Potter
- Harry Potter: Hogwarts Mystery