What did Aristotle believe was the main function of the human brain?

It was thus obvious to Aristotle that 'the seat of the soul and the control of voluntary movement--in fact of nervous functions in general-are to be sought in the heart. The brain is an organ of minor importance, perhaps necessary to cool the blood'
infidels.org/library/magazines/tsr/1993/1/1brain93.html no longer exists

The brain as a radiator -- In 335 BC, Greek philosopher Aristotle thought the brain was simply a radiator that kept the all-important heart from overheating. Around 170 BC, Roman physician Galen suggested the brain’s four ventricles (fluid-filled cavities) were the seat of complex thought, and determined personality and bodily functions. This was one of the first suggestions that the brain was where our memory, personality and thinking reside.

https://qbi.uq.edu.au/brain/intelligent-machines/understanding-brain-brief-history