Source: R.J. Hankinson, "Philosophy and Science," The Cambridge Companion to Greek and Roman Philosophy, ed. David Sedley (Cambridge: Cambridge University Press, 2003) 294-295.
"Plato thought that the brain was the seat of intelligence...Aristotle, on the other hand, located thought as well as emotion in the heart; and so did the Stoics...That the Stoics could continue to believe this after the isolation of the motor and sensory nervous systems by Herophilus (fl. c. 260 BC) scandalized Galen (AD 129-c. 215), the greatest doctor of later antiquity and a considerable philosopher as well."
These pages also reveal that dissection confirmed for Galen that "the nerves ramify from the brain." In the fourth century B.C.E., Praxagoras "plumped for the heart, perhaps because he thought that the nerves (which he may have been the first properly to distinguish from tendons) were the thinned-out ends of the arteries."
These quotes intrigue me for two reasons. First, I wonder where the Bible, the rabbis, and the early Christians located intelligence and emotion: the brain or the heart? The Bible seems to opt for the heart on numerous occasions.
Second, the philosophers appear to have had a sophisticated biological basis for their beliefs on this issue, according to the science of their day.