According to descartes view, the area in the brain most responsible for regulating behavior was the:

According to Descartes view, the area in the brain most responsible for regulating behavior was the "pineal body".

The pineal body, otherwise called the pineal gland, is a vital endocrine organ that delivers the hormone melatonin. Melatonin assumes a key part in the rest/wake cycle and the body's reaction to daylight.

The pineal gland was one of the last cerebrum organs to be found and has been the subject of much folklore and theory. The seventeenth-century French scholar Rene Descartes thought the spirit was situated in the pineal gland.