What structure in the brain did Descartes associate with the amplification of mental movements?

Descartes associated the pineal gland with the amplification of mental movements because he considered it to be the "seat of the soul" where the mind and body interact. In his dualistic view, the pineal gland was thought to play a key role in the processing and regulation of thoughts and emotions, serving as a bridge between the immaterial mind and the physical body. This association was foundational in early attempts to understand the connection between mental processes and physical actions, suggesting that the pineal gland facilitated the expression of mental states through physical behavior.

In contrast, options like the corpus callosum and thalamus, while important for various brain functions, were not pinpointed by Descartes for this specific role in the amplification of mental movements, and the cerebellum primarily focuses on motor control rather than the dynamic interplay of mind and body.