To elucidate the brain functions, it is essential not only to conduct micro-level research such as the conduction of electrical signals and chemical transmission by neurotransmitters, but also the system-level research on how they “function as a circuit” and “connect to actual thoughts and actions.” The Department of Physiology 2 grapples with this arduous but interesting problem by utilizing primates whose brain structure is similar to that of humans, by electrophysiological and pharmacological approaches. The current main theme is the elucidation of mechanisms by which emotion, memory, and attention change the decision-making process and actions. We dream of discovering the universal principle of calculation processing in the brain.