Which phrase is often used in traditional texts to describe the connection between the kidney and mental faculties?

The relationship between the kidney and mental faculties in traditional texts is commonly described by the phrase "filling the brain." This phrase highlights the concept that the kidney plays a crucial role in nourishing the mind and cognitive functions. In traditional Chinese medicine, the kidney is thought to store essence (Jing), which is essential for the development and functioning of the brain and, subsequently, for mental clarity, memory, and overall cognitive health. As the kidneys are believed to influence vitality and mental power, the idea that they "fill" the brain suggests that a healthy kidney supports optimal mental performance.

The other phrases, although relevant in their own contexts within traditional texts, do not specifically emphasize the connection between the kidneys and mental faculties. "Source of strength" may relate to the overall vitality provided by the kidneys, but it does not communicate the direct impact on mental faculties. "Protector of the heart" refers to the kidneys' relationship with the heart in maintaining emotional and physical health. "Storehouse of energy" relates to the kidneys' role in storing energy through Jing but does not specifically address the influence on cognitive functions. Thus, "filling the brain" most accurately captures the traditional view on how the kidneys support mental and cognitive abilities.