Polygala root (Polygala tenuifolia), also known as Yuan Zhi, has a long history of use in traditional Chinese medicine (TCM) for supporting cognitive function, calming the spirit, and enhancing memory. In TCM, it is commonly prescribed for conditions like forgetfulness, insomnia, and mental fatigue, which are interpreted as disruptions in the "shen" (spirit) and "heart" system, sometimes conceptually linked to what modern science recognizes as neurotransmitter-related processes, including acetylcholine function.

Some preclinical studies have suggested that extracts from Polygala tenuifolia may have neuroprotective effects and could potentially modulate cholinergic activity by increasing levels of acetylcholine in the brain, at least in animal models. For example, certain compounds in polygala root, such as tenuigenin and polygalasaponins, have been reported to inhibit acetylcholinesterase (the enzyme that breaks down acetylcholine), which could theoretically support acetylcholine levels. However, these effects have not been well-validated in human clinical trials, and the evidence remains preliminary.

In summary, the use of polygala root to support the acetylcholine system is primarily justified by tradition, with preliminary scientific data offering some plausibility but lacking robust human data. Thus, the evidence rating is modest.