A 62-year-old woman reports to the ER with multiple foot lacerations. She has been experiencing mild hand tremors over the laws few months. She experienced a particularly bad tremor while holding a glass pitcher, and dropped it on her bare foot. Her son says she has been unable to taste much lately, leading her to make batches of extra sweet tea. Her foot is being treated, but what shoud be investigated as a likely neurochemical cause of her tremors?