Tyrosine: a non-essential amino acid and a precursor to dopamine, epinephrine and norepinephrine. There is some evidence to suggest tyrosine supplementation can affect performance on working memory tasks under certain conditions, especially stress. Tyrosine may enhance convergent creative thinking. In one study tyrosine seemed to even ameliorate some of the detrimental effects of sleep deprivation on cognitive performance. However, if tyrosine increases working memory performance by enhancing catacholamine levels the effect could easily be short-lived. Some animal studies have shown dopamine levels quickly return to baseline.