Tyrosine improves working memory in a multitasking environment

Previous studies indicate that tyrosine may prove useful in promoting impro ved performance in situations in which performance is compromised by stress . To extend the generality of previous tyrosine findings, the present study examined the effects of tyrosine ingestion on performance during both a Mu ltiple Task and a Simple Task battery. The multiple task battery was design ed to measure working memory, arithmetic skills, and visual and auditory mo nitoring simultaneously, whereas the simple task battery measured only work ing memory and visual monitoring. Ten men and 10 women subjects underwent t hese batteries 1 h after ingesting 150 mg/kg of I-tyrosine or placebo. Admi nistration of tyrosine significantly enhanced accuracy and decreased freque ncy of list retrieval on the working memory task during the multiple task b attery compared with placebo. However, tyrosine induced no significant chan ges in performance on the arithmetic, visual, or auditory tasks during the Multiple Task, or modified any performance measures during the Simple Task battery. Blood levels of ACTH and cortisol were not, but heart rate and blo od pressure were significantly increased during the performance tasks. The present results indicate that tyrosine may sustain working memory when comp eting requirements to perform other tasks simultaneously degrade performanc e, and that supplemental tyrosine may be appropriate for maintaining perfor mance when mild to severe decrements are anticipated. (C) 1999 Elsevier Sci ence Inc.