Cognitive Neurophysiology, Department of Child and Adolescent Psychiatry, Carl Gustav Carus Faculty of Medicine, TU Dresden, Schubertstr. 42, D-01307 Dresden, Germany; Cognitive Psychology Unit and Leiden Institute for Brain and Cognition, Leiden University, Leiden, Netherlands.
Cognitive Psychology Unit and Leiden Institute for Brain and Cognition, Leiden University, Leiden, Netherlands; Department of Cognitive Psychology, Institute of Cognitive Neuroscience, Faculty of Psychology, Ruhr University Bochum, Bochum, Germany; Institute for Sports and Sport Science, University of Kassel, Kassel, Germany.
Eur Neuropsychopharmacol. 2018 Aug;28(8):933-944. doi: 10.1016/j.euroneuro.2018.05.010. Epub 2018 Jul 3.
Exerting cognitive control is an effortful endeavor that is strongly modulated by the availability of dopamine (DA) and norepinephrine (NE), which are both synthesized from the amino acid precursor tyrosine. Supplementing tyrosine may increase the synthesis of both catecholamines. This has been suggested to improve executive functioning and potentially even counteract depletion effects in this domain. Yet, it has remained unclear whether tyrosine also improves interference control and whether subliminally and consciously triggered response conflicts are subject to the same modulation. We investigated this question in a double-blind intra-individual study design. N = 26 young healthy subjects performed two consecutive cognitive control tasks that triggered automatic incorrect response tendencies; once with tyrosine supplementation and once with a placebo. The results show that tyrosine decreased the size of consciously perceived conflicts in a Simon Task, but not a Flanker task, thus suggesting that stimulus-response conflicts might be modulated differently from stimulus-stimulus conflicts. At the same time, tyrosine supplementation increased the size of subliminally triggered conflicts whenever a different, consciously perceived conflict was also present. This suggests that control-related DA and NE release may increase visuo-motor priming, especially when no conflict-specific top-down control may be triggered to counteract subliminal priming effects. Also, these subliminal conflicts might be aggravated by concurrent control investments in other kinds of conflict. Taken together, our data suggest that beneficial effects of tyrosine supplementation do not require depletion effects, but may be limited to situations where we consciously perceive a conflict and the associated need for conflict-specific control.
发挥认知控制需要付出努力，多巴胺（DA）和去甲肾上腺素（NE）的供应强烈调节着这种努力，而这两种神经递质都是由氨基酸前体酪氨酸合成的。补充酪氨酸可能会增加两种儿茶酚胺的合成。这被认为可以改善执行功能，甚至可能抵消该领域的耗竭效应。然而，酪氨酸是否也能改善干扰控制，以及潜意识和有意识引发的反应冲突是否受到相同的调节，仍然不清楚。我们在一项双盲个体内研究设计中研究了这个问题。N=26 名年轻健康的受试者连续进行了两项认知控制任务，这些任务引发了自动的错误反应倾向；一次是在酪氨酸补充剂的情况下，一次是在安慰剂的情况下。结果表明，酪氨酸降低了在 Simon 任务中自觉感知到的冲突的大小，但在 Flanker 任务中没有，这表明刺激-反应冲突可能与刺激-刺激冲突受到不同的调节。与此同时，无论何时存在不同的、自觉感知到的冲突，酪氨酸补充都会增加潜意识触发的冲突的大小。这表明与控制相关的 DA 和 NE 释放可能会增加视动启动，特别是当没有可以触发的冲突特异性自上而下控制来抵消潜意识启动效应时。此外，这些潜意识冲突可能会因其他类型冲突的同时控制投资而加剧。总之，我们的数据表明，酪氨酸补充的有益效果不需要耗竭效应，但可能仅限于我们自觉感知到冲突和相关的特定冲突控制需求的情况。
