Department of Neuropsychology and Psychopharmacology, Faculty of Psychology, Maastricht University, Maastricht, The Netherlands.
J Psychopharmacol. 2011 Feb;25(2):230-8. doi: 10.1177/0269881109348160. Epub 2009 Nov 25.
Dopamine is well known for involvement in reinforcement, motor control and frontal lobe functions, such as attention and memory. Tyrosine/phenylalanine depletion (TPD) lowers dopamine synthesis and can therefore be used as a model to study the effects of low dopamine levels. This is the first study to assess the effect of TPD on memory performance and its electrophysiological correlates. In a double blind placebo (PLA)-controlled crossover design, 17 healthy volunteers (six males, 11 females) aged between 18 and 25 were tested after TPD and PLA. Working memory was assessed using a Sternberg memory scanning task (SMS) and episodic memory using the Visual Verbal Learning Test (VVLT). Simultaneously, event-related potentials (ERPs) were measured. The tyrosine and phenylalanine ratio was significantly reduced after TPD and increased after PLA. Working memory performance was not affected by TPD. However, ERP measures were affected by the treatment, indicating that TPD impaired stimulus processing during working memory performance. Episodic memory was not impaired after TPD. Again, alterations in ERP measures suggested adverse effects of TPD on memory-related processing. These results suggest that dopamine is involved in both working memory and episodic memory-related processing, although the effects are too small to be detected by performance measures.
多巴胺在强化、运动控制和额叶功能（如注意力和记忆）中起着重要作用。酪氨酸/苯丙氨酸耗竭（TPD）会降低多巴胺的合成，因此可以作为研究低多巴胺水平影响的模型。这是第一项评估 TPD 对记忆表现及其电生理相关性影响的研究。在一项双盲安慰剂（PLA）对照交叉设计中，17 名年龄在 18 至 25 岁之间的健康志愿者（六名男性，11 名女性）在 TPD 和 PLA 后接受了测试。使用 Sternberg 记忆扫描任务（SMS）评估工作记忆，使用视觉言语学习测试（VVLT）评估情景记忆。同时，测量了事件相关电位（ERP）。TPD 后酪氨酸和苯丙氨酸的比值显著降低，PLA 后比值增加。TPD 对工作记忆表现没有影响。然而，ERP 测量结果受到治疗的影响，表明 TPD 损害了工作记忆表现过程中的刺激处理。TPD 后情景记忆未受损。同样，ERP 测量结果的变化表明 TPD 对与记忆相关的处理有不良影响。这些结果表明，多巴胺参与了工作记忆和情景记忆相关处理，尽管其影响太小，无法通过表现测量来检测。
