Kübler A, Murphy K, Garavan H
Department of Psychology and Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland.
Eur J Neurosci. 2005 Apr;21(7):1984-92. doi: 10.1111/j.1460-9568.2005.04027.x.
Many studies have shown the negative effects of cocaine on neuropsychological and cognitive performance in drug-dependent individuals, but little is known about the underlying neuroanatomy of these dysfunctions. The present study addressed attention switching between items held in working memory (WM) with a task in which subjects were required to store and update two items held in verbal or visuospatial WM. Attention-switching frequency varied between trials, thereby allowing us to isolate the switching component of task performance. Behavioural data revealed that cocaine addicts performed worse than healthy controls in all tasks. On the visuospatial task addicts performed at chance levels revealing particular impairment in visuospatial WM. On the verbal task, in which controls and users could be matched for performance, we identified attenuated responses in prefrontal and cingulate cortices and in striatal regions, while other areas such as dorsolateral prefrontal cortex did not differ between healthy controls and users. The results reveal that addiction may be accompanied by specific rather than ubiquitous hypoactivation in prefrontal and subcortical areas and suggest a compromised ability in users to control their attention to their thoughts as might be particularly relevant when required to switch away from drug-related thoughts, and thus the dysfunction in attention switching may contribute to the maintenance of addiction.
许多研究表明，可卡因对药物依赖个体的神经心理和认知表现具有负面影响，但对于这些功能障碍背后的神经解剖学却知之甚少。本研究通过一项任务来探讨工作记忆（WM）中所存储项目之间的注意力切换，在该任务中，要求受试者存储并更新言语或视觉空间WM中所存储的两个项目。各试验之间的注意力切换频率有所不同，从而使我们能够分离出任务表现中的切换成分。行为数据显示，在所有任务中，可卡因成瘾者的表现均不如健康对照组。在视觉空间任务中，成瘾者的表现仅为随机水平，显示出在视觉空间WM方面存在特定损伤。在言语任务中，对照组和使用者在表现上可以进行匹配，我们发现前额叶和扣带回皮质以及纹状体区域的反应减弱，而其他区域，如背外侧前额叶皮质，在健康对照组和使用者之间并无差异。结果表明，成瘾可能伴随着前额叶和皮质下区域特定而非普遍的激活不足，并表明使用者控制对自身思维注意力的能力受损，这在需要从与药物相关的思维中转移注意力时可能尤为相关，因此注意力切换功能障碍可能有助于成瘾的维持。
