Giessing C, Thiel C M, Rösler F, Fink G R
Institute of Medicine, Research Centre Jülich, 52425 Jülich, Germany.
Neuroscience. 2006 Feb;137(3):853-64. doi: 10.1016/j.neuroscience.2005.10.005. Epub 2005 Nov 23.
This functional magnetic resonance imaging study investigates the effects of nicotine in a cued target detection task when changing cue reliability. Fifteen non-smoking volunteers were studied under placebo and nicotine (Nicorette polacrilex gum 1 and 2 mg). Validly and invalidly cued trials were arranged in blocks with high, middle and low cue reliability. Two effects of nicotine were investigated: its influence on i) parietal cortex activity underlying the processing of invalid vs. valid trials (i.e. validity effect) and ii) neural activity in the context of low, middle and high informative value of the cue (i.e. cue reliability effect). Nicotine did not affect behavioral performance. However, nicotine reduced the difference in the blood oxygenation level dependent (BOLD) signal between invalid and valid trials in the right intraparietal sulcus. The reduction of parietal activity in invalid trials was smaller in the low cue reliability condition. The same posterior parietal region exhibited a nicotinic modulation of BOLD activity in valid trials which was dependent on cue reliability: Nicotine specifically enhanced the neural activity during valid trials in the context of low cue reliability, i.e. when subjects are already in a state of low certainty. We speculate that the right intraparietal sulcus might be part of two networks working in parallel: one responsible for reorienting attention and the other for the cholinergic modulation of cue reliability. By reducing the use of the cue, nicotine modulates parietal activity related to reorienting attention in conditions with higher cue certainty. On the other hand, nicotine increases parietal activity in states of low certainty. This enhanced activation might influence brain regions, such as the posterior cingulate, directly involved in the processing of cue reliability.
这项功能磁共振成像研究调查了在改变线索可靠性的提示目标检测任务中尼古丁的作用。15名非吸烟志愿者在安慰剂和尼古丁（尼古丁咀嚼胶1毫克和2毫克）条件下接受研究。有效提示和无效提示试验被安排在具有高、中、低线索可靠性的组块中。研究了尼古丁的两种作用：其对i）无效试验与有效试验处理过程中顶叶皮层活动的影响（即有效性效应），以及ii）在提示信息价值低、中、高的情况下的神经活动（即线索可靠性效应）。尼古丁不影响行为表现。然而，尼古丁降低了右侧顶内沟无效试验和有效试验之间的血氧水平依赖（BOLD）信号差异。在低线索可靠性条件下，无效试验中顶叶活动的减少较小。在有效试验中，同一后顶叶区域表现出对BOLD活动的尼古丁调节，这取决于线索可靠性：尼古丁在低线索可靠性情况下，即当受试者已经处于低确定性状态时，特异性增强了有效试验期间的神经活动。我们推测，右侧顶内沟可能是两个并行工作网络的一部分：一个负责重新定向注意力，另一个负责对线索可靠性进行胆碱能调节。通过减少线索的使用，尼古丁在提示确定性较高的情况下调节与重新定向注意力相关的顶叶活动。另一方面，尼古丁在低确定性状态下增加顶叶活动。这种增强的激活可能会影响直接参与线索可靠性处理的脑区，如后扣带回。
