Tait David S, Brown Verity J, Farovik Anja, Theobald David E, Dalley Jeffrey W, Robbins Trevor W
School of Psychology, University of St Andrews, St Mary's College, South Street, St Andrews, Fife KY16 9JP, UK.
Eur J Neurosci. 2007 Jun;25(12):3719-24. doi: 10.1111/j.1460-9568.2007.05612.x.
Rats with medial prefrontal cortex (mPFC) lesions are impaired in attentional set-shifting, when it is required to shift to a previously irrelevant perceptual dimension. The main source of noradrenergic input to the mPFC is from the locus coeruleus via the dorsal noradrenergic ascending bundle (DNAB). This study examined the effects of selective cortical noradrenaline depletion following 6-hydroxydopamine-induced lesions of the DNAB on attentional set-shifting and other aspects of discrimination learning and performance. Rats learned to dig in baited bowls, and then acquired discriminations based on one of two aspects of a bowl--odour or digging medium. The task tested acquisition of novel discriminations (both intra- and extra-dimensional) and reversal learning when contingencies were reversed with the same stimuli. At the conclusion of testing, the DNAB-lesioned rats were shown to have a selective depletion of noradrenaline of approximately 70% within the mPFC (cingulate and prelimbic cortex subregions), with no other significant changes in dopamine or 5-hydroxytryptamine. Rats required more trials to learn new discriminations when attentional shifting was required [extra-dimensional (ED)-shift]. Rats with dorsal noradrenergic ascending bundle (DNAB) lesions were impaired in novel acquisitions when an ED-shift was required, but were unimpaired in reversal learning and other aspects of discrimination learning, relative to controls. These data are consistent with other evidence implicating noradrenaline (NA) in attentional set-shifting, and contrast with effects of manipulations of 5-hydroxytryptamine (5-HT) and acetylcholine within the medial prefrontal cortex (mPFC). The findings are also relevant to recent theorizing about the functions of the coeruleo-cortical noradrenergic system.
当需要转向先前无关的感知维度时，内侧前额叶皮层（mPFC）损伤的大鼠在注意力转换方面存在缺陷。mPFC去甲肾上腺素能输入的主要来源是通过背侧去甲肾上腺素能上行束（DNAB）来自蓝斑。本研究考察了6-羟基多巴胺诱导的DNAB损伤后选择性皮质去甲肾上腺素耗竭对注意力转换以及辨别学习和表现其他方面的影响。大鼠学会在有诱饵的碗中挖掘，然后基于碗的两个方面之一——气味或挖掘介质进行辨别。该任务测试了新辨别（维度内和维度间）的习得以及当相同刺激的条件反转时的逆向学习。在测试结束时，DNAB损伤的大鼠在mPFC（扣带回和前边缘皮层亚区域）内的去甲肾上腺素选择性耗竭约70%，多巴胺或5-羟色胺没有其他显著变化。当需要注意力转换时[维度间（ED）转换]，大鼠学习新辨别需要更多试验。相对于对照组，背侧去甲肾上腺素能上行束（DNAB）损伤的大鼠在需要ED转换时新习得受损，但在逆向学习和辨别学习的其他方面未受损。这些数据与其他表明去甲肾上腺素（NA）参与注意力转换的证据一致，并且与内侧前额叶皮层（mPFC）内5-羟色胺（5-HT）和乙酰胆碱操作的影响形成对比。这些发现也与最近关于蓝斑-皮质去甲肾上腺素能系统功能的理论相关。
