Horowitz Todd S, Choi Won Yung, Horvitz Jon C, Côté Lucien J, Mangels Jennifer A
Brigham & Women's Hospital and Harvard Medical School, MA, USA.
Neuropsychologia. 2006;44(10):1962-77. doi: 10.1016/j.neuropsychologia.2006.01.037. Epub 2006 Mar 31.
Patients with Parkinson's disease (PD), a degenerative disorder primarily affecting the nigrostriatal dopamine system, exhibit deficits in selecting task-relevant stimuli in the presence of irrelevant stimuli, such as in visual search tasks. However, results from previous studies suggest that these deficits may vary as a function of whether selection must rely primarily on the "bottom-up" salience of the target relative to background stimuli, or whether "top-down" information about the identity of the target is available to bias selection. In the present study, moderate-to-severe medicated PD patients and age-matched controls were tested on six visual search tasks that systematically varied the relationship between bottom-up target salience (feature search, noisy feature search, conjunction search) and top-down target knowledge (Target Known versus Target Unknown). Comparison of slope and intercepts of the RT x set size function provided information about the efficiency of search and non-search (e.g., decision, response) components, respectively. Patients exhibited higher intercepts than controls as bottom-up target salience decreased, however these deficits were disproportionately larger under Target Unknown compared to Target Known conditions. Slope differences between PD and controls were limited to the Target Unknown Conjunction condition, where patients exhibited a shallower slope in the target absent condition, indicating that they terminated search earlier. These results suggest that under conditions of high background noise, medicated PD patients were primarily impaired in decision and/or response processes downstream from the target search itself, and that the deficit was attenuated when top-down information was available to guide selection of the target signal.
帕金森病（PD）患者主要影响黑质纹状体多巴胺系统的一种退行性疾病，在存在无关刺激（如视觉搜索任务）的情况下，在选择与任务相关的刺激方面表现出缺陷。然而，先前研究的结果表明，这些缺陷可能会因选择是否必须主要依赖于目标相对于背景刺激的“自下而上”显著性，或者是否有关于目标身份的“自上而下”信息来偏向选择而有所不同。在本研究中，对中度至重度药物治疗的PD患者和年龄匹配的对照组进行了六项视觉搜索任务测试，这些任务系统地改变了自下而上的目标显著性（特征搜索、噪声特征搜索、联合搜索）和自上而下的目标知识（目标已知与目标未知）之间的关系。RT×集合大小函数的斜率和截距比较分别提供了关于搜索效率和非搜索（如决策、反应）成分的信息。随着自下而上的目标显著性降低，患者的截距高于对照组，然而，与目标已知条件相比，在目标未知条件下这些缺陷要大得多。PD患者和对照组之间的斜率差异仅限于目标未知联合条件，在该条件下，患者在目标不存在的条件下表现出较浅的斜率，表明他们更早地终止了搜索。这些结果表明，在高背景噪声条件下，药物治疗的PD患者主要在目标搜索本身下游的决策和/或反应过程中受损，并且当有自上而下的信息来指导目标信号的选择时，这种缺陷会减弱。
