Dalrymple Kirsten A, Kingstone Alan, Barton Jason J S
Department of Psychology, University of British Columbia, Vancouver, BC, Canada.
Neuropsychologia. 2007 Mar 2;45(4):871-5. doi: 10.1016/j.neuropsychologia.2006.07.013. Epub 2006 Sep 14.
Patients with simultanagnosia often demonstrate 'local capture', meaning that they identify only the local elements of stimuli that contain a hierarchy of both local and global structures. Recent studies, however, have found that these patients may implicitly process the global form. We examined the general applicability of the concept of local capture, and specifically whether the global level of stimuli can be explicitly reported by patients with simultanagnosia. We tested a patient with simultanagnosia with globally biased stimuli such as hierarchical Arcimboldo faces and small, dense Navon letters. With Arcimboldo faces our patient often reported only the face and not the local elements--the first demonstration of global rather than local capture. With Navon letters, the patient's ability to report the global letter varied with stimulus density and inversely with stimulus size, so that local capture was found only with large and sparse stimuli. With both faces and letters, the likelihood of global capture by the patient was related to the ease of global reporting in controls, as indexed by their reaction times. This suggests that the patient's global perception is influenced by the same factors operating in healthy individuals. We conclude that attentional capture in simultanagnosia can be either global or local. Capture likely occurs because of a pathological restriction and/or rigidity of attention, but the type of capture depends upon the competitive balance between global and local salience.
患有同时失认症的患者常常表现出“局部捕获”，这意味着他们只能识别包含局部和全局结构层次的刺激的局部元素。然而，最近的研究发现，这些患者可能会隐性地处理全局形式。我们研究了局部捕获概念的普遍适用性，特别是患有同时失认症的患者是否能够明确报告刺激的全局水平。我们用全局偏向性刺激对一名患有同时失认症的患者进行了测试，比如分层的阿尔钦博尔多面孔和小而密集的纳冯字母。对于阿尔钦博尔多面孔，我们的患者常常只报告面孔而不是局部元素——这是全局而非局部捕获的首次证明。对于纳冯字母，患者报告全局字母的能力随刺激密度而变化，与刺激大小呈反比，因此仅在大而稀疏的刺激中发现局部捕获。对于面孔和字母，患者全局捕获的可能性与对照组中全局报告的难易程度相关，以他们的反应时间为指标。这表明患者的全局感知受到健康个体中相同因素的影响。我们得出结论，同时失认症中的注意力捕获可以是全局的或局部的。捕获可能是由于注意力的病理性限制和/或僵化而发生的，但捕获的类型取决于全局和局部显著性之间的竞争平衡。
