Impaired spatial working memory across saccades contributes to abnormal search in parietal neglect
Impaired spatial working memory across saccades contributes to abnormal search in parietal neglect
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DOI：
10.1093/brain/124.5.941
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发表时间：
2001-05-01
期刊：
影响因子：
14.5
通讯作者：
Kennard, C
中科院分区：
文献类型：
--
作者：
Husain, M;Mannan, S;Kennard, C
人类在右顶叶损伤后对左空间的视觉忽视涉及注意力的侧向偏倚，这在许多搜索任务中都很明显。我们假设顶叶忽视也可能涉及在视觉搜索过程中无法记住已经检查过的位置：在扫视中保留搜索过的位置的损害。使用一种新的范式，我们在搜索过程中监测凝视，同时探查观察者是否判断他们找到了一个新的目标，或者判断他们是在重新注视先前检查过的目标。一个病人左忽视局灶性右顶叶梗死反复重新固定右位置。关键的是，他常常忘记这些地点已经被搜索过了，以一种异常的速度把旧目标当作新发现。相比之下，年龄匹配的健康对照组很少重新固定目标，更很少将旧目标误认为新目标。在不同的情况下，顶叶病人犯这种错误的频率与他被忽视的严重程度相关。对照实验表明，在非搜索任务中不存在知觉定位缺陷。这些结果表明，在顶叶忽视中，除了横向空间偏误之外，在整个扫视中还存在保留搜索位置的缺陷。此外，前者的缺陷加剧了后者，以至于患者没有意识到他们偏向的右侧位置在之前的注视中已经被检查过了，因此，他们反复地跳回它们。这两种缺陷的结合（侧向偏误加上保留已经搜索过的位置的缺陷）可以解释以顶叶忽视为特征的搜索病理模式：为什么右边的刺激会被递归地重新检查，就像第一次搜索一样，因此为什么左边的刺激即使有无限的观看时间也会继续被忽略。这些建议与最近的电生理和功能成像数据一致，表明后顶叶参与了扫视目标位置的保留。
Visual neglect of left space following right parietal damage in humans involves a lateral bias in attention, apparent in many search tasks. We hypothesized that parietal neglect may also involve a failure to remember which locations have already been examined during visual search: an impairment in retaining searched locations across saccades. Using a new paradigm, we monitored gaze during search, while simultaneously probing whether observers judged they had found a new target, or judged instead that they were re-fixating a previously examined target. A patient with left neglect following focal right parietal infarction repeatedly re-fixated right locations. Critically, he often failed to remember that these locations had already been searched, treating old targets as new discoveries at an abnormal rate. In comparison, healthy age-matched control subjects rarely re-fixated targets, and mistook old targets as new targets even more rarely. The frequency of such mistakes in the parietal patient, for different conditions, correlated with the severity of his neglect. Control experiments indicated no perceptual localization deficit in non-search tasks. These results suggest a deficit in retaining searched locations across saccades in parietal neglect, in addition to the lateral spatial bias. Moreover, the former deficit exacerbates the latter, such that patients do not realize that the rightward locations favoured by their bias have already been examined during previous fixations and, for this reason, they saccade back to them repeatedly. The combination of the two deficits (a lateral bias plus a deficit in retaining locations already searched) may thus explain the pathological pattern of search that characterizes parietal neglect: why stimuli on the right are re-examined recursively, as if being searched for the first time, and hence why stimuli on the left continue to be ignored even with unlimited viewing time. These proposals accord with recent electrophysiological and functional imaging data, demonstrating posterior parietal involvement in the retention of target locations across saccades.