Dipartimento di Psicologia Generale, Università di Padova, Padova, Italy.
Neuropsychologia. 2010 Nov;48(13):3934-40. doi: 10.1016/j.neuropsychologia.2010.08.022. Epub 2010 Aug 27.
Rate and severity of contralesional loss of awareness following stroke is highly variable across patients and assessment methods. We studied whether the degree of impairment for contralesional space awareness depends on the quantity of attentional resources that are available for task performance. A new computer-based paradigm was used to assess visual extinction and single-target detection rate in four right hemisphere stroke patients. In the single-task condition, they had to report only the position of the target(s) ("right", "left", or "both" sides). In the dual-task conditions, patients also performed a second task, visual or auditory, that recruited additional attentional resources. The same tasks were also performed by healthy controls and by a left hemisphere stroke patient. Patients' performance was apparently unimpaired in the single-task condition. In contrast, dramatic failures to report the left-sided target emerged in the dual-task conditions. The performance of control participants was unaffected by the dual-task manipulation, whereas the left stroke patient showed the opposite pattern (i.e., unawareness of right-sided targets). Severe contralesional space unawareness under dual-task conditions reveals that visuospatial deficits can dramatically emerge when attentional resources are consumed by a concurrent task. Apparently spared contralesional awareness may simply reflect the availability of resources that are just sufficient to perform a single-task. This finding has important implications for the assessment of contralesional space awareness following stroke, because everyday life activities are often more demanding than most of the tests adopted for diagnosing space awareness disorders.
患者之间以及评估方法之间的对侧意识丧失的频率和严重程度差异很大。我们研究了对侧空间意识的损害程度是否取决于任务执行所需的注意力资源的数量。使用一种新的基于计算机的范式来评估四名右脑卒中患者的视觉消失和单目标检测率。在单任务条件下，他们只需报告目标（“右侧”、“左侧”或“两侧”）的位置。在双重任务条件下，患者还执行第二项视觉或听觉任务，以募集额外的注意力资源。同样的任务也由健康对照者和左脑卒中患者完成。患者在单任务条件下的表现显然没有受到影响。相比之下，在双重任务条件下，他们明显无法报告左侧目标。对照组参与者的表现不受双重任务操作的影响，而左脑卒中患者则表现出相反的模式（即无法意识到右侧目标）。在双重任务条件下出现严重的对侧空间无意识，表明当注意力资源被并发任务消耗时，视觉空间缺陷可能会显著出现。对侧意识似乎没有受到影响，可能只是反映了仅足以执行单任务的资源的可用性。这一发现对卒中后对侧空间意识的评估具有重要意义，因为日常生活活动通常比用于诊断空间意识障碍的大多数测试更具挑战性。
