Marangolo P, De Renzi E, Di Pace E, Ciurli P, Castriota-Skandenberg A
Centro Ricerche di Neuropsicologia, IRCCS S. Lucia, Rome, Italy.
Brain. 1998 Aug;121 ( Pt 8):1459-67. doi: 10.1093/brain/121.8.1459.
Following a cerebral vascular accident, a patient showed a classical disconnection syndrome: left-hand tactile anomia, apraxia and dysgraphia and right-hand constructional apraxia. What made the case unusual was the presence of hand asymmetry in the performance of some matching-to-sample tasks carried out in foveal vision. The left hand committed significantly more errors than the right hand when it was not possible to identify on a perceptual basis the stimulus that was to be matched, because it was removed (memory condition) or was indicated verbally (verbo-visual matching), or had the same name but not the same physical appearance as the match (capital and lower-case letter matching). No hand difference emerged when the stimulus remained in full view throughout the matching task (perceptual condition). The hand effect, however, was limited to colours and letters. Objects, geometrical shapes and unfamiliar faces were matched with equal proficiency by both hands under every condition of presentation. Left-hand errors also significantly outnumbered right-hand errors in sorting colours according to hue and colouring drawings. MRI showed an infarct in the left cingulate white matter that ran parallel to the trunk of the corpus callosum, and an infarct of the splenium. However, the latter did not prevent the transmission of colour and letter information between the two hemispheres, as shown by the performance on perceptual equivalence tasks and by the correct right-hand responses to stimuli projected to the left visual field. We propose that this pattern of deficit is contingent upon the specific role that the left hemisphere plays in categorizing a given colour patch as belonging to a definite colour region (red, blue, etc.) and in grapheme recognition. Without the assistance of the left side the right hemisphere lacks the benefit provided by meaning identification. In our patient the left brain did receive information from the right brain and was able to process it, but was prevented by the paracallosal lesion from transmitting what it knew to the right motor area. No hand effect emerged for objects and geometrical shapes, because their semantic memory is bilaterally represented.
脑血管意外后，一名患者表现出典型的分离综合征：左手触觉失命名、失用症和书写障碍，右手结构失用症。该病例的不同寻常之处在于，在中央凹视觉中进行的一些样本匹配任务的表现存在手的不对称性。当无法基于感知识别要匹配的刺激时，左手犯的错误明显多于右手，原因是刺激被移除（记忆条件）或通过言语指示（言语视觉匹配），或者与匹配项名称相同但外观不同（大写和小写字母匹配）。当刺激在整个匹配任务中始终处于全视野时（感知条件），未出现手的差异。然而，手的效应仅限于颜色和字母。在每种呈现条件下，双手对物体、几何形状和不熟悉面孔的匹配熟练程度相同。在根据色调对颜色进行分类和给图画上色时，左手的错误也明显多于右手。磁共振成像显示左扣带回白质有一个与胼胝体主干平行的梗死灶，以及压部梗死。然而，后者并未阻止颜色和字母信息在两个半球之间的传递，这在感知等效任务的表现以及右手对投射到左视野的刺激的正确反应中得到了体现。我们提出，这种缺陷模式取决于左半球在将给定颜色斑块归类为属于特定颜色区域（红色、蓝色等）以及在字形识别中所起的特定作用。没有左侧的协助，右半球就缺乏意义识别所提供的益处。在我们的患者中，左脑确实从右脑接收了信息并能够进行处理，但胼胝体旁病变阻止了它将所知道的信息传递到右运动区。对于物体和几何形状未出现手的效应，因为它们的语义记忆是双侧表征的。
