David A S, Cutting J C
King's College Hospital, London, UK.
Schizophr Res. 1993 Jan;8(3):263-71. doi: 10.1016/0920-9964(93)90025-e.
Divided visual field tasks were given to normal subjects, and patients with schizophrenia and affective disorder, to investigate hemisphere differences in the visual processing of standardised pictorial stimuli. There were two conditions: in the first, subjects were asked to decide whether a common entity represented by a picture was living or non-living, a task involving a categorical judgement based on semantic information; a left hemisphere task. In the second condition, subjects judged whether these depictions represented entities which were bigger or smaller than a cat; a right hemisphere task requiring visual imagery to compare spatial dimensions. It was found that the patient groups, while showing slower reaction time (RT) overall, both displayed a right hemisphere (RH) advantage on the imagery task. Furthermore, the schizophrenics' RHs showed the normal relationship between closeness of size comparison and RT, additional evidence that the visual imagery mechanism is intact. However, these patients failed to show the expected left hemisphere advantage on the visual-semantic task. There was a suggestion that performance on the semantic task was related to the experience of vivid imagery in normals and visual hallucinations in the schizophrenics. The possible contribution of hemispheric imbalance in the production of visual hallucinations from a disordered semantic system is discussed.
对正常受试者、精神分裂症患者和情感障碍患者进行了视野分割任务，以研究标准化图片刺激视觉处理中的半球差异。有两种情况：第一种情况，受试者被要求判断图片所代表的常见实体是有生命的还是无生命的，这是一项基于语义信息的分类判断任务，属于左半球任务。在第二种情况下，受试者判断这些描绘所代表的实体是比猫大还是小；这是一项右半球任务，需要视觉表象来比较空间维度。研究发现，患者组虽然总体反应时间（RT）较慢，但在表象任务上均表现出右半球（RH）优势。此外，精神分裂症患者的右半球在大小比较的接近程度与反应时间之间呈现出正常的关系，这进一步证明视觉表象机制是完整的。然而，这些患者在视觉语义任务上未能表现出预期的左半球优势。有迹象表明，语义任务的表现与正常人的生动表象体验以及精神分裂症患者的视幻觉有关。本文讨论了半球失衡在语义系统紊乱导致视幻觉产生过程中的可能作用。
