摘要目的 研究汉字左半错读和左视野失读的神经机制.方法 对1例左腹内侧枕颞区和左胼胝体压部脑梗死致阅读障碍的患者进行一系列神经心理学检查,包括注视汉字中点的速视朗读、左右分视野速视朗读,同时采用高分辨率三维稳态毁损梯度回返采集序列(3D-SPGR)磁共振成像(MRI)、弥散张量纤维束示踪成像(DTT),观察患者大脑皮质和神经通路受损细节.结果 受试患者表现出汉字左半错读和左视野失读.高分辨率脑结构像显示病灶累及左腹内侧枕颞皮质,但左中部梭状回的"视觉词形区"保留.DTT显示胼胝体压部-枕大钳纤维束通路中断.结论 胼胝体压部通路损害导致汉字视觉信息传递中断从而出现汉字左半错读、左视野失读.

abstractsObjective To investigate the underlying neural mechanism of left hemiparalexia and left hemialexia in reading Chinese characters. Methods A patient with reading disorders caused by brain infarctions at the left ventralis medialis occipitotemporal lobe and the splenium of the corpus callosum was studied. A series of neuropsychological tests, such as reading Chinese characters presented in the central foveal field or in the left and right half of the foveal field, were conducted with the patient, and neuroimaging techniques including high spatial resolution 3D-MRI and diffusion tensor tractography (DTT) were used to examine whether or not there were lesions of the neural pathway. Results The patient showed left hemiparalexia, which was characterized by making substitution or omission mistakes, mostly in the left parts of Chinese characters, and also left hemialexia(alexia for characters presented in left visual field). 3D-MRI demonstrated infarctions in the left ventral mesial occipitotemporal area and in the left side of the splenium of the corpus callosum. The left lateral mid-fusiform cortex, which has been identified as the visual word form area(VWFA), was almost intact. DTT indicated the major forceps fibers running through the splenium were all disconnected due to the infarction of the left splenium. Conclusion As a result of disruption of the splemium-major forceps pathway, visual character information in the left visual field which is initially projected to the right occipital cortex cannot be transferred from the right visual cortex to the left VWFA. This mechanism of left hemiparalexia and left hemialexia in reading Chinese characters is similar to that in reading English words.