Büchel C, Price C, Frackowiak R S, Friston K
Wellcome Department of Cognitive Neurology, Institute of Neurology, London, UK.
Brain. 1998 Mar;121 ( Pt 3):409-19. doi: 10.1093/brain/121.3.409.
A key issue in developmental neuroscience is the role of activity-dependent mechanisms in the epigenetic induction of functional organization in visual cortex. Ocular blindness and ensuing visual deprivation is one of the rare models available for the investigation of experience-dependent cortical reorganization in man. In a PET study we demonstrate that congenitally blind subjects show task-specific activation of extrastriate visual areas and parietal association areas during Braille reading, compared with auditory word processing. In contrast, blind subjects who lost their sight after puberty show additional activation in the primary visual cortex with the same tasks. Studies in blind-raised monkeys show that crossmodal responses in extrastriate areas can be elicited by somatosensory stimulation. This is consistent with the crossmodal extrastriate activations elicited by tactile processing in our congenitally blind subjects. Since primary visual cortex does not show crossmodal responses in primate studies, the differential activation in late and congenitally blind subjects highlights the possibility of reciprocal activation by visual imagery in subjects with early visual experience.
发育神经科学中的一个关键问题是，依赖活动的机制在视觉皮层功能组织的表观遗传诱导中所起的作用。眼盲及随之而来的视觉剥夺是可用于研究人类经验依赖性皮层重组的少数模型之一。在一项正电子发射断层扫描（PET）研究中，我们证明，与听觉单词处理相比，先天性失明受试者在盲文阅读过程中，纹外视觉区和顶叶联合区会出现特定任务的激活。相比之下，青春期后失明的受试者在执行相同任务时，初级视觉皮层会出现额外激活。对自幼失明的猴子的研究表明，体感刺激可引发纹外区域的跨模态反应。这与我们先天性失明受试者在触觉处理时引发的跨模态纹外激活是一致的。由于在灵长类动物研究中初级视觉皮层未表现出跨模态反应，晚期失明和先天性失明受试者的差异激活凸显了有早期视觉经验的受试者通过视觉意象进行相互激活的可能性。
