Investigation of the neural mechanisms of residual vision (blindsight) in the blind field of hemispherectomized subjects

阿兰·皮蒂托博士对神经科患者的视觉能力很感兴趣。与失去一只眼睛或视神经损伤的情况一样，枕叶皮质的破坏传统上被认为会导致对侧视野的永久性失明，可能是因为这一区域是视力不可或缺的。但是，已经描述了皮质盲区中的残余视觉功能，这种对盲区中的视觉刺激做出反应而不是有意识地体验它们的能力被称为盲视。皮蒂托博士和他的团队正在调查因治疗顽固性癫痫而将整个大脑半球切除或与其他部分断开连接的患者的残余视觉能力。这些患者是独一无二的，因为他们报告说，在手术对面的半个视野中，他们没有意识到视力。Ptito博士的研究得到了NSERC的支持，他的研究表明，这些半球切除的患者实际上拥有一些残留的视觉能力，比如检测到移动的目标，或者对两个目标(其中一个处于盲区)的反应比对完好无损的单一目标更快。皮蒂托博士和他的团队目前正在使用功能磁共振成像等脑成像技术来研究导致失明现象的神经元相关性。功能磁共振成像可以在体内可视化视觉刺激后的大脑活动，并通过扩散张量成像来帮助识别与失明相关的大脑路径。描述个体盲区中残留的视觉能力对于康复和理解视觉意识具有重要的意义。

Dr. Alain Ptito is interested in the visual abilities of neurological patients. As is the case for loss of an eye or optic nerve damage, destructions of the occipital cortex has traditionally been thought to lead to permanent blindness in the contralateral visual field presumably because this region is indispensable for vision. But, residual visual functions in a cortically blind field have been described and this ability to respond to visual stimuli in the blind visual field without consciously experiencing them has been called 'blindsight'. Dr. Ptito and his team are investigating residual visual abilities of patients in whom a whole cerebral hemisphere has been removed or disconnected from the rest of the brain for the treatment of intractable epilepsy. These patients are unique in that they report being unaware of vision in the half visual field opposite the side of their surgery. Dr. Ptito's research, supported by NSERC, has shown that these hemispherectomized patients in fact possess some residual visual abilities such as detecting moving targets or responding more quickly to two targets, one of which is in the blind field, than to a single target presented in the intact field. Dr. Ptito and his team are now investigating the neuronal correlates underlying the 'blindsight' phenomenon using brain imaging techniques such as functional magnetic resonance imaging which allows invivo visualization of cerebral activity following visual stimulation and diffusion tensor imaging to help identify the cerebral pathways involved in 'blindsight'. Depicting residual visual abilities in the blind field of individuals has important implications for rehabilitation and for understanding visual consciousness.