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

Alain Ptito博士对神经病患者的视觉能力感兴趣。 就像失去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，大概是因为这个区域对视觉是不可或缺的。 但是，皮质盲场中的残余视觉功能已经被描述，并且这种在盲视野中对视觉刺激做出反应而没有有意识地经历它们的能力被称为“盲视”。 Ptito博士和他的团队正在研究为治疗顽固性癫痫而将整个大脑半球从大脑其余部分切除或断开的患者的剩余视觉能力。 这些患者的独特之处在于，他们报告在手术侧对面的半个视野中没有视觉。 Ptito博士的研究得到了NSERC的支持，研究表明，这些大脑半球切除的患者实际上拥有一些残余的视觉能力，例如检测移动目标或对两个目标（其中一个在盲场中）的反应比对完整场中的单个目标的反应更快。 Ptito博士和他的团队现在正在使用脑成像技术研究“盲视”现象背后的神经元相关性，例如功能性磁共振成像，它允许在视觉刺激和扩散张量成像之后对大脑活动进行体内可视化，以帮助识别与“盲视”有关的大脑通路。 描绘个体盲场中的残余视觉能力对于康复和理解视觉意识具有重要意义。

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.