明视人听词分类任务时的视皮层激活——跨感觉通道的新证据

近期的脑成像研究在盲人等感官缺陷被试者身上发现了感觉替换现象，即传统上认为仅对单一感觉通道刺激反应的皮层区域也参与其他感觉通道的信息加工．类似的效应在感觉剥夺(蒙住眼睛)的明视人被试中也被观察到，提示脑内可能预存着多感觉交互作用的神经通路．通常认为，上述神经通路在常态的人脑中是以潜伏形式存在的，只有当感觉剥夺时才显露出来或得到加强．但是，感觉剥夺是否是该类神经通路发挥作用的必要条件，已有的研究尚缺乏确切的证据．采用统计力度较强的实验设计，给未蒙眼明视人被试听觉呈现一组名词，要求其对听到的每一个词语做出是人工物体还是自然物体的语义判断．对同步采集的功能磁共振信号进行统计分析，观察到视皮层脑区有显著激活．这些结果表明，跨感觉通道的神经通路在未实施感觉剥夺的条件下依然能够显示出来，因而在常态人脑中也不是完全以潜伏形式存在的．上述研究为建立多感觉交互作用神经机制的具体理论模型提供了一个约束条件．

Visual cortical activation during auditory word categorization: evidence for multiple sensory interaction from normal sighted participants

Sensory substitution has been reported in recent brain imaging studies with blind people and others with sensory deficits so that sensory cortical regions traditionally considered unimodal respond to stimulation from other sensory modalities. Similar effects are also found for normal sighted people with sensory deprivation (blindfolded), indicative of pre-existing neuronal pathways for multiple sensory interactions. Such pathways are considered latent in that they only become unmasked or potentiated in the event of sensory deafferentation, although whether sensory deprivation is necessary to expose these pathways is unclear due to inconclusive evidence. With a relatively strong power in experimental design, visual cortical activation was observed when normal sighted participants (not blindfolded) judged whether auditorily-presented nouns referred to artificial or natural objects. The results suggest the above mentioned pathways can be exposed without sensory deafferentation and therefore are not totally latent. This establishes a boundary condition constraining theoretical models for the neural basis of multiple sensory interactions.