Cortical systems for multimodal sensory integration

越来越多的证据表明，初级感觉皮层中感觉信息的获取和初始处理可以受到另一种感觉通道的影响，这对联合多通道皮层中并行感觉加工和多通道整合的经典观点提出了挑战。例如，在人类中，初级视觉皮质可以在触觉辨别任务中被激活。此外，在正常情况下，或在实验中相互连接的动物中，听觉皮质中的神经元可以对躯体感觉或单独对视觉刺激做出反应。听觉皮质跨模式激活的证据也来自音乐家和聋人受试者的成像研究。除了正常受试者初级感觉皮质的跨模式激活外，这种激活在早期盲人受试者的听觉和触觉刺激中也清晰可见。这些发现得到了最近在啮齿动物、食肉动物和非人类灵长类动物中初级听觉和视觉皮质区域之间的直接和间接解剖学联系的证明。尽管多感官知觉和整合的重要性已经确立，但潜在的神经基础仍然不清楚。有人假设，多感觉整合主要是一个“自下而上”的过程，不同的模式汇聚在大脑皮层更高阶的多模式区域。或者，强调从多式联运区域到单式联运地区的反馈(“自上而下”)预测。虽然皮质连接已经被广泛研究，但参与特定连接的皮质细胞的精细微电路和表型通常是缺乏的。这项建议的主要目的是研究皮质轴突和参与皮层水平多感觉整合的细胞的精细结构。这将允许对解释综合知觉的生理学所需的模型系统进行详细阐述。

The classical view of parallel sensory processing and multimodal integration in association multimodal cortical areas has been challenged by the increasing evidence that the acquisition and initial processing of sensory information within primary sensory cortices can be influenced by another sensory modality. For instance, in human, the primary visual cortex can be activated during tactile discrimination tasks. In addition, neurons in the auditory cortex can respond to somatosensory or to visual stimuli alone in normal or in experimentally intermodal rewired animals. Evidence for cross-modal activation of the auditory cortex also comes from imaging studies in musicians and in deaf subjects. In addition to cross-modal activations of primary sensory cortices in normal subjects, such activation are clearly shown in auditory and tactile stimulation in early blind subjects. These findings are supported by recent demonstrations of direct and indirect anatomical connections between primary auditory and visual cortical areas in rodents, carnivores and in non-human primates. Although the importance of multisensory perception and integration is well-established, the underlying neural substrates have remained unclear. It has been hypothesized that multisensory integration is predominantly a 'bottom-up' process, where different modalities converge in higher order multimodal areas in the cerebral cortex. Alternatively, feedback ('top-down') projections from multimodal to unimodal areas have been stressed. Although cortical connectivity has been widely studied, fine microcircuitry and phenotypes of cortical cells engaged in particular connections are generally lacking. The main objectives of this proposal is to investigate the fine structure of cortical axons and of cells involved in multisensory integration at the cortical level. This will allow for the elaboration of model systems that are needed to explain the physiology of integrated perception.