Meredith M A, Stein B E
J Neurophysiol. 1986 Sep;56(3):640-62. doi: 10.1152/jn.1986.56.3.640.
Convergence of inputs from different sensory modalities onto individual neurons is a phenomenon that occurs widely throughout the brain at many phyletic levels and appears to represent a basic neural mechanism by which an organism integrates complex environmental stimuli. In the present study, neurons in the superior colliculus (SC) were used as a model to examine how single neurons deal with simultaneous cues from different sensory modalities (e.g., visual, auditory, somatosensory). The functional result of multisensory convergence on an individual cell was determined by comparing the responses evoked from it by a combined-modality (multimodal) stimulus with those elicited by each (unimodal) component of that stimulus presented alone. Superior colliculus cells exhibited profound changes in their activity when individual sensory stimuli were combined. These "multisensory interactions" were found to be widespread among deep laminae cells and fell into one of two functional categories: response enhancement, characterized by a significant increase in the number of discharges evoked; and response depression, characterized by a significant decrease in the discharges elicited. Multisensory response interactions most often reflected a multiplicative, rather than summative, change in activity. Their absolute magnitude varied from cell to cell and, when stimulus conditions were altered, within the same cell. However, the percentage change of enhanced interactions was generally inversely related to the vigor of the responses that could be evoked by presenting each unimodal stimulus alone and suggest that the potential for response amplification was greatest when responses evoked by individual stimuli were weakest. The majority of cells exhibiting multi-sensory characteristics were demonstrated to have descending efferent projections and thus had access to premotor and motor areas of the brain stem and spinal cord involved in SC-mediated attentive and orientation behaviors. These data show that multisensory convergence provides the descending efferent cells of the SC with a dynamic response character. The responses of these cells and the SC-mediated behaviors that they underlie need not be immutably tied to the presence of any single stimulus, but can vary in response to the particular complex of stimuli present in the environment at any given moment.
来自不同感觉模态的输入汇聚到单个神经元上，这一现象在整个大脑的许多系统发育水平上广泛存在，似乎代表了一种基本的神经机制，生物体通过该机制整合复杂的环境刺激。在本研究中，上丘（SC）中的神经元被用作模型，以研究单个神经元如何处理来自不同感觉模态（例如视觉、听觉、体感）的同时性线索。通过比较联合模态（多模态）刺激诱发的反应与单独呈现该刺激的每个（单模态）成分诱发的反应，来确定多感觉汇聚对单个细胞的功能结果。当单个感觉刺激组合时，上丘细胞的活动表现出深刻变化。这些“多感觉相互作用”在深层细胞中广泛存在，并分为两种功能类别之一：反应增强，其特征是诱发的放电数量显著增加；反应抑制，其特征是诱发的放电显著减少。多感觉反应相互作用最常反映活动的乘法变化，而非加法变化。它们的绝对幅度因细胞而异，并且在刺激条件改变时，同一细胞内也会变化。然而，增强相互作用的百分比变化通常与单独呈现每个单模态刺激时诱发的反应强度呈负相关，这表明当单个刺激诱发的反应最弱时，反应放大的潜力最大。大多数表现出多感觉特征的细胞被证明具有下行传出投射，因此可以连接到参与SC介导的注意力和定向行为的脑干和脊髓的运动前区和运动区。这些数据表明，多感觉汇聚为SC的下行传出细胞提供了动态反应特性。这些细胞的反应以及它们所支持的SC介导的行为不必与任何单一刺激的存在固定相关，而是可以根据环境中在任何给定时刻存在的特定刺激复合体而变化。
