Neuronal Responses Below Firing Threshold for Subthreshold Cross-Modal Enhancement
Neuronal Responses Below Firing Threshold for Subthreshold Cross-Modal Enhancement
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DOI：
10.1162/neco_a_00096
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发表时间：
2011-04
影响因子：
2.9
通讯作者：
O. Hoshino
中科院分区：
文献类型：
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作者：
O. Hoshino
多感官整合(如躯体感觉-视觉、味觉-嗅觉)甚至可以发生在孤立地没有到达知觉的亚阈值刺激之间。例如，当躯体感觉(阈值以下)刺激在紧密的时空一致性内传递时，视觉(阈值以下)刺激唤起视觉感知。当体感刺激先于视觉刺激几十毫秒时，视知觉的跨模式增强最大。这种快速的调节反应与通过高阶多峰皮层区域的自上而下的机制不一致，而是低阶单峰区域之间的直接相互作用。为了阐明阈值下跨模式增强的神经元机制，我们模拟了一个神经网络模型。在该模型中，低位单峰(X，Y)和高位多峰(M)网络通过自下而上和自上而下的轴突投影相互连接。较低的网络相互横向连接。一对刺激被呈现给较低的网络，当单独呈现时，其各自的强度太弱而不能诱导显著的神经元活动(群体反应)。当跨模式刺激单独呈现给X网络时，Y网络的神经元在放电阈值以下轻微去极化。这使得Y网络能够在随后的一致刺激下做出快速(在几十毫秒内)的群体反应。如果自上而下的投影得到加强，Y网络的反应速度就会加快。我们认为，对跨模式刺激的亚阈值(非群体)反应，通过较低(主要单一感觉)区域之间的相互作用，可能是对随后的一致刺激的快速阈值(群体)反应所必需的。自上而下对跨峰增强的影响可能比预期更快，加快了对输入的反应速度，其中高阶多峰细胞对低阶单峰细胞的持续自发亚阈值兴奋可能起到积极作用。
Multisensory integration (such as somatosensation-vision, gustation-olfaction) could occur even between subthreshold stimuli that in isolation do not reach perceptual awareness. For example, when a somatosensory (subthreshold) stimulus is delivered within a close spatiotemporal congruency, a visual (subthreshold) stimulus evokes a visual percept. Cross-modal enhancement of visual perception is maximal when the somatosensory stimulation precedes the visual one by tens of milliseconds. This rapid modulatory response would not be consistent with a top-down mechanism acting through higher-order multimodal cortical areas, but rather a direct interaction between lower-order unimodal areas. To elucidate the neuronal mechanisms of subthreshold cross-modal enhancement, we simulated a neural network model. In the model, lower unimodal (X, Y) and higher multimodal (M) networks are reciprocally connected by bottom-up and top-down axonal projections. The lower networks are laterally connected with each other. A pair of stimuli was presented to the lower networks, whose respective intensities were too weak to induce salient neuronal activity (population response) when presented alone. Neurons of the Y network were slightly depolarized below firing threshold when a cross-modal stimulus was presented alone to the X network. This allowed the Y network to make a rapid (within tens of milliseconds) population response when presented with a subsequent congruent stimulus. The reaction speed of the Y network was accelerated, provided that the top-down projections were strengthened. We suggest that a subthreshold (nonpopulation) response to a cross-modal stimulus, acting through interaction between lower (primary unisensory) areas, may be essential for a rapid suprathreshold (population) response to a congruent stimulus that follows. Top-down influences on cross-modal enhancement may be faster than expected, accelerating reaction speed to input, in which ongoing-spontaneous subthreshold excitation of lower-order unimodal cells by higher-order multimodal cells may play an active role.