Peck C K
School of Optometry, University of Missouri St Louis 63121, USA.
Prog Brain Res. 1996;112:167-77. doi: 10.1016/s0079-6123(08)63328-2.
Previous physiological studies have demonstrated that inputs from different sensory modalities converge on individual neurons in the superior colliculus. Moreover, in anesthetized, paralyzed animals, those tectal neurons which are most directly connected to brain stem circuits mediating orienting eye and head movements are highly likely to exhibit significant integration of sensory inputs from multiple modalities. The purpose of the present study was to examine the responses of tectal neurons in the alert cat when visual and auditory stimuli were presented as targets for ocular fixation and orienting responses. For comparison to previous work in anesthetized, paralyzed animals, we also examined the responses of tectal neurons to the presentation of these stimuli during periods when the cats voluntarily maintained their eyes near primary position in the absence of a fixation target. Under these conditions, there were significant differences between the strength of the response to the simultaneous presentation of visual and auditory targets and the strength of response to the most effective unimodal stimulus in about 40% of the cells tested. Many tectal neurons also responded tonically during fixation of visual, auditory and bimodal targets, and some of these also exhibited significant bimodal interactions. However, among individual neurons which responded phasically to stimulus onset or offset and tonically during fixation, there was only a weak correlation between the extent of bimodal interaction under the two conditions. Finally, among saccade-related neurons, the magnitude of saccade-related activity was only slightly affected when a biomodal target was used to elicit a saccade, and the extent of bimodal interactions was generally less than was found for the onset and offset of sensory targets. Such multisensory interactions can be significant for behavior. Indeed, simply using a multisensory target has been shown to influence the probability and latency of overt orienting responses, although the extent of such effects will probably vary across both tasks and stimulus conditions. Strong multi-sensory interactions are most likely to occur when low intensity stimuli are used. Our use of moderately intense sensory stimuli probably accounts for our finding of a relatively small percentage of cells in which bimodal responses were greater than the sum of their unimodal responses.
先前的生理学研究表明，来自不同感觉模态的输入会聚于上丘的单个神经元。此外，在麻醉、瘫痪的动物中，那些与介导眼和头部定向运动的脑干回路最直接相连的顶盖神经元极有可能表现出来自多种模态的感觉输入的显著整合。本研究的目的是在视觉和听觉刺激作为眼注视和定向反应的目标呈现时，检查清醒猫的顶盖神经元的反应。为了与先前在麻醉、瘫痪动物身上的工作进行比较，我们还检查了在猫在没有注视目标的情况下自愿将眼睛保持在原位置附近的时间段内，顶盖神经元对这些刺激呈现的反应。在这些条件下，在大约40%的测试细胞中，对视觉和听觉目标同时呈现的反应强度与对最有效的单模态刺激的反应强度之间存在显著差异。许多顶盖神经元在注视视觉、听觉和双模态目标时也会持续放电，其中一些还表现出显著的双模态相互作用。然而，在对刺激开始或结束进行相位反应并在注视期间持续放电的单个神经元中，两种条件下双模态相互作用的程度之间只有微弱的相关性。最后，在与扫视相关的神经元中，当使用双模态目标引发扫视时，与扫视相关的活动幅度仅受到轻微影响，并且双模态相互作用的程度通常小于感觉目标开始和结束时的情况。这种多感觉相互作用对行为可能很重要。事实上，已经证明仅仅使用多感觉目标就会影响明显定向反应的概率和潜伏期，尽管这种影响的程度可能会因任务和刺激条件的不同而有所变化。当使用低强度刺激时，最有可能发生强烈的多感觉相互作用。我们使用中等强度的感觉刺激可能解释了我们的发现，即只有相对较小比例的细胞中双模态反应大于其单模态反应之和。
