Stanford Terrence R, Quessy Stephan, Stein Barry E
Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA.
J Neurosci. 2005 Jul 13;25(28):6499-508. doi: 10.1523/JNEUROSCI.5095-04.2005.
It is well established that superior colliculus (SC) multisensory neurons integrate cues from different senses; however, the mechanisms responsible for producing multisensory responses are poorly understood. Previous studies have shown that spatially congruent cues from different modalities (e.g., auditory and visual) yield enhanced responses and that the greatest relative enhancements occur for combinations of the least effective modality-specific stimuli. Although these phenomena are well documented, little is known about the mechanisms that underlie them, because no study has systematically examined the operation that multisensory neurons perform on their modality-specific inputs. The goal of this study was to evaluate the computations that multisensory neurons perform in combining the influences of stimuli from two modalities. The extracellular activities of single neurons in the SC of the cat were recorded in response to visual, auditory, and bimodal visual-auditory stimulation. Each neuron was tested across a range of stimulus intensities and multisensory responses evaluated against the null hypothesis of simple summation of unisensory influences. We found that the multisensory response could be superadditive, additive, or subadditive but that the computation was strongly dictated by the efficacies of the modality-specific stimulus components. Superadditivity was most common within a restricted range of near-threshold stimulus efficacies, whereas for the majority of stimuli, response magnitudes were consistent with the linear summation of modality-specific influences. In addition to providing a constraint for developing models of multisensory integration, the relationship between response mode and stimulus efficacy emphasizes the importance of considering stimulus parameters when inducing or interpreting multisensory phenomena.
上丘（SC）的多感觉神经元整合来自不同感官的线索，这一点已得到充分证实；然而，产生多感觉反应的机制却知之甚少。先前的研究表明，来自不同模态（如听觉和视觉）的空间一致线索会产生增强的反应，并且对于效果最差的模态特异性刺激的组合，相对增强最大。尽管这些现象有充分的文献记载，但对其潜在机制却知之甚少，因为没有研究系统地研究多感觉神经元对其模态特异性输入所执行的操作。本研究的目的是评估多感觉神经元在整合来自两种模态的刺激影响时所执行的计算。记录猫的上丘中单个神经元对视觉、听觉和视觉 - 听觉双峰刺激的细胞外活动。对每个神经元在一系列刺激强度下进行测试，并根据单感觉影响简单相加的零假设评估多感觉反应。我们发现，多感觉反应可能是超相加的、相加的或次相加的，但这种计算强烈地由模态特异性刺激成分的效力决定。超相加性在接近阈值的刺激效力的受限范围内最为常见，而对于大多数刺激，反应幅度与模态特异性影响的线性相加一致。除了为开发多感觉整合模型提供一个约束条件外，反应模式与刺激效力之间的关系强调了在诱导或解释多感觉现象时考虑刺激参数的重要性。
