Stein B E
Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Winston-Salem, North Carolina, 27157-1010, USA.
Exp Brain Res. 1998 Nov;123(1-2):124-35. doi: 10.1007/s002210050553.
The ability to integrate information from different sensory systems is a fundamental characteristic of the brain. Because different bits of information are derived from different sensory channels, their synthesis markedly enhances the detection and identification of external stimuli. The neural substrate for such "multisensory" integration is provided by neurons that receive convergent input from two or more sensory modalities. Many such multisensory neurons are found in the superior colliculus (SC), a midbrain structure that plays a significant role in overt attentive and orientation behaviors. The various principles governing the integration of visual, auditory, and somatosensory inputs in SC neurons have been explored in several species. Thus far, the evidence suggests a remarkable conservation of integrative features during vertebrate evolution. One of the most robust of these principles is based on spatial relationships: a striking enhancement in activity is induced in a multisensory neuron when two different sensory stimuli (e.g., visual and auditory) are in spatial concordance, whereas a profound response depression can be induced when these cues are spatially discordant. The most extensive physiological observations have been made in cat, and in this species the same principles that have been shown to govern multisensory integration at the level of the individual SC neuron have also been shown to govern overt attentive and orientation responses to multisensory stimuli. Most surprising, however, is the critical role played by association (i.e. anterior ectosylvian) cortex in facilitating these midbrain processes. In the absence of the modulating corticotectal influences, multisensory SC neurons in cat are unable to integrate the different sensory cues converging upon them in an adult-like fashion, and are unable to mediate overt multisensory behaviors. This situation appears quite similar to that observed during early postnatal life. When multisensory SC neurons first appear, they are able to respond to multiple sensory inputs but are unable to synthesize these inputs to significantly enhance or degrade their responses. During ontogeny, individual multisensory neurons develop this capacity abruptly, but at very different ages, until the mature population condition is reached after several postnatal months. It appears likely that the abrupt onset of this capacity in any individual SC neuron reflects the maturation of inputs from anterior ectosylvian cortex. Presumably, the functional coupling of cortex with an individual SC neuron is essential to initiate and maintain that neuron's capability for multisensory integration throughout its life.
整合来自不同感觉系统信息的能力是大脑的一项基本特征。由于不同的信息片段源自不同的感觉通道，它们的整合显著增强了对外部刺激的检测和识别。这种“多感觉”整合的神经基础是由接收来自两种或更多感觉模态的汇聚输入的神经元提供的。许多这样的多感觉神经元存在于上丘（SC）中，上丘是一种中脑结构，在明显的注意力和定向行为中起重要作用。在几个物种中已经探索了支配上丘神经元中视觉、听觉和体感输入整合的各种原则。到目前为止，证据表明在脊椎动物进化过程中整合特征有显著的保守性。其中最有力的原则之一基于空间关系：当两种不同的感觉刺激（如视觉和听觉）在空间上一致时，多感觉神经元的活动会显著增强，而当这些线索在空间上不一致时，则会引起深度的反应抑制。在猫身上进行了最广泛的生理学观察，在这个物种中，已证明支配单个上丘神经元水平的多感觉整合的相同原则也支配对多感觉刺激的明显注意力和定向反应。然而，最令人惊讶的是联合（即外侧前沟）皮层在促进这些中脑过程中所起的关键作用。在没有调节性皮质 - 上丘影响的情况下，猫的多感觉上丘神经元无法以成年样的方式整合汇聚到它们身上的不同感觉线索，并且无法介导明显的多感觉行为。这种情况似乎与出生后早期观察到的情况非常相似。当多感觉上丘神经元首次出现时，它们能够对多种感觉输入做出反应，但无法整合这些输入以显著增强或降低它们的反应。在个体发育过程中，单个多感觉神经元突然发展出这种能力，但在非常不同的年龄，直到出生后几个月达到成熟状态。任何单个上丘神经元这种能力的突然出现似乎反映了来自外侧前沟皮层输入的成熟。据推测，皮层与单个上丘神经元的功能耦合对于在其整个生命过程中启动和维持该神经元的多感觉整合能力至关重要。
