Burnett L R, Stein B E, Chaponis D, Wallace M T
Department of Neurobiology and Anatomy, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA.
Neuroscience. 2004;124(3):535-47. doi: 10.1016/j.neuroscience.2003.12.026.
The general involvement of the superior colliculus (SC) in orientation behavior and the striking parallels between the multisensory responses of SC neurons and overt orientation behaviors have led to assumptions that these neural and behavioral changes are directly linked. However, deactivation of two areas of cortex which also contain multisensory neurons, the anterior ectosylvian sulcus and rostral lateral suprasylvian sulcus have been shown to eliminate multisensory orientation behaviors, suggesting that this behavior may not involve the SC. To determine whether the SC contributes to this behavior, cats were tested in a multisensory (i.e. visual-auditory) orientation task before and after excitotoxic lesions of the SC. For unilateral SC lesions, modality-specific (i.e. visual or auditory) orientation behaviors had returned to pre-lesion levels after several weeks of recovery. In contrast, the enhancements and depressions in behavior normally seen with multisensory stimuli were severely compromised in the contralesional hemifield. No recovery of these behaviors was observed within the 6 month testing period. Immunohistochemical labeling of the SC revealed a preferential loss of parvalbumin-immunoreactive pyramidal neurons in the intermediate layers, a presumptive multisensory population that targets premotor areas of the brainstem and spinal cord. These results highlight the importance of the SC for multisensory behaviors, and suggest that the multisensory orientation deficits produced by cortical lesions are a result of the loss of cortical influences on multisensory SC neurons.
上丘（SC）广泛参与定向行为，且SC神经元的多感官反应与明显的定向行为之间存在显著相似之处，这使得人们认为这些神经变化和行为变化直接相关。然而，研究表明，失活同样包含多感官神经元的两个皮质区域，即外侧前沟和嘴侧外侧上沟，会消除多感官定向行为，这表明这种行为可能并不涉及上丘。为了确定上丘是否对这种行为有作用，在对上丘进行兴奋性毒性损伤前后，对猫进行了多感官（即视觉-听觉）定向任务测试。对于单侧上丘损伤，在恢复几周后，特定模态（即视觉或听觉）的定向行为已恢复到损伤前水平。相比之下，通常在多感官刺激下出现的行为增强和减弱在对侧半视野中严重受损。在6个月的测试期内未观察到这些行为的恢复。对上丘的免疫组织化学标记显示，中间层中钙结合蛋白免疫反应性锥体神经元优先缺失，这是一群假定的多感官神经元，其目标是脑干和脊髓的运动前区。这些结果突出了上丘对多感官行为的重要性，并表明皮质损伤产生的多感官定向缺陷是皮质对多感官上丘神经元影响丧失的结果。
