Peck C K, Baro J A, Warder S M
School of Optometry, University of Missouri-St. Louis 63121, USA.
Exp Brain Res. 1995;103(2):227-42. doi: 10.1007/BF00231709.
Many neurons in the deeper layers of the superior colliculus (SC) respond to multiple sensory inputs--visual, auditory, and somatic--as well as provide signals essential for saccadic eye movements to targets in different modalities. When the eyes and pinnae are in primary position, the neural map of auditory space is in rough topographic alignment with the map of visual space, and if the auditory map is based solely on headpinna coordinates, any changes in eye position in the orbit will cause misalignment of the maps. We investigated the effects of eye position on the response of sound-sensitive neurons in the SC of cats because previous work on cats and on monkeys had suggested the possibility of species differences in the representation of auditory signals in the SC. We also investigated the effects of eye position on the accuracy of saccades to auditory, visual, and bimodal stimuli. All studies were conducted in alert, trained cats with the head restrained in a fixed position. Neuronal and behavioral responses were studied during periods when the eyes were steadily directed to different positions relative to the position of the sound. Cats showed partial compensation for eye position in making saccades, regardless of the modality of the target, and they showed similar patterns of error in saccades to auditory and visual targets. These behavioral data are consistent with coding the location of visual and auditory targets in the same coordinate system. In the vast majority of intermediate-layer neurons, eye position significantly affected the number of spikes evoked by sound stimuli. For most of these neurons, changes in eye position produced significant shifts in the speaker location producing maximal response. In some neurons, eye position significantly facilitated the magnitude of neuronal response evoked by sounds from a variety of speaker locations. Because few pinna movements could be detected, in is unlikely that these changes in neuronal response could be due to changes in the position of the pinnae. Our results indicate that the deep layers of the SC contain an eye-centered representation of sound location. Because eye position did not affect the percentage of neurons exhibiting multimodal integration, visual and auditory maps appear to remain integrated in the SC even when the eyes are directed eccentrically.(ABSTRACT TRUNCATED AT 400 WORDS)
上丘（SC）深层的许多神经元对多种感觉输入（视觉、听觉和躯体感觉）都有反应，并且还为不同模态下朝向目标的眼球扫视运动提供重要信号。当眼睛和耳廓处于初始位置时，听觉空间的神经图谱与视觉空间的图谱大致呈地形对齐，如果听觉图谱仅基于头部 - 耳廓坐标，那么眼眶内眼睛位置的任何变化都会导致图谱的不对齐。我们研究了眼睛位置对猫的上丘中对声音敏感的神经元反应的影响，因为之前对猫和猴子的研究表明，上丘中听觉信号的表征可能存在物种差异。我们还研究了眼睛位置对针对听觉、视觉和双峰刺激的扫视准确性的影响。所有研究均在警觉且经过训练的猫身上进行，猫的头部被固定在一个位置。在眼睛相对于声音位置稳定地指向不同位置的时间段内，研究神经元和行为反应。无论目标的模态如何，猫在进行扫视时都表现出对眼睛位置的部分补偿，并且它们在对听觉和视觉目标的扫视中表现出相似的误差模式。这些行为数据与在同一坐标系中对视觉和听觉目标的位置进行编码一致。在绝大多数中层神经元中，眼睛位置显著影响声音刺激诱发的尖峰数量。对于大多数这些神经元，眼睛位置的变化会使产生最大反应的扬声器位置发生显著偏移。在一些神经元中，眼睛位置显著促进了来自各种扬声器位置的声音诱发的神经元反应幅度。由于几乎检测不到耳廓的运动，这些神经元反应的变化不太可能是由于耳廓位置的变化。我们的结果表明，上丘深层包含以眼睛为中心的声音位置表征。因为眼睛位置并不影响表现出多模态整合的神经元的百分比，所以即使眼睛偏心指向，视觉和听觉图谱似乎在上丘中仍保持整合。（摘要截短至400字）
