Middlebrooks J C
J Neurophysiol. 1987 Mar;57(3):688-701. doi: 10.1152/jn.1987.57.3.688.
This study explores the mechanisms of auditory spatial tuning in the superior colliculus of the anesthetized cat by correlating spatial tuning within specific regions of space with particular types of binaural interaction. The auditory spatial tuning of units was measured using a movable, broad-band stimulus presented in a free sound field. The contribution of each ear to the response of a unit was identified by acutely plugging one or the other ear. Every unit became largely or entirely unresponsive when a foam-rubber earplug was placed in the ear contralateral to the recording site. Thus, every unit exhibited an excitatory or facilitatory influence from the contralateral ear. A plug placed in the ipsilateral ear had different effects on different units. For half of the units (16/32), an ipsilateral earplug produced increases in the sizes of the units' receptive fields and increases in the magnitudes of their responses to stimuli presented from most locations. Thus, these units exhibited inhibition from the ipsilateral ear. Another class of units (9/32) exhibited ipsilateral facilitation, in that an ipsilateral earplug caused decreases in the sizes of the units' receptive fields and prominent decreases in their response magnitudes. For the remaining units (7/32), an ipsilateral earplug resulted in decreases in the sizes of the units' receptive fields, but produced both decreases in the responses of units to stimuli presented in their best areas and increases in the responses to stimuli presented away from the best areas. Thus these units exhibited mixed facilitatory and inhibitory ipsilateral influences. The influence of an ipsilateral earplug on a unit's response tended to correlate with its spatial tuning. The region of space within which a sound source was most effective in activating a unit was its "best area". The best areas of units exhibiting ipsilateral inhibition were located furthest peripherally, those of units showing ipsilateral facilitation were located furthest frontally, and the best areas of units showing mixed ipsilateral influences were located in an intermediate area. The frequency tuning of units measured using a free-field tone source also tended to correlate with the locations of their best areas. Half of the units tested (27/54) responded to tones of the sound pressure levels (SPLs) that were used (up to 50 dB SPL).(ABSTRACT TRUNCATED AT 400 WORDS)
本研究通过将特定空间区域内的空间调谐与特定类型的双耳相互作用相关联，探索麻醉猫上丘的听觉空间调谐机制。使用在自由声场中呈现的可移动宽带刺激来测量神经元的听觉空间调谐。通过急性堵塞一只耳朵或另一只耳朵来确定每只耳朵对神经元反应的贡献。当在与记录部位对侧的耳朵中放置泡沫橡胶耳塞时，每个神经元在很大程度上或完全无反应。因此，每个神经元都表现出来自对侧耳朵的兴奋性或易化性影响。在同侧耳朵中放置耳塞对不同的神经元有不同的影响。对于一半的神经元（16/32），同侧耳塞使神经元感受野的大小增加，并且对来自大多数位置的刺激的反应幅度增加。因此，这些神经元表现出来自同侧耳朵的抑制作用。另一类神经元（9/32）表现出同侧易化作用，即同侧耳塞使神经元感受野的大小减小，并且其反应幅度显著减小。对于其余的神经元（7/32），同侧耳塞导致神经元感受野的大小减小，但使神经元对在其最佳区域呈现的刺激的反应减小，而对在远离最佳区域呈现的刺激的反应增加。因此，这些神经元表现出同侧易化和抑制的混合影响。同侧耳塞对神经元反应的影响往往与其空间调谐相关。声源在其中最有效地激活神经元的空间区域是其“最佳区域”。表现出同侧抑制的神经元的最佳区域位于最外周，表现出同侧易化的神经元的最佳区域位于最前方，表现出同侧混合影响的神经元的最佳区域位于中间区域。使用自由场纯音声源测量的神经元的频率调谐也往往与其最佳区域的位置相关。测试的一半神经元（27/54）对所使用的声压级（SPL）的纯音有反应（高达50 dB SPL）。（摘要截断于400字）
