Finlayson P G, Adam T J
Department of Surgery, (Otolaryngology), University of British Columbia, Vancouver, Canada.
Hear Res. 1997 Jan;103(1-2):1-18. doi: 10.1016/s0378-5955(96)00158-x.
Short-term adaptation was examined in single unit recordings from 113 superior olive neurons of anaesthetized 3- to 6-month-old Long-Evans rats. Responses to an equal intensity BF probe tone presented 1 ms after an 'adapting' BF tone were adapted by 56.3 +/- 2.6% (mean +/- S.E.) compared to responses at a 512 ms delay. The rapid decrease in discharge rate during adapting tones often approximated exponential time courses with time constants of less than 20 ms. The recovery from adaptation was exponential with time constants of 106 +/- 20.0 ms. The magnitude of adaptation and time course of recovery following monaural stimulation of binaurally excited (EE) neurons were not significantly different in both input pathways. Additionally, in 60% of EE neurons, an 'adapting' tone presented to one ear reduced subsequent responses to probe tones presented to the opposite ear. Binaural stimulation resulted in equal or greater adaptation of responses than monaural stimulation of either ear. The recovery of binaural excitatory responses generally followed a time course between recovery functions for ipsilateral and contralateral monaural stimuli. Lateral Superior Olive (LSO) neurons encode sound source location through the interaction of ipsilateral excitation and contralateral inhibition (IE). Ipsilaterally driven excitatory responses in LSO neurons exhibited the greatest magnitude of adaptation (68.5 +/- 21.1%). Adaptation of inhibition was observed in over half of IE neurons. Responses of LSO neurons to binaural BF probe stimuli were greatest immediately after a 200 ms BF 'inhibitory adapting' stimulus to the contralateral ear, and decreased with greater interstimulus delays. Responses to binaural stimulation were constant after prior binaural adaptation, when the magnitude and recovery of adaptation to monaural stimuli were similar for excitation and inhibition (8/25 IE cells). The functional significance and possible sites of adaptation processes are discussed.
在对113只3至6个月大麻醉状态的Long-Evans大鼠的上橄榄核神经元进行的单神经元记录中，研究了短期适应性。与512毫秒延迟时的反应相比，在一个“适应”的最佳频率（BF）纯音之后1毫秒呈现的同等强度BF探测纯音的反应，适应程度为56.3±2.6%（平均值±标准误）。在适应纯音期间放电率的快速下降通常近似指数时间进程，时间常数小于20毫秒。从适应状态恢复呈指数形式，时间常数为106±20.0毫秒。在双耳兴奋（EE）神经元的两个输入通路中，单耳刺激后适应的程度和恢复的时间进程没有显著差异。此外，在60%的EE神经元中，给一只耳朵呈现“适应”纯音会降低随后对给另一侧耳朵呈现的探测纯音的反应。双耳刺激导致的反应适应程度等于或大于单耳刺激。双耳兴奋性反应的恢复通常遵循同侧和对侧单耳刺激恢复函数之间的时间进程。外侧上橄榄核（LSO）神经元通过同侧兴奋和对侧抑制（IE）的相互作用来编码声源位置。LSO神经元中同侧驱动的兴奋性反应表现出最大程度的适应（68.5±21.1%）。在超过一半的IE神经元中观察到了抑制的适应。在对侧耳朵进行200毫秒BF“抑制性适应”刺激后，LSO神经元对双耳BF探测刺激的反应在紧接着时最大，并且随着刺激间隔时间延长而降低。在先前的双耳适应后，当对单耳刺激的适应程度和恢复在兴奋和抑制方面相似时（8/25个IE细胞），对双耳刺激的反应保持恒定。讨论了适应过程的功能意义和可能的位点。
