Alluri Rishi K, Rose Gary J, Hanson Jessica L, Leary Christopher J, Vasquez-Opazo Gustavo A, Graham Jalina A, Wilkerson Jeremy
Department of Biology, University of Utah, Salt Lake City, UT 84112;
Department of Biology, University of Mississippi, Oxford, MS 38677;
Proc Natl Acad Sci U S A. 2016 Mar 29;113(13):E1927-35. doi: 10.1073/pnas.1520971113. Epub 2016 Mar 14.
Sound duration is important in acoustic communication, including speech recognition in humans. Although duration-selective auditory neurons have been found, the underlying mechanisms are unclear. To investigate these mechanisms we combined in vivo whole-cell patch recordings from midbrain neurons, extraction of excitatory and inhibitory conductances, and focal pharmacological manipulations. We show that selectivity for short-duration stimuli results from integration of short-latency, sustained inhibition with delayed, phasic excitation; active membrane properties appeared to amplify responses to effective stimuli. Blocking GABAA receptors attenuated stimulus-related inhibition, revealed suprathreshold excitation at all stimulus durations, and decreased short-pass selectivity without changing resting potentials. Blocking AMPA and NMDA receptors to attenuate excitation confirmed that inhibition tracks stimulus duration and revealed no evidence of postinhibitory rebound depolarization inherent to coincidence models of duration selectivity. These results strongly support an anticoincidence mechanism of short-pass selectivity, wherein inhibition and suprathreshold excitation show greatest temporal overlap for long duration stimuli.
声音时长在声学通信中很重要，包括人类的语音识别。尽管已经发现了对时长有选择性的听觉神经元，但其潜在机制尚不清楚。为了研究这些机制，我们结合了中脑神经元的体内全细胞膜片钳记录、兴奋性和抑制性电导的提取以及局部药理学操作。我们发现，对短时长刺激的选择性源于短潜伏期、持续性抑制与延迟性、阶段性兴奋的整合；活跃的膜特性似乎放大了对有效刺激的反应。阻断GABAA受体可减弱与刺激相关的抑制作用，揭示所有刺激时长下的阈上兴奋，并降低短通选择性而不改变静息电位。阻断AMPA和NMDA受体以减弱兴奋作用，证实抑制作用跟踪刺激时长，且未发现时长选择性巧合模型所固有的抑制后反弹去极化的证据。这些结果有力地支持了短通选择性的反巧合机制，其中抑制作用和阈上兴奋在长时长刺激时表现出最大的时间重叠。
