Department of Otolaryngology/Head Neck Surgery and Sensory Neuroscience Research Center, West Virginia University, Morgantown, West Virginia 26506-9303, USA.
J Neurosci. 2011 Aug 31;31(35):12566-78. doi: 10.1523/JNEUROSCI.2450-11.2011.
The superior paraolivary nucleus (SPON) is a prominent structure in the auditory brainstem. In contrast to the principal superior olivary nuclei with identified roles in processing binaural sound localization cues, the role of the SPON in hearing is not well understood. A combined in vitro and in vivo approach was used to investigate the cellular properties of SPON neurons in the mouse. Patch-clamp recordings in brain slices revealed that brief and well timed postinhibitory rebound spiking, generated by the interaction of two subthreshold-activated ion currents, is a hallmark of SPON neurons. The I(h) current determines the timing of the rebound, whereas the T-type Ca(2+) current boosts the rebound to spike threshold. This precisely timed rebound spiking provides a physiological explanation for the sensitivity of SPON neurons to sinusoidally amplitude-modulated (SAM) tones in vivo, where peaks in the sound envelope drive inhibitory inputs and SPON neurons fire action potentials during the waveform troughs. Consistent with this notion, SPON neurons display intrinsic tuning to frequency-modulated sinusoidal currents (1-15Hz) in vitro and discharge with strong synchrony to SAMs with modulation frequencies between 1 and 20 Hz in vivo. The results of this study suggest that the SPON is particularly well suited to encode rhythmic sound patterns. Such temporal periodicity information is likely important for detection of communication cues, such as the acoustic envelopes of animal vocalizations and speech signals.
上橄榄旁核（SPON）是听觉脑干中的一个突出结构。与主要的上橄榄核不同，主要的上橄榄核在处理双耳声源定位线索方面具有明确的作用，SPON 在听觉中的作用尚不清楚。本研究采用体外和体内相结合的方法研究了小鼠 SPON 神经元的细胞特性。脑片上的膜片钳记录显示，由两个亚阈激活的离子电流相互作用产生的短暂而定时的后抑制性反弹放电是 SPON 神经元的标志。I(h)电流决定了反弹的时间，而 T 型 Ca(2+)电流则将反弹提升到放电阈值。这种精确定时的反弹放电为 SPON 神经元对体内正弦幅度调制（SAM）音调的敏感性提供了生理解释，在体内，声音包络的峰值驱动抑制性输入，而 SPON 神经元在波形低谷时发射动作电位。与这一观点一致，SPON 神经元在体外对频率调制正弦电流（1-15Hz）表现出固有调谐，并在体内以 1-20Hz 的调制频率与 SAM 强烈同步放电。本研究结果表明，SPON 特别适合编码节奏性声音模式。这种时间周期性信息可能对检测通信线索很重要，例如动物发声和语音信号的声包络。
