Lee M F, So Edmund C, Poon Paul W F
Department of Physiology, Medical College, National Cheng Kung University, Taiwan, Republic of China.
Chin J Physiol. 2010 Dec 31;53(6):465-71. doi: 10.4077/cjp.2010.amm034.
Speech and other communication signals contain components of frequency and amplitude modulations (FM, AM) that often occur together. Auditory midbrain (or inferior colliculus, IC) is an important center for coding time-varying features of sounds. It remains unclear how IC neurons respond when FM and AM stimuli are both presented. Here we studied IC neurons in the urethane-anesthetized rats when animals were simultaneously stimulated with FM and AM tones. Of 122 units that were sensitive to the dual stimuli, the responses could be grossly divided into two types: one that resembled the respective responses to FM or AM stimuli presented separately ("simple" sensitivity, 45% of units), and another that appeared markedly different from their respective responses to FM or AM tones ("complex" sensitivity, 55%). These types of combinational sensitivities were further correlated with individual cell's frequency tuning pattern (response area) and with their common response pattern to FM and AM sounds. Results suggested that such combinational sensitivity could reflect local synaptic interactions on IC neurons and that the neural mechanisms could underlie more developed sensitivities to acoustic combinations found at the auditory cortex.
语音和其他通信信号包含经常同时出现的频率调制（FM）和幅度调制（AM）成分。听觉中脑（或下丘，IC）是编码声音时变特征的重要中枢。目前尚不清楚当同时呈现FM和AM刺激时，IC神经元如何做出反应。在此，我们研究了用氨基甲酸乙酯麻醉的大鼠在同时受到FM和AM音调刺激时的IC神经元。在对双重刺激敏感的122个单位中，其反应大致可分为两种类型：一种类似于对单独呈现的FM或AM刺激的各自反应（“简单”敏感性，占单位的45%），另一种则明显不同于它们对FM或AM音调的各自反应（“复杂”敏感性，占55%）。这些组合敏感性类型进一步与单个细胞的频率调谐模式（反应区域）以及它们对FM和AM声音的共同反应模式相关。结果表明，这种组合敏感性可能反映了IC神经元上的局部突触相互作用，并且这种神经机制可能是听觉皮层对声学组合更发达敏感性的基础。
