Neuroscience Program and Psychology Department, University of California, Riverside, CA 92521, USA.
Hear Res. 2013 Apr;298:80-92. doi: 10.1016/j.heares.2012.12.013. Epub 2013 Jan 20.
This study focused on the response properties underlying selectivity for the rate of frequency modulated (FM) sweeps in the auditory cortex of anesthetized C57bl/6 (C57) mice. Linear downward FM sweeps with rates between 0.08 and 20 kHz/ms were tested. We show that at least two different response properties predict FM rate selectivity: sideband inhibition and duration tuning. Sideband inhibition was determined using the two-tone inhibition paradigm in which excitatory and inhibitory tones were presented with different delays. Sideband inhibition was present in the majority (88%, n = 53) of neurons. The spectrotemporal properties of sideband inhibition predicted rate selectivity and exclusion of the sideband from the sweep reduced/eliminated rate tuning. The second property predictive of sweep rate selectivity was duration tuning for tones. Theoretically, if a neuron is selective for the duration that a sweep spends in the excitatory frequency tuning curve, then rate selectivity will ensue. Duration tuning for excitatory tones was present and predicted rate selectivity in ∼34% of neurons (n = 97). Both sideband inhibition and duration tuning predicted rate selectivity equally well, but sideband inhibition was present in a larger percentage of neurons suggesting that it is the dominant mechanism in the C57 mouse auditory cortex. Similar mechanisms shape sweep rate selectivity in the auditory system of bats and mice and movement-velocity selectivity in the visual system, suggesting similar solutions to analogous problems across sensory systems. This study provides baseline data on basic spectrotemporal processing in the C57 strain for elucidation of changes that occur in presbycusis.
本研究关注的是麻醉 C57BL/6（C57）小鼠听觉皮层中调频（FM）扫频选择性的反应特性。测试了频率在 0.08 至 20 kHz/ms 之间的线性下降 FM 扫频。我们表明，至少有两种不同的反应特性可以预测 FM 速率选择性：边带抑制和持续时间调谐。边带抑制是使用双音抑制范式确定的，其中以不同的延迟呈现兴奋性和抑制性音调。边带抑制存在于大多数（88%，n=53）神经元中。边带抑制的频谱时间特性预测了速率选择性，并且从扫频中排除边带降低/消除了速率调谐。第二个预测扫频速率选择性的特性是音调的持续时间调谐。从理论上讲，如果神经元对扫频在兴奋性频率调谐曲线中所花费的持续时间具有选择性，那么随后就会产生速率选择性。兴奋音调的持续时间调谐存在于约 34%的神经元中（n=97），并预测了速率选择性。边带抑制和持续时间调谐都能很好地预测速率选择性，但边带抑制存在于更大比例的神经元中，这表明它是 C57 小鼠听觉皮层中的主要机制。类似的机制在蝙蝠和小鼠的听觉系统中塑造了扫频速率选择性，以及在视觉系统中塑造了运动速度选择性，这表明在不同的感觉系统中，类似的问题具有类似的解决方案。本研究为阐明 presbycusis 中发生的变化，提供了 C57 品系中基本频谱时间处理的基线数据。
