Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia.
Institute of Neurobiology, University of Ulm, Ulm, Germany.
PLoS One. 2020 Oct 26;15(10):e0240853. doi: 10.1371/journal.pone.0240853. eCollection 2020.
The auditory midbrain (central nucleus of inferior colliculus, ICC) receives multiple brainstem projections and recodes auditory information for perception in higher centers. Many neural response characteristics are represented in gradients (maps) in the three-dimensional ICC space. Map overlap suggests that neurons, depending on their ICC location, encode information in several domains simultaneously by different aspects of their responses. Thus, interdependence of coding, e.g. in spectral and temporal domains, seems to be a general ICC principle. Studies on covariation of response properties and possible impact on sound perception are, however, rare. Here, we evaluated tone-evoked single neuron activity from the mouse ICC and compared shapes of excitatory frequency-response areas (including strength and shape of inhibition within and around the excitatory area; classes I, II, III) with types of temporal response patterns and first-spike response latencies. Analyses showed covariation of sharpness of frequency tuning with constancy and precision of responding to tone onsets. Highest precision (first-spike latency jitter < 1 ms) and stable phasic responses throughout frequency-response areas were the quality mainly of class III neurons with broad frequency tuning, least influenced by inhibition. Class II neurons with narrow frequency tuning and dominating inhibitory influence were unsuitable for time domain coding with high precision. The ICC center seems specialized rather for high spectral resolution (class II presence), lateral parts for constantly precise responding to sound onsets (class III presence). Further, the variation of tone-response latencies in the frequency-response areas of individual neurons with phasic, tonic, phasic-tonic, or pauser responses gave rise to the definition of a core area, which represented a time window of about 20 ms from tone onset for tone-onset responding of the whole ICC. This time window corresponds to the roughly 20 ms shortest time interval that was found critical in several auditory perceptual tasks in humans and mice.
听觉中脑（下丘中央核，ICC）接收多个脑干投射，并对听觉信息进行重新编码，以便在更高的中心进行感知。许多神经反应特征在 ICC 的三维空间中以梯度（图谱）的形式表示。图谱重叠表明，取决于其 ICC 位置，神经元通过其反应的不同方面同时在几个域中对信息进行编码。因此，编码的相互依赖性，例如在频谱和时域中，似乎是 ICC 的一般原则。然而，关于反应特性的协变及其对声音感知的可能影响的研究很少。在这里，我们评估了来自小鼠 ICC 的音调诱发的单个神经元活动，并比较了兴奋性频率反应区域的形状（包括兴奋性区域内和周围的抑制的强度和形状；I 类、II 类、III 类）与时间反应模式的类型和第一峰反应潜伏期。分析表明，频率调谐的锐度与对音调起始的响应的恒定性和精确性相关。最高的精度（第一峰潜伏期抖动<1 ms）和整个频率反应区域内稳定的相位响应主要是宽频调谐的 III 类神经元的特征，受抑制的影响最小。窄频调谐和主导抑制作用的 II 类神经元不适合高精度的时域编码。ICC 中心似乎专门用于高光谱分辨率（II 类存在），而外侧部分则专门用于对声音起始的恒定精确响应（III 类存在）。此外，个体神经元在频率反应区域中对音调的反应潜伏期的变化，具有相位、紧张、相位紧张或暂停反应，导致定义了一个核心区域，该区域代表了从整个 ICC 的音调起始到音调起始反应的大约 20 ms 的时间窗口。这个时间窗口与在人类和小鼠的几个听觉感知任务中发现的关键的大约 20 ms 的最短时间间隔相对应。
