Institute for Systems Research, University of Maryland, College Park, MD, USA.
Neuroscience. 2012 Jul 12;214:28-35. doi: 10.1016/j.neuroscience.2012.04.029. Epub 2012 Apr 21.
Tuning of cortical neurons is often measured as a static property, or during a steady-state regime, despite a number of studies suggesting that tuning depends on when it is measured during a neuron's response (e.g., onset vs. sustained vs. offset). We have previously shown that phase-locked tuning to feature transients evolves as a dynamic quantity from the onset of the sound. In this follow-up study, we examined the phase-independent tuning during feature transients. Based on previous results, we hypothesized phase-independent tuning should evolve on the same timescale as phase-locked tuning. We used stimuli of constant level, but alternating between flat spectro-temporal envelope and a modulated envelope with well-defined spectral density and temporal periodicity. This allowed the measure of changes in tuning to novel spectro-temporal content, as happens during running speech and other sounds with rapid transitions without a confounding change in sound level. For 95% of neurons, tuning changed significantly from the onset, over the course of the response. For a majority of these cells, the change occurred within the first 40ms following a feature onset, often even around 10-20ms. This solidifies the idea that tuning can change rapidly from onset tuning to the sustained, steady-state tuning.
尽管有许多研究表明调谐取决于神经元在其反应期间何时被测量（例如，起始时与维持时与结束时），但皮质神经元的调谐通常被测量为静态属性或在稳态期间进行测量。我们之前已经表明，特征瞬态的锁相调谐作为一个动态数量从声音的起始处演变而来。在这项后续研究中，我们研究了特征瞬态期间的与相位无关的调谐。基于先前的结果，我们假设与相位无关的调谐应该以与锁相调谐相同的时间尺度演变。我们使用恒定水平的刺激，但在具有明确定义的光谱密度和时间周期性的平坦光谱 - 时间包络和调制包络之间交替。这允许测量到对新的光谱 - 时间内容的调谐变化，就像在运行语音和其他具有快速转换而没有声音水平混淆变化的声音期间发生的那样。对于 95%的神经元，调谐从起始时开始，在反应过程中发生显著变化。对于这些细胞中的大多数，变化发生在特征起始后的前 40ms 内，通常甚至在 10-20ms 左右。这巩固了调谐可以从起始调谐快速变化到维持的稳态调谐的想法。
