The Cumulative Effects of Predictability on Synaptic Gain in the Auditory Processing Stream.
The Cumulative Effects of Predictability on Synaptic Gain in the Auditory Processing Stream.
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可预测性对听觉处理流中突触增益的累积影响。
DOI：
10.1523/jneurosci.0291-17.2017
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发表时间：
2017-07-12
期刊：
影响因子：
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通讯作者：
Friston K
中科院分区：
文献类型：
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作者：
Auksztulewicz R;Barascud N;Cooray G;Nobre AC;Chait M;Friston K
刺激的可预测性可以导致大脑活动的实质性调节，例如用脑磁图（MEG）测量的持续磁场幅度的变化。在这里，我们使用从健康人类志愿者（N = 13，7 名女性）获得的 MEG 数据对这些影响进行了机械解释。在诱导反应的源级分析中，我们建立了沿着听觉处理流的快速音调序列（即序列规律性和字母大小）的正交可预测性操作的效果。在听觉皮层中，具有较小字母的规则序列会诱导更大的伽玛活动。此外，序列规律性将额叶区域的诱发活动转向更高的频率。为了根据潜在的神经生理学对这些影响进行建模，我们使用了跨谱密度的动态因果模型，并估计了神经（突触后）增益的缓慢波动。使用基于模型的参数，我们准确地解释了传感器级持续场振幅，证明突触功效的缓慢变化与持续的感觉输入相结合，可以对可预测的感觉流的神经反应产生深远和持续的影响。意义陈述 大脑活动可以通过其当前正在处理的刺激的可预测性来强烈调节。这种调制的一个例子是用脑磁图测量的持续磁场幅度的变化。在这里，我们提供了这些影响的机制解释。首先，我们在听觉处理流的分层不同区域中建立独立可预测性操作的振荡神经相关性。接下来，我们使用生物物理现实的计算模型来根据潜在的神经生理学来解释这些影响。最后，使用描述神经增益调制的基于模型的参数，我们可以解释之前在传感器级别观察到的无法解释的效应。这表明突触增益的缓慢调节可以对神经活动产生深远而持续的影响。
Stimulus predictability can lead to substantial modulations of brain activity, such as shifts in sustained magnetic field amplitude, measured with magnetoencephalography (MEG). Here, we provide a mechanistic explanation of these effects using MEG data acquired from healthy human volunteers (N = 13, 7 female). In a source-level analysis of induced responses, we established the effects of orthogonal predictability manipulations of rapid tone-pip sequences (namely, sequence regularity and alphabet size) along the auditory processing stream. In auditory cortex, regular sequences with smaller alphabets induced greater gamma activity. Furthermore, sequence regularity shifted induced activity in frontal regions toward higher frequencies. To model these effects in terms of the underlying neurophysiology, we used dynamic causal modeling for cross-spectral density and estimated slow fluctuations in neural (postsynaptic) gain. Using the model-based parameters, we accurately explain the sensor-level sustained field amplitude, demonstrating that slow changes in synaptic efficacy, combined with sustained sensory input, can result in profound and sustained effects on neural responses to predictable sensory streams. SIGNIFICANCE STATEMENT Brain activity can be strongly modulated by the predictability of stimuli it is currently processing. An example of such a modulation is a shift in sustained magnetic field amplitude, measured with magnetoencephalography. Here, we provide a mechanistic explanation of these effects. First, we establish the oscillatory neural correlates of independent predictability manipulations in hierarchically distinct areas of the auditory processing stream. Next, we use a biophysically realistic computational model to explain these effects in terms of the underlying neurophysiology. Finally, using the model-based parameters describing neural gain modulation, we can explain the previously unexplained effects observed at the sensor level. This demonstrates that slow modulations of synaptic gain can result in profound and sustained effects on neural activity.