Gao Lixia, Kostlan Kevin, Wang Yunyan, Wang Xiaoqin
Laboratory of Auditory Neurophysiology, Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21025, USA.
Laboratory of Auditory Neurophysiology, Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21025, USA.
Neuron. 2016 Aug 17;91(4):905-919. doi: 10.1016/j.neuron.2016.07.004. Epub 2016 Jul 28.
A key computational principle for encoding time-varying signals in auditory and somatosensory cortices of monkeys is the opponent model of rate coding by two distinct populations of neurons. However, the subthreshold mechanisms that give rise to this computation have not been revealed. Because the rate-coding neurons are only observed in awake conditions, it is especially challenging to probe their underlying cellular mechanisms. Using a novel intracellular recording technique that we developed in awake marmosets, we found that the two types of rate-coding neurons in auditory cortex exhibited distinct subthreshold responses. While the positive-monotonic neurons (monotonically increasing firing rate with increasing stimulus repetition frequency) displayed sustained depolarization at high repetition frequency, the negative-monotonic neurons (opposite trend) instead exhibited hyperpolarization at high repetition frequency but sustained depolarization at low repetition frequency. The combination of excitatory and inhibitory subthreshold events allows the cortex to represent time-varying signals through these two opponent neuronal populations.
猴子听觉和体感皮层中编码时变信号的一个关键计算原则是由两类不同神经元群体进行速率编码的拮抗模型。然而，产生这种计算的阈下机制尚未明确。由于速率编码神经元仅在清醒状态下被观察到，探究其潜在的细胞机制极具挑战性。利用我们在清醒狨猴中开发的一种新型细胞内记录技术，我们发现听觉皮层中的两类速率编码神经元表现出不同的阈下反应。正向单调神经元（随着刺激重复频率增加，放电率单调增加）在高重复频率下表现出持续去极化，而负向单调神经元（趋势相反）在高重复频率下表现出超极化，但在低重复频率下表现出持续去极化。兴奋性和抑制性阈下事件的结合使皮层能够通过这两个拮抗神经元群体来表征时变信号。
