Nagel Katherine I, Hong Elizabeth J, Wilson Rachel I
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, USA.
Nat Neurosci. 2015 Jan;18(1):56-65. doi: 10.1038/nn.3895. Epub 2014 Dec 8.
Sensory stimuli fluctuate on many timescales. However, short-term plasticity causes synapses to act as temporal filters, limiting the range of frequencies that they can transmit. How synapses in vivo might transmit a range of frequencies in spite of short-term plasticity is poorly understood. The first synapse in the Drosophila olfactory system exhibits short-term depression, but can transmit broadband signals. Here we describe two mechanisms that broaden the frequency characteristics of this synapse. First, two distinct excitatory postsynaptic currents transmit signals on different timescales. Second, presynaptic inhibition dynamically updates synaptic properties to promote accurate transmission of signals across a wide range of frequencies. Inhibition is transient, but grows slowly, and simulations reveal that these two features of inhibition promote broadband synaptic transmission. Dynamic inhibition is often thought to restrict the temporal patterns that a neuron responds to, but our results illustrate a different idea: inhibition can expand the bandwidth of neural coding.
感觉刺激在许多时间尺度上波动。然而，短期可塑性会使突触起到时间滤波器的作用，限制它们能够传递的频率范围。尽管存在短期可塑性，体内的突触如何传递一系列频率却鲜为人知。果蝇嗅觉系统中的第一个突触表现出短期抑制，但能够传递宽带信号。在此我们描述两种拓宽该突触频率特性的机制。第一，两种不同的兴奋性突触后电流在不同的时间尺度上传递信号。第二，突触前抑制动态更新突触特性，以促进在很宽频率范围内信号的准确传递。抑制是短暂的，但增长缓慢，模拟结果表明抑制的这两个特征促进了宽带突触传递。动态抑制通常被认为会限制神经元所响应的时间模式，但我们的结果说明了一个不同的观点：抑制可以扩展神经编码的带宽。
