School of Life Sciences and Centre for Computational Neuroscience and Robotics, University of Sussex, Falmer, Brighton, BN1 9QG, UK.
Centro de Neurociencias, Instituto de Investigaciones Científicas y Servicios de Alta Tecnología, Ciudad de Saber, Republic of Panama.
Sci Rep. 2018 Sep 11;8(1):13629. doi: 10.1038/s41598-018-31996-0.
Reversible decreases in synaptic strength, known as short-term depression (STD), are widespread in neural circuits. Various computational roles have been attributed to STD but these tend to focus upon the initial depression rather than the subsequent recovery. We studied the role of STD and recovery at an excitatory synapse between the fast extensor tibiae (FETi) and flexor tibiae (flexor) motor neurons in the desert locust (Schistocerca gregaria) by making paired intracellular recordings in vivo. Over behaviorally relevant pre-synaptic spike frequencies, we found that this synapse undergoes matched frequency-dependent STD and recovery; higher frequency spikes that evoke stronger, faster STD also produce stronger, faster recovery. The precise matching of depression and recovery time constants at this synapse ensures that flexor excitatory post-synaptic potential (EPSP) amplitude encodes the presynaptic FETi interspike interval (ISI). Computational modelling shows that this precise matching enables the FETi-flexor synapse to linearly encode the ISI in the EPSP amplitude, a coding strategy that may be widespread in neural circuits.
突触强度的可逆性降低，即短期抑制（short-term depression，STD），在神经回路中广泛存在。STD 被赋予了各种计算作用，但这些作用往往集中在初始抑制上，而不是后续的恢复上。我们通过在体内进行成对的细胞内记录，研究了沙漠蝗（Schistocerca gregaria）快伸肌（fast extensor tibiae，FETi）和屈肌（flexor tibiae）运动神经元之间兴奋性突触上的 STD 和恢复的作用。在与行为相关的前突触尖峰频率下，我们发现这个突触经历了匹配的频率依赖性 STD 和恢复；引发更强、更快 STD 的更高频率尖峰也会产生更强、更快的恢复。这个突触上的抑制和恢复时间常数的精确匹配确保了屈肌兴奋性突触后电位（EPSP）幅度编码了前突触 FETi 脉冲间隔（interspike interval，ISI）。计算模型表明，这种精确匹配使 FETi-屈肌突触能够在线性方式下将 ISI 编码为 EPSP 幅度，这种编码策略可能在神经回路中广泛存在。
