Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Rd., Ottawa, Ontario K1H 8M5, Canada.
J Neurophysiol. 2010 Jun;103(6):3337-48. doi: 10.1152/jn.00117.2010. Epub 2010 Mar 31.
Short-term depression (STD) is observed at many synapses of the CNS and is important for diverse computations. We have discovered a form of fast STD (FSTD) in the synaptic responses of pyramidal cells evoked by stimulation of their electrosensory afferent fibers (P-units). The dynamics of the FSTD are matched to the mean and variance of natural P-unit discharge. FSTD exhibits switch-like behavior in that it is immediately activated with stimulus intervals near the mean interspike interval (ISI) of P-units (approximately 5 ms) and recovers immediately after stimulation with the slightly longer intervals (>7.5 ms) that also occur during P-unit natural and evoked discharge patterns. Remarkably, the magnitude of evoked excitatory postsynaptic potentials appear to depend only on the duration of the previous ISI. Our theoretical analysis suggests that FSTD can serve as a mechanism for noise reduction. Because the kinetics of depression are as fast as the natural spike statistics, this role is distinct from previously ascribed functional roles of STD in gain modulation, synchrony detection or as a temporal filter.
短期抑制（Short-term depression，STD）在中枢神经系统的许多突触中都有观察到，对于各种计算都很重要。我们在电感受传入纤维（P 单元）刺激诱发的锥体细胞突触反应中发现了一种快速 STD（Fast STD，FSTD）形式。FSTD 的动力学与自然 P 单元放电的均值和方差相匹配。FSTD 表现出类似于开关的行为，即在接近 P 单元的平均脉冲间隔（Interspike Interval，ISI）的刺激间隔（约 5 毫秒）时立即被激活，并在刺激后立即恢复，而这些间隔略长（>7.5 毫秒），也会在 P 单元的自然和诱发放电模式中发生。值得注意的是，诱发的兴奋性突触后电位的幅度似乎仅取决于前一个 ISI 的持续时间。我们的理论分析表明，FSTD 可以作为一种降噪机制。由于抑制的动力学与自然尖峰统计一样快，因此，与先前归因于 STD 在增益调制、同步检测或作为时间滤波器中的功能作用相比，FSTD 具有独特的作用。
