University of Oslo, Institute of Basic Medical Sciences, Department of Physiology, Oslo, Norway.
Neuroscience. 2018 Aug 1;384:76-86. doi: 10.1016/j.neuroscience.2018.05.022. Epub 2018 May 24.
Synaptic short-term plasticity (STP) regulates synaptic transmission in an activity-dependent manner and thereby has important roles in the signal processing in the brain. In some synapses, a presynaptic train of action potentials elicits post-synaptic potentials that gradually increase during the train (facilitation), but in other synapses, these potentials gradually decrease (depression). We studied STP in neurons in the visual thalamic relay, the dorsal lateral geniculate nucleus (dLGN). The dLGN contains two types of neurons: excitatory thalamocortical (TC) neurons, which transfer signals from retinal afferents to visual cortex, and local inhibitory interneurons, which form an inhibitory feedforward loop that regulates the thalamocortical signal transmission. The overall STP in the retino-thalamic relay is short-term depression, but the distinct kind and characteristics of the plasticity at the different types of synapses are unknown. We studied STP in the excitatory responses of interneurons to stimulation of retinal afferents, in the inhibitory responses of TC neurons to stimulation of afferents from interneurons, and in the disynaptic inhibitory responses of TC neurons to stimulation of retinal afferents. Moreover, we studied STP at the direct excitatory input to TC neurons from retinal afferents. The STP at all types of the synapses showed short-term depression. This depression can accentuate rapid changes in the stream of signals and thereby promote detectability of significant features in the sensory input. In vision, detection of edges and contours is essential for object perception, and the synaptic short-term depression in the early visual pathway provides important contributions to this detection process.
突触的短期可塑性（STP）以活动依赖的方式调节突触传递，从而在大脑的信号处理中发挥重要作用。在某些突触中，一连串的动作电位会引发突触后电位，在冲动传递过程中逐渐增强（易化），而在其他突触中，这些电位则逐渐减弱（抑制）。我们研究了视觉丘脑中继神经元中的 STP，即背外侧膝状体核（dLGN）。dLGN 包含两种类型的神经元：兴奋性丘脑皮质（TC）神经元，它们将来自视网膜传入的信号传递到视觉皮层，以及局部抑制性中间神经元，它们形成抑制性前馈环路，调节丘脑皮质信号传递。视网膜-丘脑中继的整体 STP 是短期抑制，但不同类型突触的可塑性的独特种类和特征尚不清楚。我们研究了中间神经元对视网膜传入刺激的兴奋性反应、TC 神经元对中间神经元传入刺激的抑制性反应以及 TC 神经元对视网膜传入刺激的双突触抑制性反应中的 STP。此外，我们还研究了来自视网膜传入的直接兴奋性输入到 TC 神经元的 STP。所有类型突触的 STP 均表现为短期抑制。这种抑制可以强调信号流的快速变化，从而提高对感觉输入中显著特征的检测能力。在视觉中，边缘和轮廓的检测对于物体感知至关重要，早期视觉通路中的突触短期抑制对这一检测过程做出了重要贡献。
