Short-term depression in thalamocortical synapses of cat primary visual cortex
Short-term depression in thalamocortical synapses of cat primary visual cortex
复制标题
DOI：
10.1523/jneurosci.1445-05.2005
复制
发表时间：
2005-08-03
影响因子：
5.3
通讯作者：
Ferster, D
中科院分区：
文献类型：
--
作者：
Boudreau, CE;Ferster, D
初级视皮层神经元在对视觉刺激的反应中表现出几种非线性，包括对重复刺激的反应递减、对比度依赖的相位提前、对比度饱和和交叉取向抑制。丘脑皮质突触抑制与这些现象有关，但尚未直接在体内视觉皮层中进行检查。我们评估抑郁症的视觉丘脑皮质突触在体内使用20 - 100赫兹列车的电刺激传递到LGN。皮质细胞接收直接输入的LGN，确定的LGN诱发的PSP的短潜伏期和低抖动，表现出适度的PSP幅度减少，在最快的列车。通过其他皮层兴奋性神经元从丘脑接收间接输入的细胞在训练过程中显示出PSP幅度的显著降低，这可以通过皮质皮层突触中的突触抑制或抑制介导的对其传入神经放电的抑制来解释。减少LGN中的自发活动（通过视网膜阻断）揭示了丘脑皮质突触处的额外抑制，但仅针对列车中的第一个刺激。也就是说，第一个PSP的幅度相对于未阻断的条件增加，但随后的反应基本上没有变化。因此，突触通过自发活动维持在显著的抑制水平。这些发现限制了丘脑皮质抑郁症在塑造皮质对视觉刺激的反应中所起的作用。
Neurons in primary visual cortex exhibit several nonlinearities in their responses to visual stimuli, including response decrements to repeated stimuli, contrast-dependent phase advance, contrast saturation, and cross-orientation suppression. Thalamocortical synaptic depression has been implicated in these phenomena but has not been examined directly in visual cortex in vivo. We assessed depression of visual thalamocortical synapses in vivo using 20 - 100 Hz trains of electrical stimuli delivered to the LGN. Cortical cells receiving direct input from the LGN, identified by short latency and low jitter of LGN-evoked PSPs, showed moderate reductions in PSP amplitude during the fastest trains. Cells receiving indirect input from the thalamus via other cortical excitatory neurons show a marked reduction in PSP amplitude during a train, which could be explained either by synaptic depression in corticocortical synapses or by an inhibition-mediated suppression of the firing of their afferents. Reducing spontaneous activity in the LGN ( by retinal blockade) unmasked additional depression at the thalamocortical synapse but only for the first stimulus in the train. That is, the first PSP was increased in amplitude relative to the unblocked condition, but subsequent responses were essentially unchanged. Thus, the synapses are maintained at significant levels of depression by spontaneous activity. These findings constrain the role that thalamocortical depression can play in shaping cortical responses to visual stimuli.