Zhu J J, Lo F S
Shanghai Brain Research Institute, Chinese Academy of Sciences, Shanghal.
Brain Res Bull. 1996;41(5):281-91. doi: 10.1016/s0361-9230(96)00201-8.
Psychological studies have revealed that a visual suppression occurs during the saccadic eye movements to maintain the stable visual image. This visual suppression is named saccadic suppression. A typical saccadic suppression precedes the saccadic eye movements by 30-60 ms, lasts 120-180 ms, and is followed by a 100-150 ms facilitation. Recently, we have revealed an inhibitory circuit connecting the deep layers of the superior colliculus (SC) to the dorsal lateral geniculate nucleus (LGN), via the central lateral nucleus in the thalamus (CL) and thalamic reticular nucleus (TRN). We speculated that this inhibitory circuit might mediate saccadic suppression in the rabbit. In the present study, we used intracellular recording technique to further examine the synaptic and intrinsic responses of CL cells, TRN cells, and LGN cells to the activation of this inhibitory circuit. We found that the stimulation of the deeper layers of the SC induced a fast excitation post-synaptic potential (EPSP) in CL cells, followed by a robust EPSP in TRN cells and a prolonged inhibitory postsynaptic potential (IPSP) in LGN cells. The EPSP in TRN cells was always followed by a small inhibitory postsynaptic potential (IPSP). The IPSP in LGN cells lasted about 133 +/- 27 ms. Sometimes, a rebound bursting occurred after the IPSP in LGN cells. We also examined whether activation of this inhibitory circuit could suppress the retino-geniculo-cortical pathway. We found that the SC stimulation always suppressed the evoked potential in the visual cortex induced by the stimulation of the optic chiasm. Our results of the inhibitory circuit can induce an inhibition in the LGN and a suppression on the retino-geniculo-cortical pathway. The time courses of the inhibition and suppression were compatible with that of saccadic suppression revealed by psychological and physiological studies. These results support the idea that the inhibitory circuit of SC (deeper layers)-CL-TRN-LGN may mediate the saccadic suppression in the rabbit LGN.
心理学研究表明，在眼球快速运动期间会发生视觉抑制，以维持稳定的视觉图像。这种视觉抑制被称为扫视抑制。典型的扫视抑制在眼球快速运动前30 - 60毫秒出现，持续120 - 180毫秒，随后是100 - 150毫秒的易化。最近，我们发现了一条抑制性回路，它通过丘脑中央外侧核（CL）和丘脑网状核（TRN），将上丘（SC）深层与背外侧膝状体核（LGN）相连。我们推测这条抑制性回路可能介导兔子的扫视抑制。在本研究中，我们使用细胞内记录技术进一步研究CL细胞、TRN细胞和LGN细胞对该抑制性回路激活的突触反应和内在反应。我们发现，刺激SC深层会在CL细胞中诱发快速兴奋性突触后电位（EPSP），随后在TRN细胞中出现强烈的EPSP，在LGN细胞中出现延长的抑制性突触后电位（IPSP）。TRN细胞中的EPSP之后总是跟着一个小的抑制性突触后电位（IPSP）。LGN细胞中的IPSP持续约133±27毫秒。有时，LGN细胞中的IPSP之后会出现反弹爆发。我们还研究了该抑制性回路的激活是否能抑制视网膜 - 膝状体 - 皮质通路。我们发现，刺激SC总是会抑制视交叉刺激在视觉皮层诱发的诱发电位。我们关于抑制性回路的研究结果表明，它能在LGN中诱导抑制，并对视网膜 - 膝状体 - 皮质通路产生抑制。这种抑制和抑制的时间进程与心理学和生理学研究揭示的扫视抑制的时间进程一致。这些结果支持了这样一种观点，即SC（深层）-CL-TRN-LGN的抑制性回路可能介导兔子LGN中的扫视抑制。
