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Visual System

開催日 2014/9/11
時間 16:00 - 17:00
会場 Poster / Exhibition(Event Hall B)

Underlying mechanisms of temporal shrinkage of receptive field of relay cells in the dorsal lateral geniculate nucleus of the cat

  • P1-170
  • 木村 晃大 / Akihiro Kimura:1,3 七五三木 聡 / Satoshi Shimegi:1,2 佐藤 宏道 / Hiromichi Sato:1,2 
  • 1:大阪大学 / Grad. Sch. of Medicine, Osaka Univ. 2:大阪大院生命機能 / Graduate School of Frontier Biosciences, Osaka University, Japan 3:大阪保健医療大学 / Osaka Health Science University 

The receptive fields (RFs) of relay cells in the LGN have been reported to shrink temporally till on average 70 ms after stimulus onset. However, the neuronal mechanisms underlying the RFs shrinkage remain unknown. Recently, we examined the effect of iontophoretic administration of GABA receptor antagonist on spatial frequency (SF) tuning of relay cells, finding that blockade of GABAergic inhibition changes the SF tuning from band-pass to low-pass. It suggests that the low-pass tuning of excitatory inputs derived from retinal ganglion cells (RGCs) is reshaped by intrageniculate GABAergic inhibition biased toward low SF range. The low-SF biased inhibition seems to contribute to the temporal shrinkage of the RF of relay cells. If it is the case, the temporal development of GABAergic inhibition should be observed in parallel with the time course of the RF shrinkage. To test this hypothesis, we examined the time course of GABAergic inhibitory effect on SF tuning of relay cells by presenting stationary sinusoidal gratings with various SFs for 500 ms with and without GABA receptor antagonist, gabazine, in which the center point of the RFs of on-center and off-center cells were constantly stimulated with bright and dark phases of the grating, respectively. We first confirmed that the SF tuning of relay cells changed from low-pass to band pass tuning in time course under no drug condition, suggesting the shrinkage of RF. Administration of gabazine attenuated the degree of the SF tuning reshaping, especially in early response, but the reshaping occurred in later response comparing to no drug condition. This means that early shrinkage of RF is due to intrageniculate GABAergic inhibition but late one derive from the shrinkage of retinogeniculate excitatory inputs. Thus, two components with different sources are responsible for the phenomenon of dynamic change of RF in relay cells.

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