Effects of stimulus spatial frequency, size, and luminance contrast on orientation tuning of neurons in the dorsal lateral geniculate nucleus of cat

Tomoyuki Naito, Masahiro Okamoto, Osamu Sadakane, Satoshi Shimegi, Hironobu Osaki, Shin Ichiro Hara, Akihiro Kimura, Ayako Ishikawa, Naofumi Suematsu, Hiromichi Sato

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

It is generally thought that orientation selectivity first appears in the primary visual cortex (V1), whereas neurons in the lateral geniculate nucleus (LGN), an input source for V1, are thought to be insensitive to stimulus orientation. Here we show that increasing both the spatial frequency and size of the grating stimuli beyond their respective optimal values strongly enhance the orientation tuning of LGN neurons. The resulting orientation tuning was clearly contrast-invariant. Furthermore, blocking intrathalamic inhibition by iontophoretically administering γ-aminobutyric acid (GABA)A receptor antagonists, such as bicuculline and GABAzine, slightly but significantly weakened the contrast invariance. Our results suggest that orientation tuning in the LGN is caused by an elliptical classical receptive field and orientation-tuned surround suppression, and that its contrast invariance is ensured by local GABAA inhibition. This contrast-invariant orientation tuning in LGN neurons may contribute to the contrast-invariant orientation tuning seen in V1 neurons.

Original languageEnglish
Pages (from-to)143-154
Number of pages12
JournalNeuroscience Research
Volume77
Issue number3
DOIs
Publication statusPublished - 2013 Nov
Externally publishedYes

Keywords

  • GABA inhibition
  • Orientation selectivity
  • Surround suppression

ASJC Scopus subject areas

  • Neuroscience(all)

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