TY - JOUR
T1 - Effects of stimulus spatial frequency, size, and luminance contrast on orientation tuning of neurons in the dorsal lateral geniculate nucleus of cat
AU - Naito, Tomoyuki
AU - Okamoto, Masahiro
AU - Sadakane, Osamu
AU - Shimegi, Satoshi
AU - Osaki, Hironobu
AU - Hara, Shin Ichiro
AU - Kimura, Akihiro
AU - Ishikawa, Ayako
AU - Suematsu, Naofumi
AU - Sato, Hiromichi
N1 - Funding Information:
We thank Drs. T. Kasamatsu and V. Bonin for discussions and comments, and Dr. P. Karagiannis for revising the manuscript. This work was supported by Grant-in-Aid for Scientific Research from MEXT, Japan ( 17022026 , 18020018 , and 20020016 to H.S.; 03J03678 , 22700339 , and 25380981 to T.N.).
PY - 2013/11
Y1 - 2013/11
N2 - 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.
AB - 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.
KW - GABA inhibition
KW - Orientation selectivity
KW - Surround suppression
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U2 - 10.1016/j.neures.2013.08.009
DO - 10.1016/j.neures.2013.08.009
M3 - Article
C2 - 24055599
AN - SCOPUS:84886594588
VL - 77
SP - 143
EP - 154
JO - Neuroscience Research
JF - Neuroscience Research
SN - 0168-0102
IS - 3
ER -