Surround suppression sharpens orientation tuning in the cat primary visual cortex.
In the primary visual cortex (V1), the response of a neuron to stimulation of its classical receptive field (CRF) is suppressed by concurrent stimulation of the extraclassical receptive field (ECRF), a phenomenon termed 'surround suppression'. It is also known that the orientation tuning of V1 neurons becomes sharper as the size of the stimulus increases beyond the CRF. However, there have been few quantitative investigations of the relationship between sharpening of orientation tuning and surround suppression. We examined this relationship in 73 V1 neurons recorded from anesthetized and paralysed cats using sinusoidal grating patches as stimuli. We found that sharpening of orientation tuning was significantly correlated with the strength of surround suppression for large stimuli that cover both CRF and ECRF. Furthermore, simulation analysis using a variety of tuning widths and most suppressive orientation of orientation-tuned surround suppression demonstrated that broadly orientation-tuned surround suppression sharpens orientation tuning for large gratings without shift in optimal orientation. Our findings suggest that one of the functional roles of surround suppression in V1 is enhancement of orientation discrimination for large and uniformly patterned objects.
Okamoto
Masahiro
M
Graduate School of Frontier Biosciences, Osaka University, Toyonaka, Osaka, Japan.
Naito
Tomoyuki
T
Sadakane
Osamu
O
Osaki
Hironobu
H
Sato
Hiromichi
H
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D002415:Cats / Q000502:physiology*; D003198:Computer Simulation; D015350:Contrast Sensitivity / Q000502:physiology*; D008959:Models, Neurological; D009433:Neural Inhibition / Q000502:physiology*; D009949:Orientation / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time; D011984:Sensory Receptor Cells / Q000145:classification / Q000502:physiology*; D013057:Spectrum Analysis; D014793:Visual Cortex / Q000166:cytology*; D014795:Visual Pathways / Q000502:physiology