Opposing effects of contextual surround in human early visual cortex revealed by functional magnetic resonance imaging with continuously modulated visual stimuli.
Spatial context in vision has profound effects on neural responses and perception. Recent animal studies suggest that the effect of surround on a central stimulus can dramatically change its character depending on the contrast of the center stimulus, but such a drastic change has not been demonstrated in the human visual cortex. To examine the dependency of the surround effect on the contrast of the center stimulus, we conducted an functional magnetic resonance imaging experiment by using a low or a high contrast in the center region while the surround contrast was sinusoidally modulated between the two contrasts. We found that the blood oxygen level-dependent response in human V1 corresponding to the center region was differentially modulated by the surround contrast, depending crucially on the center contrast: whereas a suppressive effect was observed in conditions in which the center contrast was high, a facilitative effect was seen in conditions where the center contrast was low.
Tajima
Satohiro
S
Department of Complexity Science and Engineering, The University of Tokyo, Kashiwa-shi, Japan. tajima.s-iu@nhk.or.jp
Watanabe
Masataka
M
Imai
Chihiro
C
Ueno
Kenichi
K
Asamizuya
Takeshi
T
Sun
Pei
P
Tanaka
Keiji
K
Cheng
Kang
K
D001931:Brain Mapping; D015350:Contrast Sensitivity / Q000502:physiology*; D005074:Evoked Potentials, Visual / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D009433:Neural Inhibition / Q000502:physiology; D009483:Neuropsychological Tests; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation; D012039:Regional Blood Flow / Q000502:physiology; D013028:Space Perception / Q000502:physiology*; D014793:Visual Cortex / Q000033:anatomy & histology / Q000502:physiology*; D014795:Visual Pathways / Q000033:anatomy & histology / Q000502:physiology*