The Relationship between Cortical Activation and Perception Investigated with Invisible Stimuli

The aim of this work was to study the relationship between cortical activity and visual perception. To do so, we developed a psycho-physical technique that is able to dissociate the visual percept from the visual stimulus and thus distinguish brain activity reflecting the perceptual state from that...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2002-07, Vol.99 (14), p.9527-9532
Main Authors: Moutoussis, K., Zeki, S.
Format: Article
Language:English
Subjects:
Biological Sciences
Brain
Color Perception - physiology
Color Perception Tests
Data Interpretation, Statistical
Discrimination, Psychological
Eyes
Eyes & eyesight
Face
Female
Housing conditions
Humans
Image Processing, Computer-Assisted
Magnetic Resonance Imaging
Male
Mental stimulation
Monoculars
Neurology
Neurons
Perception
Photic Stimulation
Rivalry
Sensory perception
Visual Cortex - physiology
Visual perception
Visual Perception - physiology
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Summary:The aim of this work was to study the relationship between cortical activity and visual perception. To do so, we developed a psycho-physical technique that is able to dissociate the visual percept from the visual stimulus and thus distinguish brain activity reflecting the perceptual state from that reflecting other stages of stimulus processing. We used dichoptic color fusion to make identical monocular stimuli of opposite color contrast "disappear" at the binocular level and thus become "invisible" as far as conscious visual perception is concerned. By imaging brain activity in subjects during a discrimination task between face and house stimuli presented in this way, we found that house-specific and face-specific brain areas are always activated in a stimulus-specific way regardless of whether the stimuli are perceived. Absolute levels of cortical activation, however, were lower with invisible stimulation compared with visible stimulation. We conclude that there is no terminal "perceptual" area in the visual brain, but that the brain regions involved in processing a visual stimulus are also involved in its perception, the difference between the two being dictated by a higher level of activity in the specific brain region when the stimulus is perceived.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.142305699