Data detailed in 'Measurements of long-range suppression in human opponent S-cone and achromatic luminance channels' have been presented. According to recent research published in the Journal of Vision, 'Cortical responses to spatially discrete patches of achromatic luminance contrast can be altered by the presence of high-contrast, spatially remote 'surrounds' and this achromatic 'surround suppression' has been the subject of much recent research. However, the nature of long-range contrast normalization in chromatic signals has been less studied.'
'Here we use a combination of neuroimaging data from source-imaged EEG and two different psychophysical measures of surround suppression to study contrast normalization in stimuli containing achromatic luminance and S-cone-isolating contrast. In an appearance matching task, we find strong within-channel but little between-channel suppression. However, using a contrast increment detection task, we do find evidence for weak but significant between-channel effects. Our neural measurements agree with the appearance matching data, showing significant within-channel suppression and no significant interactions between signals initiated in different pre-cortical pathways. We hypothesize that appearance judgments and V1 population responses are dominated by neurons with chromatically matched classical and extra-classical surrounds while contrast increment detection tasks rely on a subpopulation of neurons that have extra-classical surrounds sensitive to both chromatic and achromatic contrasts,' wrote B. Xiao and colleagues, Smith-Kettlewell Eye Research Institute (see also Vision Research).
The researchers concluded: 'Our psychophysical and source-imaged EEG results are consistent with a hypothesis based on natural scene statistics that long-range contrast normalization in early visual system is largely driven by signals within the same chromatic channel.'
Xiao and colleagues published their study in the Journal of Vision (Measurements of long-range suppression in human opponent S-cone and achromatic luminance channels. Journal of Vision, 2010;10(13):10).
For additional information, contact B. Xiao, Smith-Kettlewell Eye Research Institute, Brain Imaging Center, CA USA.
The publisher's contact information for the Journal of Vision is: Association Research Vision Ophthalmology Inc., 12300 Twinbrook Parkway, Rockville, MD 20852-1606, USA.
Keywords: State:CA, Country:United States, Vision Research.
This article was prepared by Health & Medicine Week editors from staff and other reports. Copyright 2011, Health & Medicine Week via NewsRx.com.
