The fMRI response of the LGN and V1 to cardinal red-green, blue-yellow, and achromatic visual stimuli

Mullen, K. T., Dumoulin, S. O., McMahon, K. L., Bryant, M., de Zubicaray, G. I. and Hess, R. F. (2005). The fMRI response of the LGN and V1 to cardinal red-green, blue-yellow, and achromatic visual stimuli. In: Journal of Vision: Proceedings of the Twenty-eighth European Conference on Visual Perception. 28th European Conference on Visual Perception, A Coruna, Spain, (27-28). 22-26 August, 2005.

Author Mullen, K. T.
Dumoulin, S. O.
McMahon, K. L.
Bryant, M.
de Zubicaray, G. I.
Hess, R. F.
Title of paper The fMRI response of the LGN and V1 to cardinal red-green, blue-yellow, and achromatic visual stimuli
Conference name 28th European Conference on Visual Perception
Conference location A Coruna, Spain
Conference dates 22-26 August, 2005
Proceedings title Journal of Vision: Proceedings of the Twenty-eighth European Conference on Visual Perception   Check publisher's open access policy
Journal name Perception   Check publisher's open access policy
Place of Publication London, United Kingdom
Publisher Sage Publications
Publication Year 2005
Sub-type Published abstract
Open Access Status Not Open Access
ISSN 0301-0066
1468-4233
Volume 34
Issue Supplement
Start page 27
End page 28
Total pages 2
Language eng
Abstract/Summary We compared the responsiveness of the LGN and the early retinotopic cortical areas to stimulation of the two cone-opponent systems (red - green and blue - yellow) and the achromatic system. This was done at two contrast levels to control for any effect of contrast. MR images were acquired on seven subjects with a 4T Bruker MedSpec scanner. The early visual cortical areas were localised by phase encoded retinotopic mapping with a volumetric analysis (Dumoulin et al, 2003 NeuroImage 18 576 - 587). We initially located the LGN in four subjects by using flickering stimuli in a separate scanning session, but subsequently identified it using the experimental stimuli. Experimental stimuli were sine-wave counterphasing rings (2 Hz, 0.5 cycle deg-1), cardinal for the selective activation of the L/M cone-opponent (RG), S cone-opponent (BY), and achromatic (Ach) systems. A region of interest analysis was performed. When presented at equivalent absolute contrasts (cone contrast = 5% - 6%), the BOLD response of the LGN is strongest to isoluminant red - green stimuli and weakest to blue - yellow stimuli, with the achromatic response falling in between. Area V1, on the other hand, responds best to both chromatic stimuli, with the achromatic response falling below. The key change from the LGN to V1 is a dramatic boost in the relative blue - yellow response, which occurred at both contrast levels used. This greatly enhanced cortical response to blue - yellow relative to the red - green and achromatic responses may be due to an increase in cell number and/or cell response between the LGN and V1. We speculate that the effect might reflect the operation of contrast constancy across colour mechanisms at the cortical level.
Keyword Psychology
Psychology, Experimental
LGN
fMRI
Q-Index Code EX
Q-Index Status Provisional Code
Institutional Status Unknown

 
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Created: Mon, 13 Aug 2007, 15:37:14 EST