Document Detail

Color discrimination along the cardinal chromatic axes with VECPs as an index of function of the parvocellular pathway. Correspondence of intersubject and axis variations to psychophysics.
MedLine Citation:
PMID:  8964258     Owner:  NLM     Status:  MEDLINE    
Chromatic information is carried only by the parvocellular pathway, giving the neurophysiologist the opportunity for eliciting specific responses. Further subdivision of the parvo chromatic system in two opponent chromatic mechanisms is potentially of great interest, given that the anatomical correlate seems to reside in subclasses of parvo ganglion cells that show differences both in size and in susceptibility to disease. We separately recorded responses arising from each chromatic opponent mechanism using visual stimuli chosen to belong to one of the "cardinal" chromatic axes. A calibrated color monitor, driven by a high resolution (14 bits/gun) computer board, was used for visualization of 1 c/deg isoluminant color gratings, sinusoidally modulated in time at 4 Hz. VECPs were recorded at several color contrasts along both cardinal axes, allowing extrapolation of contrast thresholds. Psychophysical thresholds were derived in the same stimulus conditions for comparison and found to correlate very well with the electrophysiologically derived values, both as intersubject and axis differences. The S-(L+M) opponent mechanism consistently yielded higher thresholds, smaller amplitude, and higher phase lag than the L-M mechanism. This finding was largely explained by the perceptual non-uniformity of the CIE chromaticity diagram. Correcting the VECP data for the perceptual differences yielded comparable responses, supporting the view that the two mechanisms are similarly represented in the cortex. In conclusion, recording of cortical responses to color contrast stimuli belonging to the cardinal chromatic axes seems a reliable procedure and may prove to be useful in performing clinical evaluations that refine the assessment of the physiology of the visual system.
C Macaluso; A Lamedica; G Baratta; M Cordella
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Electroencephalography and clinical neurophysiology     Volume:  100     ISSN:  0013-4694     ISO Abbreviation:  Electroencephalogr Clin Neurophysiol     Publication Date:  1996 Jan 
Date Detail:
Created Date:  1996-12-11     Completed Date:  1996-12-11     Revised Date:  2008-09-09    
Medline Journal Info:
Nlm Unique ID:  0375035     Medline TA:  Electroencephalogr Clin Neurophysiol     Country:  IRELAND    
Other Details:
Languages:  eng     Pagination:  12-7     Citation Subset:  IM    
Department of Ophthalmology, University of Parma, Italy.
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MeSH Terms
Color Perception / physiology*
Discrimination (Psychology)*
Evoked Potentials, Visual*
Sensory Thresholds
Visual Cortex / physiology*
Visual Pathways / physiology*

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