Showing items related by title, author, creator and subject.

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  Bias effects of short- and long-term color memory for unique objects

  Bloj, Marina; Weiß, D.; Gegenfurtner, K.R. (2016-03-09)

  Are objects remembered with a more saturated color? Some of the evidence supporting this statement comes from research using “memory colors”—the typical colors of particular objects, for example, the green of grass. The problematic aspect of these findings is that many different exemplars exist, some of which might exhibit a higher saturation than the one measured by the experimenter. Here we avoid this problem by using unique personal items and comparing long- and short-term color memory matches (in hue, value, and chroma) with those obtained with the object present. Our results, on average, confirm that objects are remembered as more saturated than they are.
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  An electrophysiological study of chromatic processing in the human visual system. Using visual evoked potentials and electroretinograms to study cortical and retinal contributions to human trichromatic vision.

  McKeefry, Declan J.; Challa, Naveen K. (University of BradfordBradford School of Optometry and Vision Science, 2012-01-24)

  The work in this thesis is concerned with examining the retinal and cortical contributions to human trichromatic colour vision. Chromatic processing at the cortex level was examined using visual evoked potentials (VEPs). These responses were elicited by chromatic spot stimuli, which were manipulated in order to selectively activate the chromatic processing system. Chromatic processing at the retinal level was examined using the electroretinograms (ERGs) for which cone isolating stimuli were used to assess the nature of L and M cone inputs to cone-opponent mechanisms. The results from the VEP experiments suggest VEP morphology is dependent upon 1) chromatic and or luminance contrast content of the stimulus, 2) stimulus size, and 3) extent to which the chromatic stimulus activates either the L/M or S/(L+M) opponent mechanism. The experiments indicate that chromatic stimulation is indexed by large N1 component and small offset responses. Optimal stimulus size for chromatic isolation is 2-4 ° along L/M axes and 6° along S/(L+M) axis. From the ERG experiments, It has been shown that the low (12Hz) and high (30Hz) temporal frequency flickering stimuli can isolate the chromatic and luminance processing mechanisms in the retina. For low temporal frequency ERGs, the L:M ratio was close to unity and L/M phase difference was close to 180°. For high temporal frequency ERGs, the L:M ratio was more than unity and L/M phase difference was close to 90°. In addition to this, the variation in L:M ratio across the retinal eccentricity was also examined. These results suggest, for the chromatic processing, L:M ratio is close to unity independent of retinal eccentricity and individuals. For the luminance processing, L:M ratio is more than unity and depends upon the region of the retina being stimulated. These findings indicate the maintenance of cone selective input for the chromatic processing across the human retina.
• Letter to the Editor concerning “A systematic review of controlled trials on visual stress using intuitive overlays or colorimeter"

  Griffiths, P.G.; Taylor, R.H.; Henderson, L.M.; Barrett, Brendan T. (2017)

  We read with interest the review written by Evans and Allen, and published in the Journal of Optometry, in July, 2016.