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T. Redmond, M. B. Zlatkova, A. Vassilev, D. F. Garway-Heath, R. S. Anderson; Changes in Ricco’s Area With Background Adaptation Level in the S-Cone Pathway. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3805.
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A reduction in the area of complete spatial summation (Ricco’s area) has previously been demonstrated as a function of background intensity for achromatic stimuli. It was hypothesised that increased receptive field centre-surround antagonism was responsible for such changes. In this study, we explored the effect of blue background adaptation level on Ricco’s area for the S-cone pathway.
S-cones were isolated using Stiles two-colour threshold method. The area of complete spatial summation was determined for six subjects of different ages using blue background levels ranging from 2.08 - 3.35 log S-td at 10° eccentricity in the temporal retina. 2AFC (temporal) procedures were employed. Stimulus duration was 0.2 sec. Control experiments involved repeating the measurement of Ricco's area for two subjects using simulated lens yellowing filters in order to investigate the effect of crystalline lens brunescence on our results.
Results show a decrease in Ricco’s area (average decrease = 0.35log min2) with background adaptation level for most subjects (4 out of 6), who were aged between 20-27years while remaining largely unchanged for the others who were aged 41 and 56. Control experiments altered changes in Ricco's area for both subjects, reducing the average decrease to 0.02log min2 with blue background luminance)
If increased centre-surround antagonism is accountable for changes in Ricco’s area for achromatic stimuli with background intensity, our results are not what one would initially expect from a pathway with no identified concentric receptive field system. Control experiments suggest that lens yellowing can partially explain the rate at which Ricco’s area changes with background adaptation level.
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