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A.H. Gutherie, B.R. Hammond; Macular Pigment and Scotopic Noise . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1784.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Lutein and zeaxanthin are the predominate carotenoids within the central retina (there, termed macular pigment, MP) and human brain (composing some 70% of the total carotenoids). The finding that the macular carotenoids bind to structural proteins (like tubulin) and may enhance gap junctional communication suggests a possible role for these pigments in improving neural efficiency. Consistent with this possibility, Hammond and Wooten (in press) recently showed that MP was significantly related to higher temporal processing speeds (CFF thresholds) even for young subjects. In this study, we examined the relation between MP and intrinsic noise in the scotopic system. Methods:Thirteen participants (mean age = 33.5 yrs, range = 20–52 yrs, 9 women & 4 men) were assessed. MPOD was measured using a 1–deg, 460–nm circular test stimulus using heterochromatic flicker photometry. Scotopic thresholds were assessed using a 1.85–deg, 510–nm circular test stimulus located at 10–deg eccentricity in the left visual field and presented in Maxwellian–view. Thresholds were obtained using a two–alternative forced–choice paradigm (an average of 100 trials per subject were obtained). Threshold estimates were derived using probit analysis. In this procedure, the transformed binomial data (the inverse of the normal probability integral) is fit with a weighted linear regression. Noise was defined as the average deviation from this line. Results: The average MP density was 0.34 (SD = 0.16, range = 0.07– 0.59). Variation in absolute scotopic sensitivity was small (range in log relative sensitivity = 3.3–3.7) and was not related to MP density. In contrast, intrinsic noise varied by a factor of 10 and was significantly related to MPOD (r = –0.59, p < 0.015). None of the results were related to age differences. Conclusions: Intrinsic noise tends to be high in scotopic systems. Our preliminary data suggest that MP might be related to variation in these noise levels even in relatively young subjects.
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