Development of a Spatio-temporal Contrast Sensitivity Test for Clinical Use.

PURPOSE: We developed a contrast sensitivity test that considers an integrative approach of spatial and temporal frequencies to evaluate the psychophysical channels in processing two-dimensional stimulus for clinical use. Our new procedure provides a more efficient isolation of the magnocellular and parvocellular visual pathways supporting spatiotemporal contrast sensitivity processing. METHODS: We evaluated 36 participants of both sexes aged 18-30 years with 20/20 or better best-corrected visual acuity. Two spatial frequencies (0.5 cycles per degree [cpd] and 10 cpd), being in one of the three temporal frequencies (0.5 cycle per second [cps], 7.5 cps, and 15 cps), were presented in a high-resolution gamma corrected monitor. A two-alternative forced-choice procedure was conducted, and the staircase method was used to calculate the contrast sensitivity. Reliability was assessed using a retest procedure within a month ( ± 5 days) under the same conditions. RESULTS: Results showed statistical significance in 0.5 cpd and 10 cpd spatial frequencies for 0.5 cps (F = 77.36; p < 0.001), 7.5 cps (F = 778.37; p < 0.001), and 15 cps (F = 827.23; p < 0.001) with a very high (η ² = 0.89) effect size. No statistical differences were found between the first and second sessions for all spatial frequencies. For reliability, a significantly high correlation and high internal consistency were found in all spatiotemporal conditions. The limits were calculated for normality. CONCLUSION: We developed an approach to investigate the spatiotemporal integration of contrast sensitivity designed for clinical purposes. The relative contribution of the low spatial frequencies/high temporal frequencies and the high spatial frequencies/low temporal frequencies of the psychophysical channels can also be evaluated separately.

A novel nonsense mutation in the tyrosinase gene is related to the albinism in a capuchin monkey (Sapajus apella).

BACKGROUND: Oculocutaneous Albinism (OCA) is an autosomal recessive inherited condition that affects the pigmentation of eyes, hair and skin. The OCA phenotype may be caused by mutations in the tyrosinase gene (TYR), which expresses the tyrosinase enzyme and has an important role in the synthesis of melanin pigment. The aim of this study was to identify the genetic mutation responsible for the albinism in a captive capuchin monkey, and to describe the TYR gene of normal phenotype individuals. In addition, we identified the subject's species. RESULTS: A homozygous nonsense mutation was identified in exon 1 of the TYR gene, with the substitution of a cytosine for a thymine nucleotide (C64T) at codon 22, leading to a premature stop codon (R22X) in the albino robust capuchin monkey. The albino and five non-albino robust capuchin monkeys were identified as Sapajus apella, based on phylogenetic analyses, pelage pattern and geographic provenance. One individual was identified as S. macrocephalus. CONCLUSION: We conclude that the point mutation C64T in the TYR gene is responsible for the OCA1 albino phenotype in the capuchin monkey, classified as Sapajus apella.