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  • Psychophysical analysis of contrast processing segregated into magnocellular and parvocellular systems in asymptomatic carriers of 11778 Leber's hereditary optic neuropathy

Visual Neuroscience

  • Visual Neuroscience (2008), 25 : pp 469-474
  • Copyright © Cambridge University Press 2008
  • DOI: 10.1017/S0952523808080462 (About DOI)
  • Published online: 03 July 2008

Table of Contents - 2008 - Volume 25, Issue 03  

Research Article

Psychophysical analysis of contrast processing segregated into magnocellular and parvocellular systems in asymptomatic carriers of 11778 Leber's hereditary optic neuropathy

M. GUALTIERIa1a2 c1, M. BANDEIRAa1a2, R.D. HAMERa1a8, M.F. COSTAa1a2, A.G.F. OLIVEIRAa1a2, A.L.A. MOURAa1a2, F. SADUNa3, A.M. DE NEGRIa4, A. BEREZOVSKYa5, S.R. SALOMÃOa5, V. CARELLIa6, A.A. SADUNa7 and D.F. VENTURAa1a2

a1 Departmento de Psicologia Experimental, Universidade de São Paulo, São Paulo, Brasil

a2 Núcleo de Neurociências e Comportamento, Universidade de São Paulo, São Paulo, Brasil

a3 Ospedale S. Giovanni Evangelista, Tivoli, Italy

a4 Azienda Ospedaliera S. Camillo-Forlanini, Roma, Italy

a5 Departmento de Oftalmologia, Universidade Federal de São Paulo, São Paulo, Brasil

a6 Neurology, University of Bologna, Bologna, Italy

a7 Doheny Eye Institute, Keck-USC School of Medicine, Los Angeles, California

a8 Smith-Kettlewell Eye Research Institute, San Francisco, California

Abstract

We examined achromatic contrast discrimination in asymptomatic carriers of 11778 Leber‘s hereditary optic neuropathy (LHON 18 controls) and 18 age-match were also tested. To evaluate magnocellular (MC) and Parvocellular (PC) contrast discrimination, we used a version of Pokorny and Smith's (1997) pulsed/steady-pedestal paradigms (PPP/SPP) thought to be detected via PC and MC pathways, respectively. A luminance pedestal (four 1° × 1° squares) was presented on a 12 cd/m2 surround. The luminance of one of the squares (trial square, TS) was randomly incremented for either 17 or 133 ms. Observers had to detect the TS, in a forced-choice task, at each duration, for three pedestal levels: 7, 12, 19 cd/m2. In the SPP, the pedestal was fixed, and the TS was modulated. For the PPP, all four pedestal squares pulsed for 17 or 133 ms, and the TS was simultaneously incremented or decremented. We found that contrast discrimination thresholds of LHON carriers were significantly higher than controls' in the condition with the highest luminance of both paradigms, implying impaired contrast processing with no evidence of differential sensitivity losses between the two systems. Carriers’ thresholds manifested significantly longer temporal integration than controls in the SPP, consistent with slowed MC responses. The SPP and PPP paradigms can identify contrast and temporal processing deficits in asymptomatic LHON carriers, and thus provide an additional tool for early detection and characterization of the disease.

(Received September 29 2007)

(Accepted February 27 2008)

KEYWORDS

Correspondence:

c1 Address correspondence and reprint requests to: Mirella Gualtieri, Universidade de São Paulo, Instituto de Psicologia, Av. Prof. Mello Moraes, 1721, 05508-900. Sao Paulo SP, Brasil. E-mail: mirellag@usp.br

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