Components of the electroretinogram: a reappraisal |
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Authors: | Pierre Lachapelle Stephane Molotchnikoff |
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Affiliation: | (1) Department of Ophthalmology, McGill University, Montreal Children's Hospital, H3H 1P3 Montréal, Canada;(2) Départment de Sciences Biologiques, Université de Montréal, Montréal, Canada |
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Abstract: | During light adaptation a progressive increase in the intensity of a flash stimulus yields ERGs in which the a-wave shows a gradual reduction in peak time, while the b-wave appears to do the opposite. However, close inspection of the different ERG waveforms indicates that the wave identified as the b-wave for a threshold stimulus actually decreases in peak time with progressively stronger stimulus. Furthermore, what is identified as the b-wave for a threshold stimulus delivered in light adaptation will become a part of the a-wave complex if the same stimulus is used in dark adaptation. Data presented here indicate that the identification of the a- and b-waves of the ERG must be constantly revised according to the intensity of the stimulus and/or the level of retinal adaptation. These findings seriously challenge the validity of the a-b-wave nomenclature currently used in electroretinography. An alternative nomenclature, based on the first derivative (dv/dt) of the ERG wave, is proposed. |
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Keywords: | electroretinography human oscillatory potentials retina |
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