Using electroretinograms to assess flicker fusion frequency in domestic hens Gallus gallus domesticus
2012
Abstract The assessment of
flickerfusion frequency (FFF), the stimulus frequency at which a
flickeringlight stimulus can no longer be resolved and appears continuous, and critical
flickerfusion frequency (CFF; the highest frequency at any light intensity that an observer can resolve
flicker) are useful methods for comparing temporal resolution capabilities between animals. Behavioural experiments have found that average CFFs in domestic chickens (
Gallus gallus domesticus) are in the range of ca. 75–87 Hz, measured in response to full spectrum (i.e. white light plus UV) stimuli. In order to examine whether the chicken retina is able to detect
flickerat higher frequencies, we used electroretinograms (
ERGs) to assess FFF/CFF in adult hens from two commercial genotypes, Lohmann Selected Leghorns (LSLs) and Lohmann Browns (LBs).
ERGswere recorded in response to
flickeringlight at ten
full spectrum lightintensities ranging from 0.7 to 2740 cd m −2 . Two methods were used to determine FFF/CFF from the
ERGrecordings and these methods yielded very similar results, with average FFF ranging from ca. 20 Hz at 0.7 cd m −2 to an average CFF of ca. 105 Hz at 2740 cd m −2 . In some individuals, CFFs of 118–119 Hz were recorded. The Intensity/FFF (I/FFF) curves are double-branched with a break point representing the rod-cone transition occurring between 2.5 and 5.9 cd m −2 . No significant differences in the I/FFF curves were found between the two genotypes. At stimulus light intensities >250 cd m −2 , the
ERG-derived FFF and CFF values are all higher than those from behavioural studies using the same stimuli. Although hens do not appear to be able to consciously perceive
flickerabove approximately 90 Hz, the finding that the
ERGresponses are able to remain in phase with light
flickeringat frequencies >100 Hz means that the retinae of domestic poultry housed in artificial light conditions may be able to resolve
flickerfrom
fluorescent lamps. As range of detrimental effects have been reported in humans as a result of exposure to such “invisible
flicker”, the possibility exists that
flickerfrom
fluorescent lampsalso acts as stressor in
domesticated birds.
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