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J. McAnany, K. R. Alexander; Is There an Omitted Stimulus Response in the Human Cone Flicker ERG?. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5811.
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© ARVO (1962-2015); The Authors (2016-present)
Following the offset of a repetitive stimulus train, an additional response has been observed in electrophysiological recordings from inner retina and cortex, often termed the omitted stimulus response (OSR). The purpose of this study was to determine if an OSR is present in the human cone flicker electroretinogram (ERG).
Full-field ERGs were recorded from 11 visually normal subjects using a Diagnosys stimulating and recording system and conventional recording techniques. The stimuli consisted of sinusoidal flicker trains presented at temporal frequencies ranging from 25 to 100 Hz. Stimuli were the sum of LED generated middle- and long-wavelength light, presented against a short-wavelength, rod-desensitizing adapting field. For comparison, ERGs were also recorded to single cycles of the sinusoidal flicker trains.
For temporal frequencies below approximately 32 Hz, the number of ERG response cycles equaled the number of stimulus cycles, but above that frequency, the total number of ERG response cycles exceeded the number of stimulus cycles. The amplitude of the additional response was dependent on the temporal frequency of the flicker train. For temporal frequencies between approximately 32 and 62 Hz, the latency between the peak of the last stimulus cycle and the peak of the additional response increased linearly with unit slope as a function of increasing stimulus period. The latency of the additional response was constant across this frequency range when compared to the time at which the next stimulus peak would have occurred. An additional response was also observed following the offset of single-cycle sinusoids at corresponding temporal frequencies, but the amplitude was independent of frequency, and the timing characteristics differed from those following flicker trains.
Following the offset of a flicker train, an additional response can be observed in the cone ERG with properties that resemble those of the OSR reported previously from more proximal sites within the visual pathway. The characteristics of this ERG response suggest that it may be generated by an adaptive oscillator whose resonance frequency is dependent on the stimulus frequency.
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