title: Temporal transfer and nonlinearity properties of turtle ERG: tuning by temperature, pharmacology, and light intensity.
abstract: ERG impulse response, amplitude and phase temporal spectral transfer functions, and nonlinearities were measured in turtle retina under different retinal temperatures, pharmacological treatments, and light intensities. beta-Wave amplitude is strongly temperature dependent; amplitudes of the alpha-wave and slow P-III are less sensitive. Their time courses all slow markedly as temperature decreases. ERG amplitude transfer function is bimodal bandpass with narrow low-frequency peak (below 1 Hz) and broader mid-frequency peak (5 Hz at 8 degrees C). Both peaks broaden and their frequency increases (low, 1 Hz; mid, 15 Hz, at 23 degrees C) as temperature increases. Phase transfer function slope decreases (from -70 degrees/Hz at 8 degrees C to -25 degrees/Hz at 23 degrees C) as temperature increases. Nonlinear properties of ERG at high input intensity are modelled by a quadratic nonlinearity, low-pass prefilter with cutoff above 12.4 Hz, and low-pass postfilter broadly peaked at 6-10 Hz with cutoff above 20 Hz. For low input intensity, ERG exhibits linear properties with low-pass filtering sharply cut off above 6 Hz. alpha-Wave and slow P-III were isolated by aspartate treatment; depolarizing bipolar cell activity was examined using ethanol/GABA treatment of retina. High-frequency components, including broad mid-frequency peak, were attenuated and low-frequency components were enhanced with aspartate. Transfer function narrows and peaks at a lower frequency with ethanol/GABA.
mesh_terms: D000818:Animals; D001224:Aspartic Acid / Q000494:pharmacology; D004596:Electroretinography; D000431:Ethanol / Q000494:pharmacology; D006358:Hot Temperature; D066298:In Vitro Techniques; D008027:Light; D012160:Retina / Q000187:drug effects / Q000502:physiology*; D013696:Temperature; D014426:Turtles / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
chemical_list: D001224:Aspartic Acid; D000431:Ethanol; D005680:gamma-Aminobutyric Acid