Signal transmission in the catfish retina. II. Transmission to type-N cell.
Responses from channel catfish type-N (sustained amacrine) cells were evoked either by step changes in illuminance, i.e. brightening or dimming from a mean illuminance, or by a white-noise modulated light stimulus. Current injected into the horizontal-cell soma or axon produced responses in type-N cells that were very similar to those produced by light stimuli. Light- and current-evoked responses had linear and second- and third-order nonlinear components; the former contributed 40-50%, whereas the latter contributed 20-30% to the total response. The remainder of the response could have been due to higher-order nonlinearities or to intrinsic as well as extrinsic noise. Nonlinear components in the light- and current-evoked responses were sharp transient peaks, which were prominent in white-noise-evoked responses, and oscillatory wavelets. The high-frequency components in the cell's response, which result from nonlinearity, were absent in the responses from bipolar and horizontal cells. The nonlinear responses were predicted by the second- and third-order kernels. The type-N cell response was complex because the response had both linear and nonlinear components, and because of the complexities of second- and, probably, third-order kernels. The cell's complex response reflects the complex nature of the cell's function as well as its synaptic organization.
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D000818:Animals; D004558:Electric Stimulation; D005074:Evoked Potentials, Visual; D005399:Fishes / Q000502:physiology*; D008027:Light; D008959:Models, Neurological; D009474:Neurons / Q000502:physiology; D012160:Retina / Q000166:cytology* / Q000502:physiology; D009435:Synaptic Transmission; D014785:Vision, Ocular / Q000502:physiology*