Wiener Kernel Analyses of the Functional Microstructure of a Crustacean Visual Field

The microstructure of the excitatory field of the crayfish sustaining fiber 038 was studied by Wiener kernel analysis. By treating the receptive field as a multi-input single-output system, Volterra's, and Wiener's, nonlinear functional formalisms for such systems could be invoked to define the canonical types of interactions that could, and do, underlie the field. A light emitting diode/fiber optic stimulus package was developed for these experiments to provide the required spatial configurations of independently (noise-) modulated sources; optimally excite the crayfish 1s yellow-sensitive visual system; and to eliminate the artifacts that might arise from conventional light sources' spectral dependence on drive current. The second-order cross kernels computed from 2-, and 4-input experiments indicate that a lateral excitation phenomenon is predominant in the field. Evidence for lateral inhibition (between yellow channels) is indirect, but suggestive that inhibition manifests itself through a third-order cross term. 038 does receive inputs from yellow and blue channels, and their is evidence of yellow channel inhibition of the blue channel. Periodic structure found in 038 1s spike train response to multiple stimuli can be modelled by first and second-order self kernels without the use of cross terms. Analysis of the kernel dynamics leads to a model of the functional microstructure subserving 038 1s excitatory field.