ABSTRACT
It was experimentally shown that orientation selectivity is characteristic of not only cortical but also dorsal lateral geniculate nucleus neurons in cats. With the help of mathematical modeling the factors that might influence the measurements of orientation selectivity are analyzed in the present work. Model responses on two types of stimuli, bars and brightness gradients, are qualitatively consistent with experimental data. It was shown that the non-zero orientation selectivity index may be caused by either the elongation of receptive field together with nonlinear saturation effects or the shift of the receptive field center relative to the stimulus center.
Subject(s)
Geniculate Bodies/physiology , Neurons/physiology , Orientation/physiology , Visual Cortex/physiology , Animals , Cats , Humans , Models, Theoretical , Photic StimulationABSTRACT
Neuronal mechanisms of description of local properties of visual object light-shadow surfaces are studied. Earlier we have shown the cat lateral geniculate body (LGB) neurons to have sensitivity to the value and direction of brightness vector in loci of object light-shadow surfaces. Further study of properties of orientational selectivity (OS) of these neurons has revealed that single LGB cells sensitive to direction of the brightness gradient vector also have the classical OS to direction of test bands. Such complex orientational sensitivity of neurons to direction of binary and light-shadow fragments of visual objects is of essential significance, in our opinion, for understanding of principles and mechanisms of object vision.
