Modeling study of orientation sensitivity of lateral geniculate nucleus neurons E Yakimova1, A Chizhov2 |
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1Laboratory of Visual Physiology, Pavlov Institute of Physiology RAS, Russian Federation |
| It was experimentally shown that orientation selectivity is characteristic of not only cortical but also dorsal lateral geniculate nucleus (LGN) neurons in cats. In our work it is shown that cat LGN neurons are sensitive to the orientations of both stimuli, a bar and a brightness gradient. Orientation selectivity index (OSI) is computed as OSI =(Nmax-Nmin)/Nmax, where Nmax and Nmin are amplitude of the responses to preferred and non-preferred orientations of the stimuli bar. The mean value of OSI for 37 neurons is equal to 0.49±0.07 (bar) and 0.59±0.06 (brightness gradient) (p<0.05). With the help of mathematical modeling the factors that might influence the measurements of orientation selectivity are analyzed. Model responses on two types of stimuli 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. |
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