Physiological model of orientation sensitivity in the visual cortex and its use for image processing

The objectives of the research were: (1) to investigate the dynamics of neuron responses and orientation selectivity in the primary visual cortex; (2) to find a possible source of bifurcation of visual information into `what' and `where' processing pathways; (3) to apply the obtained results for visual image processing. To achieve the objectives, a model of the iso-orientation domain (orientation column) of the visual cortex has been developed. The model is based on neurophysiological data and on the idea that orientation selectivity results from a spatial anisotropy of reciprocal lateral inhibition in the domain. Temporal dynamics of neural responses to oriented stimuli were studied with the model. It was shown that the later phase of neuron response had a much sharper orientation tuning than the initial one. The results of modeling were confirmed by neurophysiological experiments on the visual cortex. The findings allow us to suggest that the initial phase of neural response encodes the location of the visual stimulus, whereas the later phase encodes its orientation. Temporal dividing of information about object features and their locations at the neuronal level of the primary visual cortex may be considered to be a source for bifurcation of the visual processing into `what' and `where' pathways and may be used for parallel-sequential attentional image processing. The model of neural network system for image processing based on the iso-orientation domain model and the above idea is proposed. An example of test image processing is presented.