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The Role of Competitive Cortical Interactions in the Development of Orientation Selectivity Maps
Zitatschlüssel Machenschalk1998
Autor Machenschalk, B. and Pieenbrock, C. and Obermayer, K.
Buchtitel European J. Neurosc, 10(S10):pg 243
Jahr 1998
Verlag European Forum of Neuroscience ENA
Zusammenfassung We study a model for the development of orientation selectivity (OR) maps in the primary visual cortex based on competitive intracortical dynamics. The model consists of two input layers of ON and OFF neurons in the lateral geniculate nucleus (LGN) and a layer of nonlinear cortical neurons. The nonlinearity in the model, i.e. the degree of competition between the cortical neurons, can be varied systematically. In the limit of weak competition the model becomes a Correlation Based Learning (CBL) model and for strong competition it resembles a Self Organizing Map (SOM). Localized stimuli from the retina drive the Hebbian learning of the afferent projection to the primary visual cortex. We have studied the model for different types of stimuli that have been proposed to underly the OR map formation. We found that input patterns originating from spontaneous retinal activity filtered by circular center-surround receptive fields yield OR maps–-however, only for weak intracortical competition. For increasing competition, the model shows a sudden transition where the oriented receptive fields turn into localized non-oriented center-surround fields. In the limit of strong competition elongated stimuli are necessary for the emergence of OR. This effect is explained by a mathematical analysis of the model. Without any competition only the second order pattern statistics determine the receptive field profiles, whereas for strong competition the higher order statistics of the patterns become important which include information about the stimulus location and orientation.
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