Orientation Selectivity and Its Modulation by Local and Long-Range Connections in Visual Cortex

Publisher Summary This chapter presents the models and data constituting a powerful argument for the proposal that orientation selectivity is generated and modulated by a combination of thalamocortical inputs to visual cortex (VI) neurons and intracortical processing. Cortical neurons are embedded in diverse circuitry: Each neuron receives not only excitatory thalamocortical inputs but also excitatory intracortical input from local neurons, inhibitory input from local interneurons, and excitatory long range input from distant neurons. A model involving iso-orientation intracortical excitation to amplify lateral geniculate nucleus (LGN) responses at line ends is able to reproduce the subjective contour responses and representations within V1. These response properties include orientation selectivity, modulation of orientation selective responses by spatial context or surround stimuli, and modulation as well by temporal context or pattern adaptation. A linear feedforward model of orientation selectivity is adequate for explaining the simplest, first-order, responses of V1 neurons, at a time when responses to unitary stimuli presented within the receptive field center are regarded as the only significant property of V1 cells.