A central goal in sensory neuroscience is to fully characterize a neuron's input-output relation. However, strong nonlinearities in the responses of sensory neurons have made it difficult to develop models that generalize to arbitrary stimuli. Typically, the standard linear-nonlinear models break down when neurons exhibit stimulus-dependent modulations of their gain or selectivity. We studied t...

Experimental evidences [1-5] indicate that orientation selectivity develops in the absence of visual experience. Here, we present a model for pre-eye opening development of orientation selectivity. The model essentially models layer IV cortical cells and confirms the poor orientation tuning observed in layer IV ceCls. We also show that post synaptic potential to spike transformation indeed play...

Achieving selective C–H functionalization is a significant challenge that requires discrimination between many similar C–H bonds. Yet, reaction systems employing Rh2(DOSP)4 and Rh2(BPCP)4 were recently demonstrated to afford high levels of selectivity in the C–H insertion of carbenes into toluene-derived substrates. Herein, we explore the origin of this selectivity through a systematic analysis...

In this paper, we found that spatial and temporal asymmetricity of excitatory connections are able to generate directional selectivity which can be enhanced by asymmetrical inhibitory connections by reconstructing a hexagonally-arranged three-layered simulation model of retina by NEURON simulator. Asymmetric excitatory inputs to ganglion cells with randomly arborizing dendrites were able to gen...

In this paper, we offer an explanation for how selectivity for orientation could be produced by a model with circuitry that is based on the anatomy of V1 cortex. It is a network model of layer 4Calpha in macaque primary visual cortex (area V1). The model consists of a large number of integrate-and-fire conductance-based point neurons, both excitatory and inhibitory, which represent dynamics in ...

It is well known that visual cortical neurons respond vigorously to a limited range of stimulus orientations, while their primary afferent inputs, neurons in the lateral geniculate nucleus (LGN), respond well to all orientations. Mechanisms based on intracortical inhibition and/or converging thalamocortical afferents have previously been suggested to underlie the generation of cortical orientat...

It is well known that visual cortical neurons respond vigorously to a limited range of stimulus orientations while their primary a erent inputs neurons in the lateral geniculate nucleus LGN respond well to all orientations Mechanisms based on intracortical inhibition and or converging thalamocortical a erents have previ ously been suggested to underlie the generation of cortical orientation sel...

We report an experimental study of the influences of the fixed charge and bulk ionic concentrations on the conduction of biological ion channels, and we consider the results within the framework of the ionic Coulomb blockade model of permeation and selectivity. Voltage clamp recordings were used to investigate the Na/Ca anomalous mole fraction effect (AMFE) exhibited by the bacterial sodium cha...

From the intracellularly recorded responses to small, rapidly flashed spots, we have quantitatively mapped the receptive fields of simple cells in the cat visual cortex. We then applied these maps to a feedforward model of orientation selectivity. Both the preferred orientation and the width of orientation tuning of the responses to oriented stimuli were well predicted by the model. Where teste...

Visual cortical neurons are selective for the orientation of lines, and the full development of this selectivity requires natural visual experience after eye opening. Here we examined whether this selectivity develops without seeing lines and contours. Juvenile ferrets were reared in a dark room and visually trained by being shown a movie of flickering, sparse spots. We found that despite the l...