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Orientation column
About: Orientation column is a research topic. Over the lifetime, 1142 publications have been published within this topic receiving 130169 citations.
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TL;DR: In the present series of experiments, evidence for a columnar organisation of the rabbit visual cortex based on orientationand direction-selectivity has been re-examined and is suggested.
23 citations
TL;DR: Results did not support the idea of any specific receptive field compensatory mechanism, but the existence of nonspecific vestibular effects on visual cortex cells was not ruled out.
23 citations
TL;DR: It was observed that the region of higher ganglion cell density in the retina shows a flattened distribution and that the CBA intersects the retina at the temporal aspect of this region, suggesting that the ipsilateral field of both eyes may be represented in the striate cortex via the psilateral optic tract.
Abstract: Reference axes for the visuotopic study of the opossum's striate cortex were estimated from corresponding binocular response fields using multi-unit recording. These central binocular axes (CBA) were derived from experimental data based on the concept that corresponding receptive fields for each eye should be mostly in register under natural conditions. Vertical reference meridians, orthogonal to these axes, define a contralateral and an ipsilateral field for each eye with respect to the recording site. An ipsilateral field representation was observed for both eyes in the striate cortex at the transition zone with peristriate. Maximal values for the center and border of ipsilateral receptive fields were, respectively, 8 and 20 degrees for the contralateral eye and 6 and 14 degrees for the ipsilateral eye. An equivalent ipsilateral field representation was found in animals that had the anterior commissure cut prior to the recording session. This suggests that the ipsilateral field of both eyes may be represented in the striate cortex via the ipsilateral optic tract. Additionally, it was observed that the region of higher ganglion cell density in the retina shows a flattened distribution and that the CBA intersects the retina at the temporal aspect of this region.
23 citations
TL;DR: It is concluded that at least from two weeks of age onwards, intracortical tangential connections are not necessary for the development of the regular pattern of iso-orientation bands in the striate cortex of cats.
23 citations
TL;DR: The hypothesis that neurons in cortical slices emit spikes or bursts of spikes regularly in response to a suprathreshold current injection are the result of the synchronized chaos generated by the deterministic dynamics of local cortical networks is explored.
Abstract: Neurons in cortical slices emit spikes or bursts of spikes regularly in response to a suprathreshold current injection. This is in marked contrast to the behavior of cortical neurons in-vivo, whose response to electrical or sensory input displays a strong degree of irregularity. Correlation measurements show significant degree of synchrony in the temporal fluctuations of neuronal activities in cortex. We explore the hypothesis that these phenomena are the result of the synchronized chaos generated by the deterministic dynamics of local cortical networks. A model of a “hypercolumn” in the visual cortex is studied. It consists of two populations of neurons, one inhibitory and one excitatory. The dynamics of the neurons is based on a Hodgkin–Huxley type model with several cellular and synaptic conductances. The pattern of connectivity is correlated with the internal organization of hypercolumns in orientation columns. Numerical simulations of the model show that in an appropriate parameter range, the network settles in a synchronous chaotic state, characterized by a strong temporal variability of the neural activity which is correlated across the hypercolumn. Strong inhibitory feedback is essential for the stabilization of this state. Auto-correlation and cross-correlation functions of neuronal spike trains are computed, and analyzed. The relation between the results of the model and experiments in visual cortex is discussed.
22 citations