Parallel detection of orientation differences in the presence of orientation gradients

Orientation bias of the extraclassical receptive field of the relay cells in the cat's dorsal lateral geniculate nucleus

The spatial properties of the extraclassical receptive fields (ECRF) of neurons responding to a stimulus restricted to it and its interaction with the classical receptive field (CRF) in visual information processing were investigated in 74 relay cells in the dorsal lateral geniculate nucleus (LGNd) of anesthetized cats. The results demonstrate that the ECRF of most relay cells in the LGNd responded preferentially to a grating stimulus of low spatial frequency through a mechanism of spatial summation. These biased cells showed a significant orientation bias which was relatively smaller than that of the CRF. The preferred orientations of the ECRF were not correlated with those of the CRF in most relay cells. The orientation biased ECRFs and CRFs interacted with each other in a non-linear way, resulting in a great diversity of response properties. Overall, the CRF played a more significant role than the ECRF in determining a cell's orientation bias and preferred orientation. The ECRF mostly showed a modulatory role mainly in suppressing and/or in partially facilitating the neural response to stimulation in the CRF although in some cases, the ECRF did determine a cell's responsiveness and orientation sensitivity. These results suggest that the ECRF might contribute to the ability of the LGNd neurons to detect some complex features such as texture segmentation and provide a subcortical contribution to the integrative field of visual cortical cells through receiving inputs from retinal ganglion cells with similar orientation biased extended surrounds [Neuroscience 98 (2000) 207].

Biophysical vision model and learning paradigms about vision: review

A learning paradigm of a new biophysical vision model (BVM) is presented. It incorporates anatomical and physiological evidence from micro- and macroscopic research on vision as reported in the literature during the past five years. Anatomical and physiological vision research tends to drift away from the technological foundations of encoding and reproducing size-defined images of real ongoing life scenarios. White and color light waves reflecting life scenarios are converted by the retina to encoded electrical train pulses with attached real information to be decoded by cortical vision neurons. The BVM paradigm is based on the ideas that: (1) cinema technology reproduces real-life scenes just as the human eye sees them; (2) virtual reality and robotics are computerized replications of categorized human vision faculties in operation. We believe that vision-related technology may extend our knowledge about vision and direct vision research into new horizons. The biophysical vision model has three prerequisites: (1) The faculties of human vision must be categorized. (2) Logic circuits of the 'hardware' of neuronal vision must be present. (3) Vision faculties are operated by self-induced 'software'. Vision research may be enhanced with devices constructed according to BVM that would enable biophysical vision experiments in both humans and animals.