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Vision System
Published in Joseph D. Bronzino, Donald R. Peterson, Biomedical Engineering Fundamentals, 2019
Aaron P. Batista and George D. Stetten
e cells in the LGN are organized into three pairs of layers. Each pair contains two layers, one from each eye. e upper two pairs consist of parvocellular cells (P cells) that respond with preference to dierent colors and have small dendritic elds. e remaining lower pair of layers consists of magnocellular cells (M cells) with no color preference but with transient responses that contribute to motion perception. ese cells have larger dendritic elds, allowing them to integrate information over broader regions, which is required to detect motion. e topographic mapping is identical for all six layers, that is, passing an electrode through the layers at a given point yields neurons responding to a single area of the retina. Neurons in the LGN display the same center/surround response as the retinal ganglion cells. Axons from the LGN proceed to the primary visual cortex in broad bands, called optic radiations, preserving the topographic mapping found in the LGN.
Impact of Retinal Stimulation on Neuromodulation
Published in Yu Chen, Babak Kateb, Neurophotonics and Brain Mapping, 2017
As they begin the journey to the visual cortex, the vast majority of signals (approximately 90%) leaving the optic nerve travel through the lateral geniculate nucleus (LGN) of the thalamus (Goldstein 2010) for further processing in the visual cortex as part of the central and peripheral eyesight pathways. Those signals lead toward attention on a selected target. Some signals branch off at the LGN to other subcortical structures involved with neurological circuitry and others modulating chemical circuitry as discussed in “Subcortical neurological circuitry” and “Subcortical chemical circuitry.” Some of these subcortical structures include the intergeniculate leaflet, the superior colliculus in the midbrain, the suprachiasmatic nucleus of the hypothalamus, the pineal gland, and the habenula (part of the limbic system connecting with motor circuitry). New research also has demonstrated a direct retinal pathway in humans to the brain’s pulvinar region (another portion of the thalamus) (Arcaro et al. 2015). Many of those locations send signals back to the LGN through feedback loops. Signals continue from the LGN through the optic radiations that traverse the parietal and temporal lobes.
The athletes’ visuomotor system – Cortical processes contributing to faster visuomotor reactions
Published in European Journal of Sport Science, 2018
Thorben Hülsdünker, Heiko K. Strüder, Andreas Mierau
Visual stimuli in the environment first reach the rod and cone receptors in the retina. These photoreceptors form receptive fields and project to ganglion cells that in turn connect via the optic nerve, optic chiasm, lateral geniculate nucleus (LGN) and optic radiation to the primary visual cortex (V1). During this initial signal, transmission contrast and motion information are conveyed in parallel, but by different visual streams corresponding to the parvocellular and magnocellular system, respectively (Prasad & Galetta, 2011).