Thalamus nucleus {lateral geniculate nucleus}| (LGN) is for object identification [Przybyszewski et al., 2000] [Shepherd, 1998] [Sherman and Guillery, 2001] [Sherman and Koch, 1998].
input
LGN receives from all senses except olfaction, especially from retinal ganglion neurons. It is sensitive to eye position. It has dermatomal segments to represent body sensations.
Thalamus receives much more feedback from cortex than it sends to cortex. Such positive and negative feedback probably applies learned and innate information to bias stimulation, which predicts stimuli [Koch, 1987] [Mumford, 1991] [Mumford, 1994] [Rao and Ballard, 1999].
LGN has circular receptive fields.
output
LGN sends, through optic radiation {geniculostriate pathway, vision}, to visual cortex area V1 in occipital lobe. Geniculostriate and tectopulvinar pathways interact.
LGN sends to somaesthetic cortex.
LGN sends to overlapping, multiple lateral geniculate nucleus cells {relay cell}. Through dendrodendritic connections, LGN affects neurons up to five millimeters away.
Neurons inhibit themselves.
damage
Damage to lateral geniculate causes poor acuity.
anatomy: layers
Lateral geniculate nucleus has six separate cell layers, four parvocellular layers at top with small cells and two magnocellular layers at bottom with large cells. Parvocellular and magnocellular core neurons send to one cortex region.
LGN layers 1, 4, and 6 are for opposite-side eye. Layers 2, 3, and 5 are for same-side eye. Layer 1 and 2 neurons respond to OFF, at any wavelength. Layer 3 and 4 neurons respond to ON or OFF, at wavelength range. Layer 5 and 6 neurons respond to ON, at wavelength range. Layer 3 and 4 neurons have opponent cells for red-green and blue-yellow.
anatomy: magnocellular
Magnocellular cells receive from bipolar cells with bigger dendrite trees and send transient signals to visual-cortex layer 4c-alpha and layer 6. These large cells are for temporal resolution, movement, and flicker. Optic-tract axons from right and left eyes synapse on separate magnocellular neurons, in bands.
anatomy: parvocellular
Parvocellular cells receive from midget cells and send sustained signals to visual-cortex layer 4cbeta. Small cells are for color, spatial resolution, texture, shape, depth perception, and stereopsis [Merigan and Maunsell, 1993] [Schiller and Logothetis, 1990].
anatomy: koniocellular
Between layers are koniocellular neurons {matrix cell} that code for blue-yellow opponency, the difference between S cones and L+M cones [Calkins, 2000] [Chatterjee and Callaway, 2002] [Dacey, 1996] [Nathans, 1999]. Koniocellular cells go to several regions.
anatomy: Y cells
Y cells maintain activity after moving object crosses receptive field, using cortico-thalamic feedback.
color processing
Brain has four opponent processes. Cell can react oppositely to red and green or green and red. Cell can react oppositely to blue and yellow or yellow and blue. Luminance is sum of red and green. Comparisons cross, so the three colors add orthogonally.
Biological Sciences>Zoology>Organ>Nerve>Brain>Cerebrum>Diencephalon>Thalamus
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Date Modified: 2022.0224