Textbook Notes (368,652)
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Psychology (3,337)
PSYC 2390 (118)
Lana Trick (87)
Chapter 4

Chapter 4 (Part 1)

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PSYC 2390
Lana Trick

Reading 3 Ch 4a pp 7484Chapter 4 The Visual Cortex and BeyondFollowing the Signals From Retina CortexThe Visual SystemMost of the signals from the retina travel out of the eye in the optic nerve to the lateral geniculate nucleus LGN in the thalamusFrom the LGN signals travel to the primary visual receiving area in the occipital lobe of the cortexThe visual receiving area is also called the striate cortex because of the white stripes striatestriped that are created within this area of cortex by nerve fibers that run through itFrom the striate cortex signals are transmitted to temporal lobe and to the parietal lobe Visual signals also reach areas in the frontal lobe of the brainSuperior colliculus an area involved in controlling the eye movements and other visual behaviours that receives about 10 percent of the fibers from the optic nerveProcessing in the Lateral Geniculate NucleusReceptive Fields of LGN NeuronsLGN neurons have the same centresurround configuration as retinal ganglion cellsNeurons in the LGN respond best to small spots of light on the retinaMajor function of the LGN is not to create new receptive field properties but to regulate neural information as it flows from the retina to the visual cortexInformation Flow in the Lateral Geniculate NucleusNinety percent of the fibers in the optic nerve arrive at the LGN and the other 10 percent travel to the superior colliculusThe LGN also receives signals from the cortex from the brain stem from the neurons in the thalamus and from other neurons in the LGNThus the LGN receives information from many sources including the cortex and then sends its output to the cortexThe LGN receives more input back from the cortex than it receives from the retinaThe smallest signal of all is from the LGN to the cortexFor every 10 nerve impulses the LGN receives from the retina it sends only 4 to the cortexSignals arriving LGN are sorted and organized based on the eye they came from the receptors that generated them and the type of environmental information that is represented in themOrganizing by Left and Right EyesLGN is a bilateral structure meaning there is one LGN in the left hemisphere and one in the right hemisphere 6 layerseach layer receives signals from only one eyeLayers 23 and 5 red layers receive signals from the ipsilateral eye the eye on the same side of the boidy as the LGNLayers 14 and 6 blue layers receive signals from the contralateral eye the eye on the opposite side of the body from the LGN Thus each eye sends half of its neurons to the LGNthat is located in the left hemisphere of the brain and half to the LGN that is located in the right hemisphere
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