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Visual Fields (Anatomy of Striate Cortex LGNs primary visual cortex…

- - - - Cortical Magnification
        more GCs with RFs in fovea
        
        more neurons in V1 that receive info from central retina
        central retina is over represented in V1
        
        Discrete point of light
        can activate many RGCs and large pop of neurons in V1
  - - - Layer 4
        has 3 subdivisions (A,B,C)
        
        Layer 4C
        has two subdivisions: alpha and beta
        has spiny stellate cells
        
        Outside Layer 4C
        pyramidal cells
  - - - Layer 4CAlpha
        magnocellular LGN
      - Layer 4CBeta
        parvocellular LGN
        information from each eye remains segregated
      - Layers I and III
        koniocellular LGN
    - - Radial Connections
        intracortical connections extend perpendicularly through layers
        Layers 4Calpha to 4B; layer 4Cbeta to 3
        
        Pyramidal Cells
        Send Axons into white matter
        
        Layer 2, 3, 4B
        project to other cortical areas
        
        Layer 5
        project to superior colliculus and pons
        
        Layer 6
        project back to LGN
  - - - Distribution of axon terminals from injected eye
        was NOT continuous in layer 4C
        split into equally spaced patches - alternating inputs from 2 eyes
        
        Left eye and Right eye inputs to layer 4
        are series of alternating bands
        as distinct in layer 4 as in LGN
    - - columns extend through thickness of V1
        
        outside of layer 4 neurons are binocular
        see both hemispheres
    - - run full thickness of layers 2, 3, 5, 6
        
        receive input from koniocellular layers of LGN
        and magno and Parvo from layer 4C
        
        line up with ocular dominant columns
  - - - Layer 4Calpha
        insensitive to wavelength
        monocular receptive fields
        (M Type)
      - Layer 4Cbeta
        center-surround color opponency
        info from both eyes - binocular receptive fields
        (P type)
    - - most neurons in layers above 4C are binocular
        
        Layer 2 and 3
        strongly driven by eye in 4C but still binocular
  - - - Outside layer 4C
        RFs not circular
        respond to particular orientation
        
        any layer in column responds to specific orientation
    - - fire APs in direction-dependent response from moving bar
    - - respond to ON and OFF responses at particular orientation
- - - - divided into temporal and nasal retina
        
        Left Hemifield
        left nasal and right temporal retina
        
        projects to right side of brain
        
        Right Hemifield
        right nasal and left remporal
        
        projects to left side of brain
        
        Ganglion cell axons from nasal retina cross in optic chiasm
        
        needed to see image as one
  - - - Nasal Contralateral
- - - - Right LGN
        receives info from left visual field
        
        Right eye
        ipsilateral
        axons synapse in laters 2,3,5
        
        Left Eye
        contralateral
        axons synapse in layers 1,4,6
  - - - large center surround RFs
        transient bursts
        
        insensitive to differences in wavelengths (colors)
    - - small center surround RFs
        sustained responses
        
        color oppency
        specific color cells
    - - center-surround RFs
        
        light/dark or color oppency
- - - - sleep and wakefulness
        
        nucleus within hypothalamus
  - - - control size of pupil with light
        Pupillary light reflex
  - - - orients the eyes to new stimuli
        move fovea to objects of interest
        
        10% of ganglion cells project here
        
        works in conjunction with muscle cells to move
- - - - Magnocellular layer of LGN
        
        layer 4Calpha
        
        layer 4B
  - - - Parvocellular layer of LGN
        
        layer 4Cbeta
        
        layer 2 and 3 interblob
  - - - koniocellular layer of LGN
        
        blobs in layer 2 and 3
- - - - arranged into direction of motion columns
        
        have large receptive fields
    - - 3 proposed roles
        
        Navigation
        
        Directing eye movements
        
        Motion perception
- - - - lesions in pathway cause blindness in part or all
  - - - corssing midline through chiasm
        
        some info of one optic nerve will cross over
        
        info will split
        some contralateral some ipsilateral
        
        crossing at optic chiasm
        
        optic tract
        terminates visual thalamus
        
        makes first synapse in brain
        
        LGM goes another tract of optic radiation
        
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