Vision

Stimulus

• Electromagnetic Specturm

  • Visible: 400-700nm

  • there are proteins in our eyes take allow us to see

  • Hue: wavelength

  • Saturation: Purity of wavelength

  • Brightness: intensity of wavelength

Structure

• Eye

  • Cornea

  • Iris

  • Pupil

  • Fovea

    • Where most of color receptors are located

  • Blind spot

  • Retina

    • cones cells

      • process color informations

    • rod cells

      • has pigment that is sensitive to amount of light

      • Creates actions potential

      • process movement

    • Distribution of rods and cones

    • Bipolar cells

    • ganglion cells

    • Light

  • Pathways

    • retinohypothalamic: Critical for processing blue light and sends it to the superchiasmatic nucleus

      • registers amount of light and makes pupils dilate

    • Tectopulvinar

    • Geniculostriate

    • Geniculostriate

      • P-channel

        • cones

        • Has 4 layers (lateral geniculate nucleus = LGN): 3, 4, 5, 6

      • M-Channel

        • Rods

        • Has 2 layers (lateral geniculate nucleus = LGN): 1, 2

      • Striate Cortex

        • Mapping

          • tells us where we are in our enviornment

        • Blob region

          • process information from p channel

        • Inter blob regions

          • process information from m channel

    • Dorsal Stream

      • l (LIP): Eyes

        • critical for guiding movement related to visual information

      • AIP: grasp

        • helps guide grasping

          • ex. taking a drink of water from a cup will have your hand ready to grab the cup by already having the grasp of the cup

      • Parietal reaching region (PRR): Reaching

        • processes information of where in space something is

    • Ventral Stream

      • FFA: Faces

        • processes information about faces

      • PPA: Places

        • processes information about places

    • Ventral and Dorsal Streams work parallel to each other

Function

• Receptive Field: Form

  • cones

    • helps us see pixels of light forming into shape

  • Baseline

    • has few number AP

  • Excitation

    • Fires many times per sec when seeing a stimulus that excites the cell

  • inhibition

    • a type of rest after excitation

  • retinal ganglion cells

    • on-center cells

      • receptive field looks like a donut

      • if light hits the periferi then it turns off

      • if light hits the center of the cell it turns on

    • overlapping receptive fields

  • Primary Visual Cortex

    • Simple Cells

      • has a diagonal line as a

      • send axons producing EPSPs when diagonal line is stimulated perfectly

    • Complex Cells

• Hierarchical Organizations

  • Cones

  • Ganglion Cells

  • Simple Cells

  • Complex Cells

Pathology

• Receptive Field: Color

  • Tri-chromatic Theory

    • Blue Cones

    • Green Cones

    • Red Cones

  • Afterimage Painting

  • Receptive Field: Color

    • Opponent process theory: Red

      • Red Cone stimulated

      • Excited red/green ganglion

      • Signals Red

    • Opponent process theory: Green

      • Green Cone stimulated

      • Inhibits red/green ganglion

      • Signals green

    • Opponent process theory: Yellow

      • Red & Green Cone stimulated

      • Summations

    • Opponent process theory: Blue

      • Blue Cone stimulated

      • Inhibits Yellow/Blue ganglion

      • Signals Blue

• Bitemporal Hemianopis

• Apperceptive agnosia

• Object agnosia

  • Associatice agnosia

  • Prosopagnosia

• Hierachical organization

  • photoreceptors

  • Ganglion Cells

  • Simple Cells

  • Complex cells

  •