Learning Objectives

  • Anatomy and function of the visual system
  • Role of rods and cones in vision
  • Understanding monocular and binocular cues for depth perception

Anatomy of the Visual System

  • Eye Structure: Major sensory organ, light enters through the cornea and pupil.
  • Cornea: Transparent covering that focuses light.
  • Pupil: Size changes with light and emotional cues; controlled by iris muscles.
  • Lens: Curved structure that aids in focusing light on the fovea.
  • Fovea: Contains densely packed cones for detail and color detection.
  • Rods: Located outside the fovea, sensitive in low light, detect movement, low spatial resolution.
  • Photoreceptors: Cones (color, detail) vs. rods (low light, peripheral vision).

Visual Pathways

  • Optic Nerve: Carries visual information from retina to brain.
  • Blind Spot: Area with no visual input due to optic nerve exit point.
  • Optic Chiasm: Crosses visual information from each eye to opposite brain hemisphere.
  • Processing: Visual information goes to the occipital lobe in two main pathways:
    • What Pathway: Object recognition and identification.
    • Where/How Pathway: Spatial location and interaction with stimuli.

Color Vision

  • Cone Types: Three types of cones sensitive to different wavelengths (RGB).
  • Trichromatic Theory: Color perception based on combinations of red, green, and blue.
  • Opponent-Process Theory: Colors perceived in opponent pairs (black-white, yellow-blue, green-red).

Depth Perception

  • Concept: Ability to perceive spatial relationships in three dimensions.
  • Binocular Cues: Require both eyes; e.g., binocular disparity (different views from each eye).
  • Monocular Cues: Require one eye; include linear perspective, interposition, relative size.
  • Stereoblindness: Condition where one is unable to perceive depth with binocular cues but can adapt using monocular cues.

Ethical Considerations in Research

  • Animal research on visual perception has ethical implications (e.g., David Hubel and Torsten Wiesel's studies).
  • Regulations exist to ensure humane treatment of research animals.
  • Alternatives to animal testing, such as computer models and in vitro methods, are being explored for ethical research.