Vision: Introduction to Psychology & Neuroscience

Learning Objectives

• Describe the basic anatomy of the visual system
• Discuss how rods and cones contribute to different aspects of vision
• Describe how monocular and binocular cues are used in the perception of depth

Overview

The visual system constructs a mental representation of the world, allowing navigation through space and interaction with individuals and objects. This section provides an overview of the anatomy and function of the visual system, including color and depth perception.

Anatomy of the Visual System

• Eye Anatomy:

  • Cornea: Transparent covering, focuses light, barrier against the outside world.
  • Pupil: The opening through which light passes; adjusts size based on light levels and emotional arousal.
  • Iris: The colored part of the eye, controls pupil size.
  • Lens: Curved, transparent structure for additional focus; changes shape for focusing.
  • Fovea: Part of the retina, contains cones, high spatial resolution and color perception.
  • Retina: Light-sensitive lining, contains rods and cones.

• Photoreceptors:

  • Cones: Function in bright light, color and detail perception.
  • Rods: Function in low light, motion, and peripheral vision.

• Visual Pathway:

  • Optic Nerve: Transmits visual information to the brain.
  • Blind Spot: No photoreceptors, brain fills in missing information.
  • Optic Chiasm: X-shaped structure; visual information crosses to opposite sides of the brain.
  • Processing: Occurs in the occipital lobe via lateral geniculate nucleus (LGN), differentiating into 'what' (object recognition) and 'where/how' (spatial location) pathways.

Ethical Considerations in Animal Research

• Hubel & Wiesel: Nobel Prize winners for studies on visual perception in animals.
  • Techniques: Single unit recordings, ocular dominance studies.
  • Discoveries: Critical periods in vision development, neural connections, and deprivation effects.

Color and Depth Perception

Color Vision

• Trichromatic Theory: Red, green, and blue cones mediate color vision.
• Opponent-Process Theory: Colors coded in opponent pairs (e.g., black-white, yellow-blue).
• Colorblindness: Variations in color perception, with red-green being most common.

Depth Perception

• Binocular Cues: Rely on both eyes, e.g., binocular disparity.
• Monocular Cues: Require one eye, e.g., position, relative size, linear perspective, light and shadow, interposition, aerial perspective.
• Stereoblindness: Inability to perceive depth using binocular cues; use of monocular cues for depth.

Case Study: Bruce Bridgeman

• Experienced stereoblindness due to lazy eye, relied on monocular cues.
• Acquired depth perception after seeing a 3-D movie, highlighting neural plasticity.

Additional Resources

• Videos: Tricky topics on visual pathways and transduction.
• Color Vision Test: Ishihara test for color perception.