Understanding Vision and Light Processing

Oct 22, 2024

Sensation and Perception Part 2: Vision

Introduction to Vision

  • Vision originates from light, a form of energy that travels in waves.
  • Transduction: The process of converting wave energy into a neural impulse, which is then interpreted by the brain.

Light Waves and the Electromagnetic Spectrum

  • Light waves are part of the electromagnetic spectrum.
  • Longer waves are on one side of the spectrum, shorter waves on the other.
  • Visible Light:
    • Longest visible wave: Red
    • Shortest visible wave: Violet
    • ROY G. BIV: Acronym for the colors of the rainbow (Red, Orange, Yellow, Green, Blue, Indigo, Violet).
  • Brightness of color depends on wave amplitude.

Parts of the Eye

  • Iris: Muscle that controls the amount of light entering the eye.
  • Pupil: The opening that allows light into the eye; size controlled by the iris.
  • Lens: Focuses light onto the retina.
  • Retina: Located at the back of the eye, contains rods and cones.

Image Processing

  • Image is focused on the fovea and flipped upside down in the retina.
  • The brain interprets this flipped image.

Retina and Photoreceptors

  • Cones: Detect color; high detail; less sensitive to light.
  • Rods: Black and white; low detail; high sensitivity to light.
  • Distribution: Cones are central, rods are peripheral.

Neural Pathway

  • Rods and cones create a chemical reaction, sending signals to bipolar cells.
  • Bipolar cells communicate with ganglion cells, which form the optic nerve.
  • Optic nerve transmits visual information to the brain via the thalamus to the visual cortex in the occipital lobe.

Brain and Vision

  • Optic Chiasm: Point where optic nerve fibers cross in the brain.
  • Feature Detectors: Specialized brain areas for recognizing faces, objects, etc.
  • Damage to specific brain regions can impair face recognition.

Color Vision Theories

  • Color Deficient Vision: More accurately termed as color deficiency rather than color blindness.
  • Young-Helmholtz Trichromatic Theory:
    • Proposes three primary colors (blue, red, green) form all colors.
    • Issues arise explaining colors like yellow, which don't seem like mixtures.
  • Opponent Process Theory:
    • Colors exist in pairs (green-red, blue-yellow, black-white).
    • Neurotransmitters in the thalamus turn color pairs on and off.
  • Reality likely combines aspects of both theories.