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.