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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.
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