Week 1:

• Can’t explain perception which is the end result of vision
• Perception is what we are aware of
• Physical Measurements are objective
• Psychophysical Measurements are subjective
• Perception of Luminacnce
  • Relative Lightness
  • Measured with phonometer
• Spectrophotometer
• Geometry
  • Angle Perception
  • Motion Perception
  • Direction Perception
• Perception is at odds with reality
• Inverse Optics Problem ie no way of getting back the exact composition of retinal stimulus
• Inverse problems makes source of any image uncertain
• Source of Illumination
• 3D object surfaces
• Atmosphere
• Retinal Stimulus is compilation of
  • Illumination
  • Reflectance
  • Transmittance is the alteration of light by the atmosphere
• Visual Stimuli
• Light and Electromagnetic Radiation
  • Human visual system from 400 nm to 700 nm
  • To lower size range, the energy tends to damange cells
  • To greater size range, the energy tends to be present as heat
• Making an image
  • There is no image out there in the world just the mess of photons
  • Cornea orders out this photonic flux
• Eye
  • Cornea
    • Refractive Abilities
    • Refrative index is greater than air
  • Lens is attached by zonule fibres
    • Involved in fine bending of light
  • Cilliary muscles contract or relax to change the shape of lens
  • Vitreous Humor
  • Optic Disk (Papilla)
  • Macula Lutea
  • Ophtalmic Arteries and Veins
• Eye Tracking
  • Saccadic Eye movements
• Retina
  • Interface between neural and non-neural parts of eye
  • Fovea
  • Pigment Epithelium
  • Photoreceptor Layer
    • Rods and Cones
  • Ganglion Cells are output layer cells
  • Bipolar Cells responsible for high resolution
  • Amarcrine Cells responsible for capturing horizontal information
• Light -> To Optic Nerve -> Ganglion Cell -> Amacrine Cell -> Bipolar Cell -> Horizontal Cell -> Rods -> Cones -> Photoreceptors -> Pigment Eplithelium
• Photo receptors have a high metabolic rate and discs on Pigment epithelium are turned over at high rate and are being degraded and need to be removed on an ongoing basis to function properly
• Distribution of rods and cones
  • Cones are concentated near and at the center of fovea
  • Rods are concentrated near the periphery of retina
• Cone function is one to one and rod function is many to one
• At absolute thrshold of vision rods operate and in bright sunlight cones operate and in moonlight both operate
• Primary Visual Pathway
  • Eye
  • Thalamus
  • Primary visual cortex
  • Superior Colliculus
    • Concerened with eye and head movements
• Autonomic Pathway
  • Pupilary Light Reflex
    • Concerned with pupil dilation
• Optic Chaism
  • Place where visual information crossing happens
• Tail flip effect
  • Information flipping and going on opposite side of brain
• Thalamus
  • Way station responsible for sensory organs
  • Lateral Geniculate Nucleus responsible for vision
    • 4 parvo-cellular layers concerned with full view vision, precision and color
    • 2 magno-cellular layers concerned with grosser change in the image or movement
• Retinotopy
  • Neighbour relationship of pixels of image
• Ganglion Cells of retina
  • parvo-ganglion cells
  • magno-ganglion cells
• PVC in occipital lobe
• Peak are gyri and valleys are sulci in the brain
• Optic Radiation are the optic fibres going from the the thalamus to Visual Cortex and vice versa
• Striate Cortex