Health and Well-being: Lecture 3 - Light health and well being (Image forming Pathway) Flashcards
All parts of the eye from 1 to 9
- Cornea
- Pupil
- Iris
- Lens
- Sclera
- Choroid
- Retina
- Fovea
- Blindspot
Definition of ipRGC
Intrinsically photosensitive retinal ganglion cell
Info on ipRGC
- Photoreceptor
- Absorbs photon in itself, does not go to the visual cortex
- Probably biological effects of light
- Contain melanopsin, photopigment
- Connected to supra chiasmatic nuclei –> projects to pineal gland: biological clock
What is the process of receiving visual images?
- Rods and cones observe information
- Transduce into biological signal
- End up in ganglion cells and axons
- Via optic tract to brain
All 6 parts of the image forming pathway
Retina Optic nerve Optic chiasm Optic tract LGN Primary visual cortex
What are horizontal cells?
Horizontal cells connect to multiple photoreceptors. When one photoreceptor receives a photon, the horizontal cell will make the others less sensitivity.
Leads to sharp vision and color distinguishing
Differences between image forming and non-image forming pathways
Non-image forming
- Physiological
- Sums over entire environment = irradiance
- Insensitive to dim light
- Insensitive to short duration
Image forming
- Visual experience
- Radiance, specific area
- Sensitive to dim lighting conditions
- Sensitive to short duration
What is irradiance?
Capturing light from very specific region in space
What is lightness constancy?
Lightness constancy refers to our ability to perceive the relative reflectance of objects despite changes in illumination
To estimate the reflection of an object, our visual system needs to compensate for the intensity of the light source
Describle all objects in image forming pathway or the primary visual path
1 Retina 2 Optic nerve 3 Optic chiasm 4 Optic tract 5 LGN 6 Primary visual cortex
What does LGN stand for?
Lateral = to the side Geniculate = genu/knee Nucleas = kernel/seed
What is the principle of univariance?
When a photon is absorbed, its effect is the same regardless of its wavelength
o If a photon of the around yellow is there, the green and red curve both have a very large chance of firing
What are the L M and S
L = red M = green S = blue
Explain color opponency
Retina converts spectral sensitivities of L, M and S curve
Red Green = L - M
Blue Yellow = (Red + Green) - Blue
Light dark = L + M = Red + Green = spectral sensitivity curve
What is color constancy?
Our visual system compensates for the surrounding light to see the objects of colours
(perception of saturation is also influenced by the context)
