Vision Flashcards
Wavelength
Longer: Red
Shorter: Violet
Amplitude
Height determines brightness
Purity
Single wavelength: completely saturated
Multiple: Natural light (de-saturated)
Visible spectrum
Our Total range of sensitivity to wavelengths of light
Infrared Spectrum
Made up of wavelengths longer than humans are able to perceive
Cornea
Allows light to pass through, beginning focusing process
Sclera
Tougher white membrane covering eye
Pupil
Light passes through after the cornea
Iris
Controls size of pupil
Lens
Light passes through after the pupil
- Focusing of light onto the retina
Lens Accomodation
Object is close = lens gets rounder
Object is far = lens gets elongated
Vitreous Humor
Light passes through after the lens
Retina
Where physical stimulus translates into neural impulses
Photoreceptors
Translate physical stimulus into neural signal that is relayed to brain
Retinal pigment epithelium (RPE)
Where photoreceptors gets nutrients
Rods
- Low light intensities
- No colour info
- Poor acuity
- Periphery
Cones
- high light intensities
- Provide colour, sharpness and acuity
- Central
Ganglion cells
Collect info from larger segment of retina
What causes the blind spot?
Axons converge on optic disc leading there to be no photoreceptors
Horizontal and amacrine cells
Allow areas within retinal layer to communicate with each other
Receptive Field
Collection of rods and cones that when stimulated fire receptive field of that retinal ganglion cell
Right visual field
Input from right nasal and left temporal
- processed in left visual cortex
Left visual field
Input from left nasal and right temporal
- processed in right visual cortex
What is meant by receptive fields being arranged in topographic map?
Neighboring locations in retina project to neighboring locations in visual cortex
Extrastriate Cortex
Outside of Primary Visual Cortex
- Subserve functions related to colour, motion and object recognition
Dorsal Stream
Depth and motion in the field
- Runs from extrastriate cortex to parietal lobe
Ventral Stream
Colour and form of object
- Runs from extrastriate cortex to temporal love
How is visual info compressed
many photoreceptors to less ganglion cells to less LGN cells to less visual cortical cells
Eye Evolution
cumulative selection: an evolutionary process whereby new adaptations are layered upon old adaptations
First part of eye evolution
Algae used light as energy creating action potentials c
Second part of eye evolution
Light sensitive patch formed into a slight curve
- allows direction of light to be sensed
Third part of eye evolution
Curved patch turned into aperture
- allowed to resolve detail of image
Fourth part of eye evolution
Developed to crude lens
- complete with lens, cornea and spherical shape
Fifth part of eye evolution
Adjustable lens
- being able to focus and process things at different distances
Factors that influence eye architecture
- Do they live in area with light
- Does food come from above or below
- The movement, colour or shape of their prey
Simple Eyes
Eyeball, lens and retina
- Crude lenses and accommodating lenses
Compound Eyes
Arrangement of tubule units called ommatidia
- All pointing different direction to gather light that is right in front of it
- Many separate signals to one image
Two main functions of the eye
Resolution (Acuity, sharpness)
Sensitivity (ability to get enough light)
Big Eyes
Species that need better eyesight
- Either good for night vision or acuity
Eye Placement
Lateral: Prey to see all around them
Front-Facing: Predators to have good perception
Eye Development
Around 3 months old, infants ability to focus has improved to almost adult level
