Chapter 10: Vision Flashcards
Vision
The detection of light in an environment.
Light
Certain frequencies of electromagnetic waves.
Pinhole Camera
Image gets converted as it passes through an aperture
What serves a main importance in vision?
The shape of the eye
Myopia
Eye is too long so the image surrounding the retina is blurred.
How can myopia be resolved?
Glasses
What two sides are the retina divided into?
- temporal
- nasal
If the image hits the outer edge of the eye, it fields into the ___ side of the brain.
SAME
If the image hits the inner edge of the eye, it fields into the ___ side of the brain.
OPPOSITE
What side is the temporal retina on?
Left
What side is the nasal retina on?
Right
Are the things that the left and right eye see identical?
No
What is the one type of cell in the retina that produces AP?
Ganglion cells
Rods
-Work in dim light
- Black and white
(scotopic system)
Cones
- Work in bright light
- differentiate between wavelengths of light
- Color
-(photopic system)
What are the 5 types of cells in the retina?
- Photoreceptors (rods and cones)
- Bipolar cells
- Amacrine cells
- Horizontal cells
- Ganglion cells
Retina
Large convergence of inputs outside the fovea (very little inside)
What does your visual system respond to?
Changes in light
Horizontal and Amacrine Cells
Very important for interactions with the retina
Lateral Inhibition
Inhibitory connections between interneurons create a sharper border contrast.
What is an example of horizontal and amacrine cells?
Lateral inhibition
How does photoreceptor transduce light into neural signals?
Rods
What is the pathway of light?
- Light hyper polarizes neurons, which reduces neurotransmitter release
- It breaks up retinal/rhodopsin, eventually leading to the closing of Na+ channels
- The cascade of effects increase the sensitivity of cells
- Information is integrated over time, leading to increased sensitivity but not as god temporal resolution.
How do we handle a huge range in light intensity?
Pupils constrict/dilate
Range Fractionation
Rods vs Cones
Adaption
Cells themselves can adapt to ambient light
Calcium ions
Cells that regulate intracellular levels, which alters neurons sensitivity
What is needed for transduction?
Availability of chemicals
What is sensitivity of the eye influenced by?
the ratio of rate of breakdown/recombination of retinal/rhodopsin.
What do cones connect to?
Bipolar neurons
How many types of bipolar cells are there?
2
How do bipolar cells respond?
Oppositely when the cone hyper polarizes
What receptor fields are used for bipolar cells?
On center and Off center
What receptive field do ganglion and LGN cells have?
Concentric receptive fields
On Surround pairs with
off center
Off Surround pairs with
on center
Parvocellular Cells
Small receptive fields, not responsive to different wavelengths.
Magnocellular Cells
Large receptive fields, not responsive to different wavelengths.
Ganglion cells can be labeled…
M or P
(magnocellular or parvocellular)
What do cortical cells require to respond?
specific stimuli
Simple Cortical Cells
Respond to edge or bar with particular width, location, and orientation.
Complex Cortical Cells
Elongated receptive fields, not as tied to location.
High frequencies require ___ receptive fields.
small
What cells are an example of high frequency?
Cells in the fovea (detail and sharp contrasts)
Low frequency cells
Cells in the periphery with larger receptive fields
What are low frequency cells more involved in?
Gradual transitions and large uniform areas.
Where does visual information initially come from?
V1 region - layer IV cells
V2 Region
Responsible for illusory contours
(similar to V1 in processing)
V4 Region
Receives input from V2 and responds to sinusoidal frequencies.
- Concentric and radial stimuli
V5 Area
Perception of Motor
Inferior Temporal (IT)
Complex forms
What is the Inferior Temporal apart of?
Prefrontal cortex = responds to faces
Layer IV
Receives LGN input (molecular input)
How do all layers except layer IV receive input?
binocularly
How is the V1 cortex organized?
Columns (same ocular dominance through each)
How are the columns linked together?
ocular dominance slabs
Columns within the same region respond…
In the same way
What is color constructed by?
Your visual system
Trichromatic Hypothesis (Helmholtz)
Photoreceptors would have specific, defined wavelengths
-they respond to 3 of them.
What can photoreceptors not fully account for?
Color
Opponent Process Theory
Opponent pairs of colors
Red vs Green
Blue vs Yellow
Black vs White
How do you get better color discrimination?
When colors oppose each other
Why are these spectrally opposing cells so useful?
Cones show significant overlap (M and L cones have very close absorbance peaks)
Region V4 is specifically important for…
Processing color
What does processing color require?
Context (comparison with nearby colors)
What type of vision is not widespread among mammals?
Trichromatic Vision (depends on the need of the animal)
Dorsal stream processes…
Movement and location
Ventral stream processes…
objects, faces, etc.
Patient DF
Had CO2 poisoning and could not recognize objects/faces
Patient DF had damage to…
Ventral stream, but not dorsal