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What does Wavelength refer to ?
Perception of color (400-700 nms)
What does Intensity refer to ?
Perception of brightness (Bright/Dull)
What does Sensitivity refer to ?
The ability to see when light is dim
What does Acuity refer to ?
The ability to see detail
What do we see ?
Upside down & backwards in the back of the eye ball in the RETINA
How does light go through the eye ?
- Light enters the eye through pupil (Dilates and constricts; iris (colored part)
- Light then passes through the lens
- Lens focuses (becomes fatter/skinnier) image on retina (skinner to see farther/ fatter to see closer)
What is the Binocular Cue of Convergence ?
Eyes must turn slightly inward when objects are close
What is the Binocular Disparity ?
Difference between the images on the two retinas
What is the purpose of the Retina ?
- Light passes through lens & focuses light on area of retina of highest visual acuity = Fovea
- Thinning - provides less distortion (can see things clear & in detail)
- The retina is inside-out - light passes through several cell layers before reaching its receptors
What do the Photoreceptors do ?
Light is changed into neural impulse that the brain can interpret
What is the blind spot ?
- Axons of retinal ganglion cells exit forming optic nerve
- No receptors
What is Completion ?
- Brain uses information from cells around the blindspot to fill in missing info
- Perceive no gaps in vision
What are two types of photoreceptors ?
What is Duplexity Theory of Vision ?
Cone & Rods mediate different kinds of vision
Where is the location of the Cones & Rods in the Eye ?
- Cones: Located in the center of the Fovea
- Rods: on the outside of the Fovea surrounding the eye
Where is the location, lighting, qualities and types of vision of the Cones & Rods ?
What is High Convergence ?
- A lot of Convergence of Rods -> Bipolar cells -> Ganglion
- Very sensitive
- High Convergence = High Sensitivity = Low Acuity
What is Low Convergence ?
- Low Convergence = Low Sensitivity = High Acuity
- 1:1 connection
What is Saccades ?
We continually scan the world with small and quick eye movements
What is the Retinal-Geniculate-Striate Pathway ?
- Retina->Lateral Geniculate Nucleus-> Priamry Visual Cortex (VI - Striate)
- Eye ->Thalamus->Occipital Lobe
What is the Retinotopic Organization ?
- Each level of system = map of retina
- Disproportionate representation of the Fovea
- Map outside is mapped in thalamus & cortex
What is Mach Band ?
When you see edges and shadowing when there is none
What does Lateral Inhibition do ?
Contains mechanisms to enhance contrasts and make edges easier to see
In our receptive fields what does On-Center Cell refer to ?
- Light on center EXCITES cell
- Light on surround INHIBITS cell
In our receptive fields what does Off-Center Cell refer to ?
- Light on center INHIBITS cell
- Light on surround EXCITES cell
In the Striate Cortex, neurons with circular receptive fields are rare but they are either ?
SIMPLE: Rectangular, Static (on & off regions), orientation and location sensitive, MONOCULAR
COMPLEX: Rectangular, larger receptive fields, are not static, motion sensitive, BINOCULAR
As visual information flows through hierarchy, receptive fields become ?
- Respond to more complex and specific stimuli
What is the Component Theory/Trichromatic Theory ?
- 3 different kinds of cones: red, blue, green
- Every colour is a combination of cone responses
- We can see color by adding color
Trichromativ theory can not explain ?
- Red-green color blind individuals who should not be able to perceive yellow
What is the Opponent-Process Theory ?
- 3 cone types
- Each responds to 2 different wavelengths (red or green; blue or yellow; black or white
- Explains Afterimage: stare at certain color. Neural processes become fatigued. Rebound effect; receptor responds in opposite reaction
What is the Dual Process Theory ?
- Combines Component & Opponent-process theories
- 3 types of cones in retina
- Opponent processes occur higher up = ganglion cells, thalamus & visual cortex
What is the Cortical Pathway for Vision ?
Thalamus (LGN) -> Primary Visual Cortex (Striate, VI) -> Secondary Visual Cortex (Prestriate, VII) -> Visual Association Cortex
What is Sensation ?
Detecting a stimulus
What is Perception ?
Understanding the stimulus
What is Scotoma ?
- Damage to Primary Visual Cortex producing blindness in the visual field
- Completion - can not notice a persons head if has a background that is patterned
- Not consciously aware of deficit
What is Blindsight ?
- Response to visual stimuli without conscious awareness of "seeing"
- Catch ball tossed toward them while claiming not to see it
Who is Patient TN ?
- Suffered 2 strokes
- blind by normal measures
- PET & fMRI scans showed no activity in VI
- killed the occipital lobe & primary visual cortex
What are the Dorsal & Ventral Streams ?
- 2 major streams from primary visual cortex to secondary & association cortex
- Dorsal Stream: Where
- Ventral Stream : What
What is the Dorsal Stream ?
- Primary visual cortex -> Dorsal Prestriate Cortex -> Posterior Parietal Cortex
- Visual Spacial Perception
What is the Ventral Stream ?
- Primary Visual Cortex -> Ventral Prestriate Cortex -> Inferotemporal Cortex
- Conscious Visual Pattern Recognition
Who is patient A.T. ?
- Could accurately recognize objects
- could demonstrate the size of objects with fingers
- Made awkward grasps; could not preshape her hand for objects Optic Ataxia
- Damage to Dorsal Stream
Who is patient D.F ?
- Unable to recognize size, shape, or orientation of visual objects Visual Agnosia
- If asked to place object through a slot she could do so with ease
- Damage to Ventral Stream
What is Prosopagnosia ?
- Can readily recognize objects (tables) but are unable to recognize particular faces BUT patients also have n inability to recognize specific objects belonging to a complex class of objects (bird watch ect)
- Problems recognizing whose face it is - see a jumble of individual face parts
- Due to damage in Fusiform Face Stream (Ventral stream)
What is the Greeble Experiment ?
- Put into fMRI & showed Greebles & look at FFA & did not light up
- 2 week of intense greeble & name them based on features
- then FFA showed activation based on features
Is there an unconscious recognition ?
- Skin conducting response to familiar & non-familiar faces
- Skin conduction was elevated even when they say they don't recognize a person but unconsciously they do
- Implicit recognition
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