Psyc201 Test 1, Week 5 Flashcards
What is the difference in light sensitivity between rods and cones?
Rods are more sensitive, allowing vision in dim light. Cones require brighter light.
What is the difference in acuity between rods and cones?
Cones provide sharp vision (high acuity), especially in the fovea. Rods provide blurry vision (low acuity).
How does the connection between rods and bipolar cells differ from cones and bipolar cells?
Many rods converge on one bipolar cell. Each cone connects to one bipolar cell.
Why do we lose color vision in dim light?
Cones, which are responsible for color vision, require intense light to activate (since bipolar cells are connected to individual cones). In dim light, only rods are active, resulting in black and white vision.
What is the pathway of visual information from receptors to the brain?
Rods and cones → bipolar cells → ganglion cells → optic nerve → brain.
What is lateral inhibition?
A process where strongly activated neurons inhibit surrounding neurons, enhancing edge detection.
How does lateral inhibition explain the Hermann Grid illusion?
The intersections appear grey due to lateral inhibition at the edges of the dark squares, dimming the perceived brightness.
How do receptive field sizes change as signals move through the visual system?
Receptive fields get larger as signals progress from ganglion cells to higher visual areas.
Where does the thalamus send visual information?
To the lateral geniculate nucleus (LGN).
How is the visual field processed in the brain?
The left visual field goes to the right visual cortex, and the right visual field goes to the left visual cortex.
Simple visual cortical cells (V1)
Primary visual cortex (or area V1)- area of the cortex responsible for the first stage of visual processing, primarely respond to bars or edges of specific orientations.
What do complex visual cortical cells (V2) respond to?
Bars or edges of specific orientations, regardless of their exact location within the receptive field.
Hubel and Wiesel (cat experiments)/Visual development
Visual development depends on visual input.
Kittens with one eye patched for first three months of life develop very poor visual response from the deprived eye, and very good response from the seeing eye.
Within hemisphere, right eye and left eye cell are right next to each other, over time, a bunch of cell become responsive to right eye and a bunch to the left eye, at birth everything is grey, over period of time it separates into right and left eye signals, if you stop one eye from seeing all the neurons go to the other, no neurons respond to visual input
Adult cats with one eye patched for a year showed no changes in brain. What does this tell us?- critical period in first few months for visual development, after one year brain is already set
What is amblyopia?
Visual defects in the brain caused by poor visual input during the critical period.
What is strabismus?
A condition where one eye does not track properly, leading to the brain suppressing its input.
What is astigmatism?
A visual deficit where the eyeball is not spherical, causing blurry vision in one plane.
What are congenital cataracts?
A cloudy film that forms on the cornea, blocking light from entering the eye.
What are the two types of vision processing beyond the primary visual cortex?
Vision for Action and Vision for Conscious Perception
What are V2 and V3 responsible for?
V2 responds to more complex edges and rudimentary shapes. V3 is even more complex.
What is blindsight?
The ability to process visual stimuli in a “blind” field due to V1 damage, despite claiming not to see anything.
What type of visual deficit is associated with damage to V4?
Achromatopsia (loss of color vision).
What is akinetopsia?
Motion blindness, where objects appear stationary and disappear between movements.
What are the two visual processing streams, and what do they process?
Dorsal (where) stream: location, movement, spatial relations. Ventral (what) stream: color, texture, shape, size.
What tasks are affected by damage to the ventral stream and the dorsal stream?
Ventral damage: fails object discrimination. Dorsal damage: fails landmark discrimination.
Optic ataxia
difficulty with visually guided movements
What is apperceptive agnosia?
Impaired visual perception of objects despite intact visual acuity and basic feature perception.
What is associative agnosia?
Intact visual perception, but loss of meaning/knowledge of what objects are.
What is prosopagnosia?
Face blindness; difficulty recognizing faces.
What does category-selectivity in the ventral pathway mean?
The ventral pathway contains areas specialized for recognizing specific categories like faces, bodies, places, words, and objects.
What are the two main theories about why faces are special?
Evolutionary importance or simply high exposure/experience.
How does prosopagnosia affect face perception?
Faces are seen as a collection of features, not a holistic whole; recognition is impaired.
What is the difference between developmental faceblindness and super-recognizers?
Faceblindness: bottom 2-3% of face recognition ability, struggle with faces only. Super-recognizers: top 1-2%, exceptional face recognition.
What is pareidolia?
The tendency to see faces in random objects or patterns.
What do infant studies suggest about face preference?
Infants prefer facial configurations from the first day of life.
What does the Thatcher Illusion demonstrate?
We process upright faces holistically, but inverted faces are processed feature-by-feature.
What did Gauthier et al. (1999) find about expert object recognition?
Training on “greebles” led to increased FFA activity in experts (people trained to recognise their fetaures for 9 hours), suggesting experience can shape category-selective areas.
What are examples of bottom-up (stimulus-driven) factors that influence attention?
Salience, color, movement, lighting, emotional stimuli, treats, rewards, upright faces.
What are examples of top-down (goal-driven) factors that influence attention?
Goal/task, emotional/physiological state (anxiety, threat, hunger), motivation.
What is the “biased competition” model of attention?
Bottom-up and top-down factors compete for attention, and the “winner” determines what is processed.
What did Devue et al. (2012) find about eye movements and attention?
Eyes often move towards attended stimuli, even when they are not the target of a task.
