EXAM 2 Flashcards
What is the difference between sensation and perception?
Perception: mental processing of sensory information
Sensation: detection of physical stimuli and the transmission of this information to the brain
Be able to differentiate effects on perception that are due to bottom-up vs top-down processes.
Top down processing: perception that is based on previous world knowledge expectations and past experiences.
EX: put together that the horizontal lines look like a B
Bottom up processing: perception that is based on the physical properties of the stimulus
EX: light hits cells in the retina, affecting their firing rate
What does it mean to say that every receptor has an adequate stimulus?
Every sensory receptor has a particular type of stimulus energy to which it is most sensitive
I.e photons for photoreceptors, hair cells mechanically being pushed for hearing
What is the adequate stimulus for photoreceptors (e.g., vs hair cells)?
Photons
Be able to differentiate between a distal stimulus and a proximal stimulus.
Distal stimulus: an object or event out in the world
Proximal stimulus: energies related to the stimulus that we came in contact with
Be able to trace the complete pathway of visual information, from a distal stimulus to V1 (and from 10 class, out to FFA/PPA).
Distal stimulus → back of retina (if up, then lower retinal cells, if down then upper retinal cells—rod/cones, horizontal cell, bipolar cell, amacrine cell, ganglion cell) → optic nerve
Fovea: point of central focus
Photoreceptors (rods and cones) absorb photons of light
Stacks of pigment in the outer segment of rods contain opsin which changes the shape when hit by a photon of light
Left visual field → light side of retina → optic chiasm → Lateral geniculate nucleus → V1 (primary visual cortex)
What is the fovea?
Point of central focus
What are the differences between rods & cones?
Rods:
- Not color sensitive
- Respond to low intensity light (good at night)
- Distributed throughout the retina (NOT IN THE CENTER)
Cones:
- Color sensitive
- Requires higher intensities to respond
- Concentrated near the center of retina (FOVEA)
What do the layers in the lateral geniculate nucleus indicate?
Layers 2,3,5 – info from ipsilateral eye (same side)
Layers 1,4,6 – info from the contralateral eye (opposite side)
Understand the idea of a retinotopic map
- Neural activity in the retina and brain organizes information about locations of objects and parts in visual space.
- Retinotopic map: a map in which each point in brain tissue corresponds to a location in the retina
Be able to explain how visual perception of edges could be enhanced through lateral neural connections (“lateral inhibition”)
- Moch bands
- Enhanced edges is BOTTOM-UP processing (can only enhance what is already there
- When the high intensity and low intensity lights hit, the interconnected cells receive different intensities – that results in lateral inhibition as bipolar cells respond differently at the edges with 2 different shades right next to one another
Recognize / identify examples of visual perceptual grouping principles.
Perceptual grouping: sensory information is grouped into organized wholes
Gestalts: forms/shapes
Gestalt Principles:
a. Proximity: group close items together
b. Similarity: group similar items together
c. Continuity: group edges/contours together that have the same orientation
d. Closure: complete figures that have gaps
e. Illusory contours: perceive contours and cues to depth even when they do not exist
f. Object constancy: maintenance of constancy across various perceptual contexts (lighting, size, shape, ect.)
i. Tea cup in different orientations can still be identified as a stimulus
Transduction: changing the format of the stimulus to a neural signal
Be familiar with the different types of retinal cells and what they are “optimized” for with regard to the range of intensities and wavelengths of light. How does this cell specialization result in color vision? (What is the trichromatic theory of color vision?)
Wavelength: the distance between 2 corresponding points on a wave
Frequency: the number of waves that pass a point in space during any time interval, usually one second
Cones detect color; there are 3 different types of cones, small, medium, and large that corresponds to the wavelengths that they are stimulated by (small wavelengths, medium wavelengths, and large wavelengths)
Small = Blue
Medium = Green
Large = Red
Be able to identify the color that would be perceived given different wavelengths of light. (What color would you perceive if presented with “red”, “green”, and “blue” wavelengths simultaneously?)
All 3 colors simultaneously would be perceived as white where all the cones are perceived as white
Purple does not exist: mix of red and blue light
See different colors depending on the neural response which can be mixed depending on other cone cells stimulated
Be able to explain two different ways of perceiving a color such as yellow, given that there are no cones that respond to “yellow” wavelength.
One way is that you could have it is red and green light simultaneously mixed results in yellow
You see light that is about 550 nanometers and both your red and green cone cells fire to create yellow
What are some ways that mutations can affect color vision?
a. Color Blindness is commonly due to inherited deficiencies in the cones. Most of the genes are on the X chromosome so males are more often affected.
b. Can acquire via degenerative disease (age, macular degeneration, diabetes) or brain or retinal damage (exposure to UV light)
c. If you miss the cones for certain wavelengths then you cannot distinguish between long wavelengths; i.e cannot get long wavelengths, then you cannot tell between yellow, orange, red or green. (Protanopia)
d. If some cone cells overlap with one another (green recognizes the same wavelengths as red and less of its own): you would not be able to as easily see greens or distinguish it from red. Deuteranomaly
Explain what “color constancy” is and be able to recognize/give examples.
Color constancy: perceived color of objects remains constant under different illumination
EX: Snow on camera looks blue, but our brain corrects it to look white
EX: dress color where our brain corrects the blues into whites
Explain what “object constancy” is and be able to recognize/give a new example
Object constancy: maintenance of constancy across various perceptual contexts (lighting, size, shape, ect.)
I. Tea cup in different orientations can still be identified as a stimulus
NOT things hidden by things
Where is the FFA+ PPA located? (lobe? hemisphere?)
FFA: Inferior temporal cortex (both hemispheres) in the fusiform gyrus on the RIGHT side specifically
PPA: parahippocampal gyrus in BOTH hemispheres in the temporal lobe
What is binocular rivalry?
Binocular rivalry: the phenomenon in which conscious perception alternates between images shown separately to each eye, rather than the perception of a “mixed” image
EX: house and face on top of one another
What exactly does the FFA seem to do that other areas (OFA) and pSTS do not do?
Focuses specifically on faces and integrates both face parts and their configuration
What is the extrastriate cortex?
A region of the occipital lobe outside of V1
Understand the details of the research design in the Tong et al paper and be able to relate the particulars of the experiment to the research question.
What was the research question?
When/where along the visual pathway binocular rivalry is resolved? Is it before or after the extrastriate cortex?
Understand the details of the research design in the Tong et al paper and be able to relate the particulars of the experiment to the research question.
Why did they present faces and houses (rather than apples and oranges)?
Face processing and place/object processing are different so it created binocular rivalry
