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
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.
Under what conditions does someone experience binocular rivalry?
Someone can experience binocular rivalry in which each eye is shown something separate rather than the perception of a mixed image AND different regions of the brain
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 point of the non-rivalry condition?
To act as a control
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 evidence from the study that convinced the researchers that binocular rivalry is resolved before extrastriate cortex?
The study used fMRI to study whether activity in the extrastriate cortex is correlated to visual awareness during binocular rivalry and whether activity changes during rivalry might be comparable to those found during nonrivalrous stimulus alternation
IF RESPONSES EQUIVALENT then resolved before it hits the extrastriate cortex
Graphs below prove that is true
What is a double dissociation? What is the evidence for a double dissociation between object recognition and face recognition?
Double dissociation: A but not B AND B but not A so they are entirely independent
OFA conduits an early stage of face processing (face parts)
pSTS may be involved in the discrimination of gaze direction and expression
FFA carries out an integrated, holistic representation that contains both kinds of information (face parts and their configuration)
Prosopagnosia is the difficulty recognizing a face BUT can recognize objects so single dissociation
Object agnosia is the difficulty recognizing objects BUT can recognize faces so it is a double dissociation
What characteristics of a sound wave correspond to pitch and volume?
Sounds: Pressure changes as vibrations push on air and molecules get squished together resulting in waves and creates a repetition pattern of alternative high and low pressure regions
Amplitude: difference in pressure between peaks (low and high) → CORRESPONDS TO VOLUME/LOUDNESS
Frequency: number of times the wavelength occurs in one second (kHz) → CORRESPONDS TO PITCH
Compare and contrast the retina as it pertains to vision and the cochlea as it pertains to hearing.
The retina is stimulated by photons, the cochlea is stimulated by pressure changes
The retina maps directly onto the world, while the ear doesn’t have a direct map, rather is based on other metrics to identify a stimulus
SIMILAR: retina has 3 types of cone cells for short, medium and long wavelengths, and the cochlea has 3 types of hair cells for low, medium and high frequencies
What is the auditory pathway?
AUDITORY PATHWAY:
1. Sound waves enter the auditory canal of the outer ear
- Vibrations hit the eardrum
- The eardrum vibrates, passing on those vibrations to the middle ear
- Bones in the middle ear transfer vibrations transfer the vibrations to the inner ear
5a. Vibrations in the liquid in the cochlea jiggles basilar membrane
5b. The hair cells are bent as a result against the tectorial membrane because the basilar membrane pushes them up which releases an action potential (stereocilia: protein filaments that brush up against the tectorial membrane)
A. Being of stereociia causes a MECHANICAL opening of the hair cell
B. Positively charged potassium ions enter and depolarize the cell
C. This opens voltage gated channels to open, allowing calcium ions to enter the cell
D. triggers the release of neurotransmitters at the bottom of the cell
5c. Tonopoy: neural response to different frequencies lines up spatially on the basilar membrane
6, 7, 8. Info is sent to the brain stem, the midbrain, and the primary auditory cortex
Be able to point to A1 vs V1 on a brain or brain scan.
What leads to the firing of a hair cell? How does this differ from photoreceptors?
A mechanical stimulus: hair cells are bent
Photoreceptors are hit by photons
Be able to label and identify the role of the following: ear drum, cochlea, organ of corti, stereocilia, medial geniculate nucleus (in the thalamus), and primary auditory cortex (A1).
Ear drum: vibrates due to pressure changes and passes those on to the middle ear
Cochlea: Where the vibrations are turned into neural signals with hair cells. Base of cochlea corresponds to the highest frequencies (20000 Hz) while the apex corresponds to shortest frequencies (20)
Organ of corti: within the Cochlea, includes the basilar membrane, the hair cells, the tectorial membrane and the axons of sensory neurons that go to the auditory nerve
Stereocilia: the hair cells
Medial geniculate nucleus:
Acts as the principal relay nucleus for the auditory system between the inferior colliculus and auditory cortex.
Primary auditory cortex:
Aggregates and processes the sounds that you hear
Generally speaking (ventral vs dorsal areas), where is information about “what” an visual object or auditory sound is vs “where” a visual object or auditory sound is?
What a visual object/auditory abject: identifying sounds and ventral steam – starts in the temporal lobe and goes to the frontal cortex
Where a visual object/auditory object: localizing sounds, dorsal stream
Describe/apply two ways that we localize where a sound is coming from. (For example, know which ear would be in the “acoustic shadow” or would be the first to receive the sound wave.)
Interaural time difference: there is a time-delay between the two ears, depending on the location of the sound source
Interaural level difference: the head gets in the way of high frequency sound waves, creating an acoustic shadow between the 2 ears (one ear receives info first)
Be able to recognize or give examples of how auditory grouping can help us to separate the cacophony of simultaneous sounds around us into separate percepts. How do these principles also lead us to have auditory “illusions”? (Relatedly, think about how grouping principles in vision could lead to visual illusions?) Be able to explain the principles that give rise to each of: auditory stream segmentation, continuity illusion, and Shepard tone
Auditory scene analysis:
Separating stimuli into separate percepts
Auditory grouping principles:
Onset time
Location
Pitch (combo of pitches)
Perception of a group in accordance with proximity of pitches (successively rising and falling)
Timbre (quality of sound that allows you to identify a guitar vs a flute)
Illusions:
Auditory stream augmentation:
Rapid alternation of high-low sounds create the illusion of 2 sound sources due to perceptual grouping
Continuity illusion:
Perceive sounds as continuous if the gapes are “filled with something else that can be interpreted as the reason for the gap.
Shepard tones:
Playing of 1 or more sequential tones (each separated by an octave)
Sounds like it is constantly going up
Cocktail party effect:
The phenomenon of filtering out a range of stimuli (visual, auditory, touch) when focusing auditory attention on a particular stimulus
Explain how the dichotomous listening tasks and the monkey business illusion demonstrate top-down effects of attention allocation on perception? (“How” meaning, what specifically about participants performance on these tasks demonstrates the role of attention allocation. If attention allocation did not affect perception, how would participants’ performance have been different?)
Dichotic listening task: 2 different auditory stimuli are presented simultaneously
- When you focus on one, you cannot know the other
Attention allocation determines what you actually process and what you filter out
