Midterm 3 Flashcards
CH 7-10
What is perceptual organization?
Refers to how motion perception contributes to perceptual organization (figure-ground organization and perception of moving biological objects)
What is apparent motion?
Includes a visual illusion in which 2 stimuli separated in time and location are perceived as a single stimulus moving between the two locations
What is apparent motion quartet?
If spots are closer together vertically than they are horizontally, perception is strongly biased toward vertical motion.
If spots are closer together horizontally than they are vertically, perception is biased toward horizontal motion.
What does the perceptual grouping principle of proximity have to do with motion?
When it can, the visual system interprets apparent motion in a way that minimizes the distance over which the stimuli appear to move
What is figure ground organization?
Movement allows individuals to see boundaries or edges separating objects, movement is HUGLEY influential to figure-ground
What are random dot kinematograms?
Used by researchers to investigate the influence of motion on figure-ground segregation; involves random black and white dot grouping in which a subset of dots is moved and viewers has to perceive the direction of said movement.
Motion on its own is enough for us to segment something into an object
What is an example of biological motion?
A point-light walker has lights only at joints and we can see motion clearly (walking vs running)
Where in the brain is biological motion associated with?
Posterior superior temporal sulcus (STSp) in the temporal lobe (also sensitive to motion in faces)
What is transcranial magnetic stimulation?
Evidence for biological motion is STSp; renders it temporarily inactive and leads to difficulty perceiving biological motion
How does animate motion capture our attention?
Biological motion captures our attention, but it is easier to detect changes in animate objects vs inanimate objects
What are saccadic eye movements (or saccades)?
Brief, rapid movements that change the focus of the gaze from one location to another in the visual scene (~3 saccades/sec) and is the most common
What are smooth pursuit eye movements?
When you track a moving object continuously with your eyes, or when you track a stationary object while your head is moving
What is the corollary discharge signal (CDS)?
Copy of an eye-movement command from the superior colliculus to the extraocular muscles, copy is sent to the brain to inform the visual system about upcoming eye movements
What does corollary discharge signal (CDS) help with?
Differentiating what’s moving vs if we are moving, so we don’t think whole world is moving every time we move our eyes
What do sensors in the extraocular muscles do?
Brain combines information about how stretched or relaxed muscles are with information from the retinal image to construct accurate perception of visual field movement and stability
What do sensors in the superior colliculus do?
Eye movement sends commands to the extraocular muscles, copy of these commands (CDS) is sent to some region of the brain, information in the CDS is combined with the information in the signals from the retina to indicate that the object is moving
What does evidence for a Corollary Discharge Signal in the frontal eye fields (FEF) demonstrate?
Receptive field stretches and shifts in advance of saccades and is constantly changing and dynamic (light is flashed on RF or FF just before saccade = response in both receptive fields)
What does the neural basis of motion perception in Area V1 and Area MT tell us?
If the retina is absolutely stationary, then the motion of a visual feature produces an exactly corresponding change over time in the corresponding part of the retinal image
What types of motion perception do we perceive in area V1 and area MT?
Object’s position, movement direction, speed
To detect and represent the motion of some feature in the retinal image a neural circuit must:
- Monitor at least 2 different retinal locations
- Must register the order in which those locations were stimulated
- Must register how far apart in time they were stimulated
What is Neuron M?
A neuron that will selectively respond to direction and speed of motion if circuit includes a delay in the signals either from Neuron 1 or 2 (found by Reichardt)
How does a simple neural circuit explains apparent motion?
A brief flash of light on RF1 followed after a suitable delay by a brief flash of light on RF2 is perceived as motion from RF1 to RF2.
How are neurons tuned regarding motion?
Tuned to specific degrees or orientations, prefer to go through the centers of cells, and usually don’t respond to opposite direction
What is the motion aftereffect (MAE)?
Visual illusion in which a stationary element of the visual scene appears to be moving in a direction opposite the direction of motion experienced during the immediately preceding time interval (see movement downwards, aftereffect is upwards)
What does MAE suggest about motion in the brain?
Motion is represented in the brain by the output of an opponent circuit that compares opposite directions of motion
What does Area MT do?
Neurons are almost all tuned direction of motion (stands for middle temporal)
What do single-cell recordings tell us about area MT?
Their receptive fields are 5-10 times larger than V1 neurons, so the MT neurons are well suited for large-scale motions (almost all neurons are tuned for direction of motion)
What does fMRI tell us about area MT?
Area MT is much more active when viewing moving rather than stationary stimuli; activity pattern differs within area MT according to attended direction of motion
What does microstimulation tell us about area MT?
When only area MT neurons were activated, primates tended to respond as if they had seen the direction of motion that corresponded to the stimulated neuron’s directional selectivity, even though there wasn’t any motion
What are coherent motion displays?
Judgments about the direction of motion (1 circle all dots move in same direction, 1 circle most move in one direction while others move randomly)
How do MT neurons affect perception?
MT neurons, help us perceive motion and figure out which direction something is moving. When these neurons are active, they are playing an important role in how we interpret the direction of moving things.
What happens when coherence is low?
Monkey and neurons are guessing the direction
What is the aperture problem?
Perceiving the motion of objects when looking through a narrow/small space (small receptive field) - different motions yield the same things
How do we solve the aperture problem?
By combining information across many receptive fields/multiple V1 neurons
How do neurons in area MT differ from V1?
Receptive fields are larger and they receive signals from multiple V1 neurons
What is the perception action cycle?
Environment –> Perception –> Human –> Action
What is visual feedback?
Refers to visual information used to control an ongoing movement (and the way that the movement adjusts your perception)
What is the speed accuracy tradeoff?
As you increase accuracy you lose speed and as you increase speed you lose accuracy
What did Robert Woodworth propose?
That actions generate changing perceptions, that generate critical information about the changing geometry of the retinal image
What is optic flow?
Involves visual feedback to guide hand movements and body as person moves through the environment; provides crucial information to guide actions like navigation, balance, and body orientation; helps maintain stable upright body orientation when executing an action
What happens when room has stable floor, but moving walls?
Person is not expecting room to moves so brain tells them that THEY are moving and they fall over (b/c optic flow is not expected in this situtation)
What is does prism adaptation show?
That people can compensate for changes in the correspondence between the apparent visual location of an object and what must be done with the arm to react for it (when wearing goggles that change visual field)
What are the 2 componentes of prism adaptation?
Change in visually perceived directions
Change in the felt position of the arm
What are action plans?
Anticipation and computation of a particular action; planning an action increases a person’s sensitivity to the visual features important for completing the action
How do pointing and grasping tasks affect perception?
When grasping more likely to look at an object of the correct orientation instead of color (grasping or pointing has no impact on identifying the color of the object)
Does action affect vision?
Yes, changes in ability to produce action can change what is seen
What is perihand space?
The space near the hands; the visual processing of objects there is special
What do we know about visual processing in perihand space?
Recent studies demonstrate that visual information processing about nearby objects is different when hands are near objects than when hands are far away from objects
What did patient WM tell us about perihand space?
Even though they are blind, they “see” better when objects are close to their hand
What about perihand space with individuals who don’t have brain damage?
When stimuli were in perihand space participants were better at seeing the tilt of low-spatial frequency stimuli, but when stimuli were not in perihand space, participants were better at seeing the high-spatial frequency stimuli
What is low spatial-frequency useful for?
Interacting with thing near your hands
What is action-specific perception?
Perception is shaped by the ability to perform actions
What representations are provided by your perceptual system?
Take action capabilities into account, capture the relationship between your environment and your abilities
What does a heavy backpack tell us about distance perception?
As the distance, increased so did the participants’ estimates, but participants wearing a backpack judged the distance to be greater than those without; perception of distance is affected by weight
What does the ventral pathway (what) do in regards to motion?
Travels through area V4 into regions of the lateral occipital cortex and inferotemporal cortex that are specialized for various aspects of object recognition
What does the dorsal pathway (how/where) do in regards to motion?
Travels through area MT and into parietal lobe; located between early visual cortex and motor regions of frontal cortex
Which lobe is important for eye movements, reaching, and grasping?
Parietal lobe (specifically the posterior region)
What does the lateral intraparietal area (LIP) do?
Controls eye movements and visual attention
What does the medial intraparietal area (MIP) do?
Plans reach movements (parietal reach region)
What does the anterior intraparietal area (AIP) do?
Grasping movements
What does the activity of LIP reflect?
Intended eye movements; firing rates stay above baseline even when dot leaves receptive field and eye moves to receptive field once fixation point disappears (activates motor and visual area in LIP)
What are bimodal neurons?
Neurons that respond to 2 senses of stimulation; ex: audition and vision
What is a hand-centered receptive field?
The visual receptive field of a neuron that responds to visual stimuli near the hand
How have bimodal neurons evolved?
Bimodal neurons with hand-centered receptive fields have evolved the capacity to expand their receptive field in support of tool use; receptive fields expand after you learn to use a tool
Does action affect vision or does vision affect action?
There is research pointing to both being true; but expansion of the visual receptive field enhances control of visually guided action
What are mirror neurons?
Neurons that fire when an action is produced and when the same action is observed being produced by others
What is the role of mirror neurons?
Perception and action might be better though of as functions that are performed together via many of the same brain mechanisms (mirror neurons)
What is the cocktail party phenomenon?
When there is a lot of people speaking in a room and we hear one voice and tune out all the others
What is awareness?
The ability to report on internal or external knowledge
What is attention?
Increased cognitive processing of a smaller subset of sensory information, usually at the expense of unattended sensory info
What is selective attention?
Attention to some things and not to others
What are the 2 types of selected attention?
Focused attention = attending to a single stimulus
Divided attention = attending to multiple stimuli simultaneously
What is dichotic listening?
Involves listening to one message in the left ear and a different message in the right ear; we don’t hear information in unattended ear; can recall information in attended ear (some information still gets through)
What does the cocktail phenomenon demonstrate?
The dependence of awareness and comprehension on attention
What is Broadbent’s filter theory of attention?
Suggests all sensory information is first filtered by physical features (such as pitch or color), attention selects only some of those signal to be interpreted for meaning; with the rest being filtered out (only desired or attended information makes it through)
What is inattentional blindness and what does it show?
Lack of awareness of something you did not attend to; even when people look directly at something, they aren’t aware of it if they are paying attention elsewhere
What is attentional blink?
Lack of awareness despite attention
What is rapid serial visual presentation (RSVP)?
A lot of stimuli appearing very fast (letters, photos, numbers, etc.)
How does attentional blink work in RSVP?
When we are only looking for X are 100% accurate, when asked to identify X and then something else we are not accurate unless it’s sometime after the probe (X)
What is change blindness?
Inability to quickly detect changes in complex scenes; not the same as inattentional blindness; has to be a change in scenes
What is overt attention?
Attending to what you’re looking at by moving your eyes
What is covert attention?
Attending to something you are not looking at without moving your eyes
What are Posner’s attentional cuing experiments?
Using a cue about the location of an upcoming stimulus; examines how the spatial location of a person’s attention affects the speed with which the person can become aware of something and respond to it
What did Posner’s cuing task find?
Faster response to valid cues, slower responses to invalid cues
What did Moran and Desimone find about attention within monkey’s?
Neurons’ responses depended on where the monkey was attending: the response was much stronger when the monkey attended to the effective stimulus than when it attended to the ineffective stimulus
What did Motter find about attention within monkeys?
Attention affects the firing rate of neurons in V4 in response to stimuli in monkeys’ RF
What did Chiu and Yantis conclude about attention to location?
That directing attention to a particular spatial location, without moving your eyes, causes corresponding changes in brain activity
What do we know about attention?
- Can be directed to different spatial locations, enhancing awareness of stimuli that appear in those locations
- Affects the response of sensory neurons with receptive fields in attended locations
- Selects which of many competing stimuli will be represented for further cognitive operations
What is visual search?
Searching for a specific target in a scene containing one, a few, or many objects
What is a feature search?
Searching a display for an item that differs in just one feature from all other items in the display
What is a conjunction search?
Searching a display for an item that differs from all other items in the display by having a particular combination of 2 or more features
What does processing items in parallel mean?
All being processed at the same time; also number of items doesn’t change response time; is rapid and efficient
What is a serial search?
Processing each stimulus one by one until we find the target; number of items affects response time; slow and inefficient
What is the binding problem?
Problem of perceiving which visual features belong to the same object
What is the feature integration theory (FIT)?
Theory that the brain solves the binding problem by selectively attending to one object and ignoring any others
Describe the 2 stages in which objects in a scene are perceived.
Pre-attentive stage: stimulus features sensed but not bound together
Focused attention stage: attention binds object features together, creating an accurate mental representation of the scene
What are illusory conjuctions?
When object features are incorrectly combined due to lack of attention
How do stimuli compete for neural representation?
When both preferred and non-preferred stimuli are in a receptive field at the same time, visual neurons produce responses that are an average between the responses for each stimulus alone
What is the biased competition theory?
Brain resolves the competition for neural representation by selectively attending to one object and representing the features of just that object; attention biases the competition so that only the features of the attended object are represented, as if only the attended object were present
What happens when a person looks into a cluttered visual scene?
Attends to one object and ignores the rest; all the neurons with that object in their RF will respond as if only that object were there
What is top-down processing?
Emphasizes the influence of goals, knowledge, and expectations on perception; deliberate, effort and attention to a location, features, or objects in a controlled manner
What is bottom-up processing?
Stimulus-drive, effortless, and involuntary; involve unavoidable capture of attention by a salient perceptual stimulus
Which stream is heavily involved in attention?
Dorsal stream (where/how pathway)
Which brain regions are involved in attention?
Frontal eye field (FEF) and the posterior parietal cortex (PPC)
What is unilateral visual neglect?
Condition in which a person has difficulty attending to stimuli in one half of the visual field (almost always the left half), as a result of damage to the contralateral posterior parietal cortex (PPC)
What did we find about PPC in monkeys?
Activity of many PPC neurons is correlated with where the monkey is attending; neuron’s activity is not tied to a motor act (eye or hand movement) but to the shift of attention to the stimulus in the neuron’s RF location
What did studies of brain activity in humans using fMRI show?
- That human PPC and FEF are important sources of attentional control
- Confirmed PPC is important component of brain’s ability to control spatial attention
- Provided strong evidence that PPC and FEF are sources of signals that control visual attention
What are neural correlates of consciousness (NCCs)?
Correspondences between neural activity and conscious awareness (present when aware, not present when not)
What is perceptual bistability?
A phenomenon in which an unchanging visual stimulus leads to repeated alternation between 2 different perceptual experiences
What is blindsight?
The ability to point to and sometimes discriminate visual stimuli without any conscious awareness of them; caused by damage to V1
What is blindsight driven by?
LGN (lateral geniculate nucleus)
What is the relationship between ADHD and visual attention?
While those with ADHD do have attention deficits their visual attention is fairly normal
What is sound?
The cyclical increase and decrease in the pressure of a medium (usually air)
What is audition?
A material sense; a sense of pressure changes from air molecules
How does sound occur?
Sound is initiation by movement that disturbs air molecules –> molecules collide with other air molecules resulting in a change in air pressure that propagates outward from source –> As the sound wave travels outward from the source in all directions, the wave front resembles a sphere that grows continuously larger, –> sound energy at any given point on the wave front decreases with distance from the source
What are sound waves?
Waves of pressure changes in air caused by vibrations of a source
What is a cycle of sound?
In a sound wave, a repeating segment of air pressure changes
What is a compression?
A region in a longitudinal wave where the particles are closest together
What is a rarefaction?
A region in a longitudinal wave where the particles are furthest apart
What is amplitude?
The height of the wave; different between the maximum and minimum sound pressure in a sound wave
What are the physical properties of sound and their perceptual counterparts?
Frequency - pitch or tone (Hz), Amplitude - loudness or volume (dB) and Waveform - timbre
What is a pure tone?
Sound wave in which air pressure changes overtime according to a mathematical formula called a sine wave
What are Hertz (Hz)?
Number of cycles per second of a sound wave; the physical unit used to measure frequency
True or False. The larger the number or higher the Hz the lower pitched the sound and the lower the number or lower Hz the higher pitched the sound
True
What is loundness?
Perceptual dimension of sound that is relation to the physical dimension of amplitude; how intense or quiet a sound seems
What are decibels (dB)?
Physical unit used to measure sound amplitude; logarithmically related to sound pressure
How do we define the difference between 2 sounds?
As the ratio between 2 sound pressures
At how many decibels does hearing loss begin?
Prolonged exposure above 85 decibels can cause noise-induced hearing loss which is permanent
What is an audibility curve?
The absolute threshold for hearing; the intensity of the least intense sound that can be heard; most sensitive in the middle range which is the frequency of most human speech
What is the harmonic spectrum?
Energy is at integer multiples of the fundamental frequency; harmonic sounds with the same fundamental frequency can sound different
What is the fundamental frequency?
First harmonic, lowest-frequency component of sound; determines the perceived pitch of the sound
What did Joseph Fourier prove?
That waveforms of most periodic sounds have a more complex shape than a sine wave
What is Fourier analysis?
Mathematical procedure for decomposing a complex waveform into a collection of sine waves with various frequencies and amplitudes
What is the Fourier spectrum?
Depiction of the amplitudes at all frequencies that make up a complex waveform (same as SPD)
What are waveform vs spectral plots?
Waveform = amplitude against time
Spectral = amplitude against frequency (spectrum)
What is a spectrogram and what is it useful for?
A 3-dimensional plot of frequency and amplitude as a function of time; useful for representing complex waveforms like speech that change over time
What is the 1st harmonic?
The fundamental frequency
What is timbre?
Reflects spectral composition of sound waves; Relative strength of harmonics is what influences timbre perception
What is the illusion of the missing fundamental?
Is the same fundamental so we hear it as the same note
What does the manner of onset and offset tell us?
Onset (beginning) and decay (ending) of a sound effect timbre perception
What do we know about complex waveforms?
Do not sound like a pure tone, sound more rich; have sound quality that depends on frequency and each overtone (timbre)
How do sounds differ in timbre?
2 complex sounds that have the same pitch and loudness but do sound the same due to differences in relative amplitudes of various overtones
What is the ear?
Peripheral part of the auditory system; structure that transduces sound into neural signals that are sent to the brain
What are the 3 main parts of the ear?
Outer, middle and inner ear
What makes up the outer ear?
Pinna, auditory canal, and tympanic membrane
What is the pinna?
Outermost portion of the ear; shape can modify incoming sound and contribute to sound localization
What is the auditory canal?
Narrow channel that funnels sound waves gathered by the pinna onto the tympanic membrane and that amplifies certain frequencies in those waves and contributes to high sensitivity to those frequencies
What is the tympanic membrane (or eardrum)?
Thin, elastic diaphragm at the inner end of the auditory canal that vibrates in response to the sound waves that strike it; forms an airtight seal between outer ear and the middle ear
What are ossicles?
3 small bones in the middle ear that amplify sound energy from the tympanic membrane of the outer ear to the cochlea in the inner ear
What are the 3 bones that make up the ossicles?
In order:
1) Malleus (hammer)
2) Incus (anvil)
3) Stapes (stirrup)
Essentially are levers
What is the oval window?
Membrane on the base of the cochlea
How do the ossicles amplify sound?
Each move one another and take advantage of lever mechanics to amplify sound
Larger size of tympanic membrane concentrates sound energy in much smaller area and effectively amplifies its effect; physical arrangement of ossicles produce a lever action that magnifies vibrations of tympanic membrane
What are the 2 muscles in the middle ear and what do they do?
Tympani and Stapedius; purpose is to tense when sounds are very loud muffling pressure changes; regrows when damaged
What is the eustachian tube?
A tube connecting the middle ear and the top of the throat; is normally closed but can be briefly opened (by swallowing or yawning) to equalize the air pressure in the middle ear with the air pressure outside
What happens when there are pressure differences within the eustachian tube?
Causes it to be inflated or deflated which affects its ability to amplify and hear sounds; is also why ear infections happen
What is the inner ear made of?
The cochlea; wrapped in bone (skull); is a tube w/ fluid
What is the cochlea?
Coiled, fluid-filled compartment embedded inside of the skull; it is a tapered tube partitioned by the basilar membrane and Reissner’s membrane into 3 chambers
What 3 chambers make up the cochlea?
The cochlear duct, vestibular canal, and tympanic canal
What is the helicotrema?
The membranes end just before the apex of the cochlea; provides an open pathway for the perilymph to carry vibrations through the vestibular canal and then back around through the tympanic canal and out through the round window
What is the round window?
Membrane-covered opening at the base of the tympanic canal in the cochlea; serves as a king of “relief valve” for the pressure waves traveling through the perilymph
What is the basilar membrane?
Tapered membrane suspended between the walls of the cochlea; thicker, narrower, and stiffer at the base than at the apex
How do sound waves affect the basilar membrane?
Each location along the length of the basilar membrane has a characteristic frequency to which that location on the membrane responds most readily; the varying thickness and tightness creates varying resonance along the basilar membrane
Describe the base vs the apex of the basilar membrane.
Base: thicker, narrower, stiffer, high-frequency pressure waves cause greatest displacement
Apex: thinner, wider, more flexible, low-frequency pressure waves cause greatest displacement
What is the Organ of Corti?
- Located within cochlear duct, resting on and extending along length of basilar membrane
- Responsible for auditory transduction
- Anchored in bone
What is the the tectorial membrane?
Membrane that lies above the hair cells in the organ of Corti
What is the stereocilia?
Small hairlike projections on the tops of inner and outer hair cells
What is the auditory nerve?
Nerve that conveys signals from the hair cells in the organ of Corti to the brain; made up of Type I and Type II auditory nerve fibers
What happens when stereocilia move?
Opens and closes mechanically gated channels; open channels lead to depolarization and glutamate release which stimulates auditory nerve
What is the difference between inner and outer hair cells?
Inner hair cells: pear-shaped, float free in endolymph; responsible for transducing sound into neural signals
Outer hair cells: cylindrical, attached to tectorial membrane, serve to amplify and sharpen responses of inner hair cells
What do inner and outer hair cells do?
Inner: convey almost all information about sound waves to the brain (afferent fibers, type l)
Outer: receive feedback from the brain (using efferent fibers, type ll) to make parts of the cochlear partition stiffer
What are otoacoustic emissions?
Are sounds generated FROM the inner ear, due to electromotility from outer hair cells, and are frequency-specific
What is a characteristic frequency?
The frequency that increases the neuron’s firing rate at the lowest intensity (lowest point on the threshold tuning curve)
What 2 mechanisms does the cochlea use to encode sound into frequency?
Place code and temporal code
What is a place code?
Tuning of different parts of the cochlea to different frequencies, in which information about the particular frequency of an incoming sound wave is coded by the PLACE along the cochlear partition with the greatest mechanical displacement
What did mapping of type l auditory nerve fibers to position in the organ of Corti show us?
Provides strong evidence for place coding in frequency representation in the cochlea
What is temporal code (frequency theory)?
Suggests that the neurons’ firing rate matches the cycles per second (Hz); works only for lower frequency due to limitations in cell firing rates and their ability to work collectively; temporal code adds a lot of information about frequency
What is phase locking?
Firing of a single neuron at one distinct point in the period (cycle) of a sound wave at a given frequency
What is the volley principle?
Multiple neurons can provide a temporal code for frequency if each neuron fires at a distinct point in the period of a sound wave but does not fire on every period
How do audiologist test people’s hearing?
With an instrument called an audiometer, which presents pure tones with known frequency and amplitude to the right or left ear using high-quality headphones in a quiet environment
What is the normal range of hearing?
Between -10 and +20 dB
What are conductive hearing impairments?
Hearing impairments characterized by a loss of sound conduction to the cochlea, as a result of problems in the outer or middle ear
What are sensorineural hearing impairments?
Hearing impairments caused by damage to the cochlea, the auditory nerve, or the auditory areas or pathways of the brain (typically hair cells)
What are age-related hearing impairments?
One sensorineural impairment everyone eventually suffers from is one due to aging; presbycusis is the age-related loss of hearing with high frequencies lost first
What are noise-induced hearing impairments?
Prolonged exposure to sounds with an amplitude greater than about 85 dB SPL is likely to cause noise-induced hearing loss
What causes age-related hearing impairments?
Mechanical damage due to very high amplitude pressure waves pulsing through the cochlea; hair cell death
How can you prevent age-related hearing impairments?
Using hearing protection and keeping volume at safe level when listening to recorded music
What is tinnitus?
Involves perceiving sound when none is present; causes are variable and not well understood; treatments include drugs, hearing aids, etc.
What is a cochlear implant?
Directly stimulates auditory nerve to help cure deafness; a lot of debate about this technology and its implementation
