Sensation & Perception (part 2) Flashcards
The course from week 6 and on! So after exam 1.
MAE (abbreviation)
Motion aftereffect
Motion aftereffect
Illusion of motion of a stationary object that occurs after prolonged exposure to a moving object.
How do MAEs arise?
Neurons tuned to the direction of motion of the adaption stimulus become adapted. When gaze switches to stationary object, neurons sensitive to the opposite direction fire at spontaneous rate which is faster than the adapted neurons, so we perceive stationary as going in opposite direction.
Interocular transfer
The transfer of an effect (such as adaptation) from one eye to the other.
MT (abbreviation)
Middle temporal area
Middle temporal area (MT)
An area of the brain thought to be important in the perception of motion. Also called V5 in humans.
How do we know that the motion aftereffect (MAE) is due to activity in V1 or beyond?
We still find a strong MAE when one eye is adapted and the other eye tested, so effect happens where info from two eyes is combined already.
Where does the motion aftereffect (MAE) arise?
In area MT.
Apparent motion
The illusory impression of smooth motion resulting from the rapid alternation of objects that appear in different locations in rapid succession.
(Ex: two separate sparks close together soon after each other are perceived as motion)
Correspondence problem (in motion detection)
The problem faced by the motion detection system of knowing which feature in frame 2 corresponds to a particular feature in frame 1.
Aperture problem
The fact that when a moving object is viewed through an aperture (or RF), the direction of motion of a local feature of part of the object may be ambiguous.
Aperture
An opening that allows only a partial view of an object.
MST (abbreviation)
Medial superior temporal area
TO (abbreviation)
Temporal - occipital
First-order motion
The motion of an object that is defined by changes in luminance.
Second-order motion
The motion of an object that is defined by changes in contrast or texture, but not by luminance.
Luminance-defined object
An object that is delineated by differences in reflected light.
Texture-defined / contrast-defined object
An object that is defined by differences in contrast, or texture, but not by luminance.
Akinetopsia
A rare neuropsychological disorder in which the affected individual has no perception of motion. Appears to be caused by disruptions to V5 / MT area.
Double dissociation
The phenomenon in which one of two functions, such as first- and second-order motion, can be damaged without harm to the other and vice versa.
MIB (abbreviation)
Motion induced blindness
Motion induced blindness (MIB)
If you fixate a central target, stationary targets in the periphery will simply dissapear when a global moving pattern is superimposed.
Troxler effect
When an unchanging target in peripheral vision will fade and dissapear if you steadily fixate a central target.
Optic array
The collection of light rays that interact with object in the world that are in front of a viewer.
Optic flow
The changing angular positions of points in a perspective image that we experience as we move through the world.
Focus of expansion
The point in the center of the horizon from which, when we’re in motion, all points in the perspective image seem to emanate. It is one aspect of optic flow.
Outflow
Optic flow toward the periphery, indicates that you are approaching a particular destination.
Inflow
Optic flow that indicates retreat.
Focus of constriction
The focus of expansion if you’re looking forward while driving in reverse.
TTC (abbreviation)
Time to collision
time to collision (TTC)
The time required for a moving object to hit a stationary object, measured in distance/rate.
How do humans accurately estimate TTC even though they are quite bad at judging absolute time and distance?
There is an alternative source of information in the optic flow: tau.
tau
Information in the optic flow that could signal TTC without the necessity of estimating absolute distances or rates. The ratio of the retinal image size at any moment to the rate at which the image is expanding.
Biological motion
The pattern of movement of living beings (humans and animals).
Smooth pursuit
A type of voluntary eye movement in which the eyes move smoothly to follow a moving object.
Superior colliculus
A structure in the midbrain that is important in initiating and guiding eye movements.
How many muscles do we have attached to each eye?
Six.
Microsaccade
An involuntary, small, jerk-like eye movement.
Vergence
A type of eye movement in which the two eyes move in opposite directions, converging or diverging.
Convergence
When both eyes turn toward the nose.
Divergence
When both eyes turn away from the nose.
Saccade
A type of eye movement made both voluntarily and involuntarily, in which the eyes rapidly change fixation from one object or location to another.
Reflexive eye movement
A movement of the eye that is automatic and involuntary.
Vestibular eye movement
When the eyes move to compensate for head and body ovement while maintaining fixation on a particular target.
VOR (abbreviation)
Vestibulo-ocular reflex
Optokinetic nystagmus (OKN)
A reflexive eye movement in which the eyes will involuntarily track a continually moving object.
OKN (abbreviation)
Optokinetic nystagmus
Saccadic suppression
The reduction of visual sensitivity that occurs when we make saccadic eye movements. Eliminates the smear from retinal image motion during an eye movement.
Corrollary discharge signal
The outgoing signal from the motor cortex that is copied in efference copy.
Efference copy
The phenomenon in which outgoing signals from the motor cortex are copied as they exit the brain and are rerouted to other areas in the sensory cortices
Comparator
An area of the visual system that receives one copy of the command issued by the motor system when the eyes move. It compares the image motion signal with the eye motion signal and can compensate for the image changes caused by the eye movement.
When is OKN present in development?
From birth.
When is motion direction present in development?
From birth
When is global motion sensitivity present in development?
Around 3-4 years of age.
Why do we say that motion processing is robust?
There are many areas involved, so it’s not easily impaired.
What two models of motion detection are discussed?
- the Bilocal correlator
- the Reichart detector
Bilocal correlator
A model for understanding motion detection, based on fly eyes.
How does motion processing work in the bilocal correlator?
You have two receptive fields: RF A and RF B. There is a cell D that delays the signal of RF A, and a cell X that receives from D and RF B.
How does motion processing work in the Reichart detector?
You have two receptive fields, RF A and RF B. Cell D delays the signal of RF A and cell E delays the signal of RF B. Then there are two X cells: one receives from D and B and one from A and E.
What is the difference between the bilocal correlator and the Reichart detector in terms of direction selectivity?
The bilocal correlator detects motion in only one direction, the Reichart detector can detect in two directions.
How do you adjust speed selectivity in the bilocal correlator?
By changing the delay.
Prosopagnosia
The inability to recognize faces.
What is the difference in response between the bilocal correlator and the Reichart detector?
The bilocal correlator responds to motion with specific direction and speed, as well as to flickering and static stimuli. The Reichart detector gives inhibition if there is no movement or if there’s flickering.
Where does local motion processing happen?
In V1.
What RF size does local motion processing require?
Small receptive fields.
What is V1 known for?
Orientation selectivity.
What does V1 receive input from?
The LGN, V2 and MT.
Where does global motion processing happen?
In MT.
What RF size does global motion processing use?
Large receptive fields.
What does low convergence do in motion processing?
It gives information on the exact location and is less sensitive when detecting stimulus.
What does high convergence do in motion processing?
it gives loose info on specific spatial location of the input and is more sensitive when detecting a stimulus.
Where does the MT area get input from?
The superior colliculus, pulvinar and V1-4.
What kinds of cells does MT consist of?
90% direction selective cells, mainly motion processing cells with large receptive fields.
Where does complex motion processing happen?
In the MST area.
What kind of RFs does complex motion processing use?
Large receptive fields.
What processes are considered complex motion processes?
- Contraction
- Expansion
- Rotation
What three models explaining the motion after effect are discussed?
- the Ratio model
- the Disinhibition model
- the Distribution-shift model
Ratio model
A model explaining the motion after-effect. Cells responding to the adaptation direction decrease in response, so the ratio changes in favor of the opposite response when viewing a stationary pattern.
Disinhibition model
A model explaining the motion after-effect. Motion-tuned cells for opposite directions inhibit each other. After adaptation, the anti-preferred stimulus response is enhanced.
DS (abbreviation)
direction selective
Distribution-shift model
A model explaining the motion after-effect. Uses the ratio between multiple direction channels.
What motion after-effect model is based on relative activity?
The ratio model.
What motion after-effect model is based on absolute activity?
The disinhibition model.
Amplitude
The magnitude of displacement of a pressure wave, the difference between the highest pressure and the lowest pressure of the wave.
Frequency
The number of times per second that a pattern of pressure change repeats.
Hz (abbrevation)
Hertz
Hertz (Hz)
A unit of measure for frequency; 1 hertz equals 1 cycle per second.
Loudness
The psychological aspect of sound related to perceived intensity (amplitude).
Pitch
The psychological aspect of sound related mainly to the fundamental frequency.
dB (abbreviation)
decibel
decibel (dB)
A unit of measure for the physical intensity of sound. Define the difference between two sounds as the ratio between two sound pressures.
How many dB does 10:1 sound pressure equal?
20 dB
How many dB does a 100:1 sound pressure ratio equal?
40 dB
What is the usual value of p0 in the decibel equation?
0.0002 dyne / cm^2
If the pressure of the sound that you’re measuring is 0.0002 dyne/cm2, then dB =
20 log (1).
Sine wave
The waveform for which variation as a function of time is a sine function.
Spectrum
A representation of the relative energy (intensity) present at each frequency.
Harmonic spectrum
The spectrum of a complex sound in which energy is at integer multiples of the fundamental frequency.
Fundamental frequency
The lowest-frequency component of a complex periodic sound.
Timbre
The psychological sensation by which a listener can judge that two sounds with the same loudness and pitch are dissimilar.
What is the shape of the frequency spectrum called?
Spectral shape
Pinna
The outer, funnel-like part of the ear that collects sound from the environment.
Ear canal
The canal that conducts sound vibrations from the pinna to the tympanic membrane and prevents damage to the tympanic membrane.
Tympanic membrane
The eardrum; a thin sheet of skin at the end of the outer ear canal. Vibrates in response to sound.
Outer ear
The external sound-gathering portion of the ear, consisting of the pinna and the ear canal.
Middle ear
An air-filled chamber containing the middle bones, or ossicles. Conveys and amplifies vibration from the tympanic membrane to the oval window.
Ossicle
Any of the three tiny bones of the middle ear: malleus, incus and stapes.
Malleus
The most exterior of the three ossicles. Receives vibration from the tympanic membrane and is attached to the incus.
Incus
The middle of the three ossicles, connecting the malleus and the stapes.
Stapes
The most interior of the three ossicles. Connected to the incus on one end and presses against the oval window of the cochlea on the other end.
Oval window
The flexible opening to the cochlea through which the stapes transmits vibration to the fluid inside. Border between middle and inner ear.
In what two ways do the ossicles amplify sound vibrations?
- Lever action makes the energy on the other side more than on this side.
- Energy is concentrated from larger to smaller surface area
Inner ear
A hollow cavity in the temporal bone of the skull, and the structures within this cavity: the cochlea and the semicircular canals of the vestibular system.
What two muscles does the middle ear have?
- Tensor tympani
- Stapedius
Tensor tympani
The muscle attached to the malleus. Tensing the tensor tympani decreases vibration.
Stapedius
The muscle attached to the stapes. Tensing the stapedius decreases vibration.
Acoustic reflex
A reflex that protects the ear from intense sounds, via contraction of the stapedius and tensor tympani muscles.
Cochlea
A spiral structure of the inner ear containing the organ of Corti.
What are the two smallest muscles in the body?
- Tensor tympani
- Stapedius
What three canals does the cochlea have?
- Tympanic canal
- Vestibular canal
- Middle canal
Tympanic canal
One of three fluid-filled passages in the cochlea. Extends from the round window at the base of the cochlea to the helicotrema at the apex.
What is another name for the tympanic canal?
Scala tympani.
Vestibular canal
One of three fluid-filled passages in the cochlea. Extends from oval window at the base of the cochlea to the helicotrema at the apex.
What is another name for the vestibular canal?
Scala vestibuli
Middle canal
One of three fluid-filled passages in the cochlea. Sandwiched between the tympanic and vestibular canals and contains the cochlear partition.
What is another name for the middle canal?
Scala media
Helicotrema
The opening that connects the tympanic and vestibular canals at the apex of the cochlea.
Reissner’s membrane
A thin sheath of tissue separating the vestibular and middle canals in the cochlea.
Basilar membrane
A plate of fibers that forms the base of the cochlear partition and separates the middle and tympanic canals in the cochlea.
Cochlear partition
The combined basilar membrane, tectorial membrane and organ of Corti, which are together responsible for the transduction of sound waves into neural signals
Round window
A soft area of tissue at the base of the tympanic canal that releases excess pressure remaining from extremely intense sounds.
Organ of Corti
A structure on the basilar membrane of the cochlea that is composed of hair cells and dendrites of auditory nerve fibers.
Hair cell
Any cell that has stereocilia for transducing mechanical movement in the inner ear into neural activity sent to the brain.
Auditory nerve
A collection of neurons that convey information from hair cells in the cochlea to the brain stem and vice versa.
Stereocilium
Any of the hairlike extensions on the tips of hair cells in the cochlea that, when flexed, initiate the release of neurotransmitters.
Tectorial membrane
A gelatinous structure, attached on one end, that extends into the middle canal of the cochlea, floating above inner hair cells and touching outer hair cells.
Tip link
A tiny filament that stretches from the tip of a stereocilium to the side of its neighbor.
What are the two fundamental characteristics of sound?
- Amplitude
- Frequency
The larger the amplitude, the … the firing rate of neurons.
Higher
Where do high frequencies cause the largest displacements in the ear?
Close to the oval window near the base of the cochlea.
Where do lower frequencies cause the largest displacements?
Further away from the oval window, near the apex.
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 that has the greatest mechanical displacement.
Afferent fiber
A neuron that carries sensory information to the central nervous system.
Efferent fiber
A neuron that carries information from the central nervous system to the periphery.
Threshold tuning curve
A graph plotting the thresholds of a neuron in response to sine waves with varying frequencies at the lowest intensity that will give rise to a response.
Cf (abbreviation)
Characteristic frequency
Characteristic frequency (CF)
The frequency to which a particular auditory nerve fiber is most sensitive.
In what fibers do inner hair cells mostly cause synapse?
Afferent fibers
In what fibers do outer hair cells mostly cause synapse?
Efferent fibers.
AN
auditory nerve
Two-tone suppression
A decrease in the firing rate of one auditory nerve fiber due to one tone, when a second tone is presented at the same time.
AN fibers fire in response to…
the displacement of stereocilia on hair cells.
Isointensity curve
A map plotting the firing rate of an auditory nerve fiber against varying frequencies at varying intensities.
Rate saturation
The point at which a nerve fiber is firing as rapidly as possible and further stimulation is incapable of indreasing the firing rate.
Rate-intensity function
A graph plotting the firing rate of an auditory nerve fiber in response to a sound of constant frequency at indreasing intensities.
Low-spontaneous fiber
An auditory nerve fiber that has a low rate (less than 10 spikes per second) of spontanoues firing. Requires relatively intense sound before they will fire at higher rates.
High-spontaneous fiber
An auditory nerve fiber that has a high rate (30+ spikes per second) of spontaneous firing. Increases its firing rate in response to relatively low levels of sound.
Mid-spontaneous fiber
An auditory nerve fiber that has a medium rate (10-30 spikes per sec) of spontaneous firing. Intermediate between low- and high-spontanoues fibers as for firing rate increasing.
Phase locking
Firing of a single neuron at one distinct point in the period (cycle) of a sound wave at a given frequency.
Why does phase locking happen?
AN fibers fire when stereocilia of hair cells move in one direction but not the other direction.
Temporal code
Tuning of different parts of the cochlea to different frequencies, in which info about the particular frequency of an incoming sound wave is coded by the timing of neural firing as it relates to the period of the sound
Volley principle
The idea that 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.
Cochlear nucleus
The first brain stem nucleus at which afferent auditory nerve fibers synapse. Contains many types of specialized neurons.
Medial superior olive
A relay station in the brain stem where inputs from both ears contribute to detection of the interaural time difference.
Inferior colliculus
A midbrain nucleus in the auditory pathway. Neurons from cochlear nucleus & superior olive go up the brain stem to the inferior colliculus
Medial geniculate nucleus
The part of the thalamus that relays auditory signals to the temporal cortex and receives input from the auditory cortex
Tonotopic organization
An arrangement in which neurons that respond to different frequencies are organized anatomically in order of frequency
A1
Primary auditory cortex
Primary auditory cortex (A1)
The first area within the temporal lobes of the brain responsible for processing acoustic information.
Belt area
A region of cortex, directly adjacent to A1 with inputs from A1, where neurons respond to more complex characteristics of sound.
Parabelt area
A region of cortex, lateral and adjacent to the belt area, where neurons respond to more complex characteristics of sounds as well to input from other senses.
Psychoacoustics
The branch of psychophysics that studies the psychological correlates of the physical dimensions of acoustics in order to understand how the auditory system operates.
Audibility threshold
The lowest sound pressure level that can be reliably detected at a given frequency.
Equal-loudness curve
A graph plotting sound pressure level (dB SPL) against the frequency for which a listener perceives constant loudness.
Temporal integration
The process by which a sound at a constant level is perceived as being louder when it is of greater duration.
What is the limit on temporal integration?
100-200ms. So if the difference in length is more than this, the effect doesn’t hold.
Masking
Using a second sound, frequently noise, to make the detection of another sound more difficult.
White noise
Noise consisting of all audible frequencies in equal amounts.
Critical bandwidth
The range of frequencies conveyed within a channel in the auditory system.
Conductive hearing loss
Hearing loss caused by problems with the bones of the middle ear.
Otis media
Inflammation of the middle ear, commonly in children as a result of infection.
Otosclerosis
Abnormal growth of the middle-ear bones that causes hearing loss.
Sensorineural hearing loss
Hearing loss due to defects in the cochlea or auditory nerve.
In what two ways can sensorineural hearing loss be caused?
- Metabolic
- Sensory
Metabolic sensorineural hearing loss
Caused by changes in the fluid environment of the cochlea, so decreased activity of hair cells.
Sensory sensorineural hearing loss
Hearing loss by injury to hair cells.
PLD
personal listening device
Describe the road from sound wave to sound perception in broad terms:
Sound is moved into the ear by the outer ear, made more intense by the middle ear, and transformed into neural signals by the inner ear.
Vestibular organs
The set of five sense organs—three semicircular canals and two otolith organs—in each inner ear that sense head motion and head orientation with respect to gravity.
Spatial orientation
A sense consisting of three interacting modalities: perception of linear motion, angular motion, and tilt.
Vestibular system
The vestibular organs as well as the vestibular neurons in cranial nerve VIII and the central neurons that contribute to the functional roles that the vestibular system participates in.
Vertigo
A sensation of rotation or spinning. Often used more generally to mean any form of dizziness.
VOR (abbreviation)
vestibulo-ocular reflex
Vestibulo-ocular reflex (VOR)
A reflex that helps stabilize vision by counterrotating the eyes when the vestibular system senses head movement.
Balance
The neural processes of postural control by which weight is evenly distributed, enabling us to remain upright and stable.
Kinesthesia
Perception of the position and movement of our limbs in space.
Active sensing
Sensing that includes
self-generated probing of the environment.
Efferent commands
Information flowing outward from the central nervous system to the periphery.
Efferent copy
The copy of efferent motor commands.
Afferent signals
Information flowing inward to the central nervous system
from sensors in the periphery.
Graviception
The physiological structures and processes that sense the relative orientation of gravity with respect to the organism.
Angular motion
Rotational motion.
Linear motion
Translational motion: motion along the same line or direction.
Tilt
To attain a sloped position.
Transduce
To convert from one form
of energy to another.
Semicircular canal
Any of three toroidal tubes in the vestibular system that sense angular motion.
Angular acceleration
The rate of change of angular velocity.
What is the integral of angular acceleration?
Angular velocity
What is the integral of angular velocity?
Angular displacement
Otolith organ
Either of two mechanical structures (utricle and saccule) in the vestibular system that sense both linear acceleration and gravity.
Linear acceleration
The rate of change of linear velocity.
What is the integral of linear acceleration?
Linear velocity
What is the integral of linear velocity?
Linear displacement
What is linear displacement also referred to?
translation
Gravity
A force that attracts a body toward the center of the Earth.
Sensory conflict
Sensory discrepancies that arise when sensory systems
provide conflicting information.
Sense of angular motion
The perceptual modality that senses rotation
Sense of linear motion
The perceptual modality that senses translation.
Sense of tilt
The perceptual modality that sense head inclination with respect to gravity.