Perception Exam 3

Apparent motion

The illusory impression of smooth motion resulting from the rapid alternation of objects that appear in different locations in rapid succession.

Correspondence problem (motion)

The probelm faced by the motion detection system of knowing which feature in frame 2 corresponds to which feature in frame 1.

Aperture problem

The fact that when a moving object is viewed through an aperture (or a receptive field), the direction of motion of a local feature or part of an object may be ambiguous.

Motion aftereffect

The illusion of motion of a stationary object that occurs after prolonged exposure to a moving object

Interocular transfer

The transfer of an effect (such as adaption) from one eye to another.

Optic array

The collection of light rays that interact with objects in the world in front of a viewer. term coined by J.J Gibson.

Optic flow

The changing angular position 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 are in motion, all points in the perspective image seem to emanate.

Biological motion

is a special type of structure from motion that allows us to dsistinguish between animate and inanimate objects.

Tau

Information in the optic flow that could signal TTC without the necessity of estimating either absolute distances or rates.

Smooth pursuit

Voluntary eye movement in which the eyes move smoothly to follow a moving object

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.

Vergence

A type of eye movement, both voluntary and involuntary, in which the two eyes move in opposite directions

Convergent eye movement

turns the eye inward

Divergent eye movement

Turn the eyes outward

Reflexive

Automatic and involuntary eye movement

Superior colliculus

A structure in the midbrain that is important in initiating and guding eye movements.

Saccadic suppression

The reduction of visual sensitivity that occurs when we make saccadic eye movements.

Comparator

An area of the visual system that receives one copy of the order issued by the motor system when the eyes move (the other copy goes to the eye muscles).

Akinetopsia

A rare neurophysiological disorder in which the affected individual has no perception of motion.

Sounds

are created when objects vibrate.

Amplitude or Intensity

The magnitude of displacement (increase or decrease0 of a sounf pressure wave.

Frequency

for sound, the number of times per second that a pattern of pressure change repeats

hertz (Hz)

A unit of measure for frequency. One Hz equals one cycle per second.

Decibel (dB)

A unit of measure for the physical intensity of sound

Loudness

The psychological aspects of sound related to perceived intensity or amplitude.

Pitch

The psychological aspect of sound related mainly to the fundamental frequency

Since wave

The waveform for which variation as a function of time is a sine function

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.

Pinna

Outer, funnel-like part of the ear

Tympanic membrane

The eardrum. A thin sheet of skin at the end of the outer ear canal. Vibrates in response to sound

Middle ear consists of three tiny bones

Ossicles, the amplify and transmit sounds to the inner ear.

Ossicles

The smallest bones in the body

Malleus

Receives vibration from the tympanic membrane and is attached to the incus

Incus

The middle ossicle

Stapes

Connected to the incus on one end and the oval window of the cochlea on the other.

Oval window

is border between middle and inner ear

tensor tympani and stapedius

Two muscles in the middle ear that decreases ossicle vibration when tensed

Cochlea

Spiral structure of the inner ear containing the organ of corti

Vestibular canal

Extends from oval window at base of cochlea to helicotreama at the apex. Canal closest to ossicles and through which pressure waves move first

Tympanic canal

Extends from the helicotrema at the apex to the round window at the base of the cochlea

Middle canal

Sandwiched between the vestibular and tympanic canals and contains the cochlear partition

Reissner’s membrane

Thin sheath of tissue separating the vestibular and middle canals in the cochlea

Basilar membrane

Plate of fibers that forms the base of the cochlear partition and separates the middle and tympanic canals in the cochlea

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 cells

Cells that support the stereocilia, which transduce mechanical movement in the cochlea into neural activity sent to the brain stem. Some hair cells also receive input from the brain.

Tectorial membrane

A gelatinous structure, attached on one end, that extends into the middle canal of the ear, floating above inner hair cells and touching outer hair cells.

Stereocilia

Hairlike extensions on the tips of hair cells in the cochlea that intitiate the release of neurotransmitters when they are flexed

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 mechanial displacement.

Inner hair cells

Convey almost all information about sound waves to the brain (using afferent fibers).

Outer hair cells

Receive information from the brain (using efferent fibers). They are involved in an elaborate feedback system.

The auditory nerve

Responses of individual AN fibers to different frequencies are related to their place along the cochlear partition.

Frequency selectivity

Clearest when sounds are very faint

Threshold tuning curve

A graph plotting thresholds of a neuron or fiber in response or fiber in response to sine waves with varying frequencies at the lowest intensity that will give rise to a response.

Two-tone suppression

decrease in firing rate of one auditory nerve fiber due to one tone, when a second tone is presented at the same time.

Rate saturation

The point at which a nerve fiber is firing as rapidly as possible and further stimulation is incapable of increasing the firing rate.

Isointesnsity curves

A chart measuring an AN fiber’s firing rate to a wide range of frequencies, all presented at the same intensity level.

Rate- intensity function

A map plotting firing rate of an auditory nerve fiber in response to a sound of constant frequency at increasing intensities.

Phase locking

Firing of a single neuron at one distinct point in the period (cycle) of a sound wave at a given frequency

Temporal 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 timing of neural firing as it relates to the period of the sound.

The volley principle

An idea stating 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

Superior olive

An early brain stem region in the auditory pathway where inputs from both ears converge.

Inferior colliculus

A midbrain nucleus in auditory pathway

Medial geniculate nucleus

The part of the thalamus that relays auditory signal to the temporal cortex and receives input from the auditory cortex

Primary auditory cortex (A1)

The first area within the temporal lobes of the brain responsible for processing acoustic organization

Belt area

A region of cortex, directly adjacent to A1, with inputs from A1, where neruons respond to more complex characteristics of sounds

parabelt area

A region of cortex, lateral and adjacent to the belt area, where neurons respond to more complex characteristics of sounds, as well as to input from other senses.

Tonotopic organization

An arrangement in which neurons that respond to different frequencies are organized anatomically in order of frequency

Psychoacoustics

The study of the psychological correlates of the physical dimensions of acoustics

Audibility threshold

A map of just barely audible tones of varying frequencies.

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.

Masking

using a secondary sound, frequently noise, to make the detection of a primary sound more difficult: used to investigate frequency selectivity

White noise

Consists of all audible frequencies in equal amounts; used in masking.

Critical bandwidth

The range of frequencies conveyed within a channel in the auditory system

Conductive hearing loss

Caused by problems with the bones of the middle ear.

Two ears

Critical for determining auditory locations

Interaural time differences

The difference in time between a sound arriving at one ear versus the other.

Azimuth

The angle of a sound source on the horizon relative to a point in the center of tge head between the ears.

Medial superior olive

A relay station in the brain stem where inputs from both ears contribute to detection of ITDs

Interaural level difference

The difference in level (intensity) between a sound arriving at one ear versus the other.

Lateral superior olive

A relay station in the brain stem where inputs from both ears contribute to the detection of ILDs

Excitatory connections

to LSO come from ipsilateral ear

Inhibitory connections

to LSO come from contraletral ear

Cone of confusion

A region of positions in space where all sounds produce the same ITDs and ILDs

Directional transfer function

A measure that describes how the pinna, ear canal, head, and torso change the intensity of sounds with different frequencies that arrive at each ear from different locations in space

Simplest cue

relative intensity of sound

Inverse-sqaure law

Decrease in intesnity is equal to the distance squared

Spectral composition of sounds

Higher frequencies decrease in energy more than lower frequencies do as sound waves travel from source to one ear

Fundamental frequency

Lowest frequency of harmonic spectrum

Missing-fundamental effect

The pitch listeners hear corresponds to the fundamental frequency, even if it is missing

Timbre

Psychological sensation by which a listener can judge that two sounds with the same fundamental loudness and pitch are dissimilar

Attack

Part of a sound during which amplitude increases (onset)

Decay

Part of a sound during which amplitude decreases (offset).

Source segregation

Processing an auditory scene consisting of multiple sound sources into separate sound images

Auditory stream segregation

The perceptual organization of a complex acoustic signal into separate auditory events for which each stream is heard as a separate event.

Principle of good continuation

In spite of interruptions, one can still “hear” a sound