Chapter 11: The Auditory Brian And Perceiving Auditory Scenes

Question 1

Ascending Auditory Pathways From Cochlea to Cortex

Answer 1

Cochlea to cochlear nucleus: ipsilateral

Main pathway is contralateral

Question 2

Superior olivary complex

Answer 2

Structure in brain stem

• stop on ascending auditory pathway receiving signals from both cochlear nuclei

Question 3

Cochlear Nucleus

Answer 3

Structure in brain stem that receives signals via Type I auditory nerve fiber from inner hair cells in ipsilateral ear

Question 4

Inferior Colliculus

Answer 4

Structure in midbrain

- stop in ascending auditory pathway

Question 5

Medial geniculate body

Answer 5

Structure in thalamus

- next stop on ascending pathway after inferior colliculus

Question 6

Descending Pathways

Answer 6

• protective; doesn’t want to amplify loud sounds
• carry signals between auditory cortex
• modulate motile response
• protect eat from damage through acoustic reflex activation
• black task-irrelevant ascending auditory signals and pass task-relevant ones

Question 7

Acoustic Reflex

Answer 7

Contraction of tiny molecule attached to ossicles that limit their movements in presence of loud sounds and hence prevents overstimulation of cochlea

Question 8

Auditory Cortex

Answer 8

Part of cerebral cortex, tucked into lateral sulcus on top of temporal lobe

• consists of auditory core region, belt, and parabelt

Question 9

Primary Auditory Cortex (A1)

Answer 9

Part of auditory core region

Question 10

Tonotopic map

Answer 10

Arrangement of neurons within auditory brain regions such that characteristic frequencies of neurons gradually shift from lower at one end of region to higher at other end

Question 11

Auditory Core Region

Answer 11

Part of auditory cortex, located within transverse temporal gyrus in each hemisphere

• consists of primary auditory cortex, rostrum core, and rostrotemporal core

Question 12

Belt

Answer 12

Along with parabelt, region of cortex wrapped around and receiving signals from auditory core region

Question 13

Parabelt

Answer 13

Along with belts, region of cortex wrapped around and receiving signals from auditory core region

Question 14

Narrowly tuned neuron

Answer 14

Discrimination and recognition process occurs in belt and parabelt

Question 15

Broadly tuned neuron

Answer 15

Increased amplitude = broader band

Involved in integrating component frequencies of complex sounds
- part of process of discriminating and recognizing sound sources

Question 16

Regions of Interests (ROI)

Answer 16

Anterior ROI- responds to “what” task

Posterior ROI- responds to “where” task

Question 17

Identifying sound source is important because it helps guide actions

Answer 17

• cochlea is organized nonotopically, with position in the cochlea representing frequency, not spatial location
• To represent the location of sound sources, the auditory system has evolved into an exquisitely sensitive method based on comparing aspects of the sound arriving at the two ears
• Polar coordinate system based on two mutually perpendicular places centered on the head is used to specify the locations of sound sources in 3-D space

Question 18

Azimuth

Answer 18

In sound localization, location of a sound source in side-to-side dimension in horizontal plane— angle left/right of median plane

Question 19

Perceiving azimuth in localization

Answer 19

Interaural level difference (ILD) works best for frequencies greater than 1000 Hz because the head attenuates the sound arriving at the far ear

• nonexistent when in front of behind you
• elevation and distance

Question 20

Elevation

Answer 20

Location of sound source in up-down dimension in median plane (angle above or below horizontal plane)

Question 21

Distance

Answer 21

How far sound source is from center of head in any direction

Question 22

Minimum Audible Angle

Answer 22

Minimum angular separation between reference sound source and difference sound source emitting tone of same frequency that yields 75% correct judgements about relative horizontal positions of two sources

Question 23

Interaural level difference (ILD)

Answer 23

Refers to difference in the sound level of the same sound at the two ears

Question 24

Sources to the left or right of the median plane emit sounds that are more intense in the […]

Answer 24

Closer ear

• Acoustic shadow

Question 25

Acoustic shadow

Answer 25

Area on other side of head form sound source in which loudness of sound is reduced because the soundwaves are partially blocked by head - has greater effect on high-frequency sounds on low-frequency sounds

Question 26

Interaural Time Difference

Answer 26

Difference in arrival time of same sound at two ears *measures how quickly sound met each ear

Question 27

Cone of Confusion

Answer 27

Hypothetical cone-shaped surface in auditory space - when equally distant sound sources are located on a cone of confusion, their locations are confusable because they have highly similar ILD and ITD

Question 28

Perceiving elevation

Answer 28

Human pinnate provide information used to judge elevation - pinna-induced spectrum modification provides information about the elevation of a sound source (spectral shape cue) - pinna funnels sounds into ear - changes shape of sound waves

Question 29

Spectral shape cue

Answer 29

A pinna-induced modification in a sound’s frequency spectrum - provides information about the elevation of the sound source

Question 30

Perceiving Distance

Answer 30

1. Perceived loudness can be used to judge if the sound is relatively near or far if the listener knows the source sound level 2. Humans use the effect of the inverse square law to judge familiar sound distances 3. Blurring cue can be used to judge the distance of sound sources 4. Echoes can provide cues in situations in which there are hard surfaces 5. The loudness cue is also a result of the inverse square law as loudness increases as sound source approaches

Question 31

Bats localizing sounds

Answer 31

Emit high-frequency sound sequence in range of 20000-100000 Hz -they continuously track using prey-capture maneuver

Question 32

Humans localizing sounds

Answer 32

Use echolocation to judge distance from objects

Question 33

Echolocation

Answer 33

Sound localization based on emitting sounds and then processing echoes to determine nature and location of object that produced echoes

Question 34

Doppler effect

Answer 34

Frequency of sound emitted by moving sound source is higher in front of sound source than behind it - Frequency rapidly decreases as sound source passes listener

Question 35

Looking while listening: vision and sound localization

Answer 35

- when visual and auditory information conflicts, the visual information takes precedence - this is known as the ventriloquism effect, a form of visual capture

Question 36

Ventriloquism Effect

Answer 36

Tendency to localize sound on basis of visual cues when visual and auditory cues provide conflicting info

Question 37

Conditions needed for this to happen: localizing sounds

Answer 37

- Visual information should occur just before the auditory information - Events needed to make sense when linked - Two types of information must be physically close in the environment

Question 38

Precedence Effect

Answer 38

Localization of sound as originating from source in direction from which sound first arrives - minimizes effect of echoes on sound localization

Question 39

Neural basis of sound localization

Answer 39

- Proposed neurons in coincidence detectors receive signals from left and right cochlear nuclei - fire only if signals arrive at same time *Localization: Medical superior olive (MSO)

Question 40

Medial superior olive (MSO)

Answer 40

Part of superior olivary complex in brain stem - thought it contain neurons functioning as specific ITD detection mechanism - represents azimuth of sound sources - fire only if signals from two cochlear nuclei arrive at same time - similar to bipolar cells in eyes

Question 41

Auditory Regularities

Answer 41

- unrelated auditory streams rarely start or stop at exactly the same time - the features of a single auditory stream (frequency, amplitude, and timbre) tend to change slowly and gradually over time. An abrupt change often signals a new auditory stream - all the frequency components of a single auditory stream tend to change in the same way at the same time (ex. By growing louder as the sound source approaches the listener)

Question 42

Visual Regularities

Answer 42

- unrelated visual objects rarely have exactly coinciding boundaries - the surface features of a single object (e.g color and texture) tend to change slowly and gradually across adjacent locations. an abrupt change often coincides with the boundary between two objects - all the parts of a single object tend to change in the same way at the same time (eg. by moving together, if the object is rigid)

Question 43

Auditory Scene

Answer 43

All sound entering ears during current interval of time

Question 44

Auditory Scene Analysis

Answer 44

Process of extracting and grouping together frequencies emitted by specific sound sources from among complex mixture of frequencies emitted by multiple sound sources within auditory scene

Question 45

Principles of sequently grouping of auditory information

Answer 45

The auditory system groups sound like the visual system groups patterns (Gestalt grouping principles)

Question 46

Auditory grouping principles

Answer 46

- changing at the same time - having similar frequency - being temporally similar

Question 47

Auditory Stream

Answer 47

Assortment of frequencies occurring over time that were able emitted by same sound source or related sound sources

Question 48

Auditory Stream Segregation

Answer 48

Process of perceptual organization of auditory scene into set of distinct auditory streams

Question 49

Harmonic Coherence

Answer 49

Harmonic frequencies of same fundamental frequency tend to be grouped together

Question 50

Grouping by synchrony or asynchrony

Answer 50

- grouping based on synchrony or asynchrony is based on the principle of common motion - auditory system uses these regularities as very powerful grouping principles

Question 51

Sequential Grouping

Answer 51

- Grouping by frequency similarity - Auditory system uses the frequency similarity of sequential tones to group those tones into a single auditory stream or into multiple separate auditory streams

Question 52

Grouping by Temporal Proximity

Answer 52

Perceptual completion of occluded sounds - auditory system can complete occluded sounds that are partially obscured * Perceptual interpolation

Question 53

Perceptual interpolation

Answer 53

- Auditory systems have evolved to automatically make “best guesses” about what’s really going on behind occluding sounds - Making those guesses usually enable listeners to respond to environmental conditions more quickly and accurately than we other would - can put conversation together

Question 54

Sensory Substitution Device (SSD)

Answer 54

Any artificial aid in process of acquiring info via one sense that is usually acquired via another sense