lecture 8: hearing

Question 1

how are loudness and pitch related

Answer 1

loudness and pitch are related to amplitude and
frequency, but not identical

Whereas loudness depends on the energy of the wave. In general, the pitch is the reason behind the difference in voice quality of different individuals. The pitch of a sound depends on the frequency while loudness of a sound depends on the amplitude of sound waves.

Question 2

pure vs complex tones

Answer 2

a pure tone consists of only a single frequency. It’s wave form is a pure sine wave. A complex tone is not a pure sine wave but it is periodic–it has an underlying pattern that repeats

Question 3

Timbre

Answer 3

Two non-identical
sounds can have the
same loudness and
pitch.

Timbre depends on the
frequency spectrum, the
sound pressure and the
temporal characteristics
of the sound

Question 4

Shepard Tone

Answer 4

The Shepard tone is colloquially referred to as an auditory illusion. The effect is an endless ascension of pitch, seemingly rising to some sort of resolution but never getting there

illusion from manipulating loudness and pitch: barberpole of sound, seems to rise but doesnt and is great in building suspense for movies

Question 5

bones in the middle ear

Answer 5

malleus, incus, stapes

Question 6

cochlea

Answer 6

The cochlea is a fluid-filled, spiral-shaped cavity found in the inner ear that plays a vital role in the sense of hearing and participates in the process of auditory transduction. Sound waves are transduced into electrical impulses that the brain can interpret as individual sound frequencies

Question 7

eardrum

Answer 7

The eardrum vibrates from incoming sound waves and sends these vibrations to three tiny bones in the middle ear

Question 8

how many types of visual receptors do we have

Answer 8

two- rods and cones

Question 9

how many types of auditory receptors so we have

Answer 9

one- hair cells

Question 10

hair cells

Answer 10

The function of the cochlear hair cell is to convert mechanical vibration induced by sound waves into electrical signals that are transmitted to the brain via the auditory portion of the VIII cranial nerve.

The cochlear hair cells in humans consist of one row of inner hair cells and three rows of outer hair cells. The inner hair cells are the actual sensory receptors, and 95% of the fibers of the auditory nerve that project to the brain arise from this subpopulation.

Question 11

ipsilateral

Answer 11

same side

Question 12

contralateral

Answer 12

opposite sides

Question 13

what are the 3 parts of the auditory pathway

Answer 13

Neurons in secondary auditory cortex represents a greater range of frequencies, loudness, location, and combinations of features (somewhat analogous to simple
and complex cells in striate and extrastriate visual cortex)

Question 14

is the auditory system cross wired

Answer 14

not completely unlike visual system

Question 15

Overlap of what/where in vision and audition

Answer 15

Question 16

Sound Localization:
where

Answer 16

Inter-aural time difference (loudness & timing)

Distortions of sound by head & pinnae

Question 17

“what” specialization in
audition: voice selective regions

Answer 17

Beyond Auditory Cortex, two pathways. The
ventral stream is for what and a dorsal stream
for where/how

• Basic acoustic features represented in auditory
  cortex pitch, spectrotemporal properties,
  intensity
• A few categories appear to have selective
  processing regions (or neurons), but evidence
  is more sparse than in vision
• Voice recognition, music, speech

Question 18

McGurk Effect

Answer 18

an auditory-visual illusion that illustrates how perceivers merge information for speech sounds across the senses. For example, when we hear the sound “ba” while seeing the face of a person articulate “ga,” many adults perceive the sound “da,” a third sound which is a blend of the two

Question 19

visual vs auditory systems

Answer 19

Question 20

Music Processing
(Peretz & Coltheart, 2003)

Answer 20

Congenital Amusia (tone deaf) individuals show
differences in grey matter density in right auditory
cortex and right inferior frontal gyrus

Reward regions respond to pleasurable music
and ‘chills’: Nucleus accumbens, dorsal striatum

Question 21

Music and Pleasure

Answer 21

Pitch processing occurs in
the auditory cortex, but
melodies are comprised
of combinations and
sequences of pitches, as
well as temporal
information engaging
both the ventral and
dorsal routes.

Question 22

Sound and Emotion:
Music

Answer 22

Specific auditory characteristics observed in music are uniquely capable of evoking emotional responses in humans and engaging emotional brain circuitry
These responses may depend on cultural learning and previous exposure

Question 23

sound

Answer 23

The air vibrates, and that information is transformed into a
neural code to represent sound and speech.

Question 24

Frequency

Answer 24

how many times a a wave cycles every second (pitch)

Question 25

Amplitude

Answer 25

how high the wave becomes (loudness)

Question 26

How are frequency and amplitude related to what we hear every day?

Answer 26

Frequency: Pitch * Amplitude: Loudness

Question 27

Overview of Auditory Pathway

Answer 27

There is energy in the world, in the form of air compression Sound waves enter the ear, information is passed to cochlea Receptors in cochlea transform sound info into neural activity Signals transmitted down auditory pathway in brain

Question 28

Pinna

Answer 28

focus sound into the ear canal

Question 29

Ear canal:

Answer 29

carry the sound further into the ear to tympanic membrane

Question 30

* Tympanic membrane:

Answer 30

When sound waves reach the tympanic membrane they cause it to vibrate. The vibrations are then transferred to the tiny bones in the middle ear

Question 31

3 bones carry information to cochlea:

Answer 31

(stapes, maleus, incus)

Question 32

tonotopic map

Answer 32

* The cochlea is organized in a ‘tonotopy’ * cells at one end of the cochlea respond to the highest frequencies and cells at the other end respond to the lowest frequencies of sound waves, with a gradient in between

Question 33

hair cells

Answer 33

Cochlea is covered in hair cells * The movement of the fluid in the cochlea moves the hair cells * Movement of hair cells physically pulls open ion channels to start transduction of signal

Question 34

Cochlear implants

Answer 34

partially restoring hearing in those with deafness caused by cochlea damage. * Directly stimulate the auditory nerves to get information to the brain. The brain will partially rewire to interpret signals

Question 35

pro and con of cochlear implant

Answer 35

The ability to hear sounds around them for safety and better quality of life The sound experienced with a cochlear implant is different than normal hearing, and the brain needs time to learn how to use the new input.

Question 36

Partial ‘Cross-wiring’ in Auditory Pathway

Answer 36

Like visual information, auditory information crosses the axis of the body. Unlike visual information, only some of it crosses over. Auditory input leaving the cochlea is processed by a series of structure sin the brain stem, midbrain, and thalamus This auditory pathway gives input to primary auditory cortex (A1) A1 in each hemisphere receives input from both the left and right ears

Question 37

Characteristics of Auditory Cortex Organization

Answer 37

Tonotopy in primary auditory cortex * What/Where pathway * What path/ventral stream specialization * Beyond just audition: integration of information across sensory modalities

Question 38

Tonotopy in primary auditory cortex

Answer 38

Like the cochlear membrane, there is a topographic organization of frequency in the brain. Region names * Primary auditory cortex (A1), also known as the “core” area * Belt area (A2) surrounding A1 * Parabelt area (A3) adjacent to lateral side of belt

Question 39

How might you measure tonotopic maps?

Answer 39

One approach: 1. Implant electrodes in A1 and measure neural activity 2. Play sound waves that vary from low to high frequencies 3. For each neuron determine which frequency it responds the most to 4. Map preferred frequencies for each location of A1 * This technique could also be used to measure tonotopy in the basilar membrane

Question 40

How might you measure tonotopic maps?

Answer 40

Could also use fMRI to measure tonotopy in A1 * Pros: * You can record from all of auditory cortex at once * Non-invasive and can be done in humans * Cons: * Don’t have data at the neuron-level

Question 41

Neurons in belt and parabelt can be tuned to more varied patterns of input

Answer 41

Question 42

2 Pathways of Visual Perception

Answer 42

Ventral “What” Stream Dorsal “Where” Stream

Question 43

Ventral “What” Stream

Answer 43

(to inferior part of temporal lobe): Responds to what the sound is

Question 44

Dorsal “Where” Stream

Answer 44

(to parietal lobe): responds to identifying where a sound is coming from We localize sound in two ways: – Interaural time differences: when your head is titled, sound arrives at one ear before the other. – Distortion: Sound will be more distorted if it occurs on the other side of your head.

Question 45

experiment to Discovering category selectivity in the auditory cortex

Answer 45

Present every type of sound you can think of. Test whether different parts of the brain care about any specific category. * Some parts of auditory cortex (in both humans, left, and monkeys, right) respond to the identity of the person who is making vocalizations rather than the exact utterance

Question 46

McGurk effect

Answer 46

The McGurk effect is a perceptual phenomenon that demonstrates an interaction between hearing and vision in speech perception. The illusion occurs when the auditory component of one sound is paired with the visual component of another sound, leading to the perception of a third sound.

Question 47

For the ‘where’ pathway, what information do we use to localize sound?

Answer 47

distortion and intraaural time differences

Question 48

* Where are the what and where pathways located for hearing?

Answer 48

what: (to inferior part of temporal lobe) where: to parietal lobe

Question 49

* How is primary auditory cortex organized?

Answer 49

Tonotopy in primary auditory cortex Region names * Primary auditory cortex (A1), also known as the “core” area * Belt area (A2) surrounding A1 * Parabelt area (A3) adjacent to lateral side of belt

Question 50

Are there category-selective brain regions, for hearing, analogous to those found in vision? If so, what are the categories these regions are selective for, and how do we know?

Answer 50

* Some parts of auditory cortex (in both humans, left, and monkeys, right) respond to the identity of the person who is making vocalizations rather than the exact utterance. selective to identity of person making sound, specifically music (non vocal or vocal), or speech (english or foreign)

Question 51

What is the McGurk effect, and what does it tell us about our sensory systems?

Answer 51

The McGurk effect is a perceptual phenomenon that demonstrates an interaction between hearing and vision in speech perception. The illusion occurs when the auditory component of one sound is paired with the visual component of another sound, leading to the perception of a third sound. showed us we integrate of information across sensory modalities