Chapter 10: Hearing, Speaking, and Making Music Flashcards
How do we hear, speak, and make music?
sound waves: stimulus for audition
functional anatomy of the auditory system
neural activity and hearing
auditory communication in nonhuman species
What is the evolution of language and music?
languages follow similar basic structural rules
people in all cultures make and enjoy music
language and music allow us to organize and to interact socially
people who can communicate their intentions to one another and to their children presumably are better parents than those who cannot
What are sound waves?
stimulus for audition
mechanical displacement of molecules caused by changing pressure
What is the visualization of a sound wave?
air molecule density is plotted against time at a single point relative to the tuning fork’s right prong
cycle: complete peak/valley, change from min/max air pressure to next min/max air level, respectively
physicists call the resulting cyclical waves sine waves
What is frequency and pitch perception?
the rate at which sound waves vibrate is measured as cycles per second, or hertz (Hz)
low frequency (low-pitched sound)
high frequency (high-pitched sound)
What is amplitude and perception of loudness?
intensity of sound is usually measured in decibels (dB)
high amplitude (loud sound)
low amplitude (soft sound)
What is complexity and timbre (perception of sound quality)?
unlike the pure tone of a tuning fork, most sounds are a mixture of frequencies
a sound’s complexity determines its timbre, allowing us to distinguish, for example, a trombone from a violin playing the same note
simple (pure tone)
complex (mix of frequencies)
What is sound wave frequency?
the number pf cycles that a wave completes in a given amount of time
measured in hertz, or cycles per second
corresponds to our perception of pitch
low pitch, low frequency: fewer cycles/second
high pitch, high frequency: many cycles/second
differences in frequency are heard as differences in pitch, each note in a musical scale has a different frequency
What is sound wave amplitude?
the intensity, or loudness, of a sound, usually measured in decibels (dB)
the magnitude of change in air molecule density
corresponds to our perception of loudness
soft sound, low amplitude
loud sound, high amplitude
What are pure tones?
sounds with a single frequency (tuning fork)
What are complex tones?
sounds with a mixture of wave frequencies
What is fundamental frequency?
the rate at which the complex waveform pattern repeats (at regular intervals)
What are overtones?
set of higher-frequency sound waves that vibrate at whole-number (integer) multiples of the fundamental frequency
What is periodicity?
the fundamental frequency repeats at regular intervals
sounds that are aperiodic, or random, we call noise
What is the perception of sound?
a rock hitting water (making waves) is much like a tree falling to the ground
the waves that emanate from the rock’s entry point are like the air pressure waves that emanate from the place where the tree strikes the ground
the frequency of the waves determines the pitch of the sound heard by the brain
the height (amplitude) of the waves determines the sound’s loudness
auditory system converts the physical properties of sound wave energy to electrochemical activity
What are properties of spoken language and music as sounds?
language and music both convey meaning and evoke emotion
left temporal lobe analyzes speech for meaning
right temporal lobe analyzes musical sounds for meaning
language facilitates communication
music helps us regulate/affect our emotions
non-speech and nonmusical noise produced at a rate of about five segments per second is perceived as a buzz
normal speed of speech is on the order of 8 to 10 segments per second (up to 30)
What are properties of language?
experience with a language helps with rapid speech, foreigners seem to speak super fast
we hear variations of a sound as if they were identical
the auditory system has a mechanism for categorizing sounds as the same despite small differences in pronunciation, makes learning foreign languages later in life more difficult
What is loudness of music?
subjective
what is very loud to some is only moderately loud to others
What is the pitch of music?
position of each tone on a musical scale, frequency of the sound wave
any pure note is perceived as the same regardless of the instrument
What is quality of music?
the timbre of a sound, regardless of pitch
you can distinguish between a trumpet and a piano sound, quality of these sounds differs
What is the functional anatomy of the auditory system?
the ear collects sound waves from the surrounding air, converts mechanical energy to electrochemical neural energy
routed through the brainstem to the auditory cortex
the auditory system is structured to decode frequency, amplitude, and complexity, some mechanism must locate sound waves in space
neural systems for sound production and analysis must be closely related
What is the evolutionary enhancement of the auditory system?
marked expansion of auditory areas in humans
What are the steps of soundwaves travelling through the auditory system?
- the pinna catches sound waves and deflects them into the external ear canal
- waves are amplified and directed to the eardrum, causing it to vibrate
- which in turn vibrates ossicles
- ossicles amplify and convey vibrations to the oval window
- vibration of oval window sends waves through cochlear fluid
- causing the basilar and tectorial membranes to bend
- which in turn cause cilia of inner hair cells to bend, this bending generates neural activity in hair cells
What is the pinna?
funnel-like external structure designed to catch sound waves in the environment and deflect them into the ear canal
What is the external ear canal?
amplifies sound waves and directs them to the eardrum which vibrates in accordance with the frequency of the sound wave
What is the middle ear?
air-filled chamber that comprises the ossicles
What are the ossicles?
bones in the middle ear
hammer (malleus)
anvil (incus)
stirrup (staples)
connects the eardrum to the oval window of the cochlea, located in the inner ear
What are the structures of the inner ear?
cochlea
basilar membrane
hair cells
tectorial membrane
What is the cochlea?
fluid-filled structure that contains the auditory receptor cells
What is the organ of corti?
receptor hair cells and the cells that support these
What is the basilar membrane?
receptor surface in the cochlea that transduces sound waves to neural activity
What are hair cells?
specialized neurons in the cochlea tipped by cilia
What are tectorial membrane?
membrane overlying hair cells
How are sound waves transduced into neural impulses?
sound waves produce a traveling wave that moves all along the basilar membrane
all parts of the basilar membrane bend in response to incoming waves of any frequency
movement of the basilar membrane in response to sound waves creates a shearing force that bends cilia in contact with and near the overlying tectorial membrane, this bending generates neural activity in the hair cells from which the cilia extend
How is the basilar membrane responsive to frequencies?
the basilar membrane is maximally responsive to frequencies mapped as the cochlea uncoils
high frequencies caused maximum displacement near the base of the membrane
low frequencies caused maximum displacement near the membrane’s apex
What is the functions of the hair cells in the basilar membrane?
when a wave travels down the basilar membrane, hair cells at the point of peak displacement are stimulated, resulting in a maximal neural response in those cells
an incoming signal composed of many frequencies causes several points along the basilar membrane to vibrate, exciting hair cells at all these points
What are auditory receptors?
transduction of sound waves to neural activity takes place in the hair cells
3500 inner hair cells (auditory receptors)
12,000 outer hair cells (alter stiffness of tectorial membrane)
movement of the basilar membrane stimulates the hair cells via bending and shearing action
movement of cilia on hair cells changes membrane potential and alters neurotransmitter release
What are outer hair cells?
outer hair cells function by sharpening the cochlea’s resolving power, contracting or relaxing and thereby changing tectorial membrane stiffness
outer hair cells amplify sound waves, providing an energy source that enhances cochlear sensitivity and frequency selectivity
What are inner hair cells?
inner hair cells act as auditory receptors
they are embedded in the basilar membrane (the organ of Corti) are tipped by cilia
movements of the basilar and tectorial membranes displace the cilia, leading to changes in the inner hair cells’ membrane potentials
neurons in the auditory nerve have a baseline rate of firing, rate is changed by neurotransmitters released by inner hair cell
How does the movement of the cilia transfer neural activity?
movement of cilia in one direction depolarizes the cell, causing calcium influx and release of neurotransmitter, which stimulates cells that form the auditory nerve, nerve impulses increase
movement of cilia toward the opposite direction hyperpolarizes the cell, resulting in less neurotransmitter release, activity in auditory neurons decrease
What is the auditory nerve?
inner hair cells synapse on bipolar cells that form the auditory nerve (part of the 8th cranial nerve, which governs hearing and balance)
cochlear nerve axons enter the brainstem at the level of the medulla and synapse in the cochlear nucleus
What is the cochlear nucleus?
the cochlear nucleus projects to the superior olive (a nucleus in the olivary complex) and the trapezoid body
projections from the cochlear nucleus connect with cells on both hemispheres of the brain
mixes input from the two ears for single sound perception
What is the inferior colliculus?
the cochlear nucleus and the superior olive send projections to the inferior colliculus in the dorsal midbrain
What is the medial geniculate nucleus (thalamus)?
the inferior colliculus goes to the medial geniculate nucleus (thalamus)
ventral region of the medial geniculate nucleus projects to the primary auditory cortex, area A1
dorsal region projects to the auditory cortical regions adjacent to area A1
What are the two distinct pathways in the auditory system?
one is for identifying objects by their sound characteristics (temporal lobe/ventral stream/what system)
the other is for directing our movements by the sounds we hear (posterior parietal lobe/dorsal stream/how stream)
What is the auditory cortex?
primary auditory cortex, A1, lies within Heschl’s gyrus, surrounding by secondary cortical areas A2
secondary cortex lying behind Heschl’s gyrus is called the planum temporale
the cortex of the left planum forms a speech zone, Wenicke’s area
the cortex of the larger, right-hemisphere Heschl’s gyrus has a special role in analyzing music
What is lateralization?
process whereby functions become localized primarily on one side of the brain
analysis of speech takes place largely in the left hemisphere
analysis of musical sounds takes place largely in the right hemisphere
What is the insula?
located within the lateral fissure, multifunctional cortical tissue containing regions related to language, to the perception of taste, and to the neural structures underlying social cognition
injury to the insula can produce disturbances of both language and taste
What is the laterization of the auditory cortex in left-handed people?
about 70% are similar to right-handers, having language in the left hemisphere
in the remaining 30%, speech is represented either in the right hemisphere or bilaterally
What is the relationship between hearing pitch and neural activity?
hair cells in the cochlea code frequency as a function of their location on the basilar membrane
tonotopic representation: structural organization for processing of sound waves from lower to higher frequencies
the tonotopic representation of the basilar membrane is reproduced in the cochlear nucleus
this systematic representation is maintained throughout the auditory pathways and into the primary auditory cortex
similar tonotopic maps can be constructed for each level of the auditory system
What is detecting loudness?
the greater the amplitude of the incoming sound waves, the higher the firing rate of bipolar cells in the cochlea
more intense sound waves trigger more intense movements of the basilar membrane, causing more shearing action of the hair cells, leads to more neurotransmitter release onto bipolar cells
How do we detect the location of sounds?
we estimate the location of a sound both by taking cues derived from one ear and by comparing cues received at both ears
each cochlear nerve synapses on both sides of the brain to locate a sound source
neurons in the brainstem compute the difference in a sound wave’s arrival time at each ear, the interaural time difference (ITD)
another mechanism for source detection is relative loudness on the left and the right, the interaural intensity difference (IID)
What is the medial superior olivary complex?
cells in each hemisphere receive inputs from both ears and calculate the difference in arrival time between the two ears
more difficult to compare the inputs when sounds move from the side of the head toward the middle; the difference in arrival times is smaller
when we detect no difference in arrival times, we infer that the sound is coming from directly in front of us or behind us
What is the lateral superior olive and trapezoid body?
source of sound is detected by the relative loudness on the left or right side of the head
since high-frequency sound waves do not easily bend around the head, the head acts as a obstacle
as a result, higher-frequency sound waves on one side of the head are louder than on the other
How do we locate a sound?
compression waves originating on the left side of the body reach the left ear slightly before reaching the right
the ITD is small but the auditory system can discriminate it and fuse the dual stimuli
so that we perceive a single, clear sound coming from the left
What is the ventral pathway for audition?
decodes spectrally complex sounds (auditory object recognition), including the meaning of speech sounds for people
What is the dorsal pathway for audition?
integrates auditory and somatosensory information to control speech production (audition for action)
less is known about neurons in the dorsal stream
What is the uniformity of language structure?
all languages have common structural characteristics stemming from a genetically determined constraint
language is universal in human populations
humans learn language early in life and seemingly without effort, there is likely a sensitive period for language acquisition that runs from about 1 to 6 years of age
languages have many structural elements in common such as syntax and grammar
What is the Broca’s area?
anterior speech area in the left hemisphere that functions with the motor cortex to produce the movements needed for speaking
What is the Wernicke’s area?
posterior speech area at the rear of the left temporal lobe that regulates language comprehension, also called the posterior speech zone
What is aphasia?
inability to speak or comprehend language despite having normal comprehension or intact vocal mechanisms
What is Broca’s aphasia?
the inability to speak fluently despite having normal comprehension and intact vocal mechanisms
What is Wernicke’s aphasia?
the inability to understand or produce meaningful language even though the production of words is still intact
What happened to patients when their auditory cortex was stimulated?
patients often reported hearing various sounds
e.g. ringing that sounded like a doorbell, a buzzing noise, birds chirping
What happened to patients when their A1 area was stimulated?
produced simple tones (e.g. ringing sounds)
What happened to patients when their Wernicke’s area was stimulated?
apt to cause some interpretation of a sound (e.g. buzzing sound to a familiar source such as a cricket)
What structure plays a part in disrupting speech?
supplementary speech area on the dorsal surface of the frontal lobes stops ongoing speech completely (speech arrest)
What structure plays a part in eliciting speech?
stimulation of the facial areas in the motor cortex and the somatosensory cortex produces some vocalization related to movements of the mouth and tongue
What is positron emission tomography (PET)?
imaging technique that detects changes in blood flow by measuring changes in the uptake of compounds such as oxygen or glucose
What did Zatorre and his colleagues hypothesize about the A1 area and secondary auditory areas?
hypothesized that simple auditory stimulation, such as bursts of noise, are analyzed by area A1, whereas more complex auditory stimulation, such as speech syllables, are analyzed in adjacent secondary auditory areas
also hypothesize that performing a discrimination task for speech sounds would selectively activate left-hemisphere regions
How did Zatorre and his colleagues test their hypothesis?
passively listening to noise bursts activates the primary auditory cortex
listening to words activates the posterior speech area, including Wernicke’s area
making a phonetic discrimination activates the frontal region, including Broca’s area
What was found when the auditory cortex was mapped by positron emission tomography?
both types of stimuli produced responses in both hemispheres but with greater activation in the left hemisphere for the speech syllables
A1 analyzes all incoming auditory signals, speech and non-speech, whereas the secondary auditory areas are responsible for some higher-order signal processing required for analyzing language sound patterns
How is music processed?
music processing is largely a right-hemisphere specialization
the left hemisphere plays some role in certain aspects of music processing, such as those involved in making music (recognizing written music, playing instruments, and composing)
How is music processing localized in the brain?
passively listening to noise bursts activates Heschl’s gyrus
perception of melody triggers major activation in the right-hemisphere auditory cortex
making relative pitch judgments about two notes of each melody activates a right frontal love area
How is music used as a therapy treatment for Parkinson disease?
listening to rhythm activates the motor and premotor cortex and can improve gait and arm training after stroke
Parkinson patients who step to the beat of music can improve their gait length and walking speed
What is birdsong?
audition is as important to many animals as vision is to humans
like humans, many nonhuman animals communicate with other members of their species by using sound
birdsong function: attracting mates, demarcating territories, and announcing locations
What are the parallels between birdsong and language?
song development in young birds is influenced not just by genes but also by early experience and learning
gene-experience interactions are epigenetic mechanisms
brain areas that control singing in adult sparrows show altered gene expression in spring as the breeding, and singing, season starts
How is birdsong and language innate?
both appear to be innate yet are shaped by experience
humans seem to have a template for language that is programmed into the brain, and experience adds a variety of specific structural forms to this template
if a young bird is not exposed to song until it is a juvenile and then listens to recording of birdsongs of various species, the young bird shows a general preference for its own species’ song
What are whale songs?
cetaceans (whales, dolphins, and porpoises) have evolved to use a variety of AM and FM sounds for several different communication purposes
the humpbacked whale’s songs are composed of a set of predictable and regular sounds that bear striking similarities to human musical traditions
