Module 10 How Do We Hear, Speak, and Make Music Flashcards
(148 cards)
1
Q
Thomas Gessimann
A
-Among most of the 26 species of singing primates, males and females sing duets
-All singing primates are monogamous, suggesting that singing may somehow relate to sexual behaviors
~Music may also play a role in primates’ parenting behaviors
-The human brain is specialized for analyzing certain aspects of music in the right temporal lobe, which complements the left temporal lobe’s specialization for analyzing aspects of speech
-Neanderthals have long fascinated researchers; the species originated about 300,000 years ago and disappeared about 30,000 years ago at some point they coexisted in Europe and the Middle East
-Researches long hypothesized the Neanderthal culture was significantly less developed than that of early Homo sapiens, yet their brain was as large or larger than Homo sapiens
2
Q
Ivan Turk
A
-A paleontologist excavated a cave in not=rthern Slovenia that had been used by Neanderthals as a hunting ground
-Buried in the cave among a cache of stone tools was a leg bond of a young bear that looks as if it was fashioned into a flute
~The bone has holes aligned along one side that could not have been made by gnawing animals
*The holes’ spacing resembled positions found on a modern flute
3
Q
Bob Fink
A
- A musicologist, analyzed the flute’s musical qualities
- He found eight-note scale similar to a do-re-mi scale could be played on the flute; but compared with the scale most familiar in European music, one note was slightly off
- The “blue” note, a staple of Jazz, is standard in musical scales throughout Africa and India today
4
Q
Language
A
- Is the use of complex systems of communication and includes syntax (innate grammar)
- Although processing and production of certain forms of language may involve specific sensory input and structures of motor output
- Sign language uses visual input and motor output using the hands and arms, whereas spoken language uses auditory input and motor output using vocal cords
5
Q
Compression Waves
A
-The undulating energy generated by the displacement of molecules of changing air pressure to emanate from the turning fork
6
Q
Sound waves
A
- Mechanical displacement of molecules caused by changing pressure that possesses the physical properties of frequency, amplitude, and complexity.
- Also referred to as a compression wave
- In air travel at a fixed speed of 1100 feet (343 meters) per second and more than four times fates in water, but sound energy varies in wavelength
7
Q
Cycle
A
-Is one complete peak and valley on the graph-the change from one maximum or minimum air pressure level of the sound wave to the next maximum or minimum level
8
Q
Sound wave energy has three physical attributes
A
-Frequency
-Amplitude
-Complexity
~Produced by the displacement of air molecules
-The auditory system analyzes each property separately
9
Q
Frequency
A
- Number of cycles a wave completes in a given time
- Sound wave frequencies are measured in cycles per second, called hertz
10
Q
Hertz
A
- Measure of sound wave frequency (repetition rate); 1 heart equals 1 cycle per second
- 50 hertz is 50 cycles per second, 6000 hertz is 6000 cycles per second
11
Q
Low pitch
A
-Have fewer wave frequencies (fewer cycles per second)
12
Q
High Pitch
A
-Have more wave frequencies (more cycles per second)
13
Q
Health young adult
A
-The hearing range is from 20 to 20,000 hertz
14
Q
Low-frequencies
A
-Travel lone distance in water
15
Q
High-frequencies
A
-Echo that bounce back from objects
16
Q
Middle Con the piano
A
-Has a frequency of 264 hertz
17
Q
Perfect Pitch
A
- Being able to name any note they hear
- Runs in families, suggesting a genetic influence
18
Q
Amplitude
A
- Stimulus intensity; in audition, roughly equivalent to loudness, graphed by the increasing height of a sound wave
- Differences in perceived intensity, or loudness
- Differences are graphed by increasing the height of a sound wave
19
Q
Decibels (dB)
A
- Measure of the relative physical intensity of sounds
- The strength of a sound relative to the threshold of human hearing as a standard, pegging at 0 decibels
- Typical speech sounds, measure about 40 dB
- Sounds that register more than about 70 dB we perceive as loud; those of less than about 20 dB WWE perceive as soft or quiet like a person whispering
20
Q
Human nervous system
A
- Evolved to be sensitive to soft sounds and so it actually blows away by extremely loud ones
- People actually damage their hearing through exposure to very loud sounds or even by prolonged exposure to sounds that are only relatively loud
- Prolong exposure to sounds louder than 100 dB is likely to damage our hearing
21
Q
Adrian Drake-Lee
A
- Found that rock musicians had a significant loss of sensitivity to sound waves, especially at about 6000 hertz
- After a typical 90 min concert, this loss was temporarily far worse; as much as a 40-fold increase in sound pressure was needed to reach a musician’s hearing threshold
- Symphony orchestras also produce dangerously high sound levels and that hearing loss is common among symphony musicians
- Prolonged listening through headphones or earbuds to music played soundly on personal music players is responsible for significant hearing loss in many young people
22
Q
Tinnitus
A
- Ringing in the ears
- Described as ringing, whining, whistling, clicking, hissing, or roaring, and it may be soft or loud, low, or high pitched
- Can be intermittent or it can be continuous
- Estimated to affect about 10 to 15% of people under the age of 40 worldwide; its prevalence doubles with advanced age
- No medications provide effective treatment for tinnitus, and prevention is recommended
- The best way to prevent tinnitus is to avoid prolonged exposure to high-intensity would level of 70 dB or higher and to wear earplugs when those situations are unavoidable
23
Q
Two broad categories of Tinnitus
A
- Objective
- Subjective
24
Q
Objective Tinnitus
A
- Maybe the result of actual sound produced within the ear
- Muscle spasms around the middle ear or blood flow can cause sounds that some individuals can detect, which they report as an annoying tinnitus
25
Subjective Tinnitus
-More common form, is a condition of hearing a sound in the absence of an external auditory stimulus
-Most common is noise-induced damage to inner hair cells, which is why rates of tinnitus are very high among those who work in high-intensity sound environments such as war zones, certain heavy industries, and music production
-Other causes include ear infections, head and neck injuries, and exposure to certain drugs
~More than 260 medications-including aspirin-have has been reported to cause intermittent tinnitus as a side effect
26
Pure tones
- Single wave frequency
| - Turning fork or pitch pipe
27
Complex tomes
- Mix wave frequencies together in combination
| - Even when a musician plays a single note, the instrument is making a complex tone
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Fundamental Frequencies
- Wave 1 is the rate at which the complex waveform patterns repeat
- Wave 2 through 20 are overtones
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Overtones
-A set of higher-frequency soundwaves that vibrate at whole-number multiples of the fundamental frequency
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Periodicity
-The fundamental frequency repeats at regular intervals
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Noise
-Sounds that are aperiodic or random
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The brain has evolved systems that analyze sounds for meaning
- Speech in the left temporal lobe
| - Music in the right temporal lobe
33
Listening to a particular language
- Helps the brain analyze rapid speech, which is one reason people who are speaking languages unfamiliar to you often seem to be talking incredibly fast
- The brain does not know where the foreign words end and begins, so they seem to run together in a rapid-fire stream
34
The auditory system
- Have a mechanism for categorizing sounds as being the same despite small differences in pronunciation
- A major obstacle to mastering a foreign language after the age of 10 is the difficulty of learning which sound categories are treated as equivalent
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Loudness
- The magnitude of a sound as judged by a person
| - Is related to the amplitude of a soundwave measured in dB, but loudness is also subjective
36
Pitch
- The position of each tone on a musical scale, as judged by the listener
- Is clearly related to soundwave frequency, there is more to it than that
37
Prosody
- Melodic tone of the speaking voice
| - Pitch contributes to the perceived melodic tone of a voice
38
Quality (Tember)
-Perceived characteristics that distinguish a particular sound from all other od similar pitch and loudness
39
The evolution of sound-processing systems for both language and music
-Accompanied by enhancement of specialized cortical regions, especially in the temporal lobes
40
Ear a biological masterpiece in three acts
- Outer ear
- Middle ear
- Inner ear
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Pinna
-Funnel-like external structure of the outer ear
-Are made of cartilage and flesh
-Is designed to catch soundwaves in the surrounding environment and deflect them into the external ear canal
~To enhance sound detection when we want to hear better we often cup a hand around the pinna
42
Canal
- Extends a short distance from the pinna inside the head
- Are made of cartilage and flesh
- Amplifies sound waves and direct them to the eardrum
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Eardrum
-When sound strikes, it vibrates, the rate of vibration varying with the frequency of the waves
44
Middle Ear
-An air-filled chamber that contains the three smallest bones in the human body, connected in a series
45
Ossicles
- Bone of the middle ear: includes hammer, anvil, and stirrup
- Amplifies the vibrations and conveys them to the membrane that covers the cochlea's oval window
46
Oval Window
- Ossicle attach the eardrum
| - an opening in the body casing of the cochlea
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Cochlea
- Inner ear structure containing the auditory receptor cells
| - These receptor cells and the cells that support them are collectively called the ORGAN of CORTI
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Basilar Membrane
-Receptor surface in the cochlea that transduces sound waves into neural activity
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Hair cells
- Specialized neurons in the cochlea tipped by cilia; when stimulated by waves in the cochlear fluid, the cilia bend and generate graded potentials in inner hair cells, the auditory receptors cells
- At the poine of peak displacement are stimulated, resulting in a maximal neural response in those cells
50
Tectorial Membrane
-The cilia of the outer hair cells that are embedded and overlay the membrane
51
Stirrup
-On the oval window makes the cochlear fluid move because the second membranous window in the cochlea (the round window) bulges outward as the stirrup presses inward on the oval window
52
Chain reaction
-The waves traveling through the cochlear fluid bend the basilar and tectorial membranes, and the bending membranes stimulate the cilia at the tips of the outer and inner hairs cells
53
Basilar Membrane
-All sound waves cause some displacement along the entire length of the membrane, but the amount of displacement at any point varies with the frequency of soundwaves
-Uncoiling near the oval window is maximally affected by frequencies as high as about 20,000 hertz, the upper limit of our hearing range
-Incoming signal composed of many frequencies causes several points to vibrate, exciting hair cells at all these points
-Much more sensitive to changes in frequency that id the rope in our analogy because the basilar membrane varies in thickness along its entire length
-Narrow and thick at its base, near the oval window, and wider and thinner at its tightly coiled apex
~The combinations of varying width and thicknesses enhances the effect of small frequency differences
*The cochlear receptors can code small differences in sound waves frequency as neural impulses
54
Both inner and outer hair cells
- Anchored in the basilar membrane
- The tips of the cilia of the outer hair cells are attached to the overlying tectorial membrane, but the cilia in the inner hair cells only loosely touch that membrane
- The movement of the basilar and tectorial membranes causes the cochlear fluid to flow past the cilia of the inner hair cells, bending them back and forth
55
Inner hair cells
- can be destroyed by prolonged exposure to intense sound pressure waves, infections, diseases, or certain chemicals and drugs
- Do not regenerate in mammals; this, once your inner hair cell has died, hearing loss is permanent
- Movement of only about 0.3 nm is sufficient to allow soundwave detection- that's about the diameter of an atom
56
Outer hair cells
- Function by sharpening the cochlea's resolving power, contracting or relaxing, and thereby changing tectorial membrane stiffness
- Have the motor function
- Contract or relax to alter the physical stimulus detected by the inner hair cells
- Send a message to the brainstem auditory areas and receive a replay that causes the cells to alter the tension on the tectorial membrane
- Also part of a mechanism that modulates auditory nerve firing, especially in response to intense sound pressure waves, and thus offer some protection against their damaging effects
57
The neurons of the auditory nerve have a spontaneous baseline rate
- Firing action potentials, and this rate is changed by the amount of neurotransmitter the hair cells release
- Turns out that movement of the cilia changes the inner hair cell's polarization and its rate of neurotransmitter release
58
Inner hair cells continuously leak calcium
-This leakage causes a small but steady amount of neurotransmitters released into the synapse
-Movement of the cilia in one direction results in depolarization
~Calcium channels open and release more neurotransmitter onto the dendrites of the cells that form the auditory nerve, generating more nerve impulses
-Movement of the cilia in the other direction hyperpolarizes the cell membrane, and transmitter release decrease, thus decreasing activity in auditory neurons
59
Otoacoustic Emissions
-Spontaneous or evoked sound waves produced within the ear by the cochlea that escape from the ear
-Soundwaves produced by a healthy cochela
~The outer hair cells amplify soundwaves, providingan energy source that enhances cochlear sensitivity and frequency sensitivity
*Not all the energy thecocholea generates is dissipated within it, some escape towards the middle ear, which works efficiently in both directions, thus setting the eardrum inmotion
-The eardrum then acts as a loudspeaker, radiating soundwaves out of the ear
-Sensitive ,icrophones placed in the external ear canal can detect both types of otoacustic emissions
~Spontaneous
~Evoked
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Spontaneous Otoacoustic Emissions
-Occur without external stimulation
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Evoked Otoacoustic Emissions
-Are generated in response to soundwaves, and they are useful for assessing hearing impairments
-Noninvasive these can detect and evaluate, this test is particularly useful with newborns and children who are too young to take conventional hearing tests
~A small speaker and microphone are inserted into the ear; the speaker emits a click sound, and the microphone detects the resulting evoked emission without damaging the delicate workings of the inner ear
62
Epiphenomenon
-A secondary phenomenon that occurs in parallel with or above a primary phenomenon
63
Cochlear-nerve axon
- Enters the brainstem at the level of the medulla and synapses in the cochlear nucleus, which has ventral and dorsal subdivisions
- Two nearby structures in the hindbrain (brainstem), the superior olive (a nucleus in the olivary complex) and the trapezoid body receive connections from the cochlear nucleus
- Projections from the cochlear nucleus connect with cells on the same side of the brain, as well as with cells on the opposite side, this arrangement mixes the inputs from the two ears to form a single sound perception
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Medial Geniculate Nucleus
- Major thalamic region concerned with audition
- Both the cochlear nucleus and the superior olive send projections to the inferior colliculus in the dorsal midbrain, two distinct pathways emerge from the inferior colliculus
65
Primary Auditory Cortex (area A1)
-Asymmetrical structures within Heschl's gyrus in the temporal lobes; receives input from the ventral region of the medial geniculate nucleus
-The ventral region of the medial geniculate nucleus projects
~Whereas the dorsal region projects to the auditory cortical regions adjacent to area A1
66
Echolocation
- The ability to use sound to locate objects in space
- Behavioral studies of blind people reveal that echolocators make short, spectrally broad clicks y moving the tongue backward and downward from the roof of the mouth directly behind the teeth; skilled echolocators can identify properties of objects such as position, distance, size, shape, and texture
67
Thaler
-Used fMRI to investigate the neural basis of this ability; they studies two blind echolocation experts and compared brain activity for sounds that contained both clicks and returning echoes
-The investigators found that the participants use echolocation to localize objects in the environment; these individuals are able to use echolocation to perceive the shape, motion, and even identity of objects
-When the bind participants listened to recordings of their echolocation clicks and echoes compared to silence, both the auditory cortex and the primary visual cortex showed activity; sighted control showed activation only in the auditory cortex
~When the investigators compared the brain activity of the controls to recordings that contained echoes vs. those that did not, the auditory activity disappeared
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Planum Temporale
- The secondary cortex lying behind Heschl's gyrus
| - for right-handed people, is larger on the left than itis on the right side of the brain and vice versa
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Wernicke's Area
- Secondary auditory cortex (A2) lying behind Heschl's gyrus at the rear of the left temporal lobe; regulates language comprehension (posterior speech zone)
- Whereas the cortex of the larger right-hemisphere Heschl's gyrus has a special role in analyzing music
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Lateralization
-Localization of function primary on one side of the brain
-If one hemisphere is specialized for one type of analysis, the other hemisphere has a complementary function
~The left hemisphere is specialized for language, and the right hemisphere appears to be lateralized for music
71
Insula
- Multifunctional cortical tissue located within that later fissure; contains language and taste perception-related regions and neural structures underlying social cognition
- Contains not only lateralized regions related to language but also areas controlling states perception (the gustatory cortex) and areas linked to the neural structures underlying social cognition
- Injury to the insula can produce such diverse defects as disturbance of both language and taste
72
Tonotopic Representation
- In an audition, the structural organization for processing of sound waves from lower to higher frequencies
- hair cell cilia at the base of the cochlea are maximally displaced by high-frequency waves, which we hear as high-pitched sounds; those at the apex are displaced the most by low-frequency waves, which we hear as low-pitch sounds
- Each bipolar cells convey information about the spot on the basilar membrane, from the apex to base, that is being stimulated
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Recordings from single fibers in the cochlear nerve
-Reveal that although each axon transmits information about only a small part of the auditory spectrum, each cell does respond to a range of soundwave frequencies-if the wave is sufficiently loud
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Bipolar cell axons in the cochlear nucleus in an orderly manner
-Axons entering from the base of the cochlea connect with one location those entering from the middle connect to another location; and those entering from the apex connect to yet another
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Cochlear Implants
-Electronic device implanted surgically into the ear to transduce soundwaves to neural activity and allow a deaf person to hear
-Are not a cure for deafness but rather are a hearing substitute
-A miniature microphone like processor secured to the skull detects the component frequencies of incoming soundwaves and sends them to the appropriate places on the basilar membrane through tiny wires
-The nervous system does not distinguish between stimulation coming from this artificial device and stimulation coming through the middle ear
~As long as the appropriate signals go to the correct locations on the basilar membrane, the brain will hear
-A shorter time span between the hearing loss and treatment can lead to better hearing
~Early intervention can lead to better results
*Does not register anything under 200 hertz
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Interaural Time Difference (ITD)
-Neurons in the brainstem compute the difference in a soundwave's arrival time at each ear
-Differences in arrival time need not be large to be detected
-If two sounds presented through earphones are separated in time by at least 10 microseconds, the listener will perceive that a single sound came from the leading ear
-Becomes smaller and smaller until there is no difference at all
~When we detect no difference, we infer that the sound is wither directly in front of us or directly behind us
*To locate we turn our head, making the soundwaves strike one ear sooner
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Interaural Intensity Difference (IID)
-Sound's relative loudness on the left and right
-Head acts as an obstacle to higher-frequency soundwaves, which do not easily bend around the head
~Higher-frequency waves on one side of the head are louder than on the other
-The lateral part of the superior olive and the trapezoid body detects this difference
-Soundwaves coming directly in front of behind or from directly above or below require the same solution
~Tilting or turning the head
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Auditory Object Recognition
-Neurons in the ventral pathway decode spectrally complex sounds, including the meaning of speech sounds for people and species-typical vocalization in monkeys
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Audition for Action
-Less is known about the properties of neurons in the dorsal auditory system, but this path clearly has a role in integrating auditory and somatosensory information to control speech production
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Noam Chomsky
-Usually credited as the first linguist to stress similarities over differences in human language structure
-Made a sweeping claim, as have researchers such as Steve pinker
~Aruge that all languages have common structural characteristics stemming from a genetically determined constraint, and these common characteristics form the basis of universal grammar theory
-Was greeted with deep skepticism when he first proper the idea that humans have a built-in capacity for learning in 1960, but it has since become clear that the capacity for human language is indeed genetic
-Humans learn language early in life and seemingly without effort, by about 12 months in age, children everywhere have started to speak words, by 18 months in age, they are combining words, by the age of 3 they have a rich language capability
-Theory of its innateness
~which is not to say that language development is not influenced by experience
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Syntax
- Is not specified by any universal rule but rather is a characteristic of the particular language
- All the languages have both syntax and grammar
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Creolization
-Two structural pillars in all human language, the development of a new language from what was formerly a rudimentary language (pidgin)
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Broca's Area
-Anterior left-hemisphere speech area that functions with the motor cortex to produce movements needed for speaking
-Was significant because it triggered the idea that the left and right hemispheres might have different functions
-During this time, might be the only one of several left-hemisphere regions that control language
~Suspected a relation between hearing and speech
84
Karl Wernicke
-Later described patients who had difficulty comprehending language after injury to the posterior region of the left temporal lobe (Wernicke's area)
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Aphasia
- Inability to speak or comprehend language despite the presence of normal comprehension and intact vocal mechanisms
- The general term for any inability to comprehend or produce language, despite the presence of otherwise normal comprehension and intact vocal mechanisms
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Broca's Aphasia
- Is the inability to speak fluently despite the presence of normal comprehension and intact vocal mechanisms
- Can speak fluently, but their language is confused and make little sense as if they have no idea what they are saying
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Wernicke's Aphasia
- Is the inability to understand or to produce meaningful language even though word production remains intact
- Cannot speak despite having normal comprehension and intact physiology
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Arcuate Fasciculus
-A fiber pathway that connects both the Broca and Wernicke's area
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Penfield
```
-Mapped cortical language areas in two ways
~By disrupting the speech
~Then by eliciting speech
-Speech disruption took several forms
~Slurring
~Word confusion
~Difficulty finding the right word
```
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Supplementary Speech Area
-Speech production region on the left frontal lobe dorsal surface
-Speech arrest
-Stimulation of other cortical regions far removed from the temporal and frontal speech areas has no effect on ongoing speech, with the exception of motor cortex regions that control facial movements
~Facial
~Tongue
~Throat movements
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Speech Arrest
-Can even stop ongoing speech completely
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Coherent Speech
-Cortical electrical stimulation is not physiologically normal and so probably would not produce actual words or word combinations
93
PET
-A brain-imaging technique that detects changes in brain blood flow
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Robert Zatorre
-Hypothesized that simple auditory stimulation, such as a burst of noise, are analyzed by area A1, whereas more complex auditory stimulation, such as speech syllables, are analyzed in adjacent secondary auditory areas
-Hypothesized that performing a discrimination task for speech sounds would selectively activate left-hemisphere regions
~Selective activation is exactly what they found
-Increased activity in the primary auditory cortex in response to a burst of noise
-Whereas secondary auditory areas are activated by speech syllables
~Both types of stimuli produced responses in both hemispheres but with greater activation in the left hemisphere for the speech syllables
*These results imply that area A1 analyzes all incoming auditory signals, speech, and nonspeech, whereas secondary auditory areas are responsible for some higher-order signal processing required for analyzing language sound patterns
95
Maurice Ravel
-A French composer developed aphasia as a result of a previously undiagnosed degenerative brain disorder exacerbated by a severe blow to the head followed a few months later by a left-hemisphere stroke
-Many of his musical skills remained intact post-stroke because they were localized to the right hemisphere
-Still recognize melodies, pink up tiny mistakes in music he heard and even judge the tuning of a piano
-Producing music were among those destroyed
~Could no longer recognize written music, play the piano, or compose
-The left-hemisphere play at least some role in certain aspects of music processing, especially those that have to do with making music
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Amusia
-Tone-deafness-inability to distinguish between musical notes
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Robert Zatorre
- Used MIRs of the left and right hemispheres show that the cortical thickness is greater in dorsolateral frontal and superior temporal regions in musicians than in nonmusicians
- Musicians with perfect pitch have a thinner cortex in the posterior part of the dorsolateral frontal lobe
- Thicker than normal cortex can bestow both advantage and impairment
- Participant's brain showed a thick cortex in the right frontal area and in the right auditory cortex region
98
Musical Therapy
- Appears to be a useful complement to more traditional therapies, especially when there are problems with mood (depression of brain injury)
- Positive effects following major surgery, both in adults and children, by reducing both their pain perception and the amount of pain medication they use
99
Epigenetic membrane in birds
-Gene-experience interactions
~Brain areas that control singing in adult song sparrows show altered gene expression in spring as the breeding-and singing- season begins
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Subsongs
- Variable in structure, low in volume, and often produced as the bird appears to doze
- Is practiced for the later development of adult communication after the bird has left the nest
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Higher vocal control center (HVC)
-Axons connect to the RA
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Robustus Archistriatalis (RA)
-Takes the HVC axons and turn sends axons to the twelfth cranial nerve
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HVC and RA
-Te structures are asymmetrical in some bird species, with those in the left hemisphere larger than those in the right
~This asymmetry is similar to the lateralized control of language in humans: if the left-hemisphere pathways are damaged, the bird stops signing, but a similar injury in the right hemisphere has no effect on song
-Birdsong structures are sexually dimorphic: they are much larger in males than in females
~Male canaries, the structure is five times as large as in the females; this sex difference is due to the hormone testosterone in males
*Injection of testosterone in female birds causes the song-controlling nuclei to increase in size
-The size of the birdsong-controlling nuclei is related to signing skill
-Contains cells that produce birdsong as well as cells responsive to hearing song
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Cetaceans (whales, dolphins, and porpoises)
- Have also evolved to use a variety of AM and FM sounds for several different communication purposes
- Vision and smell is limited because of the way suspended particulates scatter light and odorous molecules diffuse more slowly than they would in air
- Sound travels more than four times faster in water than in air
105
How Do We Hear, Speak, and Make Music?
- Sound Waves: Stimulus for Audition
- Functional Anatomy of the Auditory System
- Neural Activity and Hearing
- Anatomy of Language and Music
- Auditory Communication in Nonhuman Species
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Sound Waves: Stimulus for Audition
| -Sound Wave
-Undulating displacement of molecules caused by changing pressure
107
Physical Properties of Sound Waves
| -Three Properties of Sound-Wave Energy
-) Frequency
~Number of cycles that a wave completes in a given amount of time
*Measured in Hertz: cycles per second
~Corresponds to our perception of pitch
*Low pitch: low frequency
*High pitch: high frequency
-Amplitude
~The intensity or loudness of a sound stimulus, 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
-Complexity
~Pure tones
*Sounds with a single frequency
~Complex tones
*Sounds with a mixture of frequencies
~Corresponds to our perception of timbre or uniqueness
*How we can distinguish between a trombone and violin playing the same note?
~Fundamental Frequency
*The rate at which the complex waveform pattern repeats
~Overtones
*Set of higher frequency sound waves that vibrate at whole-number (integer) multiples of the fundamental frequency
108
Perception of Sound
-Auditory system converts the physical properties of sound-wave energy into electrochemical neural activity that travels to the brain
-Sounds are products of the brain
-Our sensitivity to sound waves is extraordinary.
Detect the displacement of air molecules of about 10 picometers (10^-11 m)
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Properties of 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 to regulate our emotions and affect the emotions of others.
110
Properties of Language
-We hear variations of a sound as if they were identical.
~Unique to perception of speech sounds
~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
111
Properties of Music
-Loudness (related to the amplitude of a sound wave)
~“Very loud” to some is only “moderately loud” to others
-Pitch (position of each tone on a musical scale; sound-wave frequency)
~Defined as the fundamental frequency, regardless of timbre
-Quality
~The timbre of a sound, regardless of pitch
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Functional Anatomy of the Auditory System
- Ear collects sound waves from the surrounding air
- Converts mechanical energy into electrochemical neural energy
- Routed through the brainstem to the auditory cortex
113
Structure of the Ear
| -Processing Sound Waves
-Pinna
~Funnel-like external structure designed to catch sound waves in the surrounding environment and deflect them into the ear canal
-External Ear Canal
~Amplifies sound waves somewhat and directs them to the eardrum, which vibrates in accordance with the frequency of the sound wave
114
Processing Sound Waves
```
-Middle Ear
~Air-filled chamber that comprises the ossicles
~Ossicles
*Bones in the middle ear:
**Hammer
**Anvil
**Stirrup
~Connects the eardrum to the oval window of the cochlea, located in the inner ear
```
115
Processing Sound Waves
-Inner Ear
~Cochlea
*Fluid-filled inner ear structure that contains the auditory receptor cells
*Organ of Corti: receptor cells and the cells that support them
~Basilar membrane
*Receptor surface in the cochlea that transduces sound waves into neural activity
~Hair Cells
*Sensory neurons in the cochlea tipped by cilia
*When stimulated by waves in the cochlear fluid, outer hair cells generate graded potentials in inner hair cells, which act as the auditory receptor cells.
~Tectorial Membrane
*Membrane overlying hair cells
116
Transducing Sound Waves into Neural Impulses
-George von Békésy (1960s)
~Sound waves produced a traveling wave that moved all along the basilar membrane
~Mapped the responsiveness of the basilar membrane to different frequencies
*Fast wave frequencies: caused maximum displacement near the base of the membrane
*Slower wave frequencies: caused maximum displacement near the membrane’s apex
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Auditory Receptors
-Transduction of sound waves into neural activity takes place in the hair cells
~3,500 inner hair cells (auditory receptors)
~12,000 outer hair cells (alters 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.
-Movement of cilia toward the tallest cilia 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 shortest cilia hyperpolarizes the cell, resulting in less neurotransmitter release.
~Activity in auditory neurons decreases
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Pathways to the Auditory Cortex
-Inner hair cells synapse onto bipolar cells that form the auditory nerve (part of the 8th cranial nerve)
-Cochlear-nerve axons synapse in the cochlear nucleus
-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 the same side of the brain as well as with cells on the opposite side.
-The cochlear nucleus and the superior olive send projections to the inferior colliculus in the dorsal midbrain.
-Inferior colliculus goes to the medial geniculate nucleus (lies in the 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.
-Analogous to the visual system, there are two distinct pathways in the auditory system:
~One for identifying objects by their sound characteristics, and
~One for directing our movements by the sounds we hear
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Auditory Cortex
-Primary auditory cortex (A1) lies within Heschl’s gyrus, surrounded 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 known as Wernicke’s area.
-The cortex of the larger, right-hemisphere Heschl’s gyrus has a special role in analyzing music.
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Auditory Cortex
| -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
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Auditory Cortex
| -What About Left-Handed People?
- About 70% are similar to right-handers and have language in left hemisphere.
- In the remaining 30%, speech is represented either in the right hemisphere or bilaterally.
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Auditory Cortex
| -Insula
- Located within the lateral fissure, multifunctional cortical tissue that contains regions related to language, to the perception of taste, and to the neural structures underlying social cognition
- Injury can produce disturbances of both language and taste
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Neural Activity and Hearing
-Hearing Pitch
~Tonotopic Representation
- Hair cells in the cochlea code frequency as a function of their location on the basilar membrane.
- Hair-cell cilia at the base of the cochlea are maximally displaced by high-frequency waves that we hear as high-pitched sounds.
- Hair-cell cilia at the apex are displaced the most by low-frequency waves that we hear as low-pitched sounds.
- 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.
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Neural Activity and Hearing
-Hearing Pitch
~Cochlear Implant
-Electronic device implanted surgically into the inner ear to transduce sound waves into neural activity and allow deaf people to hear
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Neural Activity and Hearing
-Hearing Pitch
~What about very low frequencies?
- Tonotopic theory does not explain how sounds below 200 Hz are coded.
- Sounds in this range stimulate all cells on the very apex of the basilar membrane.
- Rate of firing is proportional to frequency
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Detecting Loudness
- The greater the amplitude of the incoming sound waves, the greater the firing rate of bipolar cells in the cochlea.
- More intense sound waves trigger more intense movements of the basilar membrane, which results in greater shearing action of the hair cells, which leads to more neurotransmitter release onto bipolar cells.
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Detecting Loudness
| -Medial Part of the Superior Olivary Complex
- Cells in each hemisphere receive inputs from both ears and calculate the difference in arrival times 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 the sound is coming from directly in front of us or behind us.
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Detecting Location
| -Lateral Part of the Superior Olive and Trapezoid Body
- Source of sound is detected by the relative loudness on the left or on the right side of the head
- Since high frequency sound waves do not easily bend around the head, the head acts as an obstacle.
- As a result, higher frequency sound waves on one side of the head are louder than on the other.
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Detecting Patterns in Sound
-Music and language are perhaps the primary sound wave patterns that humans recognize.
~Music = right hemisphere
~Language = left hemisphere
-Ventral and dorsal cortical pathway for audition
~Ventral pathway decodes spectrally-complex sounds (auditory object recognition) including the meaning of speech sounds for people
~Dorsal auditory stream integrates auditory and somatosensory information to control speech production
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Anatomy of Language and Music
| -Processing Language
- Musical ability is generally a right-hemisphere specialization complementary to language ability, localized in the left hemisphere in most people.
- Does the brain have a single system for understanding and producing any language, regardless of its structure, or are very different languages processed in different ways?
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Uniformity of Language Structure
-All languages have common structural characteristics stemming from a genetically-determined constraint (Chomsky, Pinker)
1) Language is universal in human populations.
2) Humans learn language early in life and seemingly without effort.
~There is likely a sensitive period for language acquisition that is from about 1 to 6 years of age.
3) Languages have many structural elements in common.
~Examples: syntax and grammar
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Localization of Language in the Brain
| -Broca’s area
-Anterior speech area in the left hemisphere that functions with the motor cortex to produce the movements needed for speaking
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Localization of Language in the Brain
| -Wernicke’s area
-Posterior speech area at the rear of the left temporal lobe that regulates language comprehension; also called the posterior speech zone
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Localization of Language in the Brain
| -Aphasia
- Inability to speak or comprehend language despite the presence of normal comprehension or intact vocal mechanisms
- Broca’s aphasia is the inability to speak fluently despite the presence of normal comprehension and intact vocal mechanisms.
- Wernicke’s aphasia is inability to understand or to produce meaningful language even though the production of words is still intac
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Auditory and Speech Zones Mapped by Brain Stimulation
-Penfield used a weak electrical current to stimulate the brain surface.
~Auditory cortex: patients often reported hearing various sounds (e.g., ringing that sounded like a doorbell, a buzzing noise, birds chirping)
~A1: produced simple tones (e.g., ringing sounds)
~Wernicke’s area: apt to cause some interpretation of a sound (e.g., buzzing sound to a familiar source such as a cricket)
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Auditory and Speech Zones Mapped by Brain Stimulation
| -Disrupting Speech
-Supplementary speech area on the dorsal surface of the frontal lobes stopped ongoing speech completely (speech arrest).
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Auditory and Speech Zones Mapped by Brain Stimulation
| -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
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Auditory Cortex Mapped by Positron Emission Tomography
| -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
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Auditory Cortex Mapped by Positron Emission Tomography
| -Zatorre and colleagues (1992, 1995)
- 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.
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Processing Music
-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
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Localizing Music in the Brain
| -Zatorre and colleagues (1994): PET Study
- Passively listening to noise bursts activates Heschl’s gyrus.
- Listening to melodies activates the secondary auditory cortex.
- Making relative pitch judgments about two notes of each melody activates a right-frontal-lobe area.
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Localizing Music in the Brain
-Like language, the capacity for music may be innate.
~Infants show learning preferences for musical scales versus random notes.
~Children and adults are very sensitive to musical errors: Biased toward perceiving regularity in rhythms?
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Music as Therapy
-Music is used as a treatment for mood disorders such as depression.
-Best evidence of its effectiveness lies in studies of motor disorders such as stroke and Parkinson’s disease
~Listening to rhythm activates the motor and premotor cortex and can improve gait and arm training after stroke.
~Parkinson’s patients who step to the beat of music can improve their gait length and walking speed.
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Auditory Communication in
-Nonhuman Species
~Birdsong
-Audition is as important a sense to many animals as vision is to humans.
~Like humans, many animals also communicate with other members of their species by using sound.
-Birdsong Functions
~Attracting mates, demarcating territories, and announcing locations
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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;
~For example, brain areas that control singing in adult song sparrows show altered gene expression in spring as the breeding—and singing—season begins
-Humans have a basic 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 recordings of birdsongs of different species, the young bird shows a general preference for its own species’ song.
-In many bird species, song development is heavily influenced by experience during a critical period, just as language development is in humans.
-Birds also go through stages in song development, just as humans go through stages in language development.
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Neurobiology of Birdsong
-Major Structures
~Higher vocal control center (HVC)
~Nucleus robustus archistriatalis (RA)
-Asymmetry in some species
~These structures are larger on the left side.
-Structures are larger in males (sexually dimorphic).
-Singing skill is related to size of structures.
-Cells in these structures produce and respond to birdsong.
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Echolocation in Bats
-Echolocation
~Ability to identify and locate an object by bouncing sound waves off object
*Locate targets and analyze features of the target and the environment
~Analysis of the differences in return times of echoes is key
~Echoes differ with respect to an object’s distance and texture
~Many sound waves emitted by bats are at frequencies too high for us to hear
*Example: 12,000 to 200,000 Hz
~Different cortical areas process different aspects of echo-related information.
*Distance of targets
*Velocity of moving targets
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Rarefication
-Waves of pressure changes in air molecules are sound waves
