Rob van der Willigen Rob van der Willigen http://~robvdw/cnpa04/coll4/AudPerc_2008_P4.ppt http://~robvdw/cnpa04/coll4/AudPerc_2008_P4.ppt Auditory Perception Auditory Perception
Mar 15, 2016
Rob van der WilligenRob van der Willigenhttp://~robvdw/cnpa04/coll4/AudPerc_2008_P4.ppthttp://~robvdw/cnpa04/coll4/AudPerc_2008_P4.ppt
Auditory PerceptionAuditory Perception
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- Cochlear Mechanotransduction - Neuroanatomical Organization
P4: Auditory Perception
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Sensory Coding and Transduction
Cochlear Mechanotransduction
Mammalian Auditory Pathway
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6 critical stepsSensory Coding and
Transduction
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Physical Dimensions of Sound
Amplitude- height of a cycle- relates to loudness
Wavelength (λ)- distance between peaks
Phase ( )- relative position of the peaks
Frequency (f )- cycles per second- relates to pitch
Summary
Recapitulation previous lectures
Sound is a longitudinal pressure wave: a disturbance travelling through a medium (air/water)
The Adequate Stimulus to Hearing
http://www.kettering.edu/~drussell/demos.html
Recapitulation previous lectures
Summary
The Adequate Stimulus to Hearing
http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/sound/u11l2a.html
Particles do NOT travel, only the disturbance
Particles oscillate back and forth about their equilibrium positions
Distance from source
Dura
tion
Recapitulation previous lectures
Summary
Compression
Decompression
Compression
Sensory Coding and Transduction
A Sensor Called Ear
Sensory Coding and Transduction
Peripheral Auditory Peripheral Auditory SystemSystem
Outer Ear: - Extents up to Eardrum - Visible part is called Pinna
or Auricle - Movable in non-human
primates- Sound Collection- Sound Transformation Gives clues for sound
localization
Sensory Coding and Transduction
Peripheral Auditory Peripheral Auditory SystemSystem
Sensory Coding and Transduction
Elev
atio
n (d
eg)
-40-20
0+20+40+60
The Pinna creates Sound source position dependent spectral clues.
Frequency
“EAR PRINT”
Elev
atio
n (d
eg)
-40
-20
0
+20
+40
+60
Frequency kHz
Am
plitu
de (d
B)In humans mid-
frequencies also exhibit a prominent notch that varies in frequency with changes in sound source elevation (6 – 11 kHz)
Elevation
Peripheral Auditory Peripheral Auditory SystemSystem
Sensory Coding and Transduction
Barn Owls have Asymmetric Ears and Silent Flight.
One ear points upwards, the other downwards.
Peripheral Auditory Peripheral Auditory SystemSystem
Sensory Coding and Transduction
Middle Ear: (Conductive hearing loss)- Mechanical transduction (Acoustic Coupling)- Perfect design for impedance matching Fluid in inner ear is much harder to vibrate than air- Stapedius muscle: damps loud sounds
Three bones (Ossicles) A small pressure on a large area (ear drum) produces a large pressure on a small area (oval window)
Peripheral Auditory Peripheral Auditory SystemSystem
Sensory Coding and Transduction
Inner Ear:The Cochlea is the auditory portion of the ear
Cochlea is derived from the Greek word kokhlias "snail or screw" in reference to its spiraled shape, 2 ¾ turns, ~ 3.2 cm length (Humans)
Peripheral Auditory Peripheral Auditory SystemSystem
Sensory Coding and Transduction
The cochlea’s core component is the Organ of Corti, the sensory organ of hearing
Peripheral Auditory Peripheral Auditory SystemSystem
Sensory Coding and Transduction
Cochleardeficits cause Sensorineural hearing loss
Its receptors (the hair cells) provide the sense of
hearing
The Organ of Corti mediates mechanotransduction:
Peripheral Auditory Peripheral Auditory SystemSystem
Sensory Coding and Transduction
The cochlea is filled with a watery liquid, which moves in response to the vibrations coming from the middle ear via the oval window. As the fluid moves, thousands of hair cells are set in motion, and convert that motion to electrical signals that are communicated via neurotransmitters to many thousands of nerve cells.
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Cochlear anatomy
Sensory Coding of Sound
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Cochlear anatomy (straightened)
Sensory Coding of Sound
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Pressure waves distort basilar membrane on the way to the round window of tympanic duct:
- Location of maximum distortion varies with frequency of sound
- Frequency information translates into information about position along basilar membrane
Tonotopic codingSensory Coding of Sound
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Travelling wave theory von Bekesy: Waves move down basilar membrane stimulation increases, peaks, and quickly tapers
Periodic stimulation of the Basilar membrane matches frequency of sound
Location of peak depends on frequency of the sound, lower frequencies being further away
Sensory Coding of SoundTravelling Wave TheoryTravelling Wave Theory
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Cochlear Fourier AnalysisCochlear Fourier AnalysisHigh f
Med f
Low f
Periodic stimulation of the Basilar membrane matches frequency of sound
BASE APEX
Location of the peak depends on frequency of the sound, lower frequencies being further away
Position along the basilar membrane
Sensory Coding of Sound
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Location of the peak depends on frequency of the sound, lower frequencies being further awayLocation of the peak is determined by the stiffness of the membrane
Travelling wave theory von Bekesy: Waves move down basilar membrane
Sensory Coding of Sound Place TheoryPlace Theory
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Thick & taut near baseThin & floppy at apex
TONOTOPIC PLACE MAP
Sensory Coding of SoundSensory Input is TonotopicSensory Input is Tonotopic
LOGARITHMIC: 20 Hz -> 200 Hz
2kH -> 20 kHz each occupies 1/3 of the basilar membrane
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Sensory Coding of SoundSensory input is tonotopic
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The COCHLEA: Decomposes sounds
into its frequency components
Sensory Coding of SoundSensory Input is Non-linearSensory Input is Non-linear
Has direct relation to the sounds spectral content
Represents sound TONOTOPICALLY
Has NO linear relationship to sound pressureHas NO direct relationship to the sound’s location in the outside world
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Cochlear nonlinearityCochlear nonlinearityActive processing of
sound
BM input-output function for a tone at CF (~9 kHz, solid line) and a tone one octave below (~4.5 kHz) taken from the iso-intensity contour plot.
INPUT level (dB SPL)OU
TPU
T Re
spon
se in
dB
CF= 9 kHz
~4.5kHz
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Effects of an “active”cochlea
20
80
70
60
50
40
30
20
10
3
0 2 3 4 5 6 7 8 9
Frequency (kHz)
10 11 121
40
BM
Velo
city
(dB
re.
1µ/s
)
60
Iso-level curves show sharp tuning at low sound levels, broader tuning at high levels.
Response is strongly compressive around the so-called characteristic frequency (CF).
Requires functioning outer hair cells.
Cochlear nonlinearityCochlear nonlinearityActive processing of
sound
The response of the BM at location most sensitive for ~ 9 KHz tone (CF).The level of the tone varied from 3 to 80 dB SPL (iso-intensity contours).
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20
80
70
60
50
40
30
20
10
3
0 2 3 4 5 6 7 8 9
Frequency (kHz)
10 11 121
40
BM
Velo
city
(dB
re.
1µ/s
)
60
Cochlear nonlinearityCochlear nonlinearityActive processing of
sound
The response of the BM at location most sensitive for ~ 9 KHz tone (CF).The level of the tone varied from 3 to 80 dB SPL (iso-intensity contours).
BM input-output function for a tone at CF (~9 kHz, solid line) and a tone one octave below (~4.5 kHz) taken from the iso-intensity contour plot.
INPUT level (dB SPL)O
UTP
UT
Resp
onse
in d
B
CF= 9 kHz
~4.5kHz
Frequency [kHz]
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Cochlear nonlinearityCochlear nonlinearity
1) Reduced gain: Higher thresholds in quiet; loss of audibility as measured with pure-tone audiogram2) Loss of nonlinearity: Reduced dynamic range; quiet sounds lost but loud sounds just as loud: Loudness Recruitment
GAIN equals Amplitude of motion divided by
Amplitude of stimulus pressure
No nonlinearity post mortem
Basilar-membrane intensity-velocity coding functions for a chinchilla using a tone at the 10 kHz
Rugero et al. (1997)Rugero et al. (1997)
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The Auditory NerveThe Auditory NerveFTC versus
FRCFTC data indicate the characteristics of the cochlea from which has been eliminated the non-linear response characteristics of the cochlear nerve excitation process. Response Rate versus Frequency
Curve (FRC)
FRC data indicate the limits which may be set upon the central representation of the cochlear filtering by the non-linear rate behavior of the cochlear fibers.
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Place Theory:
Place of maximum vibration along basilar membrane correlates with the place of the Tuning curve (or FTC=Frequency Threshold Curve) along the frequency axis.
Shown are tuning curves measured by finding the pure tone amplitude that produces a criterion response in an 8th nerve fiber (cat).
Tuning curves for four different fibers (A-D) are shown.
The Auditory NerveThe Auditory NerveFrequency Selectivity: CF & place
theory
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Cochlear nonlinearityCochlear nonlinearityOHC motor driven by the Tectorial
membrane
A virtuous loop. Sound evoked perturbation of the organ of Corti elicits a motile response from outer hair cells, which feeds back onto the organ of Corti amplifying the basilar membrane motion.
Q ui ckTi me™ and a TI FF (LZW) decompressor are needed to see thi s pi cture. The Problem of HearingThe Problem of Hearing
“Sound has no dimensions of space, distance, shape, or size; and the auditory periphery of all known vertebrates contains peripheral receptors that code for the parameters of the sound pressure wave rather than information about sound sources per se.”
William A. Yost (Perceiving sounds in the real world, 2007; William A. Yost (Perceiving sounds in the real world, 2007; p. p. 3461)3461)
Q ui ckTi me™ and a TI FF (LZW) decompressor are needed to see thi s pi cture. The Problem of HearingThe Problem of HearingTonotopie blijft in het auditief systeem tot en met de auditieve hersenschorsbehouden.
“De samenstelling van een geluid uit afzonderlijke tonen is te vergelijken met de manier waaropwit licht in afzonderlijke kleuren uiteenvalt wanneer het door een prisma gaat .”John A.J. van Opstal (Al kijkend hoort men, 2006; John A.J. van Opstal (Al kijkend hoort men, 2006;
p. 8)p. 8)
Q ui ckTi me™ and a TI FF (LZW) decompressor are needed to see thi s pi cture. The Problem of HearingThe Problem of Hearing
Neurons within a brain area may be organized topographically (or in a map), meaning that neurons that are next to each other represent stimuli with similar properties.
Mapping can be an important clue to the function of an area. If neurons are arrayed according to the value of a particular parameter, then that property might be critical in the processing performed by that area.
Neurons do not need to be arranged topographically along the dimensions of the reference frame that they map, even if its neurons do not form a map of that space.
Q ui ckTi me™ and a TI FF (LZW) decompressor are needed to see thi s pi cture. The Problem of HearingThe Problem of Hearing
Problem I: Sound localization can only result from the neural processing of acoustic cues in the tonotopic input!
Problem II: How does the auditory system parse the superposition of distinct sounds into the original acoustic input?
24/04/23 Joseph Dodds 2006 41
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Organ of Corti
Basilar Membrane
Auditory nerve
Inner Hair cell
OuterHair cells
Sensory Coding of SoundSummarySummary
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Mechanotransduction: Step 5:
Vibration of basilar membrane causes vibration of hair cells against Tectorial membrane (TM):
Movement displaces stereocilia/kinocilia, opens ion channels in hair cell membranesRush of ions depolarizes hair cells,which initiates the release of neurotransmitters
NEXT WEEKNEXT WEEKCochlear Innervation & Auditory
Nerve
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Neural responses in the AN: Step 6Information about region and intensity of cochlear stimulation is relayed to CNS over cochlear branch of vestibulocochlear nerve (VIII):
Called the auditory nerve (AN):
Has sensory neurons in spiral ganglion of cochlea
Carries neural information to cochlear nuclei (CN) of midbrain for distribution to other (more higher) brain centers.
NEXT WEEKNEXT WEEKCochlear Innervation & Auditory
Nerve
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NEXT WEEKNEXT WEEKCochlear Innervation & Auditory
Nerve
type 1type 2
Inner hair cells: Main source of afferent signal in auditory nerve. (~ 10 afferents per hair cell)
Outer hair cells: Primarily receiving efferent inputs.
Type I neurons (95% of all ganglion cells) have a single ending radially connected to IHCs.Type II small,
unmyelinated neurons spiral basally after entering the organ of Corti and branch to connect about ten OHCs, in the same row.
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