c. elberling oticon eriksholm denmark efficient stimuli for frequency specific assr e. stürzebecher...
TRANSCRIPT
C. ElberlingOticon ’Eriksholm’
Denmark
Efficient stimuli forfrequency specific ASSR
E. Stürzebecher & M. CebullaJohann Wolfgang Goethe-Univ. Frankfurt
Germany
T. BergerPhilips-Univ. Marburg
Germany
EHDI Conference, Atlanta, USA – March 2005
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The problem
• Auditory Steady State Response – ASSR• Diagnostic evaluation of sensitivity => threshold• Frequency specific information• Amplitude problem => longer test time
Broad band clicks Frequency specific stimuli
• How can we reduce test time? More efficient detection methods (statistics) More efficient stimuli
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0 10 20 30 40 50 ms
Click - ASSR
Freq-spec ASSR
lower amplitude
Response amplitude - 90 stimuli/second
=> longer test time
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Am
plitu
de
Time
Frequency
Am
plitu
de
FC
FMFM
Amplitude Modulation - AMFR
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90 Hz
180 Hz
270 Hz
360 Hz
450 Hz
540 Hz630 Hz
720 Hz
Frequency [Hz]0 100 200 300 400 500 600 700 800
Am
plit
ude
[dB
]Amplitude spectrum of the ASSR
Response components+ Noise
Noise
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Brainstem
The Auditory Pathway
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Am
plitu
de [
dB a
rb]
0
10
20
30
40
Frequency [Hz]
0 500 1000 1500
1000 Hz
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0 5 1 0 1 5 2 0 2 5 3 0T i m e [ m s ]
1000 Hz
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0 5 1 0 1 5 2 0 2 5 3 0T i m e [ m s ]
0 5 1 0 1 5 2 0 2 5 3 0T i m e [ m s ]
1000 Hz
10
Frequency [Hz]
0 500 1000
Am
plitu
de [
dB a
rb]
0
10
20
30
40
500 Hz
500 7cos
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0 2 4 6 8 10 12D e la y [m s]
100
1000
10000
Fre
qu
en
cy [H
z]
Cochlea delaybased on de Boer (1980) & Greenwood (1990)
Cochlea travel time
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Frequency [Hz]
0 500 1000
Am
plitu
de [
dB a
rb]
0
10
20
30
40
500 Hz
500 7cos PCPC
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Frequency [Hz]
0 500 1000
Am
plitu
de [
dB a
rb]
0
10
20
30
40
Stimulus500 7cos PC
Response
500 Hz
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Frequency [Hz]
0 500 1000
Am
plitu
de [
dB a
rb]
0
10
20
30
40
500 Hz
Response
Stimulus500 7cos PC FO
FO
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Experimental design
• 60 normally hearing young adults (age: 17 – 34 y)• Stimuli delivered at 30 dBnHL at a rate of 90/s• Each ASSR recorded for 300 s• Detection made by statistical methods:
Modified Raleigh one-sample test (first harmonic) Modified Mardia’s q-sample test (six harmonics) Error probability α = 1%
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Definition of terms
• Detection Rate [%]: % of responses detected < 300 s• Detection Time [s]: time to detect a response (< 300 s)• Performance Index, PI: Detection Rate/Detection Time
0
0.1
0.2
0 50 100 150 200 250 300
Detection time (s)
Re
lativ
e f
req
ue
ncy median
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500 7c PC One-sample 85.5 61 1.40
500 7c One-sample 77.4 76 1.02
500 7c PC FO q-sample 91.1 59 1.54
Stimulus Statistics Detection Rate [%]
Detection Time [s]
Performance Index, PI
500 AM One-sample 74.2 109 0.68
RESULTS: 500 Hz
ns ns
p < 0.05 p < 0.02
p < 0.02 p < 0.01
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Stimulus Statistics Detection Rate [%]
Detection Time [s]
Performance Index, PI
2000 AM q-sample 82.0 103 0.80
2000 7c q-sample 91.8 51 1.80
2000 7c PC One-sample 90.2 51 1.77
2000 7c PC q-sample 95.1 49 1.94
RESULTS: 2000 Hz
ns p < 0.01
p < 0.02 p < 0.01
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Stimulus Statistics Detection Rate [%]
Detection Time [s]
Performance Index, PI
1000 7c q-sample 95.2 30 3.17
1000 7c PC One-sample 88.9 37 2.40
1000 7c PC q-sample 96.8 29 3.34
4000 7c q-sample 93.4 79 1.18
4000 7c PC q-sample 95.1 67 1.42
4000 11c PC q-sample 96.7 46 2.10
BW ~ 540 Hz
BW ~ 900 Hzapp.. 1/3-oct.
RESULTS: 1000 & 4000 Hz
ns p < 0.02
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Summary & Conclusion
• ASSR stimuli designed in the frequency domain Cochlea excitation area well defined
• Correction for Cochlea traveling time, PC Same philosophy as behind the Chirp stimulus and the Stacked ABR
• Frequency off-set, FO Provide possibility to use response information at higher harmonics
• For all Stimuli: The new stimuli are significantly more efficient than traditional AM stimuli
• For low frequency stimuli (500 Hz): Phase-Correction increases efficiency significantly Frequency Off-set increases efficiency significantly by recruiting more information
• For high frequency stimuli Phase-Correction increases efficiency only marginally
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