Neural coding of interaural timing differences in the mammalian midbrain: Time and phase contributions to the internal delay.

1. Neural coding of interaural timing
differences in the mammalian midbrain:
Time and phase contributions to the
internal delay.
Torsten Marquardt
UCL EAR Institute,

2. (Clip from Brugge, http://www.neurophys.wisc.edu/ftp/pub/aud-tour)
Jeffress (1948): A place theory of sound localization.

3. Tone delay function
MSO
Time
rightleft
∫
∞
∞−
−⋅= dtITDtrighttleftITDcorrfcn )()()(

4. ∫
∞
∞−
−⋅= dtITDtrighttleftITDcorrfcn )()()(
MSO
Noise delay function
Time
rightleft

5. (MSO data from Yin & Chan, 1990).
Neural tuning to interaural time difference
Tone Noise

6. cat, IC
Hancock & Delgutte, J. Neurosci. (2004)
+π
Best frequency [kHz]
The π-limit of coded ITDspikerate
-2 -1 0 1 2
ITD [ms]
-2 -1 0 1 2
ITD [ms]
-2 -1 0 1 2
ITD [ms] ITD [ms]
-1 0 1 2 3 -1 0 1 2 3
…
ITD [ms]
Outside
π -limit!
McAlpine et al, Nat. Neurosci.(2001)
guinea pig, IC
+π

7. The π-limit of coded ITDspikerate
-2 -1 0 1 2
ITD [ms]
-2 -1 0 1 2
ITD [ms]
-2 -1 0 1 2
ITD [ms] ITD [ms]
-1 0 1 2 3 -1 0 1 2 3
…
ITD [ms]
Outside
π -limit!
McAlpine et al, Nat. Neurosci.(2001)
guinea pig, IC
+π
(McAlpine et al., 2001)

8. n = 234
best ITD × BF [cycles]
dominantfrequency,DF[Hz]
-0.75 -0.5 -0.25 0 0.25 0.5 0.75
125
250
500
1000
Best ITDs of guinea pig IC neurones
Marquardt T & McAlpine D (2007): “A pi-limit for coding ITDs: implications for binaural models”.
In Hearing - From Sensory Processing to Perception, ed. Kollmeier et al., Springer Verlag.
(McAlpine et al., 2001)

9. -1 -0.5 0 0.5 1
0
0.5
1
1.5
2
2.5
n = 49
ITD × BF [cycles]
1/6 < best ITD < 1/3
spikerate,normalized
0
0.5
1
1.5
2
2.5
-1 -0.5 0 0.5 1
n = 77
ITD × BF [cycles]
0 < best ITD < 1/6
Physiological evidence for internal phase delays
n = 234
best ITD × BF [cycles]
dominantfrequency,DF[Hz]
-0.75 -0.5 -0.25 0 0.25 0.5 0.75
125
250
500
1000
Best ITD distribution (IC, guinea pig)
Marquardt T & McAlpine D (2007): “A pi-limit for coding ITDs: implications for binaural models”.
In Hearing - From Sensory Processing to Perception, ed. Kollmeier et al., Springer Verlag.

10. Physiological evidence for internal phase delays
spikerate,normalized
0
0.5
1
1.5
2
2.5
-1 -0.5 0 0.5 1 -1 -0.5 0 0.5 1
0
0.5
1
1.5
2
2.5
n = 21n = 49n = 77
-1 -0.5 0 0.5 1
0
0.5
1
1.5
2
2.5
ITD × BF [cycles] ITD × BF [cycles] ITD × BF [cycles]
0 < best ITD < 1/6 1/6 < best ITD < 1/3 1/3 < best ITD < 1/2
-1 -0.5 0 0.5
0
0.5
1
1.5
2
1
n = 234
best ITD × BF [cycles]
dominantfrequency,DF[Hz]
-0.75 -0.5 -0.25 0 0.25 0.5 0.75
125
250
500
1000
Best ITD distribution (IC, guinea pig)
Marquardt T & McAlpine D (2007): “A pi-limit for coding ITDs: implications for binaural models”.
In Hearing - From Sensory Processing to Perception, ed. Kollmeier et al., Springer Verlag.

11. Physiological evidence for internal phase delays
spikerate,normalized
0
0.5
1
1.5
2
2.5
-1 -0.5 0 0.5 1 -1 -0.5 0 0.5 1
0
0.5
1
1.5
2
2.5
n = 21n = 49n = 77
-1 -0.5 0 0.5 1
0
0.5
1
1.5
2
2.5
ITD [cycles re. DF] ITD [cycles re. DF] ITD [cycles re. DF]
0 < best ITD < 1/6 1/6 < best ITD < 1/3 1/3 < best ITD < 1/2
n = 234
best ITD × BF [cycles]
dominantfrequency,DF[Hz]
-0.75 -0.5 -0.25 0 0.25 0.5 0.75
125
250
500
1000
Best ITD distribution (IC, guinea pig)
Marquardt T & McAlpine D (2007): “A pi-limit for coding ITDs: implications for binaural models”.
In Hearing - From Sensory Processing to Perception, ed. Kollmeier et al., Springer Verlag.
peaker trougherintermediateBestPhase[cycles]
0 0.5 1 1.5 freq
1.0
0.8
0.6
0.4
0.2
0.5 1 1.5 freq 0.5 1 1.5 f req
CD = 0
CP = 0
CD = 0
CP = 0.25 cycl
CD = 0
CP = 0.5 cycl

12. McAlpine D, Jiang D, & Palmer AR (1996):
“Interaural delay sensitivity and the classification
of low best-frequency binaural responses in the
inferior colliculus of the guinea pig.”
Hearing Research 97, 136-152.
Neural best-IPD vs. frequency plots (“phase plots”)

13. Σ
CD = 0.25 ms
CP = 0 º
CD = 0 ms
CP = 45 º
Bestphase
(degrees)
Bestphase
(degrees)
Neural best-IPD vs. frequency plots (“phase plots”)

14. Time delay (Jeffress Model)BestPhase[cycles]
…
-1 -0.5 0 0.5 1 -1 -0.5 0 0.5 1 -1 -0.5 0 0.5 1 -0.5 0 0.5 1 1.5-0.5 0 0.5 1 1.5
0.5 1 1.5 f[kHz]
1.0
0.8
0.6
0.4
0.2
CD = 0 ms
CP = 0
CD = 0.25 ms
CP = 0
CD = 0.5 ms
CP = 0
CD = 0.75 ms
CP = 0
CD = 1 ms
CP = 0
0.5 1 1.5 f[kHz] 0.5 1 1.5 f[kHz] 0.5 1 1.5 f[kHz] 0.5 1 1.5 f[kHz]

15. Physiological evidence for internal phase delays
spikerate,normalized
0
0.5
1
1.5
2
2.5
-1 -0.5 0 0.5 1 -1 -0.5 0 0.5 1
0
0.5
1
1.5
2
2.5
n = 21n = 49n = 77
-1 -0.5 0 0.5 1
0
0.5
1
1.5
2
2.5
ITD [cycles re. DF] ITD [cycles re. DF] ITD [cycles re. DF]
0 < best ITD < 1/6 1/6 < best ITD < 1/3 1/3 < best ITD < 1/2
peaker trougherintermediate
BestPhase[cycles]
1.0
0.8
0.6
0.4
0.2
CD = 0
CP = 0
CD = 0
CP = 0.25 cycl
CD = 0
CP = 0.5 cycl
Outside
π -limit!
n = 234
best ITD [cycles re. DF]
dominantfrequency,DF[Hz]
-0.75 -0.5 -0.25 0 0.25 0.5 0.75
125
250
500
1000
Best ITD distribution (IC, guinea pig)
BestPhase[cycles]
…
-1 -0.5 0 0.5 1 -1 -0.5 0 0.5 1 -1 -0.5 0 0.5 1 -0.5 0 0.5 1 1.5-0.5 0 0.5 1 1.5
0.5 1 1.5 f[kHz]
1.0
0.8
0.6
0.4
0.2
CD = 0 ms
CP = 0
CD = 0.25 ms
CP = 0
CD = 0.5 ms
CP = 0
CD = 0.75 ms
CP = 0
CD = 1 ms
CP = 0
0.5 1 1.5 f[kHz] 0.5 1 1.5 f[kHz] 0.5 1 1.5 f[kHz] 0.5 1 1.5 f[kHz]
0.5 1 1.5 f[kHz] 0.5 1 1.5 f[kHz] 0.5 1 1.5 f[kHz]

16. 1 -0.5 0 0.5 1
Interaural Time Difference [cycles re. BF]
Inherent π-Limit !
Phase delay (constant envelope) explains π-Limit

17. John Agapiou, PhD thesis 2006

18. John Agapiou, PhD thesis 2006, guinea pig
CD×BF(cycles)
CP (cycles)
-0.2 0 0.2
0
0.1
0.2
0.3
0.4
CD×BF(cycles)
CP (cycles)
-0.2 0 0.2 0.4
-0.5
0
0.5DNLL: IC:
CD × BF = 0.5 CP + 0.125

19. Guinea pig (McAlpine et al. 1996) Cat (Karino & Joris, ARO 2012)
CD vs. CP from tone ITD functions (“phase plot fits”)
N = 228
Color code indicates best ITD

20. 0.75-0.25 0.25
Gerbil DNLL (Lueling,Siveke,Grothe & Leibold, 2011)
1
CD vs. CP from tone ITD functions (“phase plot fits”)

21. Time and phase contributions to the internal delay
0.25 0.5
0
0.125
0.25
-0.25
-0.125
-0.25 0 0.750.6250.3750.125-0.125
CD×BF(cycles)
CP (cycles)
0.25
0.5
0
0.375
0.125
Best ITD
×
BF
(cycles)
CD = ⅛ − ½CP
DNLL and IC data (Agapiou, 2006)
1
2
3
4
5
Best ITD × BF = (CD × BF) + CP
DNLL
IC
BestPhase[cycles]
CD = –0.25
CP = 0.75
0 0.5 1 1.5 20 0.5 1 1.5 2
CD = –0.125
CP = 0.5
CD = 0
CP = 0.25
0 0.5 1 1.5 2
CD = 0.125
CP = 0
0 0.5 1 1.5 2
CD = 0.25
CP = –0.25
0 0.5 1 1.5 2
0.75
-0.25
0
0.25
0.5
1 Best ITD = 0 cyc 5 Best ITD = 0.5 cyc
3 Best ITD = 0.25 cyc 4 Best ITD = 0.375 cyc
2 Best ITD = 0.125 cyc
norm. frequency

22. ICdata
CD = –0.25
CP = 0.75
0 0.5 1 1.5 20 0.5 1 1.5 2
CD = –0.125
CP = 0.5
CD = 0
CP = 0.25
0 0.5 1 1.5 2
CD = 0.125
CP = 0
0 0.5 1 1.5 2
CD = 0.25
CP = –0.25
0 0.5 1 1.5 2
0.75
-0.25
0
0.25
0.5
Purephasedelay
CD = 0
CP = 0.5
CD = 0
CP = 0.375
CD = 0
CP = 0.25
CD = 0
CP = 0.125
CD = 0
CP = 0
0.75
-0.25
0
0.25
0.5
Jeffress’timedelay
CD = 0.5
CP = 0
CD = 0.375
CP = 0
CD = 0.25
CP = 0
CD = 0.125
CP = 0
CD = 0
CP = 0
0.75
-0.25
0
0.25
0.5
Time and phase contributions to the internal delay

23. Time and phase contributions to the internal delay
0.25
0.5
0
0.375
0.125
0.25 0.5
0
0.125
0.25
-0.25
-0.125
-0.25 0 0.750.6250.3750.125-0.125
CD×BF(cycles)
CP (cycles)
Best ITD
×
BF
(cycles)
CD = ⅛ − ½CP
DNLL and IC data (Agapiou, 2006)
1
2
3
4
5
DNLL
IC
norm.spikerate
noise ITD × BF (cycl)
1 Best ITD = 0 cyc 5 Best ITD = 0.5 cyc
3 Best ITD = 0.25 cyc 4 Best ITD = 0.375 cyc
2 Best ITD = 0.125 cyc
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0.25, CP = –0.25 CD = 0.125, CP = 0 CD = –0.125, CP = 0.5 CD = –0.25, CP = 0.75CD = 0, CP = 0.25
Best ITD × BF = (CD × BF) + CP
BestPhase[cycles]
CD = –0.25
CP = 0.75
0 0.5 1 1.5 20 0.5 1 1.5 2
CD = –0.125
CP = 0.5
CD = 0
CP = 0.25
0 0.5 1 1.5 2
CD = 0.125
CP = 0
0 0.5 1 1.5 2
CD = 0.25
CP = –0.25
0 0.5 1 1.5 2
0.75
-0.25
0
0.25
0.5
1 Best ITD = 0 cyc 5 Best ITD = 0.5 cyc
3 Best ITD = 0.25 cyc 4 Best ITD = 0.375 cyc
2 Best ITD = 0.125 cyc
norm. frequency

24. Cochlear disparity
Modelling cochlear disparity
(Day & Semple, 2011)
1 Best ITD = 0 cyc 5 Best ITD = 0.5 cyc
3 Best ITD = 0.25 cyc 4 Best ITD = 0.375 cyc
2 Best ITD = 0.125 cyc
CD = 1
CP = –0.5
CD = 0.75
CP = –0.375
CD = 0.5
CP = –0.25
CD = 0.25
CP = –0.125
CD = 0
CP = 0
0.75
-0.25
0
0.25
0.5
BestPhase[cycles]
0 0.5 1 1.5 20 0.5 1 1.5 20 0.5 1 1.5 20 0.5 1 1.5 20 0.5 1 1.5 2
norm. frequency
Accumulatedphase[cycles]
f [kHz]
800 1200400 1600 2000
CP
2
0
1
-1
-2
4
3
best ITD

25. Cochlear disparity
Modelling cochlear disparity
(Day & Semple, 2011)
1 Best ITD = 0 cyc 5 Best ITD = 0.5 cyc
3 Best ITD = 0.25 cyc 4 Best ITD = 0.375 cyc
2 Best ITD = 0.125 cyc
CD = 1
CP = –0.5
CD = 0.75
CP = –0.375
CD = 0.5
CP = –0.25
CD = 0.25
CP = –0.125
CD = 0
CP = 0
0.75
-0.25
0
0.25
0.5
BestPhase[cycles]
0 0.5 1 1.5 20 0.5 1 1.5 20 0.5 1 1.5 20 0.5 1 1.5 20 0.5 1 1.5 2
norm. frequency
Accumulatedphase[cycles]
f [kHz]
800 1200400 1600 2000
CP
2
0
1
-1
-2
4
3
best ITD
norm.spikerate
noise ITD × BF (cycl)
1 Best ITD = 0 cyc 5 Best ITD = 0.5 cyc
3 Best ITD = 0.25 cyc 4 Best ITD = 0.375 cyc
2 Best ITD = 0.125 cyc
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0, CP = 0 CD = 0.25, CP = 0.125 CD = 0.75, CP = –0.375 CD = 1.0, CP = –0.5CD = 0.5, CP = –0.25

26. Cochlear disparityAccumulatedphase[cycles]
f [kHz]
800 1200400 1600 2000
CP
2
0
1
-1
-2
4
3
best ITD
norm.spikerate
noise ITD × BF (cycl)
1 Best ITD = 0 cyc 5 Best ITD = 0.5 cyc
3 Best ITD = 0.25 cyc 4 Best ITD = 0.375 cyc
2 Best ITD = 0.125 cyc
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0, CP = 0 CD = 0.25, CP = -0.125 CD = 0.75, CP = –0.375 CD = 1.0, CP = –0.5CD = 0.5, CP = –0.25
Shuffled cross-correlation of AN data (Joris et al., 2006)

27. ICdata
CD = –0.25
CP = 0.75
0 0.5 1 1.5 20 0.5 1 1.5 2
CD = –0.125
CP = 0.5
CD = 0
CP = 0.25
0 0.5 1 1.5 2
CD = 0.125
CP = 0
0 0.5 1 1.5 2
CD = 0.25
CP = –0.25
0 0.5 1 1.5 2
0.75
-0.25
0
0.25
0.5
Purephasedelay
CD = 0
CP = 0.5
CD = 0
CP = 0.375
CD = 0
CP = 0.25
CD = 0
CP = 0.125
CD = 0
CP = 0
0.75
-0.25
0
0.25
0.5
Jeffress’timedelay
CD = 0.5
CP = 0
CD = 0.375
CP = 0
CD = 0.25
CP = 0
CD = 0.125
CP = 0
CD = 0
CP = 0
0.75
-0.25
0
0.25
0.5
Time and phase contributions to the internal delay

28. ICdata
CD = –0.25
CP = 0.75
0 0.5 1 1.5 20 0.5 1 1.5 2
CD = –0.125
CP = 0.5
CD = 0
CP = 0.25
0 0.5 1 1.5 2
CD = 0.125
CP = 0
0 0.5 1 1.5 2
CD = 0.25
CP = –0.25
0 0.5 1 1.5 2
0.75
-0.25
0
0.25
0.5
Purephasedelay
CD = 0
CP = 0.5
CD = 0
CP = 0.375
CD = 0
CP = 0.25
CD = 0
CP = 0.125
CD = 0
CP = 0
0.75
-0.25
0
0.25
0.5
Jeffress’timedelay
CD = 0.5
CP = 0
CD = 0.375
CP = 0
CD = 0.25
CP = 0
CD = 0.125
CP = 0
CD = 0
CP = 0
0.75
-0.25
0
0.25
0.5
Cochleardisparity CD = 1
CP = –0.5
CD = 0.75
CP = –0.375
CD = 0.5
CP = –0.25
CD = 0.25
CP = –0.125
CD = 0
CP = 0
0.75
-0.25
0
0.25
0.5

29. -3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0.25, CP = –0.25 CD = 0.125, CP = 0 CD = –0.125, CP = 0.5 CD = –0.25, CP = 0.75CD = 0, CP = 0.25
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0, CP = 0 CD = 0.25, CP = –0.125 CD = 0.75, CP = –0.375 CD = 1.0, CP = –0.5CD = 0.5, CP = –0.25
ICdataPurephasedelayJeffress’timedelayCochleardisparity
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0, CP = 0 CD = 0.125, CP = 0 CD = 0.375, CP = 0 CD = 0.5, CP = 0CD = 0.25, CP = 0
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0, CP = 0 CD = 0.125, CP = 0 CD = 0, CP = 0 CD = 0, CP = 0CD = 0, CP = 0

30. -3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0.25, CP = –0.25 CD = 0.125, CP = 0 CD = –0.125, CP = 0.5 CD = –0.25, CP = 0.75CD = 0, CP = 0.25
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0, CP = 0 CD = 0.25, CP = –0.125 CD = 0.75, CP = –0.375 CD = 1.0, CP = –0.5CD = 0.5, CP = –0.25
ICdataPurephasedelayJeffress’timedelayCochleardisparity
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0, CP = 0 CD = 0.125, CP = 0 CD = 0.375, CP = 0 CD = 0.5, CP = 0CD = 0.25, CP = 0
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0, CP = 0 CD = 0.125, CP = 0 CD = 0, CP = 0 CD = 0, CP = 0CD = 0, CP = 0
spikerate,normalized
0
0.5
1
1.5
2
2.5
-1 -0.5 0 0.5 1 -1 -0.5 0 0.5 1
0
0.5
1
1.5
2
2.5
n = 21n = 49n = 77
-1 -0.5 0 0.5 1
0
0.5
1
1.5
2
2.5
ITD [cycles re. DF] ITD [cycles re. DF] ITD [cycles re. DF]
0 < best ITD < 1/6 1/6 < best ITD <
1/3
1/3 < best ITD <
1/2

31. -3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0.25, CP = –0.25 CD = 0.125, CP = 0 CD = –0.125, CP = 0.5 CD = –0.25, CP = 0.75CD = 0, CP = 0.25
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0, CP = 0 CD = 0.25, CP = –0.125 CD = 0.75, CP = –0.375 CD = 1.0, CP = –0.5CD = 0.5, CP = –0.25
ICdataPurephasedelayJeffress’timedelayCochleardisparity
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0, CP = 0 CD = 0.125, CP = 0 CD = 0.375, CP = 0 CD = 0.5, CP = 0CD = 0.25, CP = 0
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0, CP = 0 CD = 0.125, CP = 0 CD = 0, CP = 0 CD = 0, CP = 0CD = 0, CP = 0
n = 234
best ITD × BF [cycles]
dominantfrequency,DF[Hz]
-0.75 -0.5 -0.25 0 0.25 0.5 0.75
125
250
500
1000
Best ITD distribution (IC, guinea pig)

32. Summary
 Data disagree with Jeffress’ axonal time delay
 Time delay appears even negatively correlated with best ITD
 Neither do data support a pure phase delay
 But, at least phase delay correlates positively with best ITD
 Time and phase delay are in opposition, with phase having
twice the impact on best ITD
 This all very peculiar!
norm.spikerate
1 Best ITD = 0 cyc 5 Best ITD = 0.5 cyc
3 Best ITD = 0.25 cyc 4 Best ITD = 0.375 cyc
2 Best ITD = 0.125 cyc
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0.25, CP = –0.25 CD = 0.125, CP = 0 CD = –0.125, CP = 0.5 CD = –0.25, CP = 0.75CD = 0, CP = 0.25

33. Time and phase contributions to the internal delay
0.25
0.5
0
0.375
0.125
0.25 0.5
0
0.125
0.25
-0.25
-0.125
-0.25 0 0.750.6250.3750.125-0.125
CD×BF(cycles)
CP (cycles)
Best ITD
×
BF
(cycles)
CD = ⅛ − ½CP
DNLL and IC data (Agapiou, 2006)
1
2
3
4
5
B
estITD
=
C
D
×
B
F
+
C
P
DNLL
IC
norm.spikerate
1 Best ITD = 0 cyc 5 Best ITD = 0.5 cyc
3 Best ITD = 0.25 cyc 4 Best ITD = 0.375 cyc
2 Best ITD = 0.125 cyc
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
-3 -2 -1 0 1 2 3
0
0.5
1
CD = 0.25, CP = –0.25 CD = 0.125, CP = 0 CD = –0.125, CP = 0.5 CD = –0.25, CP = 0.75CD = 0, CP = 0.25

34. (Illustrations from Grothe, Nat. Rev. Neurosci. 2003)
Asymmetries in the MSO?
Brand, Behrend, Marquardt, McAlpine & Grothe, Nature 417, pp543-544, 2002

35. Brand, Behrend, Marquardt, McAlpine & Grothe, Nature 417, pp543-544, 2002
(Illustration from Grothe, Nat. Rev. Neurosci. 2003)
Asymmetries in the MSO?

36. -10 -5 0 5 10
0
20
40
60
80
100
120
140
ITD (ms)
spikerate(Hz)
Interaural Time Difference (sec)
100 200 300 400 500 600 700 800 900
-1
0
1
2
3
frequency (Hz)
to single tones to tone complex
0 200 400 600 800 1000 1200
-3
-2
-1
0
1
2
3
-10 -5 0 5 10
0
20
40
60
80
100
120
140
Simulation of contralateral inhibition in MSO (Hodgkin-Huxley Model)
frequency (Hz)
ITD (ms)
BestPhase[rad]
spikerate(Hz)BestPhase[rad]

37. Trougher (E,I)Peaker (E,E) Tweener (E,0)
-0.5 0 0.5 ITD -0.5 0 0.5 ITD -0.5 0 0.5 ITD -0.5 0 0.5 ITD -0.5 0 0.5 ITD
Inherent π-Limit !
Inhibition causes phase shift and continuous shape change!
Results of Hodgkin-Huxley Model with precisely timed inhibition:
spikerate
-10 -5 0 5 10
60
70
80
90
100
110
120
ITD [ms] ITD [ms] ITD [ms]
-10 -5 0 5 10
70
80
90
100
110
120
-10 -5 0 5 10
70
80
90
100
110
120
Gmax_inh = 2.5 nS Gmax_exc = 0.75 nS Gmax_inh = 3.5 nS Gmax_exc = 0.45 nS Gmax_inh = 4 nS Gmax_exc = 0.3 nS
Simulation of contralateral inhibition in MSO (Hodgkin-Huxley Model)

38. (McAlpine et al, Hear. Res., 1996)
Correlation between Best IPD and Inhibition
0
20
40
60
80
F S F S F S
neurons[%]Binaurally facilitated (F): > 1
Binaurally suppressed (S): < 1
mean(NDF)
max(monaural)
mean(NDF)
max(monaural)
0 < best ITD < 0.166
n = 77
1/6 < best ITD < 0.33
n = 49
1/3 < best ITD < 0.5
n = 21

39. Simulation of contralateral inhibition in MSO by Day & Semple, 2011