The document presents research on using quantitative MRI techniques to map cortical myelination in vivo. It discusses: 1) Methods for mapping cortical myelin content including T1-weighted/T2-weighted ratio imaging and quantitative T1 mapping using MP2RAGE. 2) An application of these methods to study differences in auditory cortex myelination between musicians with absolute pitch and those without. Findings showed greater myelination in the planum polare region for musicians with absolute pitch. 3) Speculation that increased myelination in planum polare may enable pitch chroma recognition as an auditory object, relating to the ability of absolute pitch musicians to identify musical tones.

1. In-vivo intracortical myelination
mapping: quantitative morphometry
Seung-Goo KIM
Max Planck Institute for Human Cognitive and Brain Sciences
2016-02-15 CNCC

2. **Please interrupt me anytime
when you have a question!**

3. Overview
• Introduction: myeloarchitecture of cortex
• Methods: T1w/T2w, MP2RAGE, & multicontrast imaging
• Application: auditory cortex of musicians with absolute pitch

4. Overview
• Introduction: myeloarchitecture of cortex
• Methods: T1w/T2w, MP2RAGE, & multicontrast imaging
• Application: auditory cortex of musicians with absolute pitch

5. https://en.wikipedia.org/wiki/Neuron

6. Annese (2004) NI

7. Vogt (1903)
C Y T O - M Y E L O -
Beck (1928)
Myeloarchitecture of cortex
Nieuwenhuys (2013) Ed. Geyer & Turner

8. Myeloarchitecture of auditory cortex
Hopf (1954)
(HG)
STG

9. Physiological relevance of myelin
• Long-range connections (white matter)
• fasten axonal transmissions
• decrease variability of transmission speed thus increasing
synchrony
• Local connections (gray matter)
• reduce cross-talk so that increasing specificity
• prevent neuroplasticity after critical period [1]
[1] McGee et al., 2005

10. Cortical myelin limits neuroplasticity
• In normal mice, abrupt maturation of
cortical myelin(P40, P60) normally
prohibits experience-driven plasticity
(WOD) [1]
• In mutant mice without a myelin-
associated signal receptor (NgR-/-),
neuroplasticity remained as during
critical period (P20-P32) [1]
[1] McGee et al., 2005
Pxx: postnatal age (days)
MD: monocular deprivation
WT: wild type
WOD:weightedoculardominancescore

11. Modern cyto-/myeloarchitectonic works (ex-vivo)
Annese (2004) NIMorosan (2001) NI

12. Modern myeloarchitectonic works (in-vivo)
Dick (2012) CC
Morosan (2001) NI

13. Age effect
n=1555
Shafee (2015) NI

14. Cortical myelin & cognitive functions
ERN: Response-onset-locked ERP | incongruent &iIncorrect
STD of RT:
Z(T1w/T2w)
Grydeland (2013) JNSc

15. Overview
• Introduction: myeloarchitecture of cortex
• Methods: T1w/T2w, MP2RAGE, & multicontrast imaging
• Application: auditory cortex of musicians with absolute pitch

16. T1w / T2w ratio image

17. T1w/T2w..?
Glasses & Van Essen (2011) JNSc
b: B0 field bias; x: myelin contrast

18. Glasses & Van Essen (2011) JNSc

19. Glasses & Van Essen (2011) JNSc

20. Quantitative T1 mapping
(relaxometry)

21. T1 (or R1) mapping
• Longitudinal magnetization time (T1), or
relaxation rate (R1=1/T1) mapping
Geyer et al. (2011) Front Hum Neurosci[1] Eickhoff et al. (2005) Hum Brain Mapp
• R1 (=1/T1) corr. myelin

22. Stüber et al., 2014
Ex-vivo validation of relaxometry

23. Multicontrast imaging

24. Callaghan (2014) NBA

25. Effect of aging (myelin decrease, iron increase)
Callaghan (2014) NBA
Iron+
myelin-
Callaghan (2014) NBA

26. Overview
• Introduction: myeloarchitecture of cortex
• Methods: T1w/T2w, MP2RAGE, & multicontrast imaging
• Application: auditory cortex of musicians with absolute pitch

27. What is absolute pitch (AP)?
• Ability to recognize the name (or pitch chroma) of any given
tone (“C4” or “G#3”) without an external reference
• Rarely acquired ability (7% of Western musicians, 30% of East
Asian musicians [1])
• Related to early musical experience (4~7 year-old [2]) and a
training method (“fixed-Do”) that encourages absolute
recognition of tones [3]
[1] Miyazaki, 2004 [2] Zatorre, 2003 [3] Willson et al., 2012

28. Macroscopic findings related to AP
• Structural and functional
differences in auditory cortex
(HG, PT) [1~4] and prefrontal
cortex (DLPFC) in right
hemisphere [4,5]
• Unknown microstructures (i.e.,
what do those neurons do to
enable AP?)
[1] Keenan et al., 2001 [2] Wengenroth et al., 2014 [3] Ohnishi et al., 2001 [4] Dohn et al., 2015
[5] Zatorre et al., 1998
DLPFC
HG
PT
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29. Methods
• 8 absolute pitch (AP) musicians vs. 9 non-AP musicians
• MP2RAGE (0.7-mm-isovoxel) for R1 mapping for myelin quantification
• Surface-based analysis (FWHM = 7 mm); RFT-based correction

30. Kim & Knösche (in revision)

31. Kim & Knösche (in revision)

32. Pitch chroma vs. pitch height
Warren et al., 2003

33. • APs’ behaviors shows higher
sensitivity to pitch chroma [1]
• PP is sensitive to pitch chroma [2]
and related to auditory object
recognition [3,4]
• And greater cortical myelin in the
right PP in APs [5], which prohibits
plasticity after the critical period [6]
• Conjecture: “Recognition of pitch
chroma may occur as an auditory
object recognition”
DLPFC
PP
PT
Ventral pathway for pitch chroma
HG
[1] Miyazaki, 1998 [2] Warren et al., 2003 [3] Zatorre et al., 2004 [4] Kriegstein et al., 2006 [5] Kim et al., 2015
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34. Now time for discussion! :)