Inves&ga&ng the Dependence of Spontaneous Fluctua&ons in Visual Cortex on Callosal Connec&vity
Li-‐Wei Kuo, Zhongming Liu, Jacco A. de Zwart, Peter van Gelderen, and Jeff H. Duyn
Advanced MRI sec-on, Laboratory of Func-onal and Molecular Imaging, Na-onal Ins-tutes of Neurological Disorders and Stroke,
Na-onal Ins-tutes of Health, Bethesda, Maryland, USA
Declaration of Relevant Financial Interests or Relationships
Speaker Name: LI-WEI KUO I have no relevant financial interest or relationship to disclose with regard to the subject matter of this presentation.
Inter-‐hemispheric func-onal connec-vity during Rest
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- Biswal et al., MRM 1995
Kuo@ISMRM2011
ISMRM2011: - Jo et al., #430 - Tyszka et al., #431 - Zhou et al., #3686 - Li et al., #4123
Does callosal connecBon underlie inter-‐hemispheric funcBonal connecBvity?
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- Johnston et al., J. Neurosci. 2008
Seed points in V1
BEFORE callosotomy
AFTER callosotomy
Loss of inter-hemispheric functional connectivity - Mohajerani et al., J. Neurosci. 2010
- Quigley et al., AJNR 2003
Kuo@ISMRM2011
Callosal connec-ons in V1
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Acallosal
×
Horizontal Meridian (HM)
- Clarke and Miklossy, J. Comp. Neuro. 1990
Callosal
Vertical Meridian (VM)
Callosal fibers
Kuo@ISMRM2011
Aim • Our aim was to inves&gate the dependence of the strength of spontaneous fluctua&ons in V1 on callosal connec&vity
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• Hypothesis: The strength of inter-‐hemispheric correla&ons is higher in callosal regions (VM) than in acallosal regions (HM)
Kuo@ISMRM2011
Methods • Func-onal localiza-on
– Traveling-‐wave method1,2
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[1] Engel et al., Cere. Cortex 1997 [2] Wandell et al., Neuron 2007 [3] Biswal et al., MRM 1995
BOLD fMRI at 3T GRE-EPI, SENSE R2, TR/TE = 2000/30 ms, 2.3 × 2.3 × 3 mm3, matrix 96 × 96, 20 slices, 231 repetitions
VM1
VM2
HM
• Func-onal connec-vity – Eyes-‐closed res&ng-‐state3
BOLD fMRI at 7T GRE-EPI, GRAPPA R2, TR/TE = 2000/24 ms, 2.3 × 2.3 × 2.3 mm3, matrix 96 × 72, 50 slices, 300 repetitions
• Three healthy volunteers • T1 images: co-‐registra-on and
surface reconstruc-on
Kuo@ISMRM2011
Data analysis
• fMRI data pre-‐processing – Distor-on correc-on – Slice-‐-ming correc-on – Head mo-on correc-on – Temporal polynomial detrending
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• Res-ng-‐state fMRI – Temporal filtering (0.01-‐0.1 Hz) – Global mean signal regression – Nuisance signal regression
• Surface data analysis
-‐ Cor&cal surface reconstruc&on (FreeSurfer)
-‐ Re¬opic mapping -‐ Region-‐of-‐interest placement
(AFNI & SUMA)
-‐ Connec&vity mapping -‐ ROI-‐based correla&on
Kuo@ISMRM2011
ROI localiza-on
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LH
VM1
HM
VM2
V1
RH
Kuo@ISMRM2011
RH
LH
0.9
0
Connec-vity mapping (seed in RH) VM1 HM VM2
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Kuo@ISMRM2011
0.9
0
VM1 HM VM2
LH
RH 11
Connec-vity mapping (seed in LH) Kuo@ISMRM2011
Pearson’s correla-on matrix
0.55
0.85 VM1 HM VM2
VM1
HM
VM2
Right Hemisphere
Left
Hem
isph
ere
0.79 0.73 0.67
0.71 0.81 0.75
0.8 0.59 0.59
Stronger inter-hemispheric correlations in retinotopically homologous areas (Polimeni et al., ISMRM2010)
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Kuo@ISMRM2011
Comparison of VM vs. HM
VM
HM
LH RH
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Kuo@ISMRM2011
Comparison of VM vs. HM
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Kuo@ISMRM2011
VM - Callosal -
HM - Acallosal -
N = 3, p = 0.27
Z-sc
ore
Discussion • No significant difference in inter-‐hemispheric func-onal
connec-vity was found between callosal and acallosal regions in primary visual cortex – Mono-‐synap&c connec&ons may not be the most cri&cal factor driving these inter-‐hemispheric correla&ons
• Our current results suggest that a dominant involvement of a mul&-‐synap&c pathway may need to be considered
• Addi-onal subjects are being scanned to solidify our findings
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Kuo@ISMRM2011
Thank you for your aHen&on!
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Masaki Fukunaga Jongho Lee
Jacco de Zwart
Jeff Duyn
Peter van Gelderen
Karin Shmueli
Susan GuMman
Brian Yao
Steven Newman
Zhongming Liu
Molly Bright
Lei Qin
Acknowledgments: Advanced MRI Sec&on, LFMI/NINDS/NIH; Dr. Junjie Liu and Dr. Ziad Saad, NIH
Marta Bianciardi
This work was supported by the Intramural Research Program of the Na-onal Ins-tute of Neurological Disorders and Stroke, Na-onal Ins-tutes of Health
Ques&ons and comments: [email protected]
