Myelination Differences of Stripes in Human V2: Preliminary Evidence from 7 T Quantitative MRI

Poster No:

2177 

Submission Type:

Abstract Submission 

Authors:

Daniel Haenelt1,2, Robert Trampel1, Shahin Nasr3,4, Jonathan Polimeni3,4, Roger Tootell3,4, Martin Sereno5, Kerrin Pine1, Luke Edwards1, Saskia Helbling1,6, Nikolaus Weiskopf1,7

Institutions:

1Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany, 2International Max Planck Research School on Neuroscience of Communication: Function, Structure, and Plasticity, Leipzig, Germany, 3Athinoula A. Martinos Center for Biomedical Imaging, Boston, MA, 4Department of Radiology, Harvard Medical School, Boston, MA, 5Department of Psychology, San Diego State University, San Diego, CA, 6Department of Neuroscience, Max Planck Institute for Empirical Aesthetics, Frankfurt, Germany, 7Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, Leipzig University, Leipzig, Germany

First Author:

Daniel Haenelt  
Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences|International Max Planck Research School on Neuroscience of Communication: Function, Structure, and Plasticity
Leipzig, Germany|Leipzig, Germany

Co-Author(s):

Robert Trampel  
Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences
Leipzig, Germany
Shahin Nasr  
Athinoula A. Martinos Center for Biomedical Imaging|Department of Radiology, Harvard Medical School
Boston, MA|Boston, MA
Jonathan Polimeni  
Athinoula A. Martinos Center for Biomedical Imaging|Department of Radiology, Harvard Medical School
Boston, MA|Boston, MA
Roger Tootell  
Athinoula A. Martinos Center for Biomedical Imaging|Department of Radiology, Harvard Medical School
Boston, MA|Boston, MA
Martin Sereno  
Department of Psychology, San Diego State University
San Diego, CA
Kerrin Pine  
Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences
Leipzig, Germany
Luke Edwards  
Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences
Leipzig, Germany
Saskia Helbling  
Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences|Department of Neuroscience, Max Planck Institute for Empirical Aesthetics
Leipzig, Germany|Frankfurt, Germany
Nikolaus Weiskopf  
Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences|Felix Bloch Institute for Solid State Physics, Faculty of Physics and Earth Sciences, Leipzig University
Leipzig, Germany|Leipzig, Germany

Introduction:

Recent developments in ultra high field MRI (≥ 7 T) allow the study of columnar features of the human brain non-invasively. E.g., the thin-thick-pale stripe pattern in extrastriate cortex V2 (Tootell et al. 1983) can be delineated in high-resolution fMRI (Nasr et al. 2016, Dumoulin et al. 2017). Based on histological studies, these stripes are also expected to vary in myelin content although it is still debated which stripe type is more myelinated than surrounding gray matter (Horton et al. 1997). Here, we estimated myelination differences using quantitative MRI (qMRI) myelination markers (T1, T2*, PD) (Edwards et al. 2018) between stripe types which were delineated using fMRI. To the best of our knowledge, this is the first study based on qMRI myelin markers that corroborates intra-areal myelin variations at the columnar level in the living human brain.

Methods:

Experiments were performed on a Siemens MAGNETOM 7 T whole-body MR scanner (Siemens, Germany) using a 32-channel phased array head RF coil (Nova Medical, USA). 4 volunteers participated in 6 scanning sessions over different days. In separate sessions, thin and thick stripes were functionally localized by exploiting their different sensitivity to color and binocular disparity, respectively, as described in Nasr et al. (2016). For fMRI, we scanned an oblique-coronal slab (50 slices) using a GE-EPI protocol with isotropic 0.8 mm resolution (TR = 3000 ms, TE = 24 ms, GRAPPA = 3, partial Fourier = 6/8). For qMRI, we acquired an isotropic 0.5 mm resolution MPM protocol (Weiskopf et al. 2013) consisting of two multi-echo FLASH acquisitions (6 equidistant echoes) with T1- and PD-weighting (FA(PDw) = 5 deg, FA(T1w) = 24 deg, TR = 25 ms, TE = 2-16 ms, GRAPPA = 2x2), plus maps of B1+ and B0. We used an optical tracking system (Kineticor, USA) to prospectively correct head motion during the scan. T1, T2* and PD maps were computed using the hMRI toolbox (Tabelow et al. 2019). Cortex segmentation was performed with FreeSurfer (6.0.0) on a separately acquired MP2RAGE scan. The qMRI and fMRI data were co-registered and sampled at mid-cortical depth using the equi-volume layering approach. Based on a separate retinotopy fMRI scan, V2 was located in each individual. Intra-cortical smoothing (Blazejewska et al. 2019) was applied to all qMRI maps.

Results:

Fig. 1 shows an example of the functional localization of V2 stripes from one volunteer. As expected, thin and thick stripes largely alternate. Based on the functional definition of these stripes, T1, T2* and PD in thin/thick stripes were compared to a baseline value defined as overall mean within V2. Fig. 2(a) and (b) show sampled T1 and T2* distributions across individuals. T1 values in thick stripes are significantly higher than baseline, pointing to lower myelination of thick stripes. No effect was detected in T2* or PD (not shown). Since the stripe extent depends on the z-score threshold used to demarcate them, we repeated the comparison for various threshold levels (Fig. 2 (c,d)).
Supporting Image: haenelt_figure1.png
Supporting Image: haenelt_figure2.png
 

Conclusions:

In this study, we showed T1 differences between stripe types in human V2. Our results suggest a lower myelination of thick stripes which adds to the controversial topic of stripe myelination in V2 (see Tootell et al. 1983, Horton et al. 1997) but is generally in line with a recent fMRI study in macaques (Li et al. 2019). However, in contrast to previous MR studies (Dumoulin et al. 2017, Li et al. 2019), we estimated qMRI parameters which are less biased by instrumental artefacts and thus more directly linked to the tissue microstructure.

Funding
The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement n° 616905.

Neuroanatomy, Physiology, Metabolism and Neurotransmission:

Anatomy and Functional Systems
Cortical Cyto- and Myeloarchitecture 1

Novel Imaging Acquisition Methods:

Anatomical MRI
BOLD fMRI 2

Keywords:

Cortical Columns
FUNCTIONAL MRI
HIGH FIELD MR
Myelin
Vision
Other - QUANTITATIVE MRI

1|2Indicates the priority used for review

My abstract is being submitted as a Software Demonstration.

No

Please indicate below if your study was a "resting state" or "task-activation” study.

Task-activation

Healthy subjects only or patients (note that patient studies may also involve healthy subjects):

Healthy subjects

Was any human subjects research approved by the relevant Institutional Review Board or ethics panel? NOTE: Any human subjects studies without IRB approval will be automatically rejected.

Yes

Was any animal research approved by the relevant IACUC or other animal research panel? NOTE: Any animal studies without IACUC approval will be automatically rejected.

Not applicable

Please indicate which methods were used in your research:

Functional MRI
Structural MRI

For human MRI, what field strength scanner do you use?

7T

Which processing packages did you use for your study?

AFNI
SPM
FSL
Free Surfer
Other, Please list  -   Ants

Provide references using author date format

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Burt JB, Helmer M, Shinn M, Anticevic A, Murray JD. Generative modeling of brain maps with spatial autocorrelation. Neuroimage. 2020;220:1-17. doi:10.1016/j.neuroimage.2020.117038

Dumoulin SO, Harvey BM, Fracasso A, Zuiderbaan W, Luijten PR, Wandell BA, Petridou N. In vivo evidence of functional and anatomical stripe-based subdivisions in human V2 and V3. Scientific Reports. 2017;7(1):1-12. doi:10.1038/s41598-017-00634-6

Edwards LJ, Kirilina E, Mohammadi S, Weiskopf N. Microstructural imaging of human neocortex in vivo. Neuroimage. 2018;182:184-206. doi:10.1016/j.neuroimage.2018.02.055

Horton JC, Hocking DR. Myelin patterns in V1 and V2 of normal and monocularly enucleated monkeys. Cereb Cortex. 1997;7(2):166-177. doi:10.1093/cercor/7.2.166

Li X, Zhu Q, Janssens T, Arsenault JT, Vanduffel W. In Vivo Identification of Thick, Thin, and Pale Stripes of Macaque Area V2 Using Submillimeter Resolution (f)MRI at 3 T. Cereb Cortex. 2019;29(2):544-560. doi:10.1093/cercor/bhx337

Nasr S, Polimeni JR, Tootell RBH. Interdigitated Color- and Disparity-Selective Columns within Human Visual Cortical Areas V2 and V3. J Neurosci. 2016;36(6):1841-1857. doi:10.1523/JNEUROSCI.3518-15.2016

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