Reader Comments

Post a new comment on this article

Questions to the article

Posted by agaburza on 14 Mar 2013 at 18:50 GMT

Hi,
Very interesting data!

I have one clarification question:
The first part of the results concerning T2* measure is limited to the pre-defined ROIs (dorsal and ventral striatum). If I understand it correctly, similar analysis is then performed with T1-WIs. Next, the analysis is subdivided into grey and white matter using FAST. How much % of the initial grey matter ROI contained white matter? Were the relative volumes of grey and white matter different or was the analysis performed without the ROI restriction?

I would be also very grateful if you could point me to the reference describing that "capillaries are embedded in the myelin sheaths of axons". It would be very useful for interpretation of any DTI results.

Thank you and best regards,
Aga

No competing interests declared.
report a concern respond to this posting

RE: Questions to the article

DirkBW replied to agaburza on 17 Apr 2013 at 21:29 GMT

Dear Aga

We apologize for the delay in our response. We had to find the relevant data in our offline backup records. Please see below for our answers to your questions.

Q.: The first part of the results concerning T2* measure is limited to the pre-defined ROIs (dorsal and ventral striatum). If I understand it correctly, similar analysis is then performed with T1-WIs. Next, the analysis is subdivided into grey and white matter using FAST. How much % of the initial grey matter ROI contained white matter? Were the relative volumes of grey and white matter different or was the analysis performed without the ROI restriction?

A.: The segregation into grey and white matter was performed for each ROI separately. Below we include the numbers of voxels and volume percentages for the ROIs:

Caudate nucleus: Total: 666 voxels; GM: 22 voxels (3.3%); WM: 483 voxels (72.5%)
Putamen: Total: 560 voxels; GM: 559 voxels (99.8%); WM: 0
Nuceleus accumbens: Total: 224 voxels; GM: 13 voxels (5.8%); WM: 190 voxels (84.8%)

Voxels with partial WM/GM volume were excluded from this part of the analysis.

Q.: I would be also very grateful if you could point me to the reference describing that "capillaries are embedded in the myelin sheaths of axons". It would be very useful for interpretation of any DTI results.

A.: We cannot reconstruct exactly where that phrase originated in the writing process. We believe we were referring to the presence of vessels in white matter in general. See, for instance, this article about the fraction of white matter volume taken up by blood:
Leenders, KL et al., Cerebral blood flow, blood volume and oxygen utilization normal values and effect of age. Brain (1990) 113 (1): 27-47. doi: 10.1093/brain/113.1.27

We hope this answers your questions.

Best regards

Loan Vo & Dirk Bernhardt-Walther

No competing interests declared.
report a concern respond to this posting