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Hi Matt

The other variable is cortical power. Actually, we found that the ratio of thalamic mean intensity with normalized cortical gray matter volume is associated with cortical power. I was going to discard it but theoretically, it made sense, to take out the contribution of cortical gray matter and just leave the level of thalamic myelinization.

Regards Dorothy

On Thu, Mar 21, 2019 at 6:48 PM Glasser, Matthew glasserm@wustl.edu wrote:

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What is the other variable?

Matt.

From: freesurfer-bounces@nmr.mgh.harvard.edu on behalf of Dorothy Sincasto dsincasto@gmail.com Reply-To: Freesurfer support list freesurfer@nmr.mgh.harvard.edu Date: Thursday, March 21, 2019 at 8:44 PM To: Freesurfer support list freesurfer@nmr.mgh.harvard.edu Subject: [Freesurfer] Gray matter normalized intensity

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Dear Freesurfers

Usually, the mean normalized intensity in aseg.stats is not considered important. However, by mistake, I put it in my analysis and found out that the mean intensity of the thalamus explains a lot the variance of my data.

What could be the physiological meaning of higher intensity in the thalamus? Could it be associated with either increased myelinization ( more axons or synapses) or with decreased neural soma? Has anybody reported mean normalized intensity effects in subcortical structures?

Thanks Dorothy

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The intensity is partially what VBM is picking up, so it is not at all unreasonable to look at.

On 3/21/19 9:52 PM, Bruce Fischl wrote: Hi Dorothy

yes, we have looked at intensity effects in the gray matter before (David Salat for example has done this). It certainly reflects degree of myelination as well as other things. Which volume are you looking at? The norm should be ok for this

cheers Bruce On Thu, 21 Mar 2019, Dorothy Sincasto wrote:

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Dear Freesurfers Usually, the mean normalized intensity in aseg.stats is not considered important. However, by mistake, I put it in my analysis and found out that the mean intensity of the thalamus explains a lot the variance of my data.

What could be the physiological meaning of higher intensity in the thalamus? Could it be associated with either increased myelinization ( more axons or synapses) or with decreased neural soma? Has anybody reported mean normalized intensity effects in subcortical structures?

Thanks Dorothy

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