Hello,

We are looking at patients versus control group analysis. We have done a straight analysis and are now looking at covariates. DOSS produces similar results to a straight patient vs control analysis, in that some blobs are located in the same cortical regions. In the case of DODS, there is no similarity whatsoever to the straight analysis maps... which is why I am so stuck in deciding, because it really does impact on the results quite drastically.

I understand the difference between DODS and DOSS – and I know the following question is not an easy one to answer, however we have sample sizes of 15 patient vs 15 control subjects and would like to know if that is great enough such that we are better off going for DODS.

There is no reason to say that the patient cortical thickness – age relationship is any different in slope from that of normal ageing generally; however in certain cortical regions patients exhibit a thickening of the cortex, and thinning in other (albeit fewer) regions.

Do you have any comments? I would have thought that our sample sizes are rather small, but would appreciate your input.

I attach the comparison of patient vs control covaried for age under both DODS and DOSS to illustrate the differences.

Thanks!

Rysia

Ryszarda Burmicz

Research Assistant

Centre for Neuroimaging Sciences

PO89

Institute of Psychiatry