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On 11/23/10, Bhavani shankara <[log in to unmask]> wrote: > Dear Sir, > > Thank you very much for all the information, it is very useful > > On 11/23/10, Mark Jenkinson <[log in to unmask]> wrote: >> Hi, >> >> Unfortunately we don't have any other correction method implemented >> currently, although we are working on them. I cannot really comment on >> the biological implications of any of this, and caution you not to >> over-interpret >> anything as a non-significant result does *not* imply that there was >> nothing >> happening (or that it was intrinsically weaker) - it could be that, or it >> could just >> be that the specific noise you had manifest as differences in sensitivity >> that >> were like this, without any connection to biology. This is especially >> true >> if >> one result is just over and another just under the statistical threshold. >> There >> is normally no interpretation that can be made from such a result. If >> you >> are >> interested in laterality differences then you need to formulate a >> statistical >> test that directly looks for this and does not compare two different >> statistical >> results, as that is itself not a statistically valid approach. >> >> All the best, >> Mark >> >> >> On 22 Nov 2010, at 15:53, Bhavani shankara wrote: >> >>> Thanks for the reply, >>> >>> is their any other method through which i can try other correction >>> method >>> (like FWE) to check the result. But on FDR uncorrected maps both >>> hippocampus are showing difference between the groups. >>> >>> Is it may be due to biological reason of differential involvement in the >>> structure of hippocampus between dominant and non-dominant hemispheres >>> ?? >>> >>> On Mon, Nov 22, 2010 at 9:16 PM, Mark Jenkinson <[log in to unmask]> >>> wrote: >>> Hi, >>> >>> This is perfectly reasonable for a couple of reasons: >>> >>> 1 - the volume change is not very spatially specific (or consistent) >>> and hence you can have a strong overall volume change >>> without a local vertex change (that is above threshold). >>> >>> 2 - the FDR thresholding is not the most sensitive technique for >>> surface inference (we are working on coding up better ones) >>> and so it is possible that it is just not quite sensitive enough >>> although you might see interesting results in the uncorrected >>> analyses. Unfortunately, the FDR results are very dependent >>> on the small p-values which can be significantly influenced by >>> slight outliers. It is worth looking at the uncorrected results >>> to >>> see if there is some consistent change which is just failing to >>> meet the FDR threshold. >>> >>> >>> I hope this helps. >>> All the best, >>> Mark >>> >>> >>> >>> >>> >>> >>> On 22 Nov 2010, at 04:58, Bhavani shankara wrote: >>> >>> > Dear FSL experts, >>> > >>> > I am using FSL-FIRST, on extracting the Volumes and statistics were >>> > done >>> > on R software and found the subcortical structures and also both left >>> > and right hippocampus were significantly differing between the groups >>> > (AD and controls (all are right handed) ) (p<0.01). >>> > >>> > However on vertex analysis only on left side hippocampus is not >>> > differing between the groups standing out at FDR correction (on using >>> > surface_fdr input.vtk). However other structures including the >>> > sub-cortical deep gray matter regions were differing at FDR threshold >>> > output (p value) below 0.05. >>> > >>> > Is it possible ?? is it due to technical/analysis issue or due to >>> > biological reason?? >>> > >>> > Thanks in advance for your response >>> > >>> > -- >>> > Dr. BHAVANI SHANKARA BAGEPALLY >>> > MBBS, (PhD in Clinical Neuroscience) NIMHANS, >>> > Bangalore, >>> > INDIA-560029 >>> > email: [log in to unmask] >>> > >>> >>> >>> >>> -- >>> Dr. BHAVANI SHANKARA BAGEPALLY >>> MBBS, (PhD in Clinical Neuroscience) NIMHANS, >>> Bangalore, >>> INDIA-560029 >>> email: [log in to unmask] >>> >> > > > -- > Dr. BHAVANI SHANKARA BAGEPALLY > MBBS, (PhD in Clinical Neuroscience) NIMHANS, > Bangalore, > INDIA-560029 > email: [log in to unmask] > -- Dr. BHAVANI SHANKARA BAGEPALLY MBBS, (PhD in Clinical Neuroscience) NIMHANS, Bangalore, INDIA-560029 email: [log in to unmask]