[Eeglablist] time-frequency contiguity threshold?

[Morgan Hough]

Hi Paul,

Would something like Stephan Kiebel's SPM for ERPs papers be what you 
are looking for?

http://www.ncbi.nlm.nih.gov/pubmed/15193578?ordinalpos=20&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

http://www.ncbi.nlm.nih.gov/pubmed/15193579?ordinalpos=19&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum

As you can see in the two papers, they deal with the thresholding 
problem in ERPs and ERSPs using GRF theory which is pretty much standard 
practice for FMRI. Hope this helps.

Cheers,

-Morgan

-- 
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Morgan Hough, D. Phil. Student,  Oxford University FMRIB Centre

FMRIB, JR Hospital, Headington, Oxford  OX3 9DU, UK
+44 (0) 1865 222466  (fax 222717)
mhough at fmrib.ox.ac.uk  http://www.fmrib.ox.ac.uk/~mhough
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Kieffaber, Paul wrote:
>
> I’ve been looking (so far in vein) for some precedent or algorithm to 
> determine a reasonable contiguity threshold for time-frequency 
> analysis. My understanding is that the zero-masking done by newtimef() 
> is on a pixel (resel?) by pixel basis, showing only those pixels where 
> the deviation from baseline is statistically significant. I’m 
> wondering if anyone is using the added constraint of a contiguity 
> threshold in order to mask even those pixels with statistically 
> significant deviations by requiring that there be multiple consecutive 
> (in time and/or frequency) pixels with significant deviations before 
> that time-frequency perturbation is considered “significant.” Two 
> alternatives I’m imagining are: (1)a theoretically determined 
> threshold in terms of time and frequency (e.g., perturbation must span 
> 50ms and/or 5Hz) that is independent of the temporal/frequency 
> resolution and (2) an algorithmically determined threshold that is 
> based on the dimensions of the time-frequency matrix (e.g., the joint 
> probability of N consecutive time-bins and N consecutive 
> frequency-bins is less than alpha). Any comments, recommendations 
> and/or references would be greatly appreciated.
>
> Thanks!
>
> Paul
>
> ------------------------------------------------------------------------
>
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