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Dear Fieldtrippers</p>
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I've been scouring the FT documentation and mailing list but can't seem to find the answer to a fairly simple question (which seems to have remained unanswered previously <a href="https://mailman.science.ru.nl/pipermail/fieldtrip/2016-August/010816.html" target="_blank" rel="noopener noreferrer" class="x_OWAAutoLink" id="LPlnk820311" previewremoved="true">https://mailman.science.ru.nl/pipermail/fieldtrip/2016-August/010816.html</a>):
how does one know the size/'radius' of the individual source gridpoints modeled by Fieldtrip? </p>
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I've been warping MNI template source models (with RO selected from a functional atlas of ~300 regions) to individual subject MRI headmodels to extract source timeseries via LCMV beamformer. In ft_prepare_sourcemodel there are seemingly options to control the
*spacing* between gridpoints in a whole-brain source grid (cfg.grid.resolution), but nothing to control how large the individual sources are (either for whole-brain grids, or a priori cfg.grid.pos values that I've been using). </p>
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Does this mean that the size of individual gridpoints cannot be changed within ft_prepare_sourcemodel? Are they also in absolute terms fairly small (e.g. ~1mm)? If so, is the only way to extract 'larger' sources to fit a whole-brain grid (e.g. using the 4mm-spaced
source template provided by FT), identify gridpoints after ft_sourceanalysis that fall within a specified Euclidean distance (e.g. 5mm) of the functional atlas MNI coordinates, and then e.g. average over all those gridpoints? I'm concerned that larger source
gridpoints might have larger SNR...</p>
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Thanks in advance!</p>
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Ravi</p>
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Ravi Mill, PhD</div>
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Post-doctoral researcher</div>
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Center for Molecular and Behavioral Neuroscience (CMBN)</div>
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Rutgers University</div>
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