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<p>Hello,</p>
<p><br>
</p>
<p>1) As of now you would need to write a small python or matlab
script which loads the mesh file and calculates the distances from
your coil to the cortex. But I've implemented this calculation as
a part of the standard pipeline for the next version. Beginning in
version 3.2 this value will be written out in the log.</p>
<p><br>
</p>
<p>2) I'm by no means an electrophysiology specialist (my background
is physics and computer science) but the time dynamics of tDCS and
TMS are very different. While tDCS uses a direct current applied
over a long time (typically minutes), TMS happens at a quite short
time scale (typically microseconds) and have strong variations in
time, even monophasic pulses. So I guess that, while it is valid
to speculate if small fields can have an effect in TMS, direct
comparison with tDCS using only field strength is not very
appropriate. <br>
</p>
<p><br>
</p>
<p>Best Regards,</p>
<p>Guilherme</p>
<p><br>
</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 24/07/2020 18.50, Mccalley, Daniel
wrote:<br>
</div>
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Hi all, </div>
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<br>
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I have two questions about some eField models that I've
created: </div>
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<br>
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<div style="font-family: Calibri, Arial, Helvetica, sans-serif;
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1) Is there a simple way to extract the measured scalp-to-cortex
distance between the defined TMS position and the cortex? I
imagine SIMNIBs must calculate this in creating the eField. I
would be very interested in extracting that information for
other analyses. </div>
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<br>
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2) In interpolating my electric field models to .nii files, I'm
attempting to discern how best to threshold the eFields such
that I might create a Region of Interest of mask based on the
precise site of stimulation. I know that there is much debate
surrounding 1 V/m as a critical value in tDCS modeling. In TMS,
I've noticed that even in my modeling of stimulation intensities
that are particularly low (40% MSO, 58.4 dI/dT on Magventure),
the resulting eField has a rough value of about 45 V/m at the
site of stimulation (crosshairs at the first image), but even
areas near the occipital cortex have a rough value of 3-4 V/m
(crosshairs at second image). While proportionally this V/m is
much smaller than the actual site of stimulation, I could
imagine one might argue that a value of 3-4V/m may influence
cortical neurons.<br>
<br>
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Is this a typical result or is it possible I've made some
critical mistake in my modeling?</div>
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<br>
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Thank you so much for your help!</div>
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<br>
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Best,</div>
<div>
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<br>
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<div id="Signature">
<div>
<div style="font-family:Tahoma; font-size:13px">Dan McCalley
<div>Medical University of South Carolina</div>
<div>College of Graduate Studies, Neuroscience</div>
<div><br>
</div>
</div>
</div>
</div>
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<br>
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