Hi Arran,

This is a very common approach indeed. It's especially relevant when targeting regions that have large between-subject variability. I have personnally used it multiple times in the past. Let me know if you have more specific questions.

Alex

Hi Alex,

Thank you for your reply. Do you use any particular atlas or neuroanatomy book to designate regions for your localisation? Or do you think it is better to rely on previous literature for localisation? I imagine the second approach is suitable for visual or motor areas, but less so for areas associated with a number of functions e.g. the supramarginal gyrus.

Thanks,

Arran

Hi Arran,

I guess it all depends on what motivates your choice of the region to target. If you base your choice on previous studies (fMRI or TMS) then I would clearly favor using these studies to determine the anatomical landmarks to use. Given that SMG is a large region there could be several functional subregions we are not aware of (even though I'm not familiar with SMG). So you want to make sure you target the one which is consistent with the previous effects that motivated your study.

Alex

I'm not entirely sure if it would show up but you could always create masks in fsl and then try to export this to your navigation software.  The other option would be to use an fmri image from a task that activates the area of interest - although your study design might not permit for this.

Hello Arran,

Very insteresting question and dilemma you pose. As Alexandre points out above, the SMG is a rather large region, more so considering the precision and focality you can accomplish with your instrument (neuronavigated TMS).

I have a feeling that if you were to base your target based on anatomical information you would end up with MORE variability in terms of "hitting" different areas across your subjects than using a coordinate system (e.g. MNI), which is what you seem to want to prevent in the first place.

On the other hand, I would endorse Nik's suggestion re using fMRI and target the area based on that information. Mind you, the task would have to demonstrate a solid and consistent activation of the area of interest in the literature.

Best regards,

Fidel

Thank you Nik and Fidel for your answers. Unfortunately we will only be doing structural scanning, so no fMRI task to guide us. I think the best plan might be to examine mean coordinates in studies researching similar things, then compare that to anatomy in order to guide navigation. Hopefully there will be reasonably consistent activity reported in i.e. anterior or posterior parts of the SMG which will act as a guide. 

Hi Arran,

This is a very common approach especially with limited resources and time. anatomical location of area identified for stimulation is being done by 5cm rule and EEG coordinate cap. there are some error based on different size of the skull, in which anterior coordinate is taken final on EEG cap in larger skull size. but definitely these techniques are not precise.

Nice Dear Arran T Reader