Can anyone tell whether 30Hz TBS may be used as an equivalent of 50Hz TBS? Some researchers (e.g. Wu et al.) suggest that the effects of 30Hz TBS at higher intensities (90 or 100% RMT) are roughly the same as compared to those when 50Hz is applied. The question is simply practical. Our stimulator is capable of reaching 50Hz only when the intensity is set at max 30%, which limits the number of potential subjects. Does any of you use 30Hz TBS? Thanks in advance.
I don't have much experience with 30Hz TBS, and I doubt very many people do. The higher frequency burst in Human TBS were selected based on TBS protocols in hippocampal slices- frequencies higher than 50Hz provided no additional benefit (in a very small sample) according to YZH and JR. There is probably nothing special about 50Hz. However, it is worthwhile noting that the effects of 50Hz TBS are variable enough, without adding to the confusion!
TBS with little studied frequency will irk reviewers, unless you have a 'check measure' - for example an MEP measure post TBS to ensure that you've modulated cortical excitability in the right direction. Also, it will be worth your while thinking of a valid reason (other than lack of appropriate equipment) to use a barely studied protocol over one with >1000 citations. A reviewer might ask, if you didn't have the right equipment for TBS could you have used another protocol (old-fashioned 1hz) or NIBS modality (TDCS) instead?. TBS is not superior (or inferior) to these....
Thank you for your answer and your suggestions. Well, when it comes to practicality TBS seems the best choice, especially when participants (stroke patients in our case) have poor tolerance to 30-min. protocols. TDCS would be nice if it didn't elicit so widespread effects in the cortex. Adding 'check measure' seems the only option. This should convince reviewers, hopefully... As for the equipment, I think that if we can do the same kind of modulation using slightly different (although definitely not trendy) parameters the only thing that should matter is final results. Congrats on your impressive work and best regards!
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