Comments on: Home transcranial magnetic stimulation

By: Caitlin Connors

Caitlin Connors — Sun, 18 Jun 2006 18:23:06 +0000

I can add to anecdotal reports about short-term memory loss using TMS. A former colleague of a labmate’s (yes, the academic equivalent of “a friend of a friend”) reportedly TMSed his girlfriend and was rewarded with two or three days of memory trouble. I’m sure it did wonders for their relationship. My labmate had the sense that the effect was not particularly uncommon – especially while determining proper sequences.
But, yes — anecdotal.

By: Christopher Honey

Christopher Honey — Sat, 17 Jun 2006 19:28:30 +0000

Neurointerest — yes, if I remember correctly the reaction time distributions were different, although not at the levels of the mean. But this was all second hand. See the papers below, esp. the second one, for some more reliable evidence about the range of effects rTMS can produce.
Roy — TMS can be run in single strong pulses or with repeated weak pulses; the pulses can also be more or less diffuse. So the effects differ. But a quick search turned up these two papers:
“Left prefrontal activation predicts therapeutic effects of repetitive transcranial magnetic stimulation (rTMS) in major depression.”
Eschweiler et al. (2000) Psychiatry Research
“Repetitive transcranial magnetic stimulation dissociates working memory manipulation
from retention functions in prefrontal, but not posterior parietal, cortex”
Postle et al. (in press) Journal of Cog Neurosci

By: Roy

Roy — Thu, 15 Jun 2006 04:39:47 +0000

The cerebral cortex is typically a good 1-1.5cm away from the scalp surface. Since the measured electromagnetic energy from the low-intensity coils decreases as a function of the square of the distance from the source, I suspect that these devices produce extremely low amounts of EMR within the cortex which is closest to the skull. What is the evidence that there is a measurable effect?

By: Neurointerests

Neurointerests — Wed, 14 Jun 2006 19:08:20 +0000

Christopher,
Your comments on TMS I find intriguing. I agree with the paranoia about temporal areas. I’m curious, though, about your comment in regards to returning participants to testing 1 week post-TMS and their subtle difference from controls…
What kind of subtle difference are we talking about here? Are you referring to reaction times, cognitive measures? Or something more vague like emotions? Is this something that was tested or just an observation from those performing the trials on the participants?

By: Christopher Honey

Christopher Honey — Wed, 14 Jun 2006 17:57:52 +0000

I don’t know much about ‘low-strength’ rTMS, but I do know that I am not going to allow anybody to use standard lab rTMS on me. It probably is ‘harmless’ when used on areas like primary visual cortex, but who knows what it’s doing in temporal areas?
It’s a great research tool. (For one thing because it allows you to test causal relationships using perturbations/interventions, which is one of the strongest tests of a causal relationship). But I’m not signing up to be a subject.
Purely anecdotally, I’ve heard that people who run around TMS-ing each other in their labs have exhibited the occasional lost memory or brief mood changes. Anecdotally again, I’ve also heard the behavioral patterns of subjects who return for testing 1 week post-TMS are often subtly different from controls… so for example their reaction-time means might be the same, but the distributions are altered. I have also heard that TMS is being used therapeutically, which means that it must have some medium-term effects, right?