The results that can be seen in an EEG when performing transcranial magnetic stimulation
What do you see in the EEGs as you’re doing the TMS? Do you actually see the frequency that you’re applying with the TMS modulating the wave in the brain?
This is a very interesting question. I’ve been doing EEG and TMS for the last seven to eight years. What I have seen – two things which I have seen – and I think this is to be noted; any activating rhythm reduces theta activity. It reduces slow cortical potential, including delta. It also can reduce beta and beta 2 activity, especially when they are rhythmic. It makes them de-synchronized – the term which we use. It increases gamma and it increases alpha. The nesting of the gamma and alpha gets increased over and over. I’ve seen it in all the activating rhythms.
Now 1 hertz, I have stopped calling it a deactivating rhythm. I think it’s a reset rhythm and it takes care of slow-wave. It takes care of theta predominant slow-wave delta and theta. It also improves alpha (sometimes it does not). It also reduces beta 2 activity. Its impact on gamma is that it reduces gamma. So if someone asks me, based on my experience, these are the things that come to my mind and I’ve seen it over and over again.
That’s very good to know because it’s counterintuitive to a lot of practitioners. You would think that if you apply this frequency here, it would be activating, no matter what, in the area that you’ve applied it to. Obviously, there’s a lot of subtleties in what I’m saying but in a neurochemical level, and also in the way that the brain communicates, if you decrease gamma activity, aren’t you decreasing the ability of the brain to store new memory?
I think the brain has to be seen, not as a blob, producing brain waves, but there are multiple modules which are running. So when we are activating one module, we may be deactivating another module. So it has to be understood in a very careful manner, going into the detail of which circuit we are activating because it is going to deactivate another circuit. So it’s not like you throw a pulse and it’s not going to do anything else. It is going to do lots of things to what those neurons are connected to – down below it, on the other contralateral side and the back of it.
The other principal is that behind the central sulcus is the sensory area. In front of the central sulcus is the executive motor area. The motor area controls the sensory area, so when you’re activating the motor area, you’re controlling the sensory area. When you’re activating the sensory area, you are crossing the motor area. Then the cortical and subcortical; when you’re activating the cortical area, you’re deactivating the subcortical.