will you guys plz explane why this happens?

I graduated from UC Berkeley with a degree in CogSci. I got to see this in action, when the professor demonstrated on himself. It involved what looked like an all-plastic ping-pong paddle hooked up to a box. He placed the paddle on his head, had a grad-student assistant hit The Switch, and his wrist twitched. It was pretty freaky.
The problems, though, are: (a) you need to hold this thing right up next to your head, and (b) they don't quite have the resolution needed to, say, form images on the visual cortex, which seems to me like the perfect use for it. All of the important senses, in fact, are right on the surface of the brain, and ripe for TMS-ing as soon as the technology gets to that point. Who needs holography and force fields for a Holodeck when you can just make an Illusion Helmet?

I'm signed for a TMS experiment with the UC Berkeley NeuroCog department. I just can't wait. Nothing thrills me like the idea of directly fiddling with my concious experience with electromagnetic pulses.

Neat.

Spinrad's "Little Heroes" featured EM brain-zappers, used as drugs.

I saw this done with bind people where they "disabled" their visual processing sections of the brain. They had a lot of difficulty reading braille. Apparently the brain rewires this section of the brain for other uses if the eyes don't work.