EEGs and MEGs and MRIs take pictures of out brains (images in jagged lines overlaid onto regions of the brain) to diagnose problems in the hardware. But when used in conjunction with specific pictures across different individuals, it appears that the pictures cause similar enough responses that a computer can determine what picture the person is viewing 8 out of 10 times.
Keep in mind (do you like that pun?) that the 3 devices are electromagnetic in nature whereas the brain is electrochemical in nature so this brings up a number of questions:
can an electromagnetic field affect a neuron?
does an activated neuron generate an electromagnetic fieldif so, is that field strong enough to affect neighboring neuronsdoes the field have enough energy to carry information
Keep in mind that the neuron carries an electrical signal from the dendrites (inputs) to the axon with branches (output). Neurotransmitters (chemicals) carry the signal from neuron to neuron (axon to dendrites) and each neuron has a minimum activation potential which dampens weak signals. With the average brain composed of 100 billion neurons with each having an average of 7,000 synaptic connections - about 400 trillion connections.
The neurons are shielded (by a myelin sheath but it is not a continuous sheath but a series of small sheaths) and the dendrites are not insulated.
I could go on but is anyone interested?