A completely noninvasive procedure that uses an array of very sensitive sensors to pick up the magnetic fields associated with electrical activity in the brain. There are many uses for MEG, including determining the function of various parts of the brain and localizing epileptic activity. MEG has an extremely high temporal resolution, in the order of milliseconds, and unlike some other forms of neuroimaging it measures neural activity, rather than a vascular response. The only downside is that the spatial resolution is not quite as good as some other forms of brain mapping techniques. 


There are less than 100 MEG machines in the world, making it a very interesting way of looking at how the brain responds to different tasks. For more information see here and here

Transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS) uses rapidly alternating magnetic fields placed on the outside of the skull to induce an electrical current in the perpendicular direction (see diagram below). This electrical stimulation depolarises neurons in the lateral surface of the brain. We can use it in a number of different ways that help us to understand what a particular region of the brain does. 



For more see here

Magnetic resonance imaging
Lesion Mapping
Speech alterations - 'FUSP'