Evoked fields are part of the magnetoencephalogram

Magnetoencephalography

Magnetoencephalography is a technique for mapping brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain, using arrays of SQUIDs...

. They are brain signals evoked by sensory stimulation

Stimulation

Stimulation is the action of various agents on nerves, muscles, or a sensory end organ, by which activity is evoked; especially, the nervous impulse produced by various agents on nerves, or a sensory end organ, by which the part connected with the nerve is thrown into a state of activity.The word...

, but usually buried by the ongoing brain activity. Repeating the stimulus multiple times and averaging the signals reduces the uncorrelated ongoing activity and reveals the evoked field.

Evoked fields are the magnetoencephalographic equivalent to evoked potential

Evoked potential

An evoked potential is an electrical potential recorded from the nervous system of a human or other animal following presentation of a stimulus, as distinct from spontaneous potentials as detected by electroencephalography or electromyography .Evoked potential amplitudes tend to be low, ranging...

s, which are part of the electroencephalogram

Electroencephalography

Electroencephalography is the recording of electrical activity along the scalp. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain...

.

See also

• Induced activity
• Ongoing activity