Somatically Evoked Magnetic Fields of the Human Brain

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Science  06 Jan 1978:
Vol. 199, Issue 4324, pp. 81-83
DOI: 10.1126/science.199.4324.81


The human brain is found to produce a magnetic field near the scalp which varies in synchrony with periodic electrical stimulation applied to a finger. Use of a highly sensitive superconducting quantum interference device as a magnetic field detector reveals that the brain's field is sharply localized over the primary projection area of the sensory cortex contralateral to the digit being stimulated. The phase of the response at the stimulus frequency varies monotonically with the repetition rate and at intermediate frequencies yields a latency of approximately 70 milli-seconds for cortical response.