Efficient neuromagnetic determination of landmarks in the somatosensory cortex

OBJECTIVES An efficient procedure for the magnetoencephalographic determination of functional landmarks in the somatosensory cortex has been developed. METHODS Digits 2-5 are stimulated in randomized order using balloon diaphragms. The interval between two stimuli is 500 ms. Source locations in area 3b are derived by interpreting the field component with a mean latency of 48 ms in terms of an equivalent current dipole. RESULTS The signal-to-noise ratio achieved in a given time for each of the 4 stimulation sites turned out to be only slightly smaller than the one obtained by stimulating a single site with an optimal interstimulus interval (about 1 s). CONCLUSIONS Compared to a sequential investigation of the different sites, the proposed procedure allows the reduction of the overall measurement time by a factor of about 2.7.

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