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