Pii: S1388-2457(99)00120-0

Objective: High frequency oscillations (HFOs) evoked by posterior tibial nerve stimulation were recorded using magnetoencephalography (MEG). Time±frequency domain multiple signal classi®cation (TF-MUSIC) algorithm was applied, and the usefulness of this method was demonstrated. Methods: Ten normal subjects were studied. To localize sources for the HFOs of those somatosensory evoked ®elds, we applied two kinds of methods: the single moving dipole (SMD) method and the TF-MUSIC method. The SMD method was applied after digitally band-pass ®ltering the somatosensory response with a bandwidth of 500±800 Hz. To estimate the locations of sources with the TF-MUSIC algorithm, we ®rst set the target region on the spectrogram of the somatosensory responses. Then, the procedure described in Section 2.2 was applied with this target region. Results: A clear, isolated region was detected in 6 out of 10 subjects using a time±frequency spectrogram. The averaged distance of the dipole sources between the HFOs and the underlying P37m using the TF-MUSIC algorithm was smaller than using the SMD method. Conclusions: The TF-MUSIC algorithm is suitable for extracting a target response whose spectrum changes signi®cantly during the observation. q 1999 Elsevier Science Ireland Ltd. All rights reserved.