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Neural source estimation from a time-frequency component of somatic evoked high-frequency magnetic oscillations to
K Sakuma1, K Sekihara, I Hashimoto
1Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki, Japan. sakuma@nips.ac.jp
Objective:
High frequency oscillations (HFOs) evoked by posterior tibial nerve stimulation were recorded using magnetoencephalography (MEG). Time-frequency domain multiple signal classification (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 fields, 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 filtering the somatosensory response with a bandwidth of 500-800 Hz. To estimate the locations of sources with the TF-MUSIC algorithm, we first 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 significantly during the observation.