29th Annual meeting. Society for Nueroscience Abstracts (SfN1999), pp. 1930

著者:

  • Shigeki Kajihara
  • Kenji Yoshikawa
  • Noboru Murata
  • Shiro Ikeda
  • Masashi Tanigawa
  • Yoshio Ohtani
  • Yoshimichi Ejima
  • Keisuke Toyama

キーワード:

  • neuroscience
  • ICA
  • MEG

Abstract:

Independent component analysis (ICA) is a method to reconstruct individual source signals from the complex signal containing signals and noises from various sources, based on the second or higher order statistics of the complex signal, and has been found to be useful for improvement of signal to noise (S/N) ratio in electroencephalograms (EEGs) and other electrophysiological recordings. We applied ICA to magnetoencephalograms (MEGs) for separation of MEG signals arising from different cortical areas as well as for improvement of S/N ratio. MEG signals recorded from 4 male subjects using a 129 channel magnetometer focused to the left occipital cortex during presentation of visual stimuli (stationary sinusoidal grating and moving random dots) to the right visual field. A demixing matrix was determined so that 129 ICA components conveyed the minimum cross-correlation (a range of time delay, 0–70 ms). Less than 10 of the entire components were usually synchronized to the visual stimuli, and the original MEGs were reconstructed by inverse-transforming those components through the inverse demixing matrix. There was a dramatic improvement in the S/N ratio (10 times). In addition, analysis by spatial filters transforming MEGs into local currents in the brain (Toyama et al., 1999) revealed that it was possible to identify responses arising from different cortical areas based on the temporal patterns of the ICA components. Stationary sinusoidal grating produced a single response localized in VI, while moving random-dots produced multiple responses with different time courses localized in VI, V2/3 and V5, respectively. Supported by Grant-Aid from the Japanese Ministry of Edu. Sci. and Cul. and Special Coordination Funds from the Sci. and Tech. Agency of the Japanese government, Grant in Aid for Scientific Research on Priority Area, Research for the future 1996L00201.