Medical & Biological Engineering & Computing

, Volume 49, Issue 4, pp 397–407 | Cite as

Removal of large muscle artifacts from transcranial magnetic stimulation-evoked EEG by independent component analysis

  • Reeta J. Korhonen
  • Julio C. Hernandez-PavonEmail author
  • Johanna Metsomaa
  • Hanna Mäki
  • Risto J. Ilmoniemi
  • Jukka Sarvas
Original Article


We present two techniques utilizing independent component analysis (ICA) to remove large muscle artifacts from transcranial magnetic stimulation (TMS)-evoked EEG signals. The first one is a novel semi-automatic technique, called enhanced deflation method (EDM). EDM is a modification of the deflation mode of the FastICA algorithm; with an enhanced independent component search, EDM is an effective tool for removing the large, spiky muscle artifacts. The second technique, called manual method (MaM) makes use of the symmetric mode of FastICA and the artifactual components are visually selected by the user. In order to evaluate the success of the artifact removal methods, four different quality parameters, based on curve comparison and frequency analysis, were studied. The dorsal premotor cortex (dPMC) and Broca’s area (BA) were stimulated with TMS. Both methods removed the very large muscle artifacts recorded after stimulation of these brain areas. However, EDM was more stable, less subjective, and thus also faster to use than MaM. Until now, examining lateral areas of the cortex with TMS—EEG has been restricted because of strong muscle artifacts. The methods described here can remove those muscle artifacts, allowing one to study lateral areas of the human brain, e.g., BA, with TMS—EEG.


Transcranial magnetic stimulation Electroencephalography Independent component analysis Enhanced deflation method Broca’s area 



The authors want to thank the Academy of Finland and Helsinki Biomedical Graduate School for funding. J.C. Hernandez also wants to thank CIMO (Centre for International Mobility) for the Finnish Government Scholarship grant and CONACYT (Consejo Nacional de Ciencia y Tecnologia) Mexico.


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Copyright information

© International Federation for Medical and Biological Engineering 2011

Authors and Affiliations

  • Reeta J. Korhonen
    • 1
    • 2
  • Julio C. Hernandez-Pavon
    • 1
    • 2
    • 3
    Email author
  • Johanna Metsomaa
    • 1
    • 2
  • Hanna Mäki
    • 1
    • 2
  • Risto J. Ilmoniemi
    • 1
    • 2
  • Jukka Sarvas
    • 1
  1. 1.Department of Biomedical Engineering and Computational Science (BECS)Aalto UniversityEspooFinland
  2. 2.BioMag LaboratoryHUSLAB, Helsinki University Central HospitalHUS, HelsinkiFinland
  3. 3.Department of Physical EngineeringUniversity of GuanajuatoLeonMexico

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