Real-Time Subject-Independent Pattern Classification of Overt and Covert Movements from fNIRS Signals

PLoS One. 2016 Jul 28;11(7):e0159959. doi: 10.1371/journal.pone.0159959. eCollection 2016.

Abstract

Recently, studies have reported the use of Near Infrared Spectroscopy (NIRS) for developing Brain-Computer Interface (BCI) by applying online pattern classification of brain states from subject-specific fNIRS signals. The purpose of the present study was to develop and test a real-time method for subject-specific and subject-independent classification of multi-channel fNIRS signals using support-vector machines (SVM), so as to determine its feasibility as an online neurofeedback system. Towards this goal, we used left versus right hand movement execution and movement imagery as study paradigms in a series of experiments. In the first two experiments, activations in the motor cortex during movement execution and movement imagery were used to develop subject-dependent models that obtained high classification accuracies thereby indicating the robustness of our classification method. In the third experiment, a generalized classifier-model was developed from the first two experimental data, which was then applied for subject-independent neurofeedback training. Application of this method in new participants showed mean classification accuracy of 63% for movement imagery tasks and 80% for movement execution tasks. These results, and their corresponding offline analysis reported in this study demonstrate that SVM based real-time subject-independent classification of fNIRS signals is feasible. This method has important applications in the field of hemodynamic BCIs, and neuro-rehabilitation where patients can be trained to learn spatio-temporal patterns of healthy brain activity.

MeSH terms

  • Biofeedback, Psychology
  • Brain-Computer Interfaces*
  • Humans
  • Movement*
  • Spectroscopy, Near-Infrared / methods*

Grants and funding

Funded by Deutsche Forschungsgemeinschaft (DFG BI 195/59-1, DFG BI 195/56-1 and DFG 195/65-1); the Badenwürttemberg-Singapore Life Sciences Grant; the INDIGO research grant from the European Union and India; FP7-ICT-2009-258749 - CEEDs: The Collective Experience of Empathic Data Systems; FP7-ICT-2009-247935 – BETTER: BNCI-driven Robotic Physical Therapies in Stroke Rehabilitation of Gait Disorders; and the Centre for Integrative Neuroscience (CIN) (PP 2012-16).