Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations COST Meeting Istanbul 2005 Graz University of Technology BCI Lab Graz University Applied Neuropsychology

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations BCI Lab Graz Gert Pfurtscheller Alois Schlögl Gernot Müller-Putz Clemens Brunner Bernhard Graimann Eva Höfler Claudia Keinrath Robert Leeb Reinhold Scherer Doris Zimmermann

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations Current BCI Lab  BIOSIG – An open source software library for biomedical signal processing  Multivariate Autoregressive modeling including COH, pCOH, PDC, DTF, ffDTF, etc.  Time-varying (non-stationary) analysis  Single-Trial classification  Quality control and artefact processing  Standardization of Biosignal processing

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations BIOSIG An open source software library for biomedical signal processing

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations Categories within BIOSIG  T100: Data Acquisition  T200: Data Formats  T250: Preprocessing (Trigger, Artifacts, etc.)  T300: Signal Processing  T400: Classification, Statistics  T490: Evaluation criteria  T500: Presentation, Output  T550: Topographic Mapping  T600: Interactive Viewer and Scoring

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations Automated artifact processing  Correction of EOG artifacts using regression analysis  Artifact detection  Overflow / Saturation detection  Detection of muscle artifacts with inverse filters  Corrupted sample values are encoded with „Not-a- number“ (NaN) and are skipped in the further analysis  Version 2.0 of GDF data format

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations Data storage  Support of all available dataformats  Combine best features of all formats in GDF  GDF 1.x  Derived from EDF, multiple data types, support of events/annotations/markers, overflow, Y2K,...  New Features of GDF 2.0  Gender, handedness, Weight, Height, Recording location (place), impedance and position for each electrode, etc.

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations Viewing and Scoring Software

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations Signal processing (I)  Autoregressive (AR) model  Burg, Levinson-Durbin, Lattice estimators  Adaptive Autoregressive (AAR) model  LMS, RLS, Kalman filtering  Multivariate Autoregressive (MVAR)  Nutall-Strand, Levinson, „multichannel Yule-Walker“, etc. ! All estimators are able to handle „missing values“ !

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations Signal processing (II)  Spectrum  Coherence (COH)  Partial coherence (pCOH)  Partial directed coherence (PDC)  Directed transfer function (DTF)  Full-Frequency DTF (ffDTF)  Directed coupling (DC)  Phase

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations Coupling almost all the time in all frequencies !? PDC (Hypothesis: PDC>0) 0 1 Subject K3 Left hand

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations Coupling almost all the time in all frequencies !? DTF (Hypothesis: DTF>0) 0 1 Subject K3 Left hand

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations Event-related PDC (Hypothesis: PDC != ref) Increases and decreases of coupling can be observed ! pdc<ref pdc>ref Subject K3 Left hand ref=pdc(0-3s)

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations PDC (Hypothesis: PDC != ref) Increases and decreases of coupling can be observed ! pdc<ref pdc>ref Subject K3 Right hand ref=pdc(0-3s) Event-related PDC (Hypothesis: PDC != ref)

Institute for Human Computer Interfaces Institute for Computer Graphics and Vision WG1: Theoretical considerations Future plans  GDF Version 2.0  Improvement of automated quality control and artifact processing.  Statistical significance test for MVAR parameters ->  Improve visualization of MVAR results ->  Collaborations based on available methods.