institute for human computer interfaces institute for computer graphics and vision wg1: theoretical...
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Institute for Human Computer InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical considerations
COST Meeting Istanbul 2005
Graz University of TechnologyBCI Lab
Graz UniversityApplied Neuropsychology
Institute for Human Computer InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical 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 InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical considerations
Current projects @ 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 InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical considerations
BIOSIGAn open source software
library for biomedical signal processing
http://biosig.sf.net
Institute for Human Computer InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical 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 InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical considerations
Institute for Human Computer InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical 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 InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical 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 InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical considerations
Viewing and Scoring Software
Institute for Human Computer InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical 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 InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical 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 InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical considerations
Coupling almost all the time in all frequencies !?
PDC (Hypothesis: PDC>0)
0
1
Subject K3Left hand
Institute for Human Computer InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical considerations
Coupling almost all the time in all frequencies !?
DTF (Hypothesis: DTF>0)
0
1
Subject K3Left hand
Institute for Human Computer InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical considerations
Event-related PDC (Hypothesis: PDC != ref)
Increases and decreases of coupling can be observed !
pdc<ref
pdc>ref
Subject K3Left handref=pdc(0-3s)
Institute for Human Computer InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical considerations
PDC (Hypothesis: PDC != ref)
Increases and decreases of coupling can be observed !
pdc<ref
pdc>ref
Subject K3Right handref=pdc(0-3s)
Event-related PDC (Hypothesis: PDC != ref)
Institute for Human Computer InterfacesInstitute for Human Computer Interfaces Institute for Computer Graphics and VisionInstitute for Computer Graphics and Vision
WG1: WG1: Theoretical considerationsTheoretical considerations
Future plans GDF Version 2.0 Improvement of automated quality
control and artifact processing. Statistical significance test for MVAR
parameters -> http://biosig.sf.net Improve visualization of MVAR results
-> http://biosig.sf.net Collaborations based on available
methods.