institute for human computer interfaces institute for computer graphics and vision wg1: theoretical...

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.