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COST Meeting Istanbul 2005

Graz University of TechnologyBCI Lab

Graz UniversityApplied Neuropsychology

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BCI Lab Graz

• Gert Pfurtscheller

• Alois Schlögl

• Gernot Müller-Putz

• Clemens Brunner

• Bernhard Graimann

• Eva Höfler

• Claudia Keinrath

• Robert Leeb

• Reinhold Scherer

• Doris Zimmermann

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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

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BIOSIGAn open source software

library for biomedical signal processing

http://biosig.sf.net

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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

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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

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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.

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Viewing and Scoring Software

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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“ !

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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

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Coupling almost all the time in all frequencies !?

PDC (Hypothesis: PDC>0)

0

1

Subject K3Left hand

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WG1: WG1: Theoretical considerationsTheoretical considerations

Coupling almost all the time in all frequencies !?

DTF (Hypothesis: DTF>0)

0

1

Subject K3Left hand

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Event-related PDC (Hypothesis: PDC != ref)

Increases and decreases of coupling can be observed !

pdc<ref

pdc>ref

Subject K3Left handref=pdc(0-3s)

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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)

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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.