Victor Babes UNIVERSITY OF MEDICINE AND PHARMACY TIMISOARA

“Victor Babes” UNIVERSITY OF MEDICINE AND PHARMACY TIMISOARA DEPARTMENT OF MEDICAL INFORMATICS AND BIOPHYSICS Medical Informatics Division www. medinfo. umft. ro/dim 2004 / 2005

BIOSIGNAL PROCESSING. NON-PERIODICAL SIGNALS. COURSE 8

1. EEG SIGNAL

• 1. 1. EEG SIGNAL ELEMENTS: • a) TYPICAL WAVES: – DELTA : 0. 5 - 3 Hz • large; in pathological states, normal in babies only – THETA : 4 - 7 Hz • large amplitude, dominant in some sleep stages – ALPHA : 8 - 12 Hz • medium amplitude, normal in relaxed brain, originating in occipital area – BETA : 13 - 30 Hz (18 - 22) • small amplitude, associated with brain activity, typical for frontal areas

• b) TRANSITORY ELEMENTS • PEAK - WAVE COMPLEX (pathological) • ARTIFACTS: blinking, ECG, EMG etc • c) RECORDING TYPES • SPONTANEOUS SIGNAL – AWAKE – ASLEEP • EVOKED POTENTIALS

1. 2. ANALYSIS METHODS CLASSIFICATION a) ELEMENTARY METHODS • • • TEMPORAL FREQUENTIAL PARAMETRICAL b) INTEGRATIVE METHODS • PATTERN RECOGNITION • SYNTACTIC ANALYSIS c) EVOKED POTENTALS

1. 3. TEMPORAL ANALYSIS a) AMPLITUDE ANALYSIS - histograms – low / normal / high amplitude (voltage)

Amplitude Histogram

• b) INTERVAL ANALYSIS - level crossing – zero crossing • c) AMPLITUDE / INTERVAL - areas • d) SEQUENTIAL ANALYSIS – peak-to-peak

e) CORRELATION FUNCTION – shows the potential source – inter-correlation or self-correlation (auto-correlation)

1. 4. FREQUENTIAL ANALYSIS • SIGNAL REPRESENTATION: – TEMPORAL Ampl = f (time) – FREQUENTIAL (spectrum) Ampl = f (freq)

Examples: 1 Hertz sine signal and its spectrum

A 2 Hz signal

Mixed signals

• b) FILTER ANALYSIS • BAND - PASS FILTERS ( d, q, a, b ) • WAVES PROPORTIONS - mingographs • c) FOURIER ANALYSIS • Definition: SIGNAL DECOMPOSITION INTO FREQUENCIAL COMPONENTS • Domain: 0 - 30 Hz • Types of spectra: – AMPLITUDE – POWER (proportional to A 2)

• c) SPECTRAL RESOLUTION – DEFINITION: distance between two neighbour points in the spectrum – RELATION WITH EPOCH LENGTH (recorded signal duration, in seconds) D f = 1 / D T (5) • d) TIME CONSTANT • e) TESTS FOR SIGNALS – STATIONARITY, NORMALITY AND TREND TESTS

• g) TRANSITORY PHENOMENA DETECTION • SPIKES CONTRIBUTION IN SPECTRA • MOBILE WINDOW METHOD (BERG)

• h) GRAPHICAL REPRESENTATIONS • CURVES, HISTOGRAMS • BICKFORD REPRESENTATION (time course) • i) OTHER FREQUENTIAL ANALYSES • • • WALSH, HAAR, ZERO CROSSING KALMAN RECURSIVE FILTERING CONVOLUTION FUNCTION

Bickford Reprezentation

1. 5. PARAMETRIC ANALYSIS • a) STOCHASTIC PARAMETERS • PEAKS NUMBER AND INTENSITY • STATISTICAL PARAMETERS (m, s) • b) HJORTH PARAMETERS • • • ACTIVITY - amplitude MOBILITY - frequency ( 1 st derivative) COMPLEXITY - frequency variations (2 nd derivative)

• 1. 6. PATTERN RECOGNITION

• 1. 7. SYNTACTIC ANALYSIS • SHORT EPOCHS (non-stationary) • EPOCHS LABELING • SIGNAL = LABELS SEQUENCE (sentence) • 1. 8. EEG MAPPING • 16 -108 ELECTRODS • INTERPOLATION METHODS • TYPES OF MAPS: – AMPLITUDE / POWER – FREQUENCY – HJORTH PARAMETERS, ETC

1. 9. EVOKED POTENTIALS • a) TYPES OF STIMULATION: – IN STANDARD RECORDINGS • • • OPEN / CLOSED EYES HYPERVENTILATION STROBOSCOPIC LIGHT – IN EVOKED POTENTIAL RECORDINGS • • • VISUAL PATTERNS (chessboard like) AUDITORY STIMULI SOMATIC STIMULI

1. 9. EVOKED POTENTIALS

b) EVOKED POTENTALS DETECTION • VERY SMALL AMPLITUDES (2 -5 m. V compared with 50 -100 m. V ground) • AVERAGING METHOD – RANDOM SIGNAL MEAN = 0 – REPEATED STIMULATIONS – EPOCHS SUPERPOSITION • RANDOM STIMULATION

Evoked potential extraction by “averaging”

1. 10. BIOFEEDBACK • a) RHYTHM ADAPTATION • b) STATE ADAPTATION ? ? ? • c) Extension of relaxation procedures: a - band pass filter background modulated mild sound intensity controlled by a waves amplitude self-control training therapeutical effects

2. OTHER BIOSIGNALS

• 2. 1. NEUROMUSCULAR INVESTIGATIONS – EMG (electro-myography) – NCV (nervous conduction velocity) • 2. 2. RESPIRATORY INVESTIGATIONS – SPIROGRAPHY – VENTIALTION TESTS

• 2. 3. EXERCISE TESTS – MULTIPLE SIGNAL • 2. 4. PLETISMOGRAPHY – MULTIPLE SIGNAL – COMPLEX INVESTIGATION • 2. 5. CARDIOVASCULAR EXPLORATION – PHONOCARDIOGRAPHY – RHEOGRAPHY

• 2. 6. SENSE ORGANS INVESTIGATIONS – RETINOGRAMS – AUDIOGRAMS • 2. 7. ULTRASONOGRAPHY – a) ECHO SIGNALS • SYSTEMS : A, B, M • ECHOCARDIOGRAPHY • PHOETAL ULTRASONOGRAPHY – b) DOPPLER SIGNALS

2. 8. EXTRAVERBAL COMMUNICATION • GAIT ANALYSIS – WALKING PATTERNS • WRITING / DRAWING • GESTURE – POSITION MAPPING

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