EEG and Schizophrenia
Florence GOMBERT, student in biomedical engineering, Université de Technologie de Compiègne, France. Hôpital Pitié-salpêtrière, CNRS, UMR 7593
Presentation planning • Laboratory presentation and themes • Theory of EEG and Event Related Potentials (ERP) • Material and Acquisition Chain • Signal processing and cartography • Experience • The P300 wave in schizophrenia • The others waves (N1, N2, P50)
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Laboratory and Team Presentation (1) • Research laboratory CNRS, UMR 7593 « Vulnerability, Adaptation et Psychopathology », P.Jouvent, Pitié-salpêtrière, Paris. • Theme « Cognition, Social Interaction, Modeling » • Understand how information is processed, perceived, memorized, transformed, returned, via investigative methods of medical imaging and functional cerebral exploration EEG and Schizophrenia
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Laboratory and Team Presentation (2) • Main study topic : Hedonia, and Addictions. affects” ” Hedonia : “Loss of emotional affects
• Study the steps of sensitive visual processing via electrophysiology records, and study sensitive waves
• Original research on the effect of contrast variation on hedonic judgment. Physical and social contrasted images
• On schizotypical persons, and control subjects EEG and Schizophrenia
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EEG and ERP: Theories (1) EEG • Hans Berger 1924 • Brain is the seat of biochemical and spontaneous electrical activity • Non invasive technique of direct measurement of electrical activity • Excellent temporal resolution (ms) • Chronology of mental operations and dynamic of cerebral phenomena • Spontaneous signal, noise EEG and Schizophrenia
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EEG and ERP: Theories (2) ERP • ERP : Event Related Potentials, induced by stimulations • Low amplitude / spontaneous brain activity (EEG) • Superposed on cerebral activity Need averaging (SNR). Should be repeated large times (10-100) No variations between repetitions.
• Analyze the methods organization of sensitive information processing • Allow a precise analysis of the time decline of different steps of information processing • Reflect activity of a large number of neurons EEG and Schizophrenia
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EEG and ERP : Theories (3) ERP
Stimulus
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EEG and ERP: Theories (3) ERP characteristics • Succession of negative and positive peaks • Characterized by latency and amplitude • Four kinds of components: - Cerebral trunk responses between 0 and 10 ms - middle latency, 10 and 50 ms, depend on stimulation characteristics - late latency potentials (LLP), very large. Distinction between :exogenous and endogenous potentials. EEG and Schizophrenia
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EEG and ERP: Theories (4) ERP characteristics Late Latency Potentials (LLP), very large. Distinction between: - exogenous potentials = compulsory response to stimulation, physical characteristics of stimuli - endogenous potentials = reflect cerebral structures activities, recognition of stimulus nature, of its signification. Decision taken, memorization. Change according to the context and the action to do.
Great interest in cognitive studies EEG and Schizophrenia
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Acquisition Chain (1) 3 components of electroencephalographic systems Stimulus presentation system Signal Amplification and digitalization unit Data Acquisition and processing system
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Acquisition Chain (2) Neuroscan: Acquisition via 64 electrodes: Quick-cap Pre-amplification unit: Head box Digital Amplification unit: Syn-Amps Acquisition and processing software : Scan 4.2 Stimulation Unit: STIM EEG and Schizophrenia
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Collection Quick-Cap: • 64 Detectors = cupules Ag/AgCl • 10-20 international system • Ionic-electric transduction • Conductor gel • Impedance < 5 Kohms • Reference electrode, situated where there is no signal (mastoid, or ears) • Calculate ddp / reference (uV) EEG and Schizophrenia
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Digital Amplification / Acquisition • Syn-Amps preamplifier and amplifier (10 000 to 100 000) • Scan 4.2 software – – – – – –
Acquire Filter Average Storage Data processing and analysis Cartography / Source localization
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Stimulation system • Stimulation presentation • Synchronize with the acquisition system, triggering To stim = To acquisition best latency calculation best average calculation
• Response Pad, quotation system, reaction time calculation
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Neuroscan Acquisition Chain
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Data processing (1) Preliminary Steps, ERP extraction • Baseline Correction, thanks to trigger • Artifact Rejection • Ocular move artifact Reduction • Average • Filter EEG and Schizophrenia
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Data Processing (2) Statistical Analysis Relation between EEG at different localizations
• Coherence/ Pearson Correlation • Cross Correlation / Intra cross correlation • Paired t-score / t-score • z-score
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Data Processing (3) Source localization, Cartography Answer the question where and when take place the steps of information processing in brain. •
Spatial filtering Importance
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Use global and local interpolation function
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Potential field map
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Estimation of sources number by singular decomposition filtering
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Precise Generators localization by inverse problem
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2D, 3D Cartography and spectral power EEG and Schizophrenia
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Cartography 2D, 3D 2D cartography ERP Topography Successive maps, and recording waveforms on electrode, give possibility to follow temporal evolution of chronological field activation of different generators Accuracy : ms
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Cartography 2D, 3D
Link activity to region Allow source localization
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Cartography 2D, 3D
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Stimulation Test / Experience Theme and hypothesis : Contrast and hedonic judgment •
Emotional perception could improve emotional images discrimination
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Visual Associative Cortex : - would be activated easier by emotional perception, - more activated by positive stimuli (Lane and al,1999; Lang and al 1998, Reiman and al 1997)
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Decrease of hedonic judgment with contrast reduction by non pathologic subject (previous experience)
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Contrast variation effects on schizotypical subjects?
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Consequences on P300 wave? EEG and Schizophrenia
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Stimulation Test / Experience Conditions •
180 stimulations (average optimization)
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Social and physical pleasure contrasted images
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Quotation of pleasure from 1 to 5
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Original test : different from usual draught board
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Presentation time : 1.5 s (spontaneous quotation, waves optimization)
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Variable interstimuli duration (5 - 6s) : (less blinking, no wait)
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Fixation point (avoid eyes sweeping) EEG and Schizophrenia
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Stimulation Test / Experience EEG box Quick-cap
Stimulation system
Preamplifier
Cap connector EEG and Schizophrenia
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P300 wave (1) • Positive wave 300ms after stimulation • Appear only when the subject is attentive or attracted by the stimulus (Hilliard and al.,1973; Donchin et Colles 1988) • Amplitude increase when the information is actively processed – P3a : fast and automatic processes – P3b : when there is a decision taking and response, when an information is detected between the items
• Complexity and valence increase P 300 amplitude. Not the latency. P3 = measure the spread in which our treatment system is activated EEG and Schizophrenia
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P300 wave (2) •
Important amplitude decreasing in schizophrenia (Ford et al.,1997)
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Perhaps significant increasing on the latency (Blackwood et al.,2001;Muir et al.,2001)
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Temporal and Frontal lobe structure contribute to P300 generation (Manuel et al.,2000)
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P 300 localized left superior temporal area for normal subject (Youn et al., 2003)
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Diversely distributed for schizophrenics (Youn et al., 2003)
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Significant reduction in left medial temporal area and left inferior parietal area (Youn et al., 2003) EEG and Schizophrenia
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The others waves • N1 reduced amplitude, not influenced by medication (Klosterkoetter et al., 2002.) • N2 – Amplitude decrease in the midline electrode – Delayed latency • P2 increased amplitude • P50 no reduction with the repetition of auditory stimuli (Freedman et al.,2001) EEG and Schizophrenia
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The others waves Can associate latency variation to schizophrenia syndrome (Bahramali et al.,2002.) – Disorganization -- delayed left hemisphere P200 and P300 latency; – Reality Distortion -- earlier global, midline and left hemisphere N200 latency; – Psychomotor Poverty – delayed posterior N 100 latency.
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Bibliography (1) EEG, ERP theory : • Cerveau et psychologie, Houdé, Mazoyer; Tzourio-Mazoyer; PUF, 2002
Elsevier publications: P300 • The symptom severity and P300 in patients with schizophrenia; Youn et al., 2003. • P300 amplitude as a possible correlate of frontal degeneration in schizophrenia; Manuel et al., 2000. • P300 lateral asymmetries in schizophrenics syndromes; Puri et al., 2000. • Interactive ERP recording increases the amplitude of the endogenous P300 peak in schizophrenia; G.W Price, 1999. EEG and Schizophrenia
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Bibliography (2) Elsevier publications: Others waves: • Visual feature conjunction in patients with schizophrenia : an ER brain potential study; Zipursky et al., 2001. • Late component ERP´s are associated with three syndromes in schizophrenia; Bahramale et al., 2002. • N100 in medicated and unmedicated patients with schizophrenia; Klosterkoetter et al., 2002. • Auditory feature conjunction in patients with schizophrenia, Zipursky an al., 2000. • Auditory gatings, FFTS, and plasma metabolites in schizophrenia; Freedmann et al., EEG and Schizophrenia
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Thanks and Questions…
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Acquisition (3) • 10 20 schema
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The others waves N100, ERP, ERPA, N100
idem, N100bis
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P300 wave (3)
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Acquisition Chain(2)
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