An Update on EEG Connectivity Metrics For Neurotherapists Thomas F. Collura, Ph.D., QEEGT November 6, 2009 (c) 2009 Thomas F. Collura, Ph.D., QEEGT.

Current Issues Resolve definition of metrics Associate metrics with function Use for assessment & diagnosis Use for training Use for evaluation of training results New insights re. function, disorders (c) 2009 Thomas F. Collura, Ph.D., QEEGT

The Purpose of Connectivity Training To reflect whole brain function Show relationship between two sites Reflect amount of information shared Reflect speed of information sharing Real-time recording or postprocessed Useful for assessing brain function Useful for training brain connectivity Takes us beyond amplitude training (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Measurement Example - Temperature We never measure “temperature” We do observe: Position of a column of mercury (“thermometer”) Deflection of a bimetal strip (dial indicator) Electrical potential (thermocouple) Electrical resistance (thermistor) Distribution of light energy (infrared spectrometry) Color of a substance (“mood ring”) Interpret in terms of a model & theory (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Similarity Example How similar are two people? Do they speak the same language? Can they wear the same clothing? Can they eat the same food? Can they use the same medicine? Can they play the same instruments? Do they enjoy the same music? Do they practice the same religion? (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Connectivity Measures Many ways to measure connectivity Always asking “how similar are the signals?” Relative Phase sensitive or insensitive Absolute phase sensitive or insensitive Amplitude sensitive or insensitive Measurement across time or across frequency Source of raw data –Waveform –FFT –Digital Filter (IIR or FIR) or JTFA (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Connectivity (coherence & phase) Coherence: Amount of shared information Phase: Speed of shared information Thalamocortical –Theta, Alpha, SMR Corticortical –Beta, Gamma Intrahemispheric – e.g. language Interhemispheric Fronto-frontal – attention, control occipito-parietal – sensory integration, aging (c) 2008 Thomas F. Collura, Ph.D.(c) 2009 Thomas F. Collura, Ph.D., QEEGT

Connectivity Measures - Summary Pure Coherence (is relative phase stable?) –joint energy / product of self-energies Synchrony Metric (do phase and amplitude match?) –Joint energy (real parts)/ sum of self-energies Spectral Correlation Coefficient (FFT amplitudes same?) –Correlation (across frequency) between amplitude spectra Comodulation (do components wax & wane together?) –Correlation (across time) between amplitude time-series Asymmetry –Relative amplitude between two sites Phase (is relative timing stable or same?) –Arctan of ratio of sin & cosine components Sum & Difference Channels (arithmetic comparison) –Simply add or subtract raw waveforms (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Connectivity Measures - Analogs Pure Coherence –How much is information being shared? Synchrony Metric –Are the sites locked together in time? Spectral Correlation Coefficient –Are the “walkie-talkies” on the same wavelength? Comodulation –Are the sites’ C/R cycles related to each other? Asymmetry –Is there a balance/imbalance of activation? Phase –How quickly is information being exchanged? Sum & Difference Channels –How similar or different are the sites in exact activity? (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Classical or “pure” Coherence Measure of phase stability between two signals – gets “inside” signals Wants them to be at the same frequency Doesn’t care about absolute phase separation Doesn’t care about relative amplitude Measures of amount of shared information Useful when sites have different timing Can use FFT or JTFA to calculate (c) 2009 Thomas F. Collura, Ph.D., QEEGT

“Training” Coherence/Similarity (BrainMaster) Similarity measure using Quad filters (JTFA) Measure of phase and amplitude match between two signals – gets “inside” signals Wants them to have zero phase separation Wants them to have same amplitude Useful for synchrony training Random signals will have low similarity Special case of coherence (“0 is a constant”) (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Spectral Correlation Coefficient (Lexicor) Measure of amplitude similarity in spectral energy – uses FFT amplitude data Wants two signals to have similar power spectral shape Completely ignores phase relationship Meaningful for a single epoch Random signals may have large correlation if spectra are similar (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Comodulation (Sterman/Kaiser) Measures similarity in amplitudes across time – classically uses FFT amplitude data Correlation between envelopes of two signals Completely ignores phase relationship Must be considered across time epoch Reflects how similarly signals wax and wane together Can be computed using digital filters Random signals will have low comodulation (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Phase measurement Various methods to compute Attempts to extract phase relationship using mathematical technique Stability and “wraparound” issues FFT or Quad Digital Filters Reflects how well signals line up in time Measure of speed of information sharing Useful for synchrony training (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Sum-channel Adds two signals together in time domain Gets “inside” signals Peaks and valleys reinforce in time Very sensitive to phase relationship Wants signals to be in phase Largest when both signals are large Useful for synchrony training Can uptrain coherence with sum-channel mode Random signals: sum & difference will look the same (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Difference-channel Same as bipolar montage Similar signals will cancel Emphasizes differences Useful for coherence downtraining Cannot uptrain coherence with bipolar Random (uncorrelated) signals: sum & difference signals will look the same (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Channel Sum & Difference The following animation shows the relationship between the phase of two signals and the amplitude of their sum and difference: sumphase4.avi (c) 2009 Thomas F. Collura, Ph.D., QEEGT

(c) 2008 Thomas F. Collura, Ph.D. Normal Distribution males vs. females Photo by Gregory S. Pryor, Francis Marion University, Florence, SC. From: (C. Starr and R. Taggart. 2003. The Unity and Diversity of Life. 10th Ed. Page 189.) (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Live Z-Scores Absolute Power (8 bands per channel) Relative Power (8 bands per channel) Power Ratios (10 ratios per channel) Asymmetry (8 bands per path) Coherence (8 bands per path) Phase (8 bands per path) Based on database of >600 subjects Based on age, eyes open/closed (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Z-Score Targeting Options Train Z Score(s) up or down –Simple directional training Train Z Score(s) using Rng() –Set size and location of target(s) Train Z Score(s) using PercentZOK() –Set Width of Z Window via. PercentZOK(range) –Set Percent Floor as a threshold Combine the above with other, e.g. power training (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Choice of sites Modular / Functional Approach (Walker et. al.) Functional Hubs (Demos / Thatcher) Symptom-based (Demos / Thatcher / Soutar / Brownback) Choice of “boxes” (Stark / Lambos / Rutter) (c) 2009 Thomas F. Collura, Ph.D., QEEGT

(c) 2007-9 T. F. Collura, Ph.D. Other Common Quads 1. F3 F4 P3 P4 – “Little Box” - General 2. F3 F4 C3 C4 – “Front Box” - Attention 3. C3 C4 P3 P4 – “Rear Box” - Perception 4. F7 F8 T5 T6 – “Big Box” - Assessment 5. C3 C4 Fz Pz – “Cross” – Motor strip (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Observations with LZT Cyclic normalization of power and connectivity Typical individual signatures Trainees respond to variations in challenge Brain capable of choosing which parameters to normalize Brain must explore functional boundaries Excessive freedom can produce abreaction (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Range Function Rng(VAR, RANGE, CENTER) = 1 if VAR is within RANGE of CENTER = 0 else Rng(BCOH, 10, 30) –1 if Beta coherence is within +/-10 of 30 Rng(ZCOB, 2, 0) –1 if Beta coherence z score is within +/-2 of 0 (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Range training with multiple ranges X = Rng(ZCOD, 2,0) + Rng(ZCOT, 2, 0), + Rng(ZCOA, 2, 0) + Rng(ZCOB, 2, 0) = 0 if no coherences are in range = 1 if 1 coherence is in range = 2 if 2 coherences are in range = 3 if 3 coherences are in range = 4 if all 4 coherences are in range Creates new training variable, target = 4 (c) 2009 Thomas F. Collura, Ph.D., QEEGT

PercentZOK() function PercentZOK(RANGE) –Gives percent of Z Scores within RANGE of 0 –1 channel: 26 Z Scores total –2 channels: 76 Z Scores total –4 channels: 248 Z Scores total Value = 0 to 100 Measure of “How Normal?” (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Z Score training using percent Z’s in target range Size of range window (UTHR - currently 1.4 standard deviations) Threshold % for Reward (CT: between 70% and 80%) %Z Scores in range (between 50 and 90%) % Time criterion is met (between 30% and 40%) (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Z-score based targeting Threshold replaced with target size Feedback contingency determined by target size and % hits required Eliminates need for “autothresholding” Integrates QEEG analysis with training in real time Protocol automatically and dynamically adapts to what is most needed Consistent with established QEEG-based procedures with demonstrated efficacy (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Live Z-Score Training Policy EEG deviation(s) should be consistent with clinical presentation(s) EEG normalization should be reasonable Consider coping, compensatory traits Consider “peak performance” traits Consider phenotypes & recommendations Monitor subjective and clinical changes (c) 2008 Thomas F. Collura, Ph.D.(c) 2009 Thomas F. Collura, Ph.D., QEEGT

Normalize using Live Z-Scores Excessive Frontal Slowing Excessive Beta or high beta Hypercoherence, not left hemisphere (F3- P3) Hypocoherence, not central (C3-C4) Localized (focal) excess or deficit (c) 2008 Thomas F. Collura, Ph.D.(c) 2009 Thomas F. Collura, Ph.D., QEEGT

Coping/Compensating Z-Scores Diffuse Low alpha – chronic pain (barrier) Diffuse high alpha –chronic anxiety coping mechanism Posterior asymmetries –PTSD, stress coping, cognitive dissonance Substance Abuse, Addiction –Effects of EEG normalization not well understood (c) 2008 Thomas F. Collura, Ph.D.(c) 2009 Thomas F. Collura, Ph.D., QEEGT

“Peak Performance” Z-Scores Left Hemispheric Hypercoherence( F3-P3) Central Intrahemispheric Hypocoherence (C3-C4) “Excess” SMR C4 “Excess” posterior alpha “Fast” posterior alpha Note: normalization can be avoided by keeping EEG sensors away from affected sites (c) 2008 Thomas F. Collura, Ph.D.(c) 2009 Thomas F. Collura, Ph.D., QEEGT

Phenotypes and Live Z-Scores Most Phenotypes “map” to live z-scores –Diffuse Slow –Focal Abnormalities, not epileptiform –Mixed Fast & Slow –Frontal Lobe Disturbances – excess slow –Frontal Asymmetries –Excess Temporal Lobe Alpha –Spindling Excessive Beta –Generally Low Magnitudes –Persistent Alpha –+ Diffuse Alpha deficit Exceptions: –“Epileptiform” (requires visual inspection of EEG waveforms) –Faster Alpha Variants, not Low Voltage (requires live z-score for peak frequency) Many phenotypes can be addressed via. LZT Training –Inhibits, rewards referenced to normal population or biased for enhance/inhibit Phenotypes do not (currently) consider connectivity deviations –Hypocoherent Intrahemispheric (L or R) –Hypercoherent Interhemispheric (e.g. frontal) –Diffuse Coherence / Phase Abnormalities (c) 2008 Thomas F. Collura, Ph.D. (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Summary Wide range of methods available Various perspectives on the concept of “similar” All have strengths and weaknesses Important to understand basis of each metric and its application to NF All have value Importance of normative data to interpret (c) 2009 Thomas F. Collura, Ph.D., QEEGT

Case of SL 7YO Male, discipline problem, AD/HD, easily excited, aggressive QEEG Pre and post z-score training 21 sessions between QEEG’s PercentZ training at 85% reward Begin F3 F4 P3 P4, later F3 F4 C3 C4 Begin at +/- 2.0 S.D. All scores except 1 within 1.5 S.D. after training Significant clinical improvement Data courtesy Drs. C. Stark & W. Lambos (c) 2008 Thomas F. Collura, Ph.D.(c) 2009 Thomas F. Collura, Ph.D., QEEGT

Summary Approaches to Brain Connectivity are proliferating Blending of QEEG and NF techniques Increasing symptom-based approach Exploring Brain’s ability to decipher FB General model of cyclic excitability and modulation of connectivity Opportunity for Brain to design its own strategy for normalization (c) 2009 Thomas F. Collura, Ph.D., QEEGT

An Update on EEG Connectivity Metrics For Neurotherapists Thomas F. Collura, Ph.D., QEEGT November 6, 2009 (c) 2009 Thomas F. Collura, Ph.D., QEEGT.

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An Update on EEG Connectivity Metrics For Neurotherapists Thomas F. Collura, Ph.D., QEEGT November 6, 2009 (c) 2009 Thomas F. Collura, Ph.D., QEEGT.

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Presentation on theme: "An Update on EEG Connectivity Metrics For Neurotherapists Thomas F. Collura, Ph.D., QEEGT November 6, 2009 (c) 2009 Thomas F. Collura, Ph.D., QEEGT."— Presentation transcript:

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