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Neural Correlates of Cognitive Performance

Conjunct COST B27 and SAN Scientific Meeting, Swansea, UK, 16-18 September 2006. Neural Correlates of Cognitive Performance. M. Doppelmayr, W. Klimesch.

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Neural Correlates of Cognitive Performance

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  1. Conjunct COST B27 and SAN Scientific Meeting, Swansea, UK, 16-18 September 2006 Neural Correlates of Cognitive Performance M. Doppelmayr, W. Klimesch The brain is a complex of widely and reciprocally interconnected systems and the dynamic interplay of neural activity within and between these systems is the very essence of brain functionMountcasle 1979

  2. Overview • Brief definition of the terms „Cognitive Performance“ and „Neural correlates“ • Structural differences • ERP-Results • Differences in Power (Amplitude) and Alpha-Peak-Frequency (IAF) • Difference in the amount of the ERD in the Upper Alpha and Theta band Neural Efficiency Hypothesis, Inhibition Hypothesis • Conclusions • Preview Overview Definitions Structural Differences ERP Power ERD Neuronale Effizienz vs. Inhibition Hypothesis Conclusion Preview

  3. Cognitive Performance Intelligence, Working Memory Processes, Memory in general Most results focussing on the relation between intelligence and EEG are based on typical intelligence tests as LGT 3 (Bäumler), CFT-3 (Cattell und Weiss 1971), IST-70 (Amthauer 1970), IST-2000 (Amthauer et al. 1999), RAVENS (RAVEN 1998), WILDE Intelligence Test (Jäger und Althoff 1994) or subtests of these and similar tests or different parameters of memory capacity Baddeley A. (2003)Working Memory System: Tulving E.: (1983)Elements of episodic Memory: semantic vs. episodic memory Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview

  4. Structuraldifferences Number / Volume of gray or white matter as measured by means of CT, MRI, Lesion- studies Post mortem etc. Differences in the activity of neurons or cortical areas EEG, MEG, ECGfMRI, NIRSPET, SPECT „Neural Correlates“ Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview

  5. gray matter white matter template template Structural Differences • Total brain volume correlates positive with general intelligence (g).Gignac et al. (2003) r = 0.40. Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview • Haier et al. (2004) Sig. Correlationen of gray and white matter with WAIS (full scale FSIQ).More pronounced positive correlation with gray matter, with strongest effects at frontal, temporal and occipital areas N = 47

  6. µV time Intelligence related differences in neural (EEG) activityCorrelation: String length of ERP and intelligence (WAIS) (Review Batt et al. 1999) Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview VIQ P = passive listening, AN Active response - NON targets AT Active response - targets PIQ

  7. ERPs String length Powerspektra Coherence Amplitude Amplitude/Power Coherence time Frequency ERDERSWavelets Source Localization Phase-Locking Changes in amplitude time Different methods for analysis Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview

  8. µV µV time time ERP Resultsusually stimuli without specific meaning are presented In general ERP- latencies are shorter for more intelligent subjects Jausovec & Jausovec (2000) Widaman et al. (1990)Johnson et al. (1995) ERP components have higher amplitudes in more intelligent subjects Doppelmayr et al. (2000) Gevins & Smith (2000)Stauder et al. (2003)

  9. Intelligenz-Struktur-Test Amthauer, R. (1970). Complete a sentence Find a correct word Analogies Find similarities Calculation task Complete a number sequence Figure - template matching Mental rotation task Memory task Lern-u. GedächtnistestBäumler, G. (1974). Learn and recalla Mapturkisch vocablesobjectstelephone numbersspecific signs Alpha Power (Amplitude)and intelligenceDoppelmayr 2002 AmplitudePower • 3 min rest with eyes closed • IQ test followed EEG recording • 74 Vpn out of 89 Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview

  10. Power µV2 Lower- 1Lower-2Upper AlphaAlpha Alpha P4 High IQ P3 5 10 15 P4 Low IQ P3 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Hz More intelligent subjects exhibited a significantly higher alpha power (6-12 Hz) Doppelmayr et al. (2002) Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview Similar results have been reported by Klimesch et al. 1990, 1993, 2000 und Vogt et al.1998with respect to memory performanceSchmid et al. 2002: Alpha Bandpower FSIQ WAIS r = 0.38, p<0.0001. Anokhin & Vogel 1996

  11. LGT-3 IST-70 0.5 0.4 0.3 0.2 0.5 0.4 0.3 0.2 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Correlations of IQ-scores with alpha band power, depending on test specifity Lower- 1Lower-2Upper AlphaAlpha Alpha Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview Doppelmayr et al. (2002) IQ-tests based on attention and STM abilities show positive correlations with powerestimates in all three alpha-bands Tests addressing selectively semantic memory, correlate positively only with upper alpha power

  12. Neural activity during actual cognitive performanceOrigin of the neural "efficiency hypothesis“ Haier et al. (1988) VpIQ- Vp IQ+ Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview PET-Scans micromol/glucose/100g brain tissue/minute Negative correlation of PET activity and RAMP – Scores no topographically restricted effects

  13. ERD-calculation Pfurtscheller & Aranibar 1977 Stimulus 1 Sek Rawdata Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview Filtered data 10-12 Hz Reference Test Rectified (or squared) Average Amplitude 7,5µV 2,5µV 4,0 µV e.g. 65,7 % 45,2 % ERD 100 50 0 -50 -100 Desynchronisation Decrease Synchronisation Increase Pfurtscheller & Aranibar (1977)

  14. Functional relevance of frequency bands (Klimesch W. 1996, Klimesch W. et al. 1998, 1999, Doppelmayr et al. 1997,1998,2000) 0 2 4 6 8 10 12 14 16 18 20 Hz Direction of changes during activation Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview ThetaAmplitude-increase EpisodicMemory Working Memory Processes Lower-1 Alpha Amplitudedecrease phasic alertness Lower-2 Alpha Amplitudedecrease reflects expectancy Upper Alpha Amplitudedecrease SemanticMemory stimulus related processing.

  15. Theta Range Average Performance WeakPerformane HighPerformance Alpha Range ERS 70% Average performance Weak performance 20% 40% High performance 30% Power µV ERD 80% 60% 30% Power µV Referenz Referenz Test Referenz Test Test Referenz Referenz Referenz Test Test Test Klimesch et al. 2001 Model of Klimesch (1997,1999) Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview

  16. Stronger activity(Model proposed by Klimesch) Subjects with better memory performance exhibited a significantly stronger upper alpha ERD (=MORE ACIVATION) during semantic memory paradigms (Klimesch et al. 1997a,b, 1998…) Less activity Neural efficiency In a sentence verification task subjects with higher IQ scores exhibited a weaker upper alpha ERD (LESS ACTIVATION).Neubauer et al. 1995, Jausovec 1998 Conflicting theories about the amount of activity during task solving Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview Neubauer et al., 1995 Modified according Klimesch et al. 1997

  17. Ref WS Onset TASK RT BLANK 2 0,5 1 2 to 60 Sek 8 Sek ERD changes during solving of Raven matricesDoppelmayr et al 2005 • 29 Subs. (6M, 23F) • Rest: 2 Min. • RAVEN SPM Intelligence-Test 60 Items – EEG recording • Rest: 2 Min. • Comparing Raven Scores to CFT-3 intelligence test; Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview Analysis-intervall 2 Sek. in the middle of the response time. Easy/difficult according to individual response timeonly correct answers analyzed ERD according to ITV method CFT-3 test scores correlated with the number of correctly solved RAVEN items r = +0,65 Total = 119, IQ+ = 129, IQ- = 109 RAVEN: IQ+ 51 correct, IQ- 43 correct

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  20. Results RAVENs 3-fakt. ANOVA IQ X TASK X LOC Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview IQ F(1,27)= 10.95; p < 0.01 LOC F(4,108) = 8,71; p<0.001 IQ X TASK F(1,27)= 7,32; p < 0.05 LOC F(4,108)= 8,26; p < 0.001 Upper Alpha more pronounced ERD IQ- easy tasks IQ+ difficult tasks Thetamore pronounced Theta ERS for IQ+

  21. RAVENs-Results • Theta:The neural efficiency hypothesis is insufficient to explain the results observed in the theta band because IQ+ showed significantly more activation (ERS). • Upper Alpha:For the upper alpha band the neural efficiency hypothesis is valid only for easy tasks, not for tasks that are cognitively more demanding. Those matrices that are easy to solve, only by means of matching processes, but without any specific strategy can be explained by the neural efficiency hypothesis (weaker activation for IQ+). • The fact that upper alpha is related to semantic memory might be a possible explanation for this contradictory findings (neural efficiency vs model of Klimesch). Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview

  22. (Upper) Alpha Inhibition Hypothesis • If for a specific task, semantic processing is required, then subjects with high IQ will show a more pronounced ERD = more activity (thus, in this case the neural efficiency hypothesis is incorrect) • If, on the other hand, semantic processing is NOT necessary, thus, an activation of upper alpha useless or contraproductive, then this frequency band (upper alpha) will be inhibited or less activated by subjects with better performance (low ERD oder higher ERS – no difference to neural efficiency hypothesis). Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview

  23. TIME (ms) Warning Signal 500 Hz, 500 ms 0 ms 1000 ms 3000 ms 8000 ms 2 Sek. Analysis intervall max. 1 Min. later Reaction 68000 ms 7000 ms Inter-Trial-Intervall ERD in a verbal- semantic task:AnalogiesDoppelmayr et al. 2005 Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview 67 items of IST-2000 and WIT 34 Vpn (out of 50) ERD according to ITV basis CFT-3 Median Split to divide IQ+/IQ- IQ+ 50 correct, IQ- 45 correct CFT- 3 and number of correct answers r=0,49, p<0.05

  24. Results verbal-semantic 3-fakt. ANOVA IQ X LOC X HEMISPHERE Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview IQ F(1,32)= 4,17; p < 0.05 HEMI F(1,32) = 16,5; p<0.001 LOC F(3,96)=11,86; p<0,001 LOC F(3,96)=11,86; p<0,001 IQ X HEMI F(1,32)=5,97, p<0,05 More activity (neg ERD = ERS)for IQ+ for the left hemisphere More activity (positive ERD) for IQ+ in the left hemisphere

  25. Summary of the „Inhibition Hypothesis“ • If, and only if, upper alpha activation is necessary and relevant for the solution of a given task, subjects with high IQ show a stronger activation in the relevant brain areas. • If, on the other hand, upper alpha band is unrelevant, subjects with high IQ will actively inhibit this band (or at least show a weaker activation) Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview

  26. Neural Efficiency Hypothesis is: contradicted in the theta band and insufficient in the alpha band because: • 1) In the theta-frequency band a stronger activation (ERS) has been reported repeatedly for more intelligent subjects. • 2) In the upper alpha band in several (but not all) cases a stronger activation has been reported for subjects with better performance (IQ+ or M+) • 3) The neural efficiency hypothesis, thus, has been contradicted for the theta band, and proofed useful in the upper alpha only if no semantic memory processes were required. Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview

  27. General Summary • Studies focussing on structural differences according to intelligence („g“) yielded positive correlations between several brain areas, more pronounced for gray, as compared to white matter. • ERP-results indicated that latency is negatively and amplitude of several components positively correlated with intelligence • EEG-Power and IAF (individual alpha frequency): In general subjects with higher IQ-scores (or memory performance) exhibited higher power and a faster IAF. • ERD-Results: Alpha: If the alpha band is of functional relevance for the requested task (semantic content), participants with higher performance (IQ) show a stronger activation (Model Klimesch). Contrary, if this frequency band is not relevant IQ+ subjects will show a weaker activation – or inhibition (inhibition hypothesis).Theta: Subjects with higher performance show a stronger activation of the theta frequency as indicated by a stronger ERS. Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview

  28. Preview • Several remaining questions:EEG / fMRI combinedSource LokalisationPartial or directed CoherencePhase-Locking • Possible applications in NeurofeedbackHanslmayr et al. (2005)Klimesch, Sauseng, Gerloff (2003)Stroke patients Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview

  29. Thank you for your attention Overview Definitions Structural Differences ERP Power ERD Neuronal Efficiency vs. Inhibition Hypothesis Conclusion Preview Acknowledgements:P. Sauseng, W. Gruber, K. Hödlmoser, W. Stadler, T. Pecherstorfer, R. Freunberger, S. Hanslmayr

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