Slides from the talk Open Data Fest 3, Moscow

1. Neural networks in the
brain
Ilya Zakharov
Research associate
Developmental behavioral genetics lab
Psychological Institute
Russian Academy of Education

2. Neural networks

4. Networks on different levels.
Spikes

5. Networks on different levels.
Brain areas

6. Networks on different levels.
Electrophysiology

7. Neural coupling

8. Measures

9. Phase synchrony

10. Perfect synchronization
Synchronization with
time lag
No synchronization

11. Coherence coefficient
Coherence - the frequency domain
equivalent to the time domain cross-
correlation function.
*Phase Locking Value
Coherence for normalized Fourier-
transformed signals

12. Phase lag index
The PLI is a metric that evaluates the distribution of phase
differences across observations.
Stam et al., 2007
the PPC is computed from the distribution of all pairwise
differences (between pairs of observations) of the relative
phases.
Pairwise phase consistency
Vinck et al., 2010
Non-directed

13. Phase slope index
Granger causality
Computed from the complex-valued coherency, and
quantifies the consistency of the direction of the change
in the phase difference across. The sign of the PSI
informs about which signal is temporally leading the
other
Nolte et al., 2008
Directed
Represents the result of a model comparison. It is rooted in the autoregressive
modeling framework, where future values of time series are modeled as a
weighted combination of past values of time series. Specifically, the quality of an
AR-model can be quantified by the variance of the model’s residuals, and Granger
causality is defined as the natural logarithm of a ratio of residual variances,
obtained from two different AR-models.
Ding et al., 2006

14. Common reference problem
Bipolar referencing?

15. Common input problem
Partial out third input?
Granger causality?

16. Common source problem/
Volume conduction/field spread
Current source density?
Imanigary coherence?
Source localization?

17. Back to graph analysis

18. Back to graph analysis
Your suggestions?

19. References
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• Vinck, Martin, Marijn van Wingerden, Thilo Womelsdorf, Pascal Fries, and Cyriel M. A. Pennartz. “The Pairwise Phase Consistency: A Bias-Free Measure of
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• Ding, M., Chen, Y., & Bressler, S. L. (2006). 17 Granger causality: basic theory and application to neuroscience. Handbook of time series analysis: recent
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20. Thanks for your attention!
We are always ready to
cooperate!
iliazaharov@gmail.com