International Conference on NonLinear Theory and its Applications NOLTA2004

1
International Conference on NonLinear Theory and
its Applications NOLTA2004

• Macroscopic Manifestation of
• Neural Connectivity in EEG Signals
• Cristian CARMELI, Oscar DE FEO, Giorgio INNOCENTI
• 30 November 2004

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Outline

• Why and How do neurons cooperate?
• The Binding Problem
• Assessment of cooperative activity
• Synchrony
• Its Drawbacks
• Alternative approach
• Application to EEG signals
• Results
• Conclusions

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A Simple Example The Visual Pathway
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• The Binding Problem
• Binding is the process responsible for
  functionally linking the distributed activity of
  large neuronal populations.
• Problem identification of the mechanisms of such
  process.

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The Traditional Binding Solution

• Cooperativeness
  Synchronous Activity
• Interactions Synchronization

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The Common Synchronization Measures

• Correlation, Spectral Coherence, Mutual
  Information, Phase Synchronization, etc.
• Widely applied
• Limitations
• They address bivariate measures
• They are symmetric
• Weak or non-synchronizing interactions may not be
  observable

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An Alternative Approach

• The cooperation among neuronal assemblies is
  simpliciter given by interactions that
• not necessarily imply synchronization.
• A new method to assess the functional
  interactions (connectivity) among multiple
• measurements
• Today at 1630, Room D
• Session Tu4-D Nonlinear Time Series Analysis
• Identifying Dependencies among Multivariate Time
  Series
• Oscar DE FEO, Cristian CARMELI

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Brief Description of the Method

• Hp. 1. Brain as a network of weakly interacting
  dynamical oscillators
• 2. A local oscillator behind each
  measurement
• The method proceeds along two steps
• Local self-model identification
• Linear modeling of the interactions by
  cross-relation of all the measurements to the
  dynamics unjustified by the local models

TODAY 16.30 ROOM D
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Proposal

• Application of the method to high density EEG
  signals induced by visual stimuli

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Experimental Framework
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Previous Analyses

• 70-71
  
  84-90

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Result
71
84
84
71
70
90
90
70
71
70
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Conclusions

• The result emphasizes the complexity of the
  changes in the macroscopic manifestation of
  functional connectivity induced by very simple
  stimuli
• First step toward the assessment of the
  macroscopic manifestation of functional
  cortico-cortical connectivity
• The study on more subjects is needed