Intertrial coherence and causal interaction among independent EEG components

Over the past few years there has been an increased interest in studying the underlying neural mechanism of attention and cognitive brain activity. This paper aims towards identifying and analyzing distinct responses in an auditory working memory paradigm, as independent components with variable latency, frequency and phase characteristics. The event-related nature of components (either phase or non-phase-locked) over multiple trials is thoroughly examined through intertrial coherence measures. Furthermore, the functional coupling of independent components is investigated through the concept of partial directed coherence depicted as a directed graph. Using these tools, the paper compares issues of activation, connectivity and directionality in the synchronization maps of two populations, of control and Alzheimer's subjects. The results on real data from an oddball experiment verify and further enhance the findings of previous studies and illustrate the potential of the proposed analysis framework.

Research highlights► We present a complete framework for studying even related brain dynamics. ► For this purpose an auditory oddball experiment (P300 response) is used. ► We introduce measures for the evaluation of the phase-related nature of components. ► We use the PDC measure to consider the dynamic synchronization of components. ► The synchronization graph of evoked and induced components is thus derived.