Konwersatorium im. J.Pniewskiego i L.Infelda

The evaluation of interactions between brain structures plays a central rolein understanding normal and pathological brain function. At present, a largebulk of evidence concerning the localization of active areas in the brain isavailable due to neuroimaging methods. However, much less is known aboutinteractions between them. The connectivity patterns in the brain may bedetermined by means of electroencephalographic (EEG) activity analysis,providing that adequate signal processing methods are applied. The mostappropriate methods involve multivariate autoregressive measures and, amongthem, Directed Transfer Function (DTF). Based on the Granger causalityprinciple, this measure exposes directed relations between brain structuresas a function of frequency, is robust in respect to noise, mitigates volumeconduction, can identify reciprocal interactions, and is free from the commondrive effect. Contrary to popular bivariate methods (e.g., correlation orcoherence), which are biased by spurious connections, it yields sparse,clear-cut functional connectivity patterns. In its time-varying form, DTFreveals dynamical interactions between brain structures. The applicationof DTF to motor and cognitive tasks and to the assessment of pathologicalbrain states will be presented. Moreover, the suitability of DTF for theanalysis of signals of different origins will be shown.

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