Transmission of Brain Activity During Cognitive Task

Abstract

The transmission of brain activity during constant attention test was estimated by means of the short-time directed transfer function (SDTF). SDTF is an estimator based on a multivariate autoregressive model. It determines the propagation as a function of time and frequency. For nine healthy subjects the transmission of EEG activity was determined for target and non-target conditions corresponding to pressing of a switch in case of appearance of two identical images or withholding the reaction in case of different images. The involvement of prefrontal and frontal cortex manifested by the propagation from these structures was observed, especially in the early stages of the task. For the target condition there was a burst of propagation from C3 after pressing the switch, which can be interpreted as beta rebound upon completion of motor action. In case of non-target condition the propagation from F8 or Fz to C3 was observed, which can be connected with the active inhibition of motor cortex by right inferior frontal cortex or presupplementary motor area.

Application of directed transfer function and network formalism for the assessment of functional connectivity in working memory task

“…This kind of deterministic structure of brain activity should have an impact on functional connectivity, so a random or barely distinguishable from random connectivity structure reported in some works may be considered as a surprising phenomenon. When multivariate robust measures of connectivity are used a clear picture of functional connectivity emerges [19,20,24,25,27,28,51].…”

Brain connectivity measures: computation and comparison

“…An example of unfaithful connectivity pattern avoiding to show many more connected links, where selected-marked connections could be determined as desirable ones, is shortly reviewed here (reproduced from [19], Figure 9). Without getting involved in the nature of the experimentation with cognitive modeling by connectivity patterns, we briefly touch their technical elements.…”

“…Differential diagrams alone are insufficient, since large/verylarge can become small/negligible, thus inappropriately reflecting reality. For example, the Figures 11 and 12, which are reproduced from [19], show connectivity matrices with 400 frequency distributions, each ranging in the 0-40 Hz interval, from which the conclusions http://www.epjnonlinearbiomedphys.com/content/1/1/2 on connectivity patterns related to cognitive states, i.e. "memory" versus "reasoning" tasks are "deduced", as presented in Figure 9.…”

“…In the cited articles, dynamic spectral behavior is nowhere mentioned in measure comparison considerations, but it is modestly present in some examples of brain connectivity modeling -illustrating PDC applicability to the analysis focused on specific event -details in [2,3]; also, in [19] authors recently started using matrices of spectrogram distributions instead of matrix distributions as in Figure 1. Comparison of PDC and DTF as in here analyzed articles, shows no concerns related to spectral stability /spectral dynamics and comparison results.…”

The DECIDE Science Gateway

“…• GridEEG [12][13][14]: based on a comparison of pathological versus normal subjects, implements EEG processing algorithms with the aim of detecting early symptoms of AD and distinguishing different forms of degenerative impairment.…”