LAUSR

Background Information processing in the brain involves the synchronization of brain structures realized by the transmission of rhythmic activity. The aim of our work was to find connectivity patterns between brain structures during the same mental activity performed during tasks with different stimuli modality. Material and methods The task: the paradigm of linear syllogism was performed with visual (12 subjects) and auditory stimuli (29 subjects). The EEG activity transmission was analyzed by means of the short-time Directed Transfer Function (sDTF), a frequency dependent estimator of directed coupling between time series based on the Granger causality principle. Results and conclusions The obtained patterns showed similar coupling for both modalities involving EEG propagation mainly between the frontal and posterior areas which communicated intermittently. Our results indicate that the fronto-parietal network operated mainly in the theta frequency range as well as in other frequency ranges, especially gamma. By means of the assortative mixing approach, the strengths of coupling between the regions of interests (ROIs) were determined. For both modalities, the results showed stronger coupling within the ROIs than between them in agreement with the theories considering information transfer efficiency and metabolic energy savings. The patterns differences were minor and concerned stronger propagation from the posterior electrodes towards the frontal ones during the visual task and from the temporal sites to the frontal ones during the auditory task, which can be explained as bottom-up communication from specific sensory sites. Our results support a modality-free process of information retrieval and integration in a reasoning task.