Measures of connectivity among the different brain areas during an attention task.

The functional connectivity of the brain is investigated through the study of multivariate autoregressive models (MVAR) applied to multichannel EEG recordings. After the identification of the model, different indices can be calculated that are able to quantify direct and indirect functional connections between cortical areas. These methodology is used for the investigation of possible connectivity alterations in patients after Traumatic Brain Injury (TBI) who suffered from Diffuse Assonal Injury (DAI). As one of main consequences of DAI are cognitive and attention impairment, the subjects underwent an attention test (Conners CPT) during EEG recording. In order to avoid spurious coherences, related to the volume effect of the head, a Laplacian transformation was applied to the data before connectivity evaluation. The MVAR was fitted to the different phases of the test and different indices were calculated. Even if the general connectivity is not different between patients and controls, differences were found in inter hemispheric connectivity. Both in beta and in gamma bands central electrodes C3 and C4 seem the main sources of activity that is directed mainly towards Fp1 and Fp2. Such connectivity is less intense in DAI subjects.