EFFECTIVE CONNECTIVITY OF THE AGING BRAIN
Bálint File1, 2, 3, Brigitta Tóth1, Zsófia Kardos1, Roland Boha1, István Ulbert1, 2, Zoltán Somogyvári3, Márk Molnár1
Neural interactions between brain regions were modeled by the strength and direction of the information propagation. A common consequence of these models was to characterize aging as the functional disconnection of distant brain regions. However, previous methods to characterize information propagation based on EEG signals limited the understanding of the neural interactions by assuming predominantly unidirectional connections and negligible circular causality. In the current study, we applied Sugihara causality on resting-state EEG data to demonstrate the changes of the unidirectional causal interactions alongside with the circular connections in the aging brain. Eyes closed resting-state EEG was recorded in young (N=22; mean age= 22.4 ±3.1) and elderly (N=19; mean age= 66.3 ±3.9) healthy subjects. Causality was estimated between the reconstructed cortical signals in theta (4-8 Hz), alpha1 (8-10 Hz), alpha2 (10-13 Hz) and beta (13-30 Hz) frequency bands. Balance of the unidirectional and circular connections, and distance-dependence of the causality were compared between the two age groups. The circularity of the connections was increased (along with the decrease of unidirectionality) in the elderly in alpha2 band. Causality was decreased by distance, and this effect was stronger in the elderly compared to the young in alpha1 and alpha2 bands. These findings suggest that frequency specific diminish of long-distance connections are accompanied by the loss of hierarchical connections in advanced age.