Abnormal effective connectivity in migraine with aura under photic   stimulation
  Migraine patients with aura show a peculiar pattern of visual reactivity compared with those of migraine patients without aura: an increased effective connectivity, connected to a reduced synchronization among EEG channels, for frequencies in the beta band. The effective connectivity is evaluated in terms of the Granger causality. This anomalous response to visual stimuli may play a crucial role in the progression of spreading depression and clinical evidences of aura symptoms. 
Sebastiano Stramaglia, Daniele Marinazzo, Mario Pellicoro, and Marina   de Tommaso
q-bio.NC cond-mat.dis-nn physics.med-ph