Coherent neural activity and brain synchronization during seizure-induced loss of consciousness.

Epileptic seizures are often characterized by profound alteration of consciousness (AOC). This is particularly frequent in temporal lobe seizures (TLS), a subgroup of seizures originating in the temporal (and usually mesial temporal) brain areas. The mechanisms of AOC in TLS have long been discussed and several theories have been proposed. Recent investigations have provided new hypotheses linking abnormal synchrony provoked by epileptic discharges and the dysfunction of brain regions involved in consciousness processing. In particular, the global workspace (GW) theory proposes that conscious processing results from coherent neuronal activity between widely distributed brain regions, with fronto-parietal associative cortices as key elements. Recently, we have shown that AOC was contemporary to non-linear increases of neural synchrony within distant cortico-cortical and cortico-thalamic networks. We have interpreted these results in the light of GW theory, and suggest that excessive synchrony could prevent this distributed network from reaching the minimal level of differentiation and complexity necessary to the coding of conscious representations.