Theta band zero-lag long-range cortical synchronization via hippocampal dynamical relaying

Growing evidence suggests that synchronization among distributed neuronal networks underlie functional integration in the brain. Neural synchronization is typically revealed by a consistent phase delay between neural responses generated in two separated sources. But the influence of a third neuronal assembly in that synchrony pattern remains largely unexplored. We investigate here the potential role of the hippocampus in determining cortico-cortical theta synchronization in different behavioral states during motor quiescent and while animals actively explore the environment. To achieve this goal, the two states were modeled with a recurrent network involving the hippocampus, as a relay element, and two distant neocortical sites. We found that cortico-cortical neural coupling accompanied higher hippocampal theta oscillations in both behavioral states, although the highest level of synchronization between cortical regions emerged during motor exploration. Local field potentials recorded from the same brain regions qualitatively confirm these findings in the two behavioral states. These results suggest that zero-lag long-range cortico-cortical synchronization is likely mediated by hippocampal theta oscillations in lower mammals as a function of cognitive demands and motor acts. © 2011 Gollo et al.

The authors acknowledge the financial support from the European Commission Project GABA (FP6-NEST Contract 043309). LLG and CM also acknowledge the Ministerio de Educacio ́ n y Ciencia (Spain) and Fondo Europeo de Desarrollo Regional (FEDER) under project FIS2007-60327 (FISICOS). This research was also supported by grants from the Spanish Ministry of Science and Innovation (SAF2008-03300, PSI2008-06141) to JLC and MA, respectivel y, and from the Regional Ministry of Innovation, Science and Enterprise, Junta de Andalucı ́ a (CTS-4604) to JLC.