Zero-lag synchronous dynamics in triplets of interconnected cortical areas

Oscillatory and synchronized activities involving widespread populations of neurons in neocortex are associated with the execution of complex sensorim otor tasks and have been proposed to participate in the 'binding' of sensor y attributes during perceptual synthesis. How the brain constructs these co herent firing patterns remains largely unknown. Several mechanisms of intra cortical synchronization have been considered, in particular mutual inhibit ion and reciprocal excitation. These mechanisms fail to account for the zer o-lag correlations observed among areas located at different levels in the visual hierarchy because the asymmetric laminar organization of ascending a nd descending connections in this hierarchy would predict systematic inter- areal phase lags. Here we show through detailed computer simulations that, when triplets rather than pairs of reciprocally connected areas in a cortic al hierarchy are considered, zero-lag synchronization emerges naturally fro m their three-way interactions. These simulations were motivated by the obs ervation that most areas in the cat and macaque monkey visual cortex are or ganized in such triplets. Our results suggest that patterns of anatomical c onnections in the mammalian neocortex provide a structural basis for the mu lti-level synchronization of neuronal activity. (C) 2001 Elsevier Science L td. All rights reserved.