  Cognitive function depends on an adaptive balance between flexible dynamics
and integrative processes in distributed cortical networks. Patterns of
zero-lag synchrony likely underpin numerous perceptual and cognitive functions.
Synchronization fulfils integration by reducing entropy, whilst adaptive
function mandates that a broad variety of stable states be readily accessible.
Here, we elucidate two complementary influences on patterns of zero-lag
synchrony that derive from basic properties of brain networks. First, mutually
coupled pairs of neuronal subsystems -- resonance pairs -- promote stable
zero-lag synchrony amongst the small motifs in which they are embedded, and
whose effects can propagate along connected chains. Second, frustrated
closed-loop motifs disrupt synchronous dynamics, enabling metastable
configurations of zero-lag synchrony to coexist. We document these two
complementary influences in small motifs and illustrate how these effects
underpin stable versus metastable phase-synchronization patterns in
prototypical modular networks and in large-scale cortical networks of the
macaque (CoCoMac). We find that the variability of synchronization patterns
depends on the inter-node time delay, increases with the network size, and is
maximized for intermediate coupling strengths. We hypothesize that the
dialectic influences of resonance versus frustration may form a dynamic
substrate for flexible neuronal integration, an essential platform across
diverse cognitive processes.
