Developmental Changes in Neuronal Oscillations and Synchrony: Evidence for a Late Critical Period

The role of synchronized oscillations Synchronised neural oscillations in low(delta, theta and alpha) and high(beta and gamma) frequency bands are a fundamental mechanism for enabling coordinated activity during normal brain functioning [Buzsaki & Draguhn, 2004; Fries, 2009]. A large body of evidence from invasive electrophysiology in non-human primates and electroand magnetoencephalographic(EEG/MEG) recordings in humans that have tested the amplitude and synchrony of neural oscillations have demonstrated close relations between synchronous oscillatory activity and a variety of cognitive and perceptual functions. An important link between oscillations and cortical computations was the discovery of the role of oscillatory rhythms in the beta/gamma range (20-80 Hz) in establishing precise synchronization of distributed neural responses. Gray and colleagues [Gray et al., 1989] showed that action potentials generated by cortical cells align with the oscillatory rhythm in the beta and gamma range, which has the consequence that neurons participating in the same oscillatory rhythm synchronize their discharges with high precision. Thus, it is a central role of cortical oscillations in the beta/gamma range to enable neuronal synchronization and by virtue of establishing systematic phase lags, to define precise temporal relations between the discharges of distributed neurons [Womelsdorf et al., 2007]. Self-generated oscillations and synchronization are highly dynamic phenomena and depend on numerous conditions, such as central states [Herculano et al., 1999], stimulus configuration [Gray and Singer, 1989; Gray et al., 1989] or attention [Fries et al., 2001]. The strength of synchrony is closely correlated