  Since the earliest electroencephalography experiments, large scale
oscillations have been observed in the mammalian brain. More recently, they
have been identified not only in the cerebral cortex and thalamus, but
pervasively in the healthy basal ganglia. The basal ganglia mediated
synchronization model, introduced here, implicates these oscillations in the
combination of cortical association mechanisms with stimulus-response and
reinforcement mechanisms in the basal ganglia. In the core mechanism of the
model, oscillatory patterns in cortex are selected by and routed through the
basal ganglia to the thalamus phase-coherently, then circulated back to widely
separated areas of cortex, synchronizing those areas and functionally
connecting them. Corticostriatal and striatonigral conduction delays are
crucial to this mechanism, and evidence suggests that these delays are
unusually long, and unusually varied, in arrangements that might facilitate
learning of useful time alignments and associated resonant frequencies. Other
structural arrangements in the basal ganglia show further specialization for
this role, with convergence in the inputs from cortex, and divergence in many
of the return paths to cortex, that systematically reflect corticocortical
anatomical connectivity. The basal ganglia also target the dopaminergic,
cholinergic, and serotonergic centers of the brainstem and basal forebrain, and
the reticular nucleus of the thalamus, structures broadly implicated in the
modulation of oscillatory network activity and expressions of plasticity. By
learning to coordinate these various output channels, the basal ganglia are
positioned to facilitate and synchronize activity in selected areas of cortex,
broadly impart selective receptivity, attenuate and disconnect interfering
activity, and recurrently process the resulting patterns of activity,
channeling cognition and promoting goal [...]
