SYNCHRONIZATION Of neuronal activity is fundamental in the operation of cortical networks(1).
With respect to an ongoing synchronized oscillation, the precise timing of action
potentials is an attractive candidate mechanism for information coding(2-5) Networks
of inhibitory interneurons have been proposed to have a role in entraining cortical,
synchronized 40-Hz activity(6,7). Here we demonstrate that individual GABAergic interneurons(8)
can effectively phase spontaneous firing and subthreshold oscillations in hippocampal
pyramidal cells at theta frequencies (4-7 Hz). The efficiency of this entrainment
is due to interaction of GABA(A)-receptor-mediated hyperpolarizing synaptic events
with intrinsic oscillatory mechanisms tuned to this frequency range in pyramidal cells.
Moreover, this GABAergic mechanism is sufficient to synchronize the firing of pyramidal
cells. Thus, owing to the divergence of each GABAergic interneuron(9,10), more than
a thousand pyramidal cells may share a common temporal reference established by an