Neuron Article Theta Oscillations Provide Temporal Windows for Local Circuit Computation

Theta oscillations are believed to play an important role in the coordination of neuronal firing in the ento-rhinal (EC)-hippocampal system but the underlying mechanisms are not known. We simultaneously re-corded from neurons in multiple regions of the EC-hippocampal loop and examined their temporal rela-tionships. Theta-coordinated synchronous spiking of EC neuronal populations predicted the timing of current sinks in target layers in the hippocampus. However, the temporal delays between population activities in successiveanatomical stageswere longer (typically by a half theta cycle) than expected from axon conduction velocities and passive synaptic inte-gration of feed-forward excitatory inputs. We hypoth-esize that the temporal windows set by the theta cycles allow for local circuit interactions and thus a considerable degree of computational indepen-dence in subdivisions of the EC-hippocampal loop