High frequency oscillations in the intact brain

High frequency oscillations (HFOs) constitute a novel trend in neurophysiology that is fascinating neuroscientists in general, and epileptologists in particular. But what are HFOs? What is the frequency range of HFOs? Are there different types of HFOs, physiological and pathological? How are HFOs generated? Can HFOs represent temporal codes for cognitive processes? These questions are pressing and this symposium volume attempts to give constructive answers. As a prelude to this exciting discussion, we summarize the physiological high frequency patterns in the intact brain, concentrating mainly on hippocampal patterns, where the mechanisms of high frequency oscillations are perhaps best understood.

► High frequency oscillations are local.
► Replay of waking experience in hippocampal ripples assists with memory consolidation.
► Ripples reflects internal dynamics and may constrain waking firing patterns.
► Ripples and fast gamma oscillations share common mechanisms.
► Ripples (and fast gamma) in local field largely reflect synchronous spiking.