Ripples reflect a spectrum of synchronous spiking activity in human anterior temporal lobe

Direct brain recordings have provided important insights into how
high-frequency activity captured through intracranial EEG (iEEG) supports
human memory retrieval. The extent to which such activity is comprised of
transient fluctuations that reflect the dynamic coordination of underlying
neurons, however, remains unclear. Here, we simultaneously record iEEG,
local field potential (LFP), and single unit activity in the human
temporal cortex. We demonstrate that fast oscillations within the
previously identified 80–120 Hz ripple band contribute to broadband
high-frequency activity in the human cortex. These ripple oscillations
exhibit a spectrum of amplitudes and durations related to the amount of
underlying neuronal spiking. Ripples in the macro-scale iEEG are related
to the number and synchrony of ripples in the micro-scale LFP, which in
turn are related to the synchrony of neuronal spiking. Our data suggest
that neural activity in the human temporal lobe is organized into
transient bouts of ripple oscillations that reflect underlying bursts of
spiking activity.