Effects of neuronal morphology on firing rate dynamics.

The attenuation of neuronal voltage responses to high-frequency current
inputs by the membrane capacitance is believed to limit single-cell
bandwidth. However, neuronal populations subject to stochastic
fluctuations can follow inputs beyond this limit.Ê We investigated this
apparent paradox theoretically and experimentally using Purkinje cells
in the cerebellum, a motor structure that benefits from rapid
information transfer. We analyzed the modulation of firing in response
to the somatic injection of sinusoidal currents.Ê Computational
modelling suggested that instead of decreasing with frequency,
modulation amplitude can increase up to high frequencies due to cellular
morphology.Ê Electrophysiological measurements confirmed this
prediction, and displayed a marked resonance at 200 Hz.Ê We elucidated
the underlying mechanism, showing that the two-compartment morphology of
the Purkinje cell, interacting with a simple spiking mechanism and
dendritic fluctuations, is sufficient to create high-frequency signal
amplification.Ê This mechanism, which we term morphology-induced
resonance, is selective for somatic inputs, which in the Purkinje cell
are exclusively inhibitory. The resonance sensitizes Purkinje cells in
the frequency range of population oscillations observed in vivo.

Nicholas Brunel

The University of Chicago