RT Journal Article
SR Electronic
T1 Spike Resonance Properties in Hippocampal O-LM Cells Are Dependent on Refractory Dynamics
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 3637
OP 3651
DO 10.1523/JNEUROSCI.1361-11.2012
VO 32
IS 11
A1 Kispersky, Tilman J.
A1 Fernandez, Fernando R.
A1 Economo, Michael N.
A1 White, John A.
YR 2012
UL http://www.jneurosci.org/content/32/11/3637.abstract
AB During a wide variety of behaviors, hippocampal field potentials show significant power in the theta (4–12 Hz) frequency range and individual neurons commonly phase-lock with the 4–12 Hz field potential. The underlying cellular and network mechanisms that generate the theta rhythm, however, are poorly understood. Oriens-lacunosum moleculare (O-LM) interneurons have been implicated as crucial contributors to generating theta in local hippocampal circuits because of their unique axonal projections, slow synaptic kinetics and the fact that spikes are phase-locked to theta field potentials in vivo. We performed experiments in brain slice preparations from Long–Evans rats to investigate the ability of O-LM cells to generate phase-locked spike output in response to artificial synaptic inputs. We find that O-LM cells do not respond with any preference in spike output at theta frequencies when injected with broadband artificial synaptic inputs. However, when presented with frequency-modulated inputs, O-LM spike output shows the ability to phase-lock well to theta-modulated inputs, despite their strong low-pass profiles of subthreshold membrane impedance. This result was dependent on spike refractory dynamics and could be controlled by real-time manipulation of the postspike afterhyperpolarization. Finally, we show that the ability of O-LM cells to phase-lock well to theta-rich inputs is independent of the h-current, a membrane mechanism often implicated in the generation of theta frequency activity.