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Neuroscience. 2014 Mar 28;263:15-26. doi: 10.1016/j.neuroscience.2014.01.007. Epub 2014 Jan 15.

Emergence of a 600-Hz buzz UP state Purkinje cell firing in alert mice.

Author information

1
Laboratory of Electrophysiology, Université de Mons, 7000 Mons, Belgium; Laboratory of Neurophysiology and Movement Biomechanics, CP601, ULB Neurosciences Institut, Université Libre de Bruxelles, 1070 Brussels, Belgium. Electronic address: gcheron@ulb.ac.be.
2
Laboratory of Electrophysiology, Université de Mons, 7000 Mons, Belgium; Laboratory of Neurophysiology and Movement Biomechanics, CP601, ULB Neurosciences Institut, Université Libre de Bruxelles, 1070 Brussels, Belgium.
3
División de Neurociencias, Universidad Pablo de Olavide, 41013 Sevilla, Spain.
4
Department of Physical Sciences, IBM T.J. Watson Research Center, Yorktown Heights, NY 10598, USA; Department of Neurology, Columbia University, New York, NY 10032, USA.
5
Laboratory of Neurophysiology and Movement Biomechanics, CP601, ULB Neurosciences Institut, Université Libre de Bruxelles, 1070 Brussels, Belgium.

Abstract

Purkinje cell (PC) firing represents the sole output from the cerebellar cortex onto the deep cerebellar and vestibular nuclei. Here, we explored the different modes of PC firing in alert mice by extracellular recording. We confirm the existence of a tonic and/or bursting and quiescent modes corresponding to UP and DOWN state, respectively. We demonstrate the existence of a novel 600-Hz buzz UP state of firing characterized by simple spikes (SS) of very small amplitude. Climbing fiber (CF) input is able to switch the 600-Hz buzz to the DOWN state, as for the classical UP-to-DOWN state transition. Conversely, the CF input can initiate a typical SS pattern terminating into 600-Hz buzz. The 600-Hz buzz was transiently suppressed by whisker pad stimulation demonstrating that it remained responsive to peripheral input. It must not be mistaken for a DOWN state or the sign of PC inhibition. Complex spike (CS) frequency was increased during the 600-Hz buzz, indicating that this PC output actively contributes to the cerebello-olivary loop by triggering a disinhibition of the inferior olive. During the 600-Hz buzz, the first depolarizing component of the CS was reduced and the second depolarizing component was suppressed. Consistent with our experimental observations, using a 559-compartment single-PC model - in which PC UP state (of about -43mV) was obtained by the combined action of large tonic AMPA conductances and counterbalancing GABAergic inhibition - removal of this inhibition produced the 600-Hz buzz; the simulated buzz frequency decreased following an artificial CS.

KEYWORDS:

600Hz; Purkinje cells; bistability; cerebellum; complex spike; simple spike

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