The Journal of Neuroscience, October 17, 2007, 27(42):11263-11270; doi:10.1523/JNEUROSCI.2559-07.2007
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Behavioral/Systems/Cognitive
Intraburst and Interburst Signaling by Climbing Fibers
Jun Maruta,
Robert A. Hensbroek, and
John I. Simpson
Department of Physiology and Neuroscience, New York University School of Medicine, New York, New York 10016
Correspondence should be addressed to John I. Simpson, Department of Physiology and Neuroscience, 550 First Avenue, New York University School of Medicine, New York, NY 10016. Email: john.simpson{at}med.nyu.edu
Although cerebellar Purkinje cell complex spikes occur at low frequency (
1/s), each complex spike is often associated with a high-frequency burst (500/s) of climbing fiber spikes. We examined the possibility that signals are present within the climbing fiber bursts. By intracellularly recording from depolarized, nonspiking Purkinje cells in anesthetized pigmented rabbits, climbing fiber burst patterns were investigated by determining the number of components in the induced compound EPSPs during spontaneous activity and during visual stimulation. For our sample of 43 cells, >70% of all EPSPs were of the compound type composed of two or three EPSPs. During spontaneous activity, the number of components in each compound EPSP was not related to the latency to the succeeding compound EPSP. Conversely, the number of components in each compound EPSP was related to its latency after the preceding compound EPSP. This latency increased from 0.62 s for one-component EPSPs to 1.69 s for compound EPSPs with four or more components. The effect of visual stimulation on the climbing fiber activity was studied in 19 floccular Purkinje cells whose low-frequency interburst climbing fiber response was modulated by movement about the vertical axis. During sinusoidal oscillation (0.1 Hz, ±10°), compound EPSPs with a larger number of components tended to be more prevalent during movement in the excitatory direction than in the inhibitory direction. Thus, climbing fibers can, in addition to modulation of their low interburst frequency, transmit signals in the form of the number of spikes within each high-frequency burst.
Key words: inferior olive; cerebellum; afterdepolarization; model; Purkinje neurons; complex spike
Received June 6, 2007;
revised Aug. 23, 2007;
accepted Sept. 5, 2007.
Correspondence should be addressed to John I. Simpson, Department of Physiology and Neuroscience, 550 First Avenue, New York University School of Medicine, New York, NY 10016. Email: john.simpson{at}med.nyu.edu
