Differences in transmission properties and susceptibility to long-term depression reveal functional specialization of ascending axon and parallel fiber synapses to Purkinje cells

Robert E. Sims, Nicholas A. Hartell*

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

An understanding of the patterns of mossy fiber transmission to Purkinje cells, via granule cell axons, is fundamental to models of cerebellar cortical signaling and processing. Early theories assumed that mossy fiber input is widely disseminated across the cerebellar cortex along beams of parallel fibers, which spread for several millimeters across the cerebellar cortex. Direct evidence for this has, however, proved controversial, leading to the development of an alternative hypothesis that mossy fiber inputs to the cerebral cortex are in fact vertically organized such that the ascending segment of the granule axon carries a greater synaptic weight than the parallel fiber segment. Here, we report that ascending axon synapses are selectively resistant to cerebellar long-term depression and that they release transmitter with higher mean release probabilities and mean quantal amplitudes than parallel fiber synapses. This novel specialization of synapses formed by different segments of the same axon not only explains the reported patterns of granule cell→ Purkinje cell transmission across the cerebellar cortex but also reveals an additional level of functionality and complexity of cerebellar processing. Consequently, ascending axon synapses represent a new element of cortical signal processing that should be distinguished from parallel fiber synapses in future experimental and theoretical studies of cerebellar function.

Original languageEnglish
Pages (from-to)3246-3257
Number of pages12
JournalJournal of Neuroscience
Volume25
Issue number12
DOIs
Publication statusPublished - 23 Mar 2005

Bibliographical note

Copyright© 2005 Society for Neuroscience. Articles are released under a Creative Commons Attribution License after a 6 months embargo

Keywords

  • Cerebellum
  • Granule cell
  • Long-term depression
  • Purkinje cell
  • Synaptic
  • Transmission

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