title: Distinct neuronal coding schemes in memory revealed by selective erasure of fast synchronous synaptic transmission.
abstract: Neurons encode information by firing spikes in isolation or bursts and propagate information by spike-triggered neurotransmitter release that initiates synaptic transmission. Isolated spikes trigger neurotransmitter release unreliably but with high temporal precision. In contrast, bursts of spikes trigger neurotransmission reliably (i.e., boost transmission fidelity), but the resulting synaptic responses are temporally imprecise. However, the relative physiological importance of different spike-firing modes remains unclear. Here, we show that knockdown of synaptotagmin-1, the major Ca(2+) sensor for neurotransmitter release, abrogated neurotransmission evoked by isolated spikes but only delayed, without abolishing, neurotransmission evoked by bursts of spikes. Nevertheless, knockdown of synaptotagmin-1 in the hippocampal CA1 region did not impede acquisition of recent contextual fear memories, although it did impair the precision of such memories. In contrast, knockdown of synaptotagmin-1 in the prefrontal cortex impaired all remote fear memories. These results indicate that different brain circuits and types of memory employ distinct spike-coding schemes to encode and transmit information.
authors.affiliation: Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.forename: Wade
authors.initials: W
authors.lastname: Morishita
authors.forename: Paul S
authors.initials: PS
authors.lastname: Buckmaster
authors.forename: Zhiping P
authors.initials: ZP
authors.lastname: Pang
authors.forename: Robert C
authors.initials: RC
authors.lastname: Malenka
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Südhof
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000235:genetics; D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D003213:Conditioning, Psychological; D004558:Electric Stimulation; D004569:Electroencephalography; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005239:Fear; D006624:Hippocampus / Q000502:physiology; D008568:Memory / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000502:physiology*; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D011810:Quinoxalines / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D050863:Synaptotagmin I / Q000172:deficiency; D014161:Transduction, Genetic
chemical_list: D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; D050863:Synaptotagmin I; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline