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PMID: 16899721 Published · ppublish English Journal Article

Background synaptic activity is sparse in neocortex.

The Journal of neuroscience : the official journal of the Society for Neuroscience ·Vol. 26 ·No. 32 ·2006-08-09 ·Pages 8267-77

Waters J, Helmchen F

Abstract

Neurons are continually exposed to background synaptic activity in vivo. This is thought to influence neural information processing, but background levels of excitation and inhibition remain controversial. Here we show, using whole-cell recordings in anesthetized rats, that spontaneous depolarizations ("Up states") in neocortical pyramidal neurons are driven by sparse, mostly excitatory synaptic activity (less than five inputs per millisecond; approximately 10% inhibitory). The mean synaptic conductance change is small (<10 nS at the soma) and opposed by anomalous rectification, resulting in a net increase in input resistance during Up states. These conditions enhance the effectiveness of each synapse at depolarized potentials. Hence, neocortical networks are relatively quiet at rest, and the effect of synaptic background is weaker than previously thought.

MeSH Terms
Action Potentials/physiology Animals Biological Clocks/physiology Computer Simulation Differential Threshold/physiology Excitatory Postsynaptic Potentials/physiology Membrane Potentials/physiology Models, Neurological Models, Statistical Neocortex/physiology Neural Inhibition/physiology Neurons/physiology Rats Rats, Wistar Synaptic Transmission/physiology
Authors & Affiliations
2 authors, click to expand affiliations / ORCID
Waters Jack
Abteilung Zellphysiologie, Max-Planck-Institut für Medizinische Forschung, 69120 Heidelberg, Germany. [email protected]
Helmchen Fritjof
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Article Info
Journal
The Journal of neuroscience : the official journal of the Society for Neuroscience
Abbr.
J Neurosci
ISSN
1529-2401
DOI
10.1523/JNEUROSCI.2152-06.2006
Email
[email protected]
Published
2006-08-09
Pages
8267-77
Language
English
Region
United States
NLM ID
8102140
PMCID
PMC6673816
Subset
IM
External Links
PubMed source DOI: 10.1523/JNEUROSCI.2152-06.2006 PMC Full Text View journal details
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