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Linear integration of spine Ca2+ signals in layer 4 cortical neurons in vivo.

Authors
  • Jia, Hongbo
  • Varga, Zsuzsanna
  • Sakmann, Bert
  • Konnerth, Arthur
Type
Published Article
Journal
Proceedings of the National Academy of Sciences
Publisher
Proceedings of the National Academy of Sciences
Publication Date
Jun 24, 2014
Volume
111
Issue
25
Pages
9277–9282
Identifiers
DOI: 10.1073/pnas.1408525111
PMID: 24927564
Source
Medline
Keywords
License
Unknown

Abstract

Sensory information reaches the cortex through synchronously active thalamic axons, which provide a strong drive to layer 4 (L4) cortical neurons. Because of technical limitations, the dendritic signaling processes underlying the rapid and efficient activation of L4 neurons in vivo remained unknown. Here we introduce an approach that allows the direct monitoring of single dendritic spine Ca(2+) signals in L4 spiny stellate cells of the vibrissal mouse cortex in vivo. Our results demonstrate that activation of N-methyl-D-aspartate (NMDA) receptors is required for sensory-evoked action potential (AP) generation in these neurons. By analyzing NMDA receptor-mediated Ca(2+) signaling, we identify whisker stimulation-evoked large responses in a subset of dendritic spines. These sensory-stimulation-activated spines, representing predominantly thalamo-cortical input sites, were denser at proximal dendritic regions. The amplitude of sensory-evoked spine Ca(2+) signals was independent of the activity of neighboring spines, without evidence for cooperativity. Furthermore, we found that spine Ca(2+) signals evoked by back-propagating APs sum linearly with sensory-evoked synaptic Ca(2+) signals. Thus, our results identify in sensory information-receiving L4 cortical neurons a linear mode of dendritic integration that underlies the rapid and reliable transfer of peripheral signals to the cortical network.

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