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Science 7 August 2009:
Vol. 325. no. 5941, pp. 756 - 760
DOI: 10.1126/science.1171958
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Reports

Synaptic Integration in Tuft Dendrites of Layer 5 Pyramidal Neurons: A New Unifying Principle

Matthew E. Larkum,1,*,{dagger} Thomas Nevian,1,* Maya Sandler,2 Alon Polsky,2 Jackie Schiller2,{dagger}

Tuft dendrites are the main target for feedback inputs innervating neocortical layer 5 pyramidal neurons, but their properties remain obscure. We report the existence of N-methyl-D-aspartate (NMDA) spikes in the fine distal tuft dendrites that otherwise did not support the initiation of calcium spikes. Both direct measurements and computer simulations showed that NMDA spikes are the dominant mechanism by which distal synaptic input leads to firing of the neuron and provide the substrate for complex parallel processing of top-down input arriving at the tuft. These data lead to a new unifying view of integration in pyramidal neurons in which all fine dendrites, basal and tuft, integrate inputs locally through the recruitment of NMDA receptor channels relative to the fixed apical calcium and axosomatic sodium integration points.

1 Department of Physiology, University of Berne, Bühlplatz 5, 3012 Berne, Switzerland.
2 Department of Physiology, The Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Bat-Galim, Haifa 31096, Israel.

* These authors contributed equally to this work.

{dagger} To whom correspondence should be addressed. E-mail: matthew.larkum{at}gmail.com (M.E.L.); jackie{at}tx.technion.ac.il (J.S.)

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Properties of Piriform Cortex Pyramidal Cell Dendrites: Implications for Olfactory Circuit Design.
B. Bathellier, T. W. Margrie, and M. E. Larkum (2009)
J. Neurosci. 29, 12641-12652
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Science. ISSN 0036-8075 (print), 1095-9203 (online)