Abstract
Basal dendrites are a major target for synaptic inputs innervating cortical pyramidal neurons1. At present little is known about signal processing in these fine dendrites. Here we show that co-activation of clustered neighbouring basal inputs initiated local dendritic spikes, which resulted in a 5.9 ± 1.5 mV (peak) and 64.4 ± 19.8 ms (half-width) cable-filtered voltage change at the soma that amplified the somatic voltage response by 226 ± 46%. These spikes were accompanied by large calcium transients restricted to the activated dendritic segment. In contrast to conventional sodium or calcium spikes, these spikes were mediated mostly by NMDA (N -methyl-D-aspartate) receptor channels, which contributed at least 80% of the total charge. The ionic mechanism of these NMDA spikes may allow ‘dynamic spike-initiation zones’, set by the spatial distribution of glutamate pre-bound to NMDA receptors, which in turn would depend on recent and ongoing activity in the cortical network. In addition, NMDA spikes may serve as a powerful mechanism for modification of the cortical network by inducing long-term strengthening of co-activated neighbouring inputs.
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Acknowledgements
We thank. D. E. Clapham, F. Prendergast, B. Sakmann, W. Denk and D. Tank for assistance and support, A. Larkman for reconstructing the cell used in the simulations, and M. Hausser and G. Stuart for reading early versions of the manuscript. In addition we thank the Mayo Foundation, Leo & Frances Kogan endowment fund (J.S.), Wellcome Trust, Lucent Technologies and Marine Biological Laboratory (G.M.) for financial support.
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Schiller, J., Major, G., Koester, H. et al. NMDA spikes in basal dendrites of cortical pyramidal neurons. Nature 404, 285–289 (2000). https://doi.org/10.1038/35005094
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DOI: https://doi.org/10.1038/35005094
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