How sleep influences brain plasticity is not known. In particular, why certain electroencephalographic (EEG) rhythms are linked to memory consolidation is poorly understood. Calcium activity in dendrites is known to be necessary for structural plasticity changes, but this has never been carefully examined during sleep. Here, we report that calcium activity in populations of neocortical dendrites is increased and synchronised during oscillations in the spindle range in naturally sleeping rodents. Remarkably, the same relationship is not found in cell bodies of the same neurons and throughout the cortical column. Spindles during sleep have been suggested to be important for brain development and plasticity. Our results provide evidence for a physiological link of spindles in the cortex specific to dendrites, the main site of synaptic plasticity.

In the originally published version of this Article, incorrect references were cited on two occasions in the Results section. Under the subheading 'Ca 2+ activity in single dendrites and somata of L5 neurons', the final sentence of the second paragraph incorrectly cited reference 29 instead of reference 31. Under the subheading 'Spiking of L5 cell bodies is not influenced by spindles', the first sentence cited reference 30 instead of reference 29. These errors have now been corrected in both the PDF and HTML versions of the Article.Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.