Figure 1.

Somato-dendritic decoupling in neurons. (A) Optical imaging using microbial rhodopsin in an immature (10–14 days in vitro) hippocampal neuron. Red indicates an action potential. As noted by the authors, “the process extending to the top left of the cell body does not appear in the red channel; it is electrically decoupled from the cell” (indicated here by the yellow arrows). Panel (A) adapted by permission from Macmillan Publishers Ltd: Nature Methods (Kralj et al., 2011), copyright (2011) http://www.nature.com/naturemethods/. (B) Identified high-order temporal lobe neocortical dormant neurons (left) from Chomiak et al. (2016) that exhibit somato-dendritic decoupling. Yellow arrows indicate observable dendrites that lack biocytin labeling. Biocytin was delivered via patch pipette during patch-clamp recordings to electrophysiologically confirm a non-excitable and functionally compartmentalized soma (not shown here). Spiking neurons (right) exhibit somato-dendritic coupling; dendritic biocytin dye labeling and associated membrane capacitance confirmation. (C) A schematic illustrating that the development of somato-dendritic coupling (bottom) in the high-order temporal lobe is protracted (top), with a greater proportion of neurons in the juvenile stage exhibiting decoupling. Here dendrites can receive afferent inputs and even spike (denoted in red), but this information does not converge at the level of the soma. This may help keep recurrent connections “off-line” during postnatal development. Panel (B) taken, and Panel (C) modified, from Chomiak et al. (2016); Springer Nature (2016) © Chomiak et al. (2016) Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/).