Does a dendritic democracy need a ruler? ?
In hippocampal CA1 cells, distance-dependent synaptic scaling (Nat. Neurosci. 3 (2000) 895, J. Neurosci. 21 (2001) 9151) helps maintain a dendritic democracy (Curr. Biol. 11 (2001) R10) where distal and proximal synapses on average contribute equally to the cell's firing. A dendritic ruler, for example a concentration gradient, might be necessary for synaptic scaling. Alternatively, synapses could self-regulate by gauging their distance from the soma using properties of backpropagating spikes. We show in a model CA1 cell (Neuron 37 (2003) 977) that the delay between a synchronous burst of simulated Schaffer collateral input and the arrival of backpropagating spikes at synapses predict the synapse's location and amplitude at the soma well, though the amplitude of the spikes do not. This suggests that a dendritic ruler is not required to scale synapses.
ca1 synaptic plasticity backpropagating action potentials