Synaptic democracy in active dendrites.
Given the extensive attenuation that can occur along dendritic cables, location within the dendritic tree might appear to be a dominant factor in determining the impact of a synapse on the postsynaptic response. By this reasoning, distal synapses should have a smaller effect than proximal ones. However, experimental evidence from several types of neurons, such as CA1 pyramidal cells, indicates that a compensatory strengthening of synapses counteracts the effect of location on synaptic efficacy. A form of spike-timing-dependent plasticity (STDP), called anti-STDP, combined with non-Hebbian activity-dependent plasticity can account for the equalization of synaptic efficacies. This result, obtained originally in models with unbranched passive cables, also arises in multi-compartment models with branched and active dendrites that feature backpropagating action potentials, including models with CA1 pyramidal morphologies. Additionally, when dendrites support the local generation of action potentials, anti-STDP prevents runaway dendritic spiking and locally balances the numbers of dendritic and backpropagating action potentials. Thus in multiple ways, anti-STDP eliminates the location dependence of synapses and allows Hebbian plasticity to operate in a more "democratic" manner.
Rumsey
Clifton C
CC
The University of Texas at Austin, Center for Learning and Memory, 1 University Station C7000, Austin, TX 78712, USA. rumsey@mail.clm.utexas.edu
Abbott
L F
LF
D000200:Action Potentials / Q000502:physiology; D001369:Axons / Q000502:physiology / Q000648:ultrastructure; D002118:Calcium / Q000502:physiology; D003712:Dendrites / Q000502:physiology* / Q000648:ultrastructure; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D008959:Models, Neurological; D017966:Pyramidal Cells / Q000502:physiology / Q000648:ultrastructure; D013569:Synapses / Q000502:physiology* / Q000648:ultrastructure
D002118:Calcium