A Cooperative Switch Determines the Sign of Synaptic Plasticity in Distal Dendrites of Neocortical Pyramidal Neurons

Wolfson Institute for Biomedical Research, Department of Physiology, University College London, London WC1E 6BT, United Kingdom.
Neuron (Impact Factor: 15.05). 08/2006; 51(2):227-38. DOI: 10.1016/j.neuron.2006.06.017
Source: PubMed


Pyramidal neurons in the cerebral cortex span multiple cortical layers. How the excitable properties of pyramidal neuron dendrites allow these neurons to both integrate activity and store associations between different layers is not well understood, but is thought to rely in part on dendritic backpropagation of action potentials. Here we demonstrate that the sign of synaptic plasticity in neocortical pyramidal neurons is regulated by the spread of the backpropagating action potential to the synapse. This creates a progressive gradient between LTP and LTD as the distance of the synaptic contacts from the soma increases. At distal synapses, cooperative synaptic input or dendritic depolarization can switch plasticity between LTD and LTP by boosting backpropagation of action potentials. This activity-dependent switch provides a mechanism for associative learning across different neocortical layers that process distinct types of information.

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Available from: Per Jesper Sjöström
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    • "An example could be the co-location of cortico-striatal synapses and dopaminergic terminals on the same spine of neurons in the striatum (Freund et al., 1984;Schultz, 1998Schultz, , 2002). However, the involvement of GABAergic neurons raises the possibility that neuromodulation may affect synapses indirectly (Bissière et al., 2003), for example by allowing inhibition-mediated suppression of back-propagating action potentials (Figure 2B) known to influence the induction of STDP (Golding et al., 2002;Sjöström and Häusser, 2006). Neuromodulators influencing ion channels could affect action potential back-propagation (Figure 2C), or dendritic Ca 2+ signaling, in turn modulating LTP and LTD induction (see e.g.,Couey et al., 2007, for an example of acetylcholine modulation of STDP along these lines).Goldman-Rakic et al., 1989). "
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    • ", 2002 ; Waters et al . , 2003 ; Sjöström and Häusser , 2006 ) . Because of their relation to global variables such as concentration of calcium in neurons or firing rate of neuronal populations , mechanisms of homeostatic regulation of synaptic weights might be embedded into a multi - level system of neuronal homeostasis and thus could be triggered by signals from several different levels . "
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