Scientific Understanding of Consciousness
Consciousness as an Emergent Property of Thalamocortical Activity

Learning and Memory in Pyramidal Neuron Dendrites


Nature 450, 1195-1200 (20 December 2007)

Locally dynamic synaptic learning rules in pyramidal neuron dendrites

Christopher D. Harvey & Karel Svoboda

Janelia Farm Research Campus, HHMI, Ashburn, Virginia 20147, USA

Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA

Long-term potentiation (LTP) of synaptic transmission underlies aspects of learning and memory. LTP is input-specific at the level of individual synapses, but neural network models predict interactions between plasticity at nearby synapses. Here we show in mouse hippocampal pyramidal cells that LTP at individual synapses reduces the threshold for potentiation at neighbouring synapses. These local interactions between neighbouring synapses support clustered plasticity models of memory storage and could allow for the binding of behaviourally linked information on the same dendritic branch.

Long-lasting modifications of synaptic strength (LTP) are critical for learning and memory in many parts of the brain, including the hippocampus. The extent to which LTP is synapse-specific influences the information processing and storage of a neuron. LTP can be input-specific, even at the level of individual synapses, indicating that synapses may function as independent units of plasticity. However, neighbouring synapses might be co-regulated due to the heterosynaptic spread of LTP over short stretches of dendrite.

We have shown that the induction of plasticity at individual synapses can be influenced by events at neighbouring synapses. The coordinated regulation of groups of 1020 synapses within a dendritic neighbourhood indicates that individual synapses do not necessarily function as independent units of plasticity. Models of clustered plasticity propose that individual engrams could be stored in synapses sharing the same dendritic branch, which would increase the information storage capacity of the neuron through the nonlinear summation of synaptic inputs. Clustered plasticity implies the binding of inputs that are active during the same behavioural epochs on the same dendritic branch.




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