PT  - JOURNAL ARTICLE
AU  - Thomas M Bartol
AU  - Cailey Bromer
AU  - Justin Kinney
AU  - Michael A. Chirillo
AU  - Jennifer N. Bourne
AU  - Kristen M. Harris
AU  - Terrence J Sejnowski
TI  - Hippocampal Spine Head Sizes Are Highly Precise
AID  - 10.1101/016329
DP  - 2015 Jan 01
TA  - bioRxiv
PG  - 016329
4099  - http://biorxiv.org/content/early/2015/03/11/016329.short
4100  - http://biorxiv.org/content/early/2015/03/11/016329.full
AB  - Hippocampal synaptic activity is probabilistic and because synaptic plasticity depends on its history, the amount of information that can be stored at a synapse is limited. The strong correlation between the size and efficacy of a synapse allowed us to estimate the precision of synaptic plasticity. In an electron microscopic reconstruction of hippocampal neuropil we found single axons making two or more synaptic contacts onto the same dendrites which would have shared histories of presynaptic and postsynaptic activity. The postsynaptic spine heads, but not the spine necks, of these pairs were nearly identical in size. The precision is much greater than previous estimates and requires postsynaptic averaging over a time window many seconds to minutes in duration depending on the rate of input spikes and probability of release.One Sentence Summary Spine heads on the same dendrite that receive input from the same axon are the same size.