Who's been nibbling on my PSD: Is it LTD?

Lisman, John; Harris, Kristen M.

doi:10.1016/0928-4257(94)90005-1

Cited by 10 publications

(10 citation statements)

References 5 publications

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“…Synapse size well-correlated with the number of docked presynaptic vesicles suggesting coordination between pre- and post-synaptic composition and dimensions occurs in the human hippocampus like in the rat hippocampus (Harris and Stevens, 1989; Harris and Sultan, 1995; Lisman and Harris, 1994). Epileptic seizures have long been associated with dendritic spine loss (Jiang et al, 1998; Multani et al, 1994; Scheibel and Scheibel, 1977; Swann et al, 2000), which has been attributed to calcium- and glutamate-mediated excitotoxicity (Swann et al, 2000).…”

Section: Discussionmentioning

confidence: 92%

Three‐dimensional relationships between perisynaptic astroglia and human hippocampal synapses

Witcher

Park

Lee

et al. 2009

Glia

103

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Perisynaptic astroglia are critical for normal synaptic development and function. Little is known, however, about perisynaptic astroglia in the human hippocampus. When mesial temporal lobe epilepsy (MTLE) is refractory to medication, surgical removal is required for seizure quiescence. To investigate perisynaptic astroglia in human hippocampus, we recovered slices for several hours in vitro from three surgical specimens and then quickly fixed them to achieve high-quality ultrastructure. Histological samples from each case were found to have mesial temporal sclerosis with Blumcke Type 1a (mild, moderate) or 1b (severe) pathology. Quantitative analysis through serial section transmission electron microscopy in CA1 stratum radiatum revealed more synapses in the mild (10/10 µm 3 ) than the moderate (5/10 µm 3 ) or severe (1/10 µm 3 ) cases. Normal spines occurred in mild and moderate cases, but a few multisynaptic spines were all that remained in the severe case. Like adult rat hippocampus, perisynaptic astroglial processes were preferentially associated with larger synapses in the mild and moderate cases, but rarely penetrated the cluster of axonal boutons surrounding multisynaptic spines. Synapse perimeters were only partially surrounded by astroglial processes such that all synapses had some access to substances in the extracellular space, similar to adult rat hippocampus. Junctions between astroglial processes were observed more frequently in moderate than mild case, but were obscured by densely packed intermediate filaments in astroglial processes of the severe case. These findings suggest that perisynaptic astroglial processes associate with synapses in human hippocampus in a manner similar to model systems and are disrupted by severe MTLE pathology.

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Section: Discussionmentioning

confidence: 92%

Three‐dimensional relationships between perisynaptic astroglia and human hippocampal synapses

Witcher

Park

Lee

et al. 2009

Glia

103

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“…Regression lines in red and error bars for each data point represent SEM based on multiple tracers who also edited each spine. Equations are based on the log-log distributions, with r 2 values indicated, and n=288 complete spines.…”

Section: Figmentioning

confidence: 99%

“…C) Number of docked vesicles is correlated with PSD area and D) spine head volume, but not correlated with E) spine neck volume. Regression lines, SEM, and r 2 are as in Fig. 1, n = 237 complete axonal boutons, each associated with one of the 288 complete spines.…”

Section: Figmentioning

confidence: 99%

Hippocampal Spine Head Sizes Are Highly Precise

Bartol

Bromer

Kinney

et al. 2015

Preprint

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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.

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“…Excitatory synapses on dendritic spines of hippocampal pyramidal neurons have a wide range of sizes. Anatomical measurements of the spine size, the area of the postsynaptic density (PSD), the number of AMPA receptors, the area of the presynaptic active zone and the number of docked vesicles in the presynaptic terminal are all highly correlated with each other and with physiological measurements of the release probability and the efficacy of the synapse ( Harris and Stevens, 1989 ; Lisman and Harris, 1994 ; Harris and Sultan, 1995 ; Schikorski and Stevens, 1997 ; Murthy et al, 2001 ; Branco et al, 2008 ; Bourne et al, 2013 ). Thus, each of these individual characteristics is a correlate of synaptic strength.…”

Section: Introductionmentioning

confidence: 99%

Nanoconnectomic upper bound on the variability of synaptic plasticity

Bartol

Bromer

Kinney

et al. 2015

eLife

243

271

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Information in a computer is quantified by the number of bits that can be stored and recovered. An important question about the brain is how much information can be stored at a synapse through synaptic plasticity, which depends on the history of probabilistic synaptic activity. The strong correlation between size and efficacy of a synapse allowed us to estimate the variability of synaptic plasticity. In an EM reconstruction of hippocampal neuropil we found single axons making two or more synaptic contacts onto the same dendrites, having shared histories of presynaptic and postsynaptic activity. The spine heads and neck diameters, but not neck lengths, of these pairs were nearly identical in size. We found that there is a minimum of 26 distinguishable synaptic strengths, corresponding to storing 4.7 bits of information at each synapse. Because of stochastic variability of synaptic activation the observed precision requires averaging activity over several minutes.DOI: http://dx.doi.org/10.7554/eLife.10778.001

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Who's been nibbling on my PSD: Is it LTD?

Cited by 10 publications

References 5 publications

Three‐dimensional relationships between perisynaptic astroglia and human hippocampal synapses

Three‐dimensional relationships between perisynaptic astroglia and human hippocampal synapses

Hippocampal Spine Head Sizes Are Highly Precise

Nanoconnectomic upper bound on the variability of synaptic plasticity

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