spine resistance debates

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wwlytton
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Joined: Wed May 18, 2005 10:37 pm

spine resistance debates

Post by wwlytton » Tue Apr 25, 2017 5:29 pm

There is great variability in spine resistance estimates in different studies and models. Eg Carnevale

in 2013 said
"Notably, our experimental data was closely modeled using a neck resistance of 520 M , similar to the value reported for hippocampal pyramidal neurons (26). "
("Compartmentalization of GABAergic Inhibition by Dendritic Spines" Science 340:759)

whereas in 2015 noted that "experiments showed the mean values of Rneck=27+/-6 M "
("Electrical behaviour of dendritic spines as revealed by voltage imaging Popovic, Carnevale, Rozsa, Zecevic)

these are different areas, ?species, ages, dendritic locations so it may be that both are true (and many more in between as well) but I'm wondering whether there are further considerations for reconciling these vastly different esimates?

ted
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Re: spine resistance debates

Post by ted » Tue Apr 25, 2017 8:10 pm

First consider which is the more reliable basis for an estimate of spine neck resistance:
a value obtained from objective measurements produced by a series of experiments designed to generate the highest quality data from which one might calculate spine neck resistance directly,
or
a value calculated from a modeler's "plausible" but conscious assumptions about spine shape and the electrical properties of cytoplasm--assumptions that were made in the context of a "known at an earlier time" body of multisourced experimental estimates, of varying quality and indirectness, of spine neck resistance?
The former is what (Popovic et al., Nature Communications, DOI 10.1038/ncomms9436 (2015)) provide; the latter is what (Chiu et al., Science 340:759 (2013)) offer.

Bottom line: if you're seriously concerned about spine neck resistance, experimental design and suitability of methods to a particular task are of paramount importance.

That said, my suspicion is that the electrical properties of spines will eventually be discovered to differ between species, between cell classes within a given species, and even between spines located in different regions on the same cell. Besides, we already know of age- and disease-related differences in spine morphology that should affect their electrical properties.

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