Question regarding resting membrane potentials and junction potentials

[torbjone]

When I try to run cell models through the AllenSDK, like this one,
http://celltypes.brain-map.org/experiment/electrophysiology/490387590
I get very low resting membrane potentials, around - 93 mV, while the same link states that the resting membrane potential should be -79.2 mV. This stated value of -79.2 mV is also consistent with both the experimental data shown, and the simulation results shown.

The discrepancy between my simulated resting potentials and the given resting potentials does however go away if I subtract the given junction potential of -14 mV from my simulations, like what is for example done here:

AllenSDK/allensdk/model/biophysical/utils.py

Line 303 in 7dd9dfe

v = (v - junction_potential) * mV

However, I find this very confusing, since it seems to indicate that the stated value of the resting potential of -79.2 mV has not been corrected for the junction potential, and that the "true" resting potential is about - 93 mV? Does anybody know what is going on here? Am I missunderstanding something? The resting potentials of neurons are typically said to be ~ -65 mV to -70 mV, so to me - 93 mV seems extremely low?

[tmchartrand]

You're not misunderstanding, just underestimating the diversity of resting potentials I think. This one is indeed very hyperpolarized, but it's normal to vary far beyond -65 to -70. The fact that voltages are corrected in models and not in reported ephys properties is indeed confusing, but just reflects conventions that differ between fields - most electrophysiologists report uncorrected values, while most modelers work with corrected values. I can't say it's ideal, but we've at least documented it in the ephys and modeling whitepapers (http://help.brain-map.org/display/celltypes/Documentation).