Daniel K. Hartline and Ann M. Castelfranco


presented at the Neurons, Networks and Motor Behavior Symposium, University of Arizona, Tucson, AZ November 8-10, 1995 and at the 25th Annual Meeting of the Society for Neuroscience at San Diego, CA, November 12, 1995*.


In voltage clamp experiments on neurons with attached processes, measurements are subject to error owing to failure of space clamp. As much current research involves voltage clamp under these less-than-iedal conditions, it would be very helpful to be able to assess the seriousness of such errors and, if possible, to correct them reliably. We have been conducting a systematic study of such space-clamp errors and in this poster present corrections for errors in the case of a single uniformly distributed voltage-dependent conductance. Simulated clamp runs were made on model neurons with a passive soma attached to an equivalent-cylinder representation of a dendritic tree possessing Hodgkin-Huxley-type channels with voltage independent time constants. Clamp currents were fitted to the equation:

Errors in the parameters gbar, Vrev, taum, q, tauh, V0 and nu were determined as a function of apparent (i.e. measured) gbar, expressed as a ratio, Gamma', to leak conductance. The figure shows corrections for the four steady-state parameters in the case of an outward current mechanism distributed along a dendrite of electrotonic length L=0.5.

{Note: corrections in the poster (additive or multiplicative) are of the opposite sense from corrections shown in the abstract (subtractive or divisive).}


  1. The question
  2. Studies conducted
  3. Procedure
  4. Non-inactivating currents
  5. Inactivating currents
  6. Variable length
  7. Length-dependence
  8. Conclusions

Panel 1

Notes: Parameters approximate conditions for motorneurons of the spiny lobster stomatogastric ganglion; see Hartline et al. (1993)
; Modeling program NEURON available from Michael Hines.
Panel 2

Panel 3

Panel 4

Panel 5

Panel 6

Panel 7

Panel 8

Panel 9

Panel 10

* see Soc. Neurosci.Abstr. 21: 63 (1995). Support: Human Frontiers Science Program.
Return to Hartline Home Page. Return to PBRC Home Page.