Associate Researcher, Békésy Laboratory of Neurobiology (PBRC)
University of Iowa, Ph.D. (Applied Mathematical Sciences)
University of Iowa, M.S. (Mathematics)
University of California at Davis, B.S. (Mathematics)
My research is concerned with the interaction between cellular morphology and the computational properties of neurons, which I study using mathematical and computational modeling techniques based on the biophysical properties of neurons. This is joint work with Dr. Daniel Hartline.
A current focus is on how the structure of "myelin" - a multilayered, lipid-rich membranous sheath that surrounds some axons - changes the properties of nerve impulse conduction and whether this can provide insight into how natural selection might drive myelin evolution. Although it is a relatively complex structure, myelin has evolved independently several times: at least twice in crustaceans, once in annelids, as well as once in higher vertebrates (gnathostomes). Using biophysical models, we have investigated: 1) the effects of hypothetical intermediate stages in myelin evolution on nerve impulse conduction velocity, and 2) the transition from continuous to saltatory conduction with the addition of segments of insulation to an unmyelinated axon. We are currently developing models to investigate invertebrate neuron-glial cell interactions.
Another series of studies has looked at how the morphology of neurons with active conductances located at a distance from the cell body can lead to space-clamp errors in voltage clamp experiments. The nature of the distortions in the measured properties of the voltage-dependent conductances and possibilities for recognizing and correcting these errors were investigated using simple theoretical models. This approach was used to investigate space-clamp errors in measuring transient potassium current in crab stomatogastric neurons using detailed multi-compartment models of dye-filled cells.
Young, R.G. Castelfranco, A.M., and Hartline D.K., (2013) The “Lillie Transition”:models of the onset of saltatory conduction in myelinating axons. J. Comput. Neurosci. 34: 533-546. DOI 10.1007/s10827-012-0435-3.
Castelfranco, A. M., and Hartline, D.K, (2004) Corrections for space-clamp errors in measured parameters of voltage-dependent conductances in a cylindrical neurite. Biol. Cybern. 90: 280-290.
Hartline, D.K., and Castelfranco, A.M., (2003) Simulations of voltage clamping poorly space-clamped voltage-dependent conductances in a uniform cylindrical neurite. J. Comput. Neurosci. 14: 253-269.
Castelfranco, A. M., and Hartline, D.K, (2002) Simulations of space-clamp errors in estimating parameters of voltage-gated conductances localized at different electrotonic distances. Neurocomputing 44-46: 75-80.
Verderber, A., Castelfranco, A. M., Nishioka, D., and Johnson, K. G. (1999) Cardiovascular risk factors and cardiac surgery outcomes in a multiethnic sample of men and women. Am. J. Crit. Care 8:140-148.