58 Computational Neuroscience: Simulated Demyelinating Neuropathies and Neuronopathies
demyelinated cases (Figs. 11b,c and 15b,c). Much of the externally
recorded nodal current (I
m
, in Fig. 16a) does not fl ow across the
axolemma, since the I
a
(dotted line) is much smaller, but passes
longitudinally via the paranodal seal resistance to the periaxonal
space. The decrease of the paranodal seal resistance causes an
increase in the nodal external membrane current (I
m
, PFD, in Fig.
16a), whereas the internodal demyelination causes a decrease in this
current for the IFD and PIFD cases. Conversely, considerably more
currents fl ow across the paranodal and internodal axolemma (I
a
,
dotted line in Fig. 16b,c) than is apparent from the current fl owing ...