THRESHOLDS AND SUPEREXCITABILITY

[Lyle J. Borg-Graham]

RE: Peter Cariani's message

With the ever-increasing types (or as Paul Adams puts it,
"Balkanization") of voltage/time/2nd-messenger(e.g. Ca++)-dependent
channels being identified in various cells, it is clear that any
canonical threshold model per se (tri-phasic time-dependency or
otherwise) is problematic. The emerging picture is that there are a
broad spectrum of channel combinations which may be participating in
different contexts/neurons, resulting in quite different response
modes.

Whether a given model reproduces that spectrum or not depends, of
course, on what the model is claiming to represent. The intricate and
subtle interactions between channels in bullfrog slime neurons or
hippocampal pyramidal cells (for example) are neat, and may *actually*
be important for function. But that does not mean a much simpler
membrane model would be more appropriate for a given simulation.

Lyle Borg-Graham