Routine Name:
scaletabchan
Description:
tables
Performs scaling and offsets of the tabchannel A and B
for a specified gate.
Usage:
duplicate
scaletabchan channel-element gate mode sx sy ox oy channel-element
gate
sx
sy
ox
oy
mode
Example:
name of a the tabcahnnel
gate to be modified; one of: X, Y, or Z
x-axis (voltage) scale factor
y-axis scale factor
x-axis (voltage) offset
y-axis offset
one of: a[lpha] b[eta] t[au] m[inf]
// double (spread out) the voltage range for the Na
// activation alpha rate constant.
scale_tabchan Na X alpha 2.0 1.0 0.0 0.0
// increase the K_dr activation time constant by 20%.
scaletabchan K_dr X tau 1.0 1.2 0.0 0.0
// shift the Na inactivation curve (Y gate) left by 5 mV.
scale_tabchan Na Y minf 1.0 1.0 -0.005 0.0
// increase the K_dr activation time constant by 0.1 sec.
scaletabchan K_dr X tau 1.0 1.0 0.0 0.1
Notes:
The tabchannel internal tables for the specified gate are
modified to provide scalings and/or offsets to the
voltage
dependent function specified by the mode.
Here, alpha
and
beta are the Hodgkin-Huxley rate constants, tau is the
time
constant for activation or inactivation, and minf is the
steady state activation or inactivation. The effect of
applying these scalings and offsets may be viewed by
using the
edit_channel menu of Neurokit.
Note that the scale and offset is always relative to the
last
operation, and not to the original values.
One can
reverse
changes in oy and sy because they just shift and scale
the
table values.
However, ox and sx perform offsets and
scaling
of the horizontal axes by moving data in the tables.
This can
cause data to spill out of the ends of the tables and be
lost.
Thus, large changes in the x-axis should be avoided, if
you
plan to reverse your changes.
In a large compartmental model or large network, one may
have
many copies of a particular prototype channel.
Usually,
one
wants these to behave identically.
It is also desirable
to
minimize the amount of storage space used by the internal
tables. For these reasons, copies of the channel which
are
created by the copy command or by readcell use the same
tables
as the original prototype, rather than creating new
copies of
the tables.
This is true of all objects which contain
tabular
fields.
Sometimes you may want to change just the one
copy of
the channel.
In this case, use the "-duplicate" option
with
scaletabchan.
See also:
tabchannel, Tables.