Routine Name:
syndelay
Description:
This command is used to set or to add a small "synaptic"
component to the delay fields of synapses. It is useful
for when cells are very close together and thus where
planardelay or volumedelay give unrealistically small
delays.
Usage:
syndelay path delay
-add
-uniform scale
-gaussian stdev maxdev
-exponential mid max
-absoluterandom
path
\
\
\
\
\
A wildcarded list of elements which must be synchans or
objects derived from synchan.
delay -- This sets all the synaptic delays in question to be
equal to "delay", or adds "delay" to the existing
delay if the -add option is selected.
-add
This option causes the delays to be added to the
preexisting delays in the synapses instead of
overwriting them.
The next four options are used to add random components to
the
delay.
How these random components are added to the delays
is
explained below.
-uniform scale -- This option gives a random number taken
from a uniform distribution in the range
{-scale, scale}.
-gaussian stdev maxdev -- This option gives a random number
taken from a gaussian distribution centered on zero,
with a standard deviation equal to "stdev" and with
a maximum value of "maxdev". The maximum value is
used to limit the random component to a given range.
-exponential mid max -- This option gives a random number
taken from an exponential distribution with a
minimum value of zero, a 1/e point of "mid" and a
maximum value of "max". This is mainly for backwards
compatibility with genesis 1.4.
-absoluterandom This option alters the way the random number
is combined with the nominal delay to give the actual
delay, as described below.
Once a random component has been created for a given delay,
it is used to set the delay as follows. If the
-absoluterandom option has not been selected the delay is set
to be:
final_delay = delay + (delay * random_number)
Whereas if the -absoluterandom option has been selected then
we have
final_delay = delay + random_number
Thus the default is to have the amount of randomness as a
constant proportion of the delay value.
Example:
syndelay /cell[]/apical_dend/Ex_chan 0.001 \
-add -gaussian 0.1 0.3
This command will add a small delay to the delay fields in
the
synapses in /cell[]/soma/apical_dend/Ex_chan. The "synaptic"
delay added will be 1 millisecond plus a random component.
Notes:
large
The delays are never allowed to go negative even if a
negative random component is added.
Negative delays are
set
to zero.
If the -add option is chosen, the random component modifies
only the delay added and not the total delay.
See also:
18
planardelay, volumeconnect, volumeweight, syndelay; Chapter
of the Book of GENESIS (2nd ed.) has a lengthy discussion
on
this and related commands.