Object Type:
ddsyn
Description:
modified synchan with table front end to transform
voltage
to activation, for dendro-dendritic synapses. Calculates
channel current therefore needs membrane state.
Author:
U. S. Bhalla, Caltech (5/91)
----------------------------------------------------------------------------ELEMENT PARAMETERS
DataStructure:
Size:
Fields:
dd_syn_type
[in src/olf/olf_struct.h]
164 bytes
Gk
channel conductance
channel current
channel reversal potential
maximum conductance
tau1
open time constant of channel activation
tau2
close time constant of channel activation
transf
table for transform from Vm to activation;
usual interpolation element with the normal
set of fields; set up using TABCREATE, filled
by indexing as usual, and interpolated using
TABFILL
activation channel activation; set either by a table
lookup of the transform of the incoming
VOLTAGE message or by synaptic input
transf_alloced
flag for allocation of transform
X
state variable for time response
Y
state variable for time response
Ik
Ek
gmax
----------------------------------------------------------------------------SIMULATION PARAMETERS
Function:
DDSyn
[in src/olf/dd_syn.c]
Classes:
segment, channel
Actions:
INIT
PROCESS
RESET
CHECK
SET
DUMP
SAVE2
RESTORE2
TABCREATE
TABFILL
Messages:
VOLTAGE voltage
[tells channel what membrane
potential is]
ACTIVATION activation
[sends activation directly
to
channel; sums linearly with
other ACTIVATION input and
transformed V_PRESYN input]
V_PRESYN presynaptic-voltage
[sends presynaptic voltage
to
transform table; sums linearly
at output of table, so
multiple V_PRESYN inputs are
first transformed, then their
activations are summed]
RAND_ACTIVATION
[rather than sending direct
probability amplitude
activation signal, specifies
probability (from 0 to 1) that
activation of size amplitude
will occur at synapse (useful
for sending random synaptic
input to synapse)]
----------------------------------------------------------------------------Notes:
Dendrodendritic synapse with tabulated transform
from presyn potential to postsyn activation.
The table for the transform is created using tabcreate
and is shared with all copies of the element
The ddsyn element is the equivalent of a synchan element
with a tabulated transform from input voltage to channel
activation. This serves as a way of representing
dendro-dendritic synapses. The usual fields and messages for
the synchan element remain available. The table entries are
filled in the usual ways from the script interface, and can
be
shared between ddsyn elements.
Example:
Here we create a ddsyn channel to act as the synaptic input
for granule cells in an olfactory bulb model.
// for dd, ax, and centrif inputs
create
ddsyn
glu_gran_usb
call glu_gran_usb TABCREATE 10 -0.070
setfield glu_gran_usb \
Ek
{EGlu} \
tau1
4.0e-3 \
// sec
tau2
6.0e-3 \
// sec
0.05
gmax
{GGlu} \
// Siemens
// Setting up the table for transforming
// from presyn Vm to activation
transf->table[0] 0 \
transf->table[1] 0.05 \
transf->table[2] 0.1 \
transf->table[3] 0.2 \
transf->table[4] 0.5 \
transf->table[5] 0.7 \
transf->table[6] 0.8 \
transf->table[7] 0.9 \
transf->table[8] 0.95 \
transf->table[9] 0.98 \
transf->table[10] 1
call glu_gran_usb TABFILL 1000 0
See also:
Scripts/examples/ddsyn