COMMENT
Modification by Johannes Luthman of the builtin NetStim.mod of NEURON 6.1.
NB, this code has not been used with CVode.
Changes from NetStim:
The output events can be set to follow gamma distributions of order 16,
where 1 corresponds to the original Poisson process generated by NetStim.mod.
The gamma process is generated in the same way as that given by timetable.c
in GENESIS 2.3.
A refractory period has been added.
The output length is determined by duration in ms instead of number of events.
Parameters:
interval: mean time between spikes (ms)
start: start of first spike (ms)
noise: amount of randomness in the spike train [01], where 0 generates
fully regular spiking with isi given by parameter interval.
duration: length in ms of the spike train.
order: Integers [16] giving the order of gamma distribution.
refractoryPeriod (ms)
ENDCOMMENT
NEURON {
ARTIFICIAL_CELL GammaStim
RANGE interval, start, duration, order, noise, refractoryPeriod
}
PARAMETER {
interval = 10 (ms) <1e9,1e9> : time between spikes (msec)
start = 1 (ms) : start of first spike
noise = 0 <0,1> : amount of randomness (0.0  1.0) in spike timing.
duration = 1000 (ms) : input duration
order = 1 <1,6> : order of gamma distribution. 1=pure poisson process.
refractoryPeriod = 0 (ms)
}
ASSIGNED {
event (ms)
on
end (ms)
}
PROCEDURE seed(x) {
set_seed(x) : Calling .seed() from hoc affects the event streams
: generated by all NetStims, see http://www.neuron.yale.edu/phpBB2/viewtopic.php?p=3285&sid=511cb3101cc8f4c12d47299198ed40c2
}
INITIAL {
on = 0 : off
if (order < 1  order > 6) {
order = 1
}
if (noise < 0) {
noise = 0
}
if (noise > 1) {
noise = 1
}
if (start >= 0) {
: randomize the first spike so on average it occurs at
: start + noise*interval
event = start + invl(interval)  interval*(1.  noise)
: but not earlier than 0
if (event < 0) {
event = 0
}
net_send(event, 3)
}
}
PROCEDURE init_sequence(t(ms)) {
on = 1
event = t
end = t + 1e6 + duration
}
FUNCTION invl(mean (ms)) (ms) {
: This function returns spiking interval
if (mean <= 0.) {
mean = .01 (ms)
}
if (noise == 0) {
invl = mean
}else{
invl = (1.  noise)*mean + noise*meanRndGamma(order, refractoryPeriod, mean)
}
}
PROCEDURE event_time() {
event = event + invl(interval)
if (event > end) {
on = 0
}
}
NET_RECEIVE (w) {
if (flag == 0) { : external event
if (w > 0 && on == 0) { : turn on spike sequence
init_sequence(t)
net_send(0, 1): net_send args: duration of event, flag to a NET_RECEIVE block,
: see The NEURON book ch 10 p343
}else if (w < 0 && on == 1) { : turn off spiking
on = 0
}
}
if (flag == 3) { : from INITIAL
if (on == 0) {
init_sequence(t)
net_send(0, 1)
}
}
if (flag == 1 && on == 1) {
net_event(t) : See NEURON book p. 345. Sum: net_event tells NetCon something has happened.
event_time()
if (on == 1) {
net_send(event  t, 1)
}
net_send(.1, 2)
}
}
FUNCTION meanRndGamma(gammaOrder(1), refractoryPeriod(ms), mean(ms)) (1) {
: Code translated from the timetable object of GENESIS 2.3.
LOCAL x
x = 1.0
FROM i = 0 TO gammaOrder1 {
x = x * scop_random()
}
x = log(x) * (interval  refractoryPeriod) / gammaOrder
meanRndGamma = x + refractoryPeriod
}
