NEURON vector play should use continuous=0 in stimuli.py

[WeinaJi]

Description

In stimuli.py, we usually inject the stimuli with "continuous=1", which is linear interpolation​.

  stim_vec.play(seg.extracellular._ref_e, time_vec, 1)​

But the points of time_vec and stim_vec out of the injection time window doesn't work as what we expect.
Ex:​

time_vec=[ 0.  1.5    2.  2.5    3.   3.] ​
stim_vec =[  0.  10.   0. 100.  10.  0.]​
dt = 0.5, duration = 5​
[  0.           3.33333333   6.66666667  10.       0.  100.          10.           5.           5.           5.        5.        ]​

According to​ Neuron docs

When continuous is 1 then linear interpolation is used to define the values between time points. ... When a value is greater than the range of the t vector, linear extrapolation of the last two points is used instead of a constant last value. If a constant outside the range is desired, make sure the last two points have the same y value and have different t values (if the last two values are at the same time, the constant average will be returned).

To Reproduce

from neuron import h
h.load_file("stdrun.hoc")
sec = h.Section(name="sec")
sec.insert("extracellular")
seg = sec(0.5)
t1 = h.Vector([ 0., 1.5,  2.,  2.5,   3.,   3.])
v1 = h.Vector([ 0., 10.,  0.,  100.,  10.,  0])
v1.play(seg.extracellular._ref_e, t1, 1)
rec = h.Vector()
rec.record(seg.extracellular._ref_e)
h.dt = 0.5
h.finitialize()
h.continuerun(5)
print(rec.as_numpy())
[  0.           3.33333333   6.66666667  10.           0.
 100.          10.           5.           5.           5.
   5.        ]

Expected behavior

We should turn off interpolation, continuous=0, add the last point duration+dt with amp=0 to the vectors​

from neuron import h
h.load_file("stdrun.hoc")
sec = h.Section(name="sec")
sec.insert("extracellular")
seg = sec(0.5)
t1 = h.Vector([ 0., 1.5,  2.,  2.5,   3.,   3.5])
v1 = h.Vector([ 0., 10.,  0.,  100.,  10.,  0])
v1.play(seg.extracellular._ref_e, t1, 0)
rec = h.Vector()
rec.record(seg.extracellular._ref_e)
h.dt = 0.5
h.finitialize()
h.continuerun(5)
print(rec.as_numpy())
[  0.   0.   0.   0.  10.   0. 100.  10.   0.   0.   0.]

Acceptance criteria

• How does pulse stimulus interact with play?