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Fig. 10.3: Comparison of peristimulus time histograms (PSTH) of reciprocally or-
ganized neurons (column 1; reproduced with permission from [19, Fig. 4A, p. 182],
Copyright Springer-Verlag) in area 4, simulated area's 4 reciprocally organized pha-
sic (DVV) cell activities (column 2), PSTH of area's 4 bidirectional neurons (col-
umn 3; reproduced with permission from [19, Fig. 4A, p. 182], Copyright Springer-
Verlag), and simulated area's 4 co-contractive (P) cells activities (column 4) for a
flexion (row 1) and extension (row 2) movements in normal monkey. The vertical
bars indicate the onset of movement. Note a clear triphasic AG1-ANT1-AG2 pattern
marked with arrows is evident in PSTH of reciprocally and bidirectionally organized
neurons. The same triphasic pattern is evident in simulated DVV cell activities. The
second peak in simulated activities marked with an arrow arises from the spindle
feedback input to area's 5 DV activity.
whereas the
α
−
MN population activity was described by
dM
i
dt
=
φ
(
λ
B
i
−
M
i
)
·
(
A
i
+
P
+
χ
·
E
i
)
−
(
M
i
+
2
)
·
(
1
+
Ω
·
max
(
R
i
,
0
)
I
j
0
+
ρ
·
max
(
X
i
,
0
)+
max
(
))
,
(10.6)
where
X
i
was the type
I
b
interneuron (
I
b
IN) force feedback,
E
i
was the stretch feed-
back, and
I
j
was the type
I
a
interneuron. The type
I
a
interneuron (
I
a
IN) population
activity was defined as
dI
i
dt
=
φ
·
(
I
j
0
15
−
I
i
)
·
(
A
i
+
P
+
χ
E
i
)
−
I
i
(
1
+
Ω
·
max
(
R
i
,
0
)+
max
(
))
.
(10.7)
The
I
b
IN population activity without dopamine was given by
dX
i
dt
=
φ
·
(
15
−
X
i
)
F
i
−
X
i
·
(
0
.
8
+
2
.
2max
(
X
j
,
0
))
,
(10.8)
