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11.6 The Extended VITE-FLETE Models with Dopamine
Figure 11.4 depicts the extended VITE-FLETE with dopamine model of volun-
tary movement preparation and execution in Parkinson's disease. In the previous
chapter, the temporal development of the model without dopamine was discussed.
The model under normal conditions successfully predicted the origin of the tripha-
sic pattern of muscle activation and its neural substrates. In this chapter and al-
though a much larger set of experimental data has been briefly described in the
previous section, I will describe how the triphasic pattern and its neural and EMG
substrates change when dopamine is depleted in basal ganglia, cortex, and spinal
cord. Detailed descriptions of the model and its complete mathematical formalism
Extended-VITE
T
1
GO
T
2
V
1
V
2
GV
1
GV
2
DA
DA
P
A
1
A
2
Extended-FLETE
DA
I
1
I
2
DA
M
2
S
2
D
2
D
1
S
1
M
1
DA
R
1
R
2
DA
X
1
X
2
spindle response
spindle response
Fig. 11.4: Extended VITE-FLETE models with dopamine (DA).
Top
: DA-VITE
model for variable-speed trajectory generation.
Bottom
: DA-FLETE model of the
opponent processing spinomuscular system.
Arrow lines
: excitatory projections;
solid dot lines
: inhibitory projections;
diamond-dotted green lines
: dopamine mod-
ulation;
dotted arrow lines
: feedback pathways from sensors embedded in muscles.
GO
: basal ganglia output signal;
P
: bidirectional co-contractive signal;
T
: target po-
sition command;
V
: DV activity;
GV
: DVV activity;
A
: current position command;
M
: alpha motoneuronal (MN) activity;
R
: renshaw cell activity;
X, Y, Z
: spinal in-
hibitory interneuron (IN) activities;
I
a
: spinal type a inhibitory IN activity;
S
: static
gamma MN activity;
D
: dynamic gamma MN activity;
1,2
: antagonist cell pair.
