MOTOR CONTROL FOR SPEECH
R.
Port
-based on D. Rosenbaum Human Motor
Control, Chapter 1.
A. Skilled movement vs. unskilled
reaches: 2 phases -
ballistic
motion + refined end
B. Efficiency problem: how to minimize effort to achieve a goal
-minimizing jerk
-synergies: special-purpose combination
of constraints on muscles
C. Serial order problem (Karl Lashley, 1951 `The problem
of serial order in behavior', PsyRev)
1. response chain model:
a) Each item excites the next item: n->n+1->n+2
or, for greater speed, each might excite the next but one:
n -> n+2
n+1 -> n+3 ...
2. interelement
inhibition.
The first item ihibits the second and the second inhibits
the 3d, etc.
Thus, making the first one fire, releases the inhibition
on the 2d, which releases the 3d, etc.
3. hierarchical
models
eg, comb model, schemas
D. Degrees of freedom problem : How to control all the
thousands of possible variables in a manageable way.
path planning
(kinematics vs dynamics) and motor equivalence
inverse kinematics: find
a path given a goal
joint angle
coordinates vs. spatial coordinates
inverse dynamics problem:
find muscle activtn pattern given a path
cooarticulation problem
E. Feedback (perceptual-motor integration)
1. closed loop
control (eg, a thermostat or the Watt steam governor
but: a) What
is the right correction when there are many possible reasons for an
error?
The problem of a multidimensional system
b) Sherrington's `spinal cat' (which spine severed) could still walk
normally
(if its body was suspended over a treadmill).
2. open loop
- actions are performed without feedback. Especially
needed
for skilled action
F. Mass-Spring model:
a) helps greatly to solve
the degrees-of-freedom problem
b) sets a target, not a
movement - so no start/stop control is needed.
c) thus it is open loop
d) rate of motion,
peak velocity location, etc require no explicit control
G. Multiple Coordinated Movements
1. Two limbs: Haken-Kelso-Bunz (1985) model for
finger
wagging
2. . Jaw + Lower Lip + Upper Lip
Folkins-Abbs etc.
neural model of David
Rosenbaum