Transcript ppt file

New perspectives on spinal motor
systems.
Bizzi E, Tresch MC, Saltiel P, d'Avella A
Nat Rev Neurosci 2000 Nov;1(2):101-8
The role of the spinal cord
The production and control of complex motor functions
are usually attributed to central brain structures such as
cortex, basal ganglia and cerebellum. In traditional
schemes the spinal cord is assigned a subservient
function during the production of movement, playing a
predominantly passive role by relaying the commands
dictated to it by supraspinal systems. This review
challenges this idea by presenting evidence that the
spinal motor system is an active participant in several
aspects of the production of movement, contributing to
functions normally ascribed to 'higher' brain regions.
Isometric force fields
Bizzi et al. 1991
Smooth fields
The dynamics
Mussa-Ivaldi et al. 1990
3D forcefields in the rat spinal cord
Summation of force fields
F(x1)
F(x2)
F(x1) + F(x2)
F(x1+x2)
r > 0.9
Mussa-Ivaldi et al. 1994
Control I: Iontophorese
Taken together, these results
support the concept of a
modular organization of the
motor system in the frog’s
spinal cord and delineate the
topography of these modules.
They also suggest that these
modules are used by the
circuitry underlying rhythmic
pattern generation by the
spinal cord.
P. SALTIEL, M.C. TRESCH & E. BIZZI, J. Neurophysiol., 2000
Control II: random activation
r median = 0.871
Loeb et al., J. Cog. Neurosci., 2000
Control II: random activation
Only few of the random activations leed to robust synergies
Loeb et al., J. Cog. Neurosci., 2000
Control III: Dimensionality
A. D’AVELLA AND E. BIZZI, PNAS, 1998
The involvement of spinal interneurons in the
preparation for movement.
Y. Prut & E.E. Fetz, Nature, 1999
A comparison of different motor structures
Y. Prut & E.E. Fetz, Nature, 1999
The process of motor adaptation following
ankle extensor nerve cut
The sensory side
... We found that 14%
neurons represented one
or more specific joint
angles. The activity of
another 39% neurons
was significantly affected
by limb geometry
changes, but 47%
consistently elaborated a
foot position representation in the coordinates
of the limb axis.
G. Bosco, R.E. Poppele, & J. Eian, J. Neurophysiol. 2000
The end
Muscle activation patterns