The construction of movement by the spinal cord


We used a computational analysis to identify the basic elements with which the vertebrate spinal cord constructs one complex behavior. This analysis extracted a small set of muscle synergies from the range of muscle activations generated by cutaneous stimulation of the frog hindlimb. The flexible combination of these synergies was able to account for the large number of different motor patterns produced by different animals. These results therefore demonstrate one strategy used by the vertebrate nervous system to produce movement in a computationally simple manner.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Muscle activation patterns evoked from cutaneous stimulation of the frog hindlimb.
Figure 2: Example of muscle covariation patterns within evoked responses.
Figure 3: The contribution of each muscle synergy to responses evoked from different regions of the skin surface for three different animals (a, b, c).
Figure 4: The ability of synergies from sites on the rostral and caudal margins of the hindlimb to explain responses evoked from other skin regions.


  1. 1

    Bernstein, N. The Coordination and Regulation of Movements (Pergamon Press, New York, 1967).

  2. 2

    Lee, W. A. Neuromotor synergies as a basis for coordinated intentional action. J. Motor Behav. 16, 135–170 (1984).

  3. 3

    Macpherson, J. M. in Motor Control: Concepts and Issues (eds. Humphrey, D. R. & Freund, H.–J) 33–47 (Wiley, Chichester, 1991).

  4. 4

    Sherrington, C. S. Flexion–reflex of the limb, crossed extension–reflex and reflex stepping and standing. J. Physiol. (Lond.) 40, 28–121 (1910).

  5. 5

    Grillner, S. in Handbook of Physiology, sec. 1, vol. 2 (ed. Brooks, V. B.) 1179 –1236 (American Physiological Society, Bethesda, MD, 1981).

  6. 6

    Stein, P. S. G. & Smith J. L. in Neurons, Networks, and Motor Behavior (eds. Stein P. S. G., Grillner, S., Selverston A. I. & Stuart D. G.) 61–73 (MIT Press, Cambridge, MA, 1997).

  7. 7

    Jacobs, R. & Macpherson, J. M. Two functional muscle groupings during postural equilibrium tasks in standing cats. J. Neurophysiol. 76, 2402–2411 ( 1996).

  8. 8

    Bizzi, E., Mussa–Ivaldi, F A. & Giszter S. F. Computations underlying the production of movement: a biological perspective. Science 253, 287–291 (1991).

  9. 9

    Giszter, S. F., Mussa–Ivaldi, F. A. & Bizzi, E. Convergent force fields organized in the frog spinal cord. J. Neurosci. 13, 467– 491 (1993).

  10. 10

    Mussa–Ivaldi, F. A., Giszter, S. F., & Bizzi, E. Linear combinations of primitives in vertebrate motor control. Proc. Natl. Acad. Sci. USA 91, 7534–7538 (1994).

  11. 11

    Bishop, C. M. Neural Networks for Pattern Recognition (Oxford Univ. Press, Oxford, 1995).

  12. 12

    Hertz, J., Krogh, A. & Palmer R. G. Introduction to the Theory of Neural Computation (Addison–Wesley, Reading, MA 1991).

  13. 13

    d'Avella, A. & Bizzi, E. Low dimensionality of supraspinally induced force fields. Proc. Natl. Acad. Sci. USA 95, 7711–7714 (1998).

  14. 14

    Fleshman, J. W., Lev–Tov, A. & Burke, R. E. Peripheral and central control of flexor digitorum longus and flexor hallucis longus motoneurons: the synaptic basis of functional diversity. Exp. Brain Res. 54, 133– 149 (1984).

  15. 15

    Pratt, C. A., Chanaud, C. M. & Loeb, G. E. Functionally complex muscles of the cat hindlimb. IV. Intramuscular distribution of movement command signals and cutaneous reflexes in broad, bifunctional thigh muscles. Exp. Brain Res. 85, 281–299 (1991).

  16. 16

    Schouenborg, J. & Kalliomaki, J. Functional organization of the nociceptive withdrawal reflexes I. Activation of hindlimb muscles in the rat. Exp. Brain Res. 83, 67–78 (1990).

  17. 17

    Schouenborg, J. & Weng, H.–R. Sensorimotor transformations in a spinal motor system. Exp. Brain Res. 100, 170–174 (1994).

  18. 18

    Schouenborg, J., Weng, H.–R. & Holmberg, H. Modular organization of spinal nociceptive reflexes: a new hypothesis. News Physiol. Sci. 9, 261–265 (1994).

  19. 19

    Berkinblitt, M. B., Feldman, A. G. & Fukson, O. I. Adaptability of innate motor patterns and motor control mechanisms. Behav. Brain Sci. 9, 585– 638 (1986).

  20. 20

    Lawson, C. L. & Hanson, R. J. Solving Least Squares Problems. (Prentice–Hall, Englewood Cliffs, NJ, 1974).

  21. 21

    Harman, H. H. Modern Factor Analysis (Univ. of Chicago Press, Chicago, 1976).

  22. 22

    Olshausen, B. A. & Field, D. J. Emergence of simple–cell receptive field properties by learning a sparse code for natural images. Nature 381, 607– 609 (1996).

Download references


We thank Sandro Mussa–Ivaldi and Andrea d'Avella for reading versions of this manuscript and Simon Giszter, Peter Dayan, Kuno Wyler and James Galagan for suggestions. M.C.T. was supported by a HHMI predoctoral fellowship. This research was supported by NIH NS09343 and ONR N00014–95–I0445 to E.B.

Author information

Correspondence to Emilio Bizzi.

Rights and permissions

Reprints and Permissions

About this article

Further reading