Poster Abstract Low Dimensionality of Supraspinally Induced Force Fields Andrea d'Avella and Emilio Bizzi Department of Brain and Cognitive Sciences Massachusetts Institute of Technology Cambridge, MA 02139-4307 Recent experiments using electrical and NMDA microstimulation of the spinal cord gray matter and cutaneous stimulation of the hindlimb of spinalized frogs have provided evidence for a modular organization of the frog's spinal cord circuitry. The output of a module can be characterized as a force field, the collection the isometric forces generated at the ankle over different locations in the leg's workspace.
Different modules can be independently combined so that their force fields linearly sum.
The goal of this study was to ascertain whether the force fields generated by the supraspinal structures result from the combinations of a small number of modules. We recorded a set of force fields generated by the electrical stimulation of the vestibular nerve in seven frogs and we performed a Principal Component Analysis to study their dimensionality. This result is compatible with the hypothesis that vestibular fields are generated by combinations of a small number of spinal modules.