M.Sc Thesis

M.Sc StudentDe-Castro Sharon
SubjectThe Minimum Transition Hypothesis
DepartmentDepartment of Electrical and Computer Engineering
Supervisors DR. Karniel Amir
PROFESSOR EMERITUS Gideon Inbar (Deceased)


Nature sets in motion by signs and watchwords, which are made with little momentum…Just as in the army the soldiers are set in motion by one word as if by a given signal and continue to move until they receive another signal to stop, so the muscles move in order and harmony from established custom .”  William Harvey (1578-1657 ( .

The complexity of the motor system is among other things due to its great redundancy which enables to perform even the simplest action in many ways. Muscle synergies provide the functional connection between the neural control signal and the muscle activation signal and may serve as a mean to employ and reduce some of the redundancy in the motor system .

The goal of this study is to develop computational tools in order to explore the minimum transition hypothesis (MTH). The hypothesis asserts that the muscle synergies have been developed in order to minimize the effort of the CNS (central nervous system) as measured by the number of transitions in the control command .

Two algorithms were developed. The first one is a modified ICA algorithm which enables the reconstruction of sparse control signals. The second algorithm finds the dominant synergies, using clustering, and reconstructs the control signals. We show that the modified ICA algorithm is superior to the original ICA and demonstrate its performance on synthesized sparse signals

 We employed these algorithms to extract the synergies from an EMG database from 13 muscles in the hind limb of behaving intact and deafferented frogs. We show that the residual error for the intact preparations is larger than that of the deafferent preparation. By means of the Clustering algorithm we show that the number of synergies as well as the number of transitions in the intact preparation is similar to those of the deafferent preparation.

These results are consistent with the MTH .