A mathematical model of arm movement during rhythmic motor activity

There is physiological evidence that Central Pattern Generators (CPG´s), at the level of spinal cords, are responsible for generating rhythmic movements in some species of animals like salamanders. There are also other researches suggesting that in human beings there are CPGs at higher levels of the Central Nervous System (CNS) which facilitate the control of rhythmic movements. We proposed a model using the idea of CPG´s to mimic human rhythmic arm movement. This model is a neural oscillator which consists of two neurons coupled by reciprocal inhibitions and exhibits different types of bursting and tonic neuronal behaviors. We consider once a one-compartment (the whole neuron or the soma) and then a two-compartment (soma-dendrite) model to describe the two neurons of the CPG, that describes here the motor control system. Each compartment is described by Hodgkin-Huxley (HH) equations. We show that bursting frequency and the number of action potentials can be controlled by variation of intracellular parameters in both models. In addition, considering dendrite component will allow us to make transition between different neural activities. To describe arm rhythmic movement, the motor control system will be coupled into two motoneurons by inhibitory and excitatory connections. The motoneurons drive the extensor and flexor muscles. We found out that both synaptic coupling and motor control parameters have direct impacts on the spiking frequency of motoneurons which play a critical role in the behavior of arm movement.