Evaluation of the effect of dendritic branching on signal processing in hippocampus pyramidal cells



Since branching region of an active nerve fiber is an abrupt widening of the structure, two concepts emerge: first, the stimulating current must be sufficient to raise the outgrowing fibers above the thresh¬old, and secondly, the stimulating current will be divided in proportion to the characteristic admittance of the branches. On the other hand, blocking of the nerve impulse in this region is an important issue that has been evaluated in several different ways including Hodgkin-Huxely, Markin-Chizmadzhev, general leading edge, cubic leading edge, and piecewise linear leading edge models. Each of these models has its advantages and disadvantages, but none of them can be completely accounted. Meanwhile, hippocampus is a part of the nervous system that is involved in sophisticated functions including memory. Hence, we have evaluated the behavior of branching dendrites in pyramidal cells of the hippocampus not only to elucidate the effect of branching on signal processing, but also to understand more precisely the function of pyramidal cells. In this study, MATLAB software (6.5) was used to design a program that evaluates the effect of branching point on propagation or blockade of impulse. In order to execute this program, we have modeled the nerve fiber as an electrical circuit and exerted some neurobiological features of pyramidal cell to this model. Finally, a MATLAB program was introduced that can be used as a model of pyramidal cells in experimental researches.