Damage To The Nervous Spontaneous Discharge Relocated Rule, Under The Two-parameter Adjustment

The information transition and the rhythm of neural firing are very important for the elucidation of neural coding mechanism, which have attracted much attention. Recent study on the neural firing patterns and the firing pattern transitions suggest that there is signal information hidden in the dynamical bifurcations.Neurons are able to adapt to the internal and external environments by adjust their activity level, and show a great variety of rhythms and bifurcations during this process. Recent researches indicate that with the decreasing of [Ca2+]0, the neural firing appears several patterns and pattern transitions. On the other hand, with the increase of K+ channel blocker TEA, there are three bifurcation between period 1 and period 2 bursting.These results indicate that the neural firing patterns can be changed with the excitation related parameters change, i.e., the activation of ion channel. But there are several parameters which can influent the neural firing, and the influence is nonlinear. they have a complex combined action. So it is necessary to have a comprehensive consideration of the ion channels, to make the results approach actual conditions.In addition, many theoretical researches suggest that the bifurcation will be different under the dual-parameter modulation. Fixing the conditional parameter at one level, we have observed a series bifurcation scenarios by adjusting the bifurcation parameter, then fixing the conditional parameter at another level, a different bifurcation scenarios under the same bifurcation parameter at one neural pacemaker model was observed. The results suggest that under different conditional parameter, different bifurcation scenarios of firing patterns were exhibited in an identical neural pacemaker.Based on the previous studies, this work takes a comprehensive consideration of the influence of Ca2+ and K+ channel to neural firing patterns and patterns transitions. The main experiments are as follows:the first is to have an observation of the bifurcation senarios with the decreasing of [Ca2+]0; the second is to have an observation of the bifurcation scenarios with the increasing of [K+]0; finally, we study the conjunct influence of Ca2+ and K+ channel activation on bifurcation scenarios in an identical neural pacemaker, by taking the 4-AP as conditional parameter and [Ca2+]0 as the bifurcation parameter. The purpose is to have an intensive and all-round understanding of the neural firing patterns.The main results are as follows: 1. The neural pacemaker was perfumed with normal Kreb's solution and Ca2+ free solution, with the decreasing of Ca2+, the neural firing was increased and several firing pattern transitions were observed, such as adding-bifurcation, doubling-bifurcation.2. When [K+]o was changed, the neural firing patterns can be different. In the experimental pacemaker, gradually increased the [K+]o from normal concentration to 40 mmol/L, the neural firing rate was increased. Many different firing patterns appeared, including a bifurcation scenario from period 1 bursting to period 1 spiking directly, a bifurcation scenario from period 1 to period 1 spiking via period 2 bursting, some of the transitions was via period-doubling bifurcation, and some via period-adding bifurcation. A complex and a complete rhythm transitions patterns also observed in the high [K+]o Kreb's solution.3. We chose the conductance of voltage-dependent potassium ion channels as conditional parameter, and the extracellular calcium concentration as bifurcation parameter, to give a demonstration of how the firing pattern of neural pacemaker responses to dual parameter adjusting. Briefly, when concentration of the 4-aminopyridine (4-AP), a voltage-dependent potassium ion channels blocker, was kept at a different level and extracellular Ca2+ concentration was decreased gradually, different bifurcation scenarios of firing patterns were exhibited in the identical neural pacemaker. Furthermore,4-AP perfusion makes the bifurcation of some neural pacemakers becoming more complex, but others becoming simpler.The results show that under the same bifurcation parameter, different neural firing pattern transitions can get on identical neural pacemaker with different conditional parameter. Experimental observation indicates that such an adjustment of multi-parameters plays important roles in the central nervous system. Simultaneous changes in calcium and potassium conductance underpin not only the acute changes in synaptic strength but also the expression of learning related synaptic plasticity. We believe that, nonlinear dynamic study of the firing pattern transition principles corresponding to multi-parameters will be beneficial to exploring the mechanisms of neural information processing, such as synaptic plasticity and learning.