![]() By means of a novel measure called mean electrotonic path length, we show that the influence of dendritic morphology on burst firing is attributable to the effect both dendritic size and dendritic topology have, not on somatic input conductance, but on the average spatial extent of the dendritic tree and the spatiotemporal dynamics of the dendritic membrane potential. Interestingly, the results are largely independent of whether the cells are stimulated by current injection at the soma or by synapses distributed over the dendritic tree. Either reducing or enlarging the dendritic tree, or merely modifying its topological structure without changing total dendritic length, can transform a cell's firing pattern from bursting to tonic firing. We found that there is only a range of dendritic sizes that supports burst firing, and that this range is modulated by dendritic topology. Using computational models of neocortical pyramidal cells, we here show that not only the total length of the apical dendrite but also the topological structure of its branching pattern markedly influences inter- and intraburst spike intervals and even determines whether or not a cell exhibits burst firing. Dendritic morphology is not fixed but can undergo significant changes in many pathological conditions. However, the underlying mechanisms are poorly understood, and the impact of morphology on burst firing remains insufficiently known. Besides ion-channel composition, dendritic morphology appears to be an important factor modulating firing pattern. A particularly relevant pattern for neuronal signaling and synaptic plasticity is burst firing, the generation of clusters of action potentials with short interspike intervals. The dendrites are also common in cast products, where they may become visible by etching of a polished specimen.ĭendrites also form during the freezing of many nonmetallic substances such as ice.ĭendrites usually form under non-equilibrium conditions.Ĭommon dendritic metal material is nickel carbonyl, where the particles have a classical "spiky" morphology.Neurons display a wide range of intrinsic firing patterns. One application where dendritic growth and resulting material properties can be seen is the process of welding. Smaller dendrites generally lead to higher ductility of the product. Conversely, a rapid cooling cycle with a large undercooling will increase the number of nuclei and thus reduce the size of the resulting dendrites(and often lead to small grains). The dendritic growth will result in dendrites of a large size. If the metal is cooled slowly, nucleation of new crystals will be less than at large undercooling. Note also that a curved interface is less energetically favourable, thus limiting the sharpness of the dendrites. This fact increases the solidification rate at the most protruding points, thus resulting in dendrite formation. A small distance away from the solidification front, the concentration is more favourable for solidification as well as the temperature is lower. Solidification also releases energy, thus impeding solidification even more. The increased concentration results in an increased melting point impeding solidification near the front. But, at increased cooling rates, the solidification may be so rapid that the alloy concentration at the solidification front will be different from the overall concentration. At slow cooling rates, the solidification front will be planar and stable. The requirement is that the molten metal is supercooled below the freezing point of the metal. Safe Weighing Range Ensures Accurate Resultsĭendrites usually form in multiphase alloys. ![]()
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