By determining the spatial pattern of action potential signaling, dendritic morphology thus helps to define the size and interdependence of functional compartments in the neuron. They also suggest that changes in dendritic geometry during development and plasticity will critically affect propagation. If this threshold is met, the action potential occurs and the message travels down the axon via a process of depolarization. This only occurs if the neuron’s threshold has been met - meaning it has received enough stimulation from the original sending neuron. As an action potential travels down the axon, the polarity changes across the. These findings indicate that differences in dendritic geometry act in concert with differences in voltage-gated channel density and kinetics to generate the diversity in dendritic action potential propagation observed between neurons. Action potential must occur for the message to continue to travel down the axon. Transmission of a signal within a neuron (in one direction only, from dendrite to axon terminal) is carried out by the opening and closing of voltage-gated ion channels, which cause a brief reversal of the resting membrane potential to create an action potential. Dendrites can be thought of as analogous to transistors in a computer, performing simple operations using electrical signals. We show that these functional consequences of the differences in dendritic geometries can be explained quantitatively using simple anatomical measures of dendritic branching patterns, which are captured in a reduced model of dendritic geometry. We also demonstrate that forward propagation of dendritically initiated action potentials is influenced by morphology in a similar manner. Thus in Purkinje cells and dopamine neurons, backpropagation is relatively insensitive to changes in channel densities, whereas in pyramidal cells, backpropagation can be modulated over a wide range. These cells generate electrical impulses (action potientials) that travel as waves of depolarization along the cells membrane. 83 Abstract The active electrical properties of dendrites shape neuronal input and output and are fundamental to brain function. Dendritic geometry also determines the extent to which modulation of channel densities can affect propagation. These action potentials allow single neurons to solve two long-standing computational problems in neuroscience that were considered to require multilayer neural networks. Remarkably, the range of backpropagation efficacies observed experimentally can be reproduced by the variations in dendritic morphology alone. With identical complements of voltage-gated channels, different dendritic morphologies exhibit distinct patterns of propagation. Synaptic inputs to the dendrite distant from the action potential initiation zone would be expected to have relatively less impact on cell firing. All graded potentials travel from the dendrites. To examine the contribution of dendritic morphology to the efficacy of propagation, simulations were performed in detailed reconstructions of eight different neuronal types. Each neuron has a threshold that must be met before an action potential travels the length of the neurons axon. Action potential propagation links information processing in different regions of the dendritic tree.
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