Dependence of Transformation of Intrinsic Rhythmic Impulse Activity of Neurons on Spatio-Temporal Organization of Synaptic Actions on Dendrites: A Simulation Study |
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Authors: | I B Kulagina S M Korogod |
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Institution: | 1.International Center for Molecular Physiology (Dnipropetrovsk Division),National Academy of Sciences of Ukraine,Dnipropetrovsk,Ukraine |
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Abstract: | The aim of the study to elucidate the biophysical mechanisms able to determine specific transformations of the patterns of
output signals of neurons (neuronal impulse codes) depending on the spatio-temporal organization of synaptic actions coming
to the dendrites. We studied mathematical models of the neocortical layer 5 pyramidal neurons built according to the results
of computer reconstruction of their dendritic arborizations and experimental data on the voltage-dependent conductivities
of their dendritic membrane. This work is a continuation of our previous studies that showed the existence of certain relations
between the complexity of neural impulse codes, on the one hand, and the complexity, size, metrical asymmetry of branching,
and nonlinear membrane properties of the dendrites, on the other hand. This relation determines synchronous (with some phase
shifts) or asynchronous transitions of asymmetrical dendritic subtrees between high and low depolarization states during the
generation of output impulse patterns in response to distributed tonic activation of dendritic inputs. In this work we demonstrate
the first time that the appearance and pattern of transformations of complex periodical impulse trains at the neuron’s output
associated with receiving a short series of presynaptic action potentials are determined not only by the time of arrival of
such a series, but also by their spatial addressing to asymmetric dendritic subtrees; the latter, in this case, may be in
the same (synchronous transitions) or different (asynchronous transitions) electrical states. Biophysically, this phenomenon
is based on a significant excess of the driving potential for a synaptic excitatory current in low-depolarization regions,
as compared with that in high-depolarization dendritic regions receiving phasic synaptic stimuli. These findings open a novel
aspect of the functioning of neurons and neuronal networks. |
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