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Dendritic spikes have been recorded in numerous types of neurons in the brain and are thought to have great implications in neuronal communication, memory, and learning. They are one of the major factors in long-term potentiation. A dendritic spike is initiated in the same manner as that of an axonal action potential.
A dendritic spine (or spine) is a small membrane protrusion from a neuron's dendrite that typically receives input from a single axon at the synapse.Dendritic spines serve as a storage site for synaptic strength and help transmit electrical signals to the neuron's cell body.
Neural backpropagation is the phenomenon in which, after the action potential of a neuron creates a voltage spike down the axon (normal propagation), another impulse is generated from the soma and propagates towards the apical portions of the dendritic arbor or dendrites (from which much of the original input current originated).
If sufficient signals are received within a short period of time (i.e. before the overall voltage decays to background), the voltage of the segment will rise above a threshold, giving rise to a non-linear dendritic spike, which travels, effectively undiminished, all the way to the cell body, and which causes it to become partially depolarised.
Back-propagation is not completely passive, but modulated by the presence of dendritic voltage-gated potassium channels. Furthermore, in certain types of neurons, a train of back-propagating action potentials can induce a calcium action potential (a dendritic spike) at dendritic initiation zones. [22] [23]
Recent conjecture suggests that each neuron might function as a collection of independent threshold units. It is suggested that a neuron could be anisotropically activated following the origin of its arriving signals to the membrane, via its dendritic trees. The spike waveform was also proposed to be dependent on the origin of the stimulus. [108]
In 1973, M. M. Taylor [1] suggested that if synapses were strengthened for which a presynaptic spike occurred just before a postsynaptic spike more often than the reverse (Hebbian learning), while with the opposite timing or in the absence of a closely timed presynaptic spike, synapses were weakened (anti-Hebbian learning), the result would be an informationally efficient recoding of input ...
Dendritic cells are present in tissues that are in contact with the body's external environment, such as the skin (where there is a specialized dendritic cell type called the Langerhans cell), and the inner lining of the nose, lungs, stomach and intestines.