Neural facilitation
Encyclopedia
Neural facilitation, also known as paired pulse facilitation, is a concept in neuroscience
where an increase in the postsynaptic potential (EPP
or EPSP
) is evoked by a second impulse.
The phenomena of paired-pulse facilitation (PPF) and depression (PPD) are well known short-term forms of synaptic plasticity
. They are expressed in electrophysiological experiments as changes in the amplitude of a test EPSC evoked by a second presynaptic spike that follows the first (conditioning) one in the paired-pulse paradigm. The second PSP can be up to five times the size of the first. Successive PSPs can grow the original PSP several dozen times within a second in some synapses. Facilitation often occurs with a build and decay time course of about 100 milliseconds.
Facilitation has been shown to be a phenomenon that occurs solely at the presynaptic side of a synapse
, where synaptic vesicles containing neurotransmitter are released from a pool. As such, facilitation is thought to be the result of an increase in probability of vesicle release from this pool. Early experiments by Del Castillo & Katz in 1954 and Dudel & Kuffler in 1961 showed that facilitation was possible at the neuromuscular junction even if transmitter release does not occur. Experiments by Katz & Miledi in 1968 demonstrated that the presence of calcium
ions was necessary for both facilitation and neurotransmitter release. This led to the residual Ca2+ hypothesis: that facilitation is caused by an action of calcium remaining in the nerve terminals after the conditioning stimulus. Calcium channels are present in neurons which are capable of allowing calcium to flow in.
The presence of PPF or PPD is dependent on the types of synapse
s and the experimental conditions. It varies strongly according to the interval between the conditioning and test pulses.
Short-term plasticity can be responsible for cognitive abilities involving temporal processes, eg. the determination of: order, duration, and interval.
This is an example of a dynamic synapse.
Neuroscience
Neuroscience is the scientific study of the nervous system. Traditionally, neuroscience has been seen as a branch of biology. However, it is currently an interdisciplinary science that collaborates with other fields such as chemistry, computer science, engineering, linguistics, mathematics,...
where an increase in the postsynaptic potential (EPP
End-plate potential
End plate potentials are the depolarizations of skeletal muscle fibers caused by neurotransmitters binding to the postsynaptic membrane in the neuromuscular junction. They are called "end plates" because the postsynaptic terminals of muscle fibers have a large, saucer-like appearance...
or EPSP
Excitatory postsynaptic potential
In neuroscience, an excitatory postsynaptic potential is a temporary depolarization of postsynaptic membrane potential caused by the flow of positively charged ions into the postsynaptic cell as a result of opening of ligand-sensitive channels...
) is evoked by a second impulse.
The phenomena of paired-pulse facilitation (PPF) and depression (PPD) are well known short-term forms of synaptic plasticity
Synaptic plasticity
In neuroscience, synaptic plasticity is the ability of the connection, or synapse, between two neurons to change in strength in response to either use or disuse of transmission over synaptic pathways. Plastic change also results from the alteration of the number of receptors located on a synapse...
. They are expressed in electrophysiological experiments as changes in the amplitude of a test EPSC evoked by a second presynaptic spike that follows the first (conditioning) one in the paired-pulse paradigm. The second PSP can be up to five times the size of the first. Successive PSPs can grow the original PSP several dozen times within a second in some synapses. Facilitation often occurs with a build and decay time course of about 100 milliseconds.
Facilitation has been shown to be a phenomenon that occurs solely at the presynaptic side of a synapse
Synapse
In the nervous system, a synapse is a structure that permits a neuron to pass an electrical or chemical signal to another cell...
, where synaptic vesicles containing neurotransmitter are released from a pool. As such, facilitation is thought to be the result of an increase in probability of vesicle release from this pool. Early experiments by Del Castillo & Katz in 1954 and Dudel & Kuffler in 1961 showed that facilitation was possible at the neuromuscular junction even if transmitter release does not occur. Experiments by Katz & Miledi in 1968 demonstrated that the presence of calcium
Calcium in biology
Calcium plays a pivotal role in the physiology and biochemistry of organisms and the cell. It plays an important role in signal transduction pathways, where it acts as a second messenger, in neurotransmitter release from neurons, contraction of all muscle cell types, and fertilization...
ions was necessary for both facilitation and neurotransmitter release. This led to the residual Ca2+ hypothesis: that facilitation is caused by an action of calcium remaining in the nerve terminals after the conditioning stimulus. Calcium channels are present in neurons which are capable of allowing calcium to flow in.
The presence of PPF or PPD is dependent on the types of synapse
Synapse
In the nervous system, a synapse is a structure that permits a neuron to pass an electrical or chemical signal to another cell...
s and the experimental conditions. It varies strongly according to the interval between the conditioning and test pulses.
Short-term plasticity can be responsible for cognitive abilities involving temporal processes, eg. the determination of: order, duration, and interval.
This is an example of a dynamic synapse.