Unit 3: Long-Term Potentiation

Learning

Modification of behaviour by experience

Perpectual learning

Learning to recognize a stimulus

Memory

Retention of learned info

Synaptic plasticity

Modifiability of synaptic strength as a result of changes in electrical activity; important for refinement of connections during development and remodelling neural circuits

Synaptic potentiation

An increase in the amplitude of an EPSP following a brief burst of APs in a presynaptic neuron

EPSP (excitatory postsynaptic potential)

Synaptic potential that makes a postsynaptic neuron more likely to generate an action potential

Synaptic depression

A decrease in EPSP amplitude following presynaptic activity

Donald Hebb

Learning is associated with synaptic plasticity and involves simultaneous, coincident synaptic activation of connected neurons

Long-term potentiation (LTP)

An increase in a cell's firing potential after brief, rapid stimulation. Cellular mechanism for learning an memory; hippocampal excitatory synapses show persistent, long-lasting increase in synaptic transmission following brief periods of increased electrical activity

- A long term increase in excitability of a neuron to a particular synaptic input caused by repeatedly high-frequency activity of that input

Induction of LTP

Giving brief, repeated trains of high frequency electrical stimulation, usually 100 Hz for 1 s, to a population of presynaptic excitatory fibres

Cooperativity

Likelihood of inducing LTP increases when number of stimulated fibres is increased

Associativity

LTP can be induced in a weaker pathway when its activity is associated/paired with activity in a stronger pathway

Synapse specificity

LTP is evident only at activated synapses

Process of LTP induction

1. High frequency stimulation releases Glu from presynaptic terminals

2. Entry of Ca2+ into postsynaptic cell through VGCCs and NMDARs

3. Several protein kinases implicated in induction and maintenance

LTP expression

-Increased number of effective release sites in presynaptic terminals

-Increased probability of NT recreation because of AP broadening/enhanced excitation-secretion coupling in nerve terminals

-Increase in number of postsynaptic receptors and/or increased receptor sensitivity to NT

Anisomycin, cycloheximide

Drugs blocking translation

Actinomycin-D (L-LTP)

Drugs blocking transcription

NMDA receptor

A receptor site on the hippocampus that influences the flow of information between neurons by controlling the initiation of long-term potentiation

AMPA receptor

An ionotropic glutamate receptor that controls a sodium channel; stimulated by AMPA.

Stronger connections between neurons

1. Changes in strength and efficiency of synaptic connections

2. Structural changes such as more dendrite spine which gives an additional site where synaptic connections can happen

3. Increase release in neurotransmitters since there is active activity going on in the synapse