Long-term potentiation

Long term potentiation is the form of learning at the synaptic level, by strengthening of a specific synapse. Induction of these changes results from repeated, high frequency stimulation of a synapse, also known as tetanus. The stimulated AMPA receptors open with glutamate binding, and allow Na2+ into the cell. When enough of these are opened, the voltage-gated NMDA receptors become unblocked by Mg2+ and allow Ca2+ in. NMDA receptors need both glutamate and depolarization to open. This elicits a positive feedback loop in which retrograde gaseous neurotransmitters like nitric oxide are produced to stimulate glutamate release in the presynaptic cell. Late phase long-term potentiation is characterized by structural changes such as fatter synapses, more dendritic spines, more terminal buttons, and a larger number of synapses.