Synaptic strength

Synapsic strength is defined by the amplitude of the change in membrane potential as a result of a presynaptic action potential. A "synapse" usually refers to a group of connections (or individual synapses) from the presynaptic neuron to the postsynaptic neuron. The strength of a synapse can be accounted for by the number and size of each of the connections from the presynaptic neuron to the postsynaptic neuron. The amplitude of postsynaptic potentials (PSPs) can be as low as 0.4mV to as high as 20mV. The amplitude of a PSP can be modulated by neuromodulators or can change as a result of previous activity. Changes in synaptic strength can be short-term, lasting seconds to minutes, or long-term (long-term potentiation, or LTP), lasting hours. Learning and memory are believed to result from long-term changes in synaptic strength, via a mechanism known as synaptic plasticity.