Augmentation is one of four components of short-term synaptic plasticity that increases the probability of releasing synaptic vesicles during and after repetitive stimulation such that when all the other components of enhancement and depression are zero, where
Augmentation can be differentiated from the other components of enhancement by its kinetics of decay and by pharmacology.
Augmentation selectively decays with a time constant of about 7 seconds and its magnitude is enhanced in the presence of barium.
All four components are thought to be associated with or triggered by increases in internal calcium ions that build up and decay during repetitive stimulation.
During a train of impulses the enhancement of synaptic strength due to the underlying component
Augmentation is differentiated from the three other components of enhancement by its time constant of decay.
This is shown in Table 1 where the first and second components of facilitation, F1 and F2, decay with time constants of about 50 and 300 ms, and potentiation, P, decays with a time constant than ranges from tens of seconds to minutes depending on the duration of stimulation.
Depression at some synapses may arise from depletion of synaptic vesicles available for release.
Depression of synaptic vesicle release may mask augmentation because of overlapping time courses.
Also included in the table is the fraction change in transmitter release arising from one impulse.
The balance between various components of enhancement and depression at the mammalian synapse is affected by temperature so that maintenance of the components of enhancement is greatly reduced at temperatures lower than physiological.