How Neurons Integrate

The first way is that a collateral forms a strong excitatory (+) input back onto itself. If an action potential arrived as input it would be sent as an output as well as used to re-activate the neuron itself after a small delay. This would produce a second action potential and a third etc.

A second way is the 'figure eight' network through two inhibitory synapses. Two inhibitory connections in series can act like a net excitation.

These neural networks are the simplest examples of short term memory.