When isolated from all synaptic input, each cell fires at
its own natural interspike interval (ISI), so the network is
asynchronous (see raster plot above; horizontal axis in ms,
vertical axis "cell number").
Synchrony can be achieved by making synaptic connections
inhibitory (negative weights) and propagation delays > 0,
although the slowest cells may miss some beats or drop out
entirely. Notice the slight phase delay with increasing natural
ISI.