<unk>  are a type of EEG abnormality with periodicity less than 4.0 seconds. They can consist of sharp waves or spikes, spike and wave, polyspikes or triphasics with background attenuation in between transients.
Periodic short-interval diffuse discharges
Intermittent rhythmic delta activity
Inter-ictal spiking
Periodic lateralized epileptiform discharges
Generalized periodic epileptiform discharges
Cyclic alternating pattern
Depolarization-induced suppression of inhibition
Biphasic and polyphasic sleep