What is "posthypnotic amnesia"

n. selective amnesia after being in a hypnotic state of events occurring during hypnosis or of information designated by the hypnotist

Post-hypnotic amnesia is the inability in hypnotic subjects to recall events that took place while under hypnosis. This can be achieved by giving individuals a suggestion during hypnosis to forget certain material that they have learned either before or during hypnosis. Individuals who are experiencing post-hypnotic amnesia cannot have their memories recovered once put back under hypnosis and is therefore not state dependent. Nevertheless, memories may return when presented with a pre-arranged cue. This makes post-hypnotic amnesia similar to psychogenic amnesia as it disrupts the retrieval process of memory. It has been suggested that inconsistencies in methodologies used to study post-hypnotic amnesia cause varying results.