Amnesia

Amnesia is defined as a global impairment in the ability to acquire new memories regardless of sensory modality, and a loss of some memories, especially recent ones, from the period before amnesia began.^[1] During states of amnesia a person will usually retain functional perceptual abilities and short-term memory which can still be used to recall events that recently occurred; this effect is distinct from the memory impairment produced by sedation.^[2] As such, a person experiencing amnesia may not obviously appear to be doing so, as they can often carry on normal conversations and perform complex tasks.

This state of mind is commonly referred to as a "blackout", an experience that can be divided into 2 formal categories: "fragmentary" blackouts and "en bloc" blackouts.^[3] Fragmentary blackouts, sometimes known as "brownouts", are characterized by having the ability to recall specific events from an intoxicated period but remaining unaware that certain memories are missing until reminded of the existence of those gaps in memory. Studies suggest that fragmentary blackouts are far more common than "en bloc" blackouts.^[4] In comparison, En bloc blackouts are characterized by a complete inability to later recall any memories from an intoxicated period, even when prompted. It is usually difficult to determine the point at which this type of blackout has ended as sleep typically occurs before this happens.^[5]

Amnesia is often accompanied by other coinciding effects such as disinhibition, sedation, and memory suppression. It is most commonly induced under the influence of heavy dosages of GABAergic depressants, such as alcohol,^[6] benzodiazepines,^[7] GHB,^[8] and zolpidem^[9]. However, it can also occur to a much lesser extent under the influence of extremely heavy dosages of hallucinogenic compounds such as psychedelics, dissociatives, Salvia divinorum, and deliriants.