Memory replays are a multisensory subtype of internal hallucinations that result in a person reliving memories through the experience of vivid daydreams, reoccurring emotions or sensations, and hallucinations. At higher levels of intensity, these are often referred to as "flashbacks". The memories themselves can be significant life events with high levels of personal meaning attributed to them, generic recent occurrences, or long forgotten experiences from childhood.   At extremely high levels of this experience, the effect can result in the person experiencing every memory they've ever had. These memories can be presented in linear order as the person's life flashes before their eyes, or they can be presented simultaneously in the often overwhelming form of a vast network of memories that the person sees, experiences, and innately understands.
Memory replays are often accompanied by other coinciding effects, such as scenarios and plots, internal hallucinations, and introspection. They are most commonly induced under the influence of heavy dosages of hallucinogenic compounds, such as psychedelics, dissociatives, and deliriants. However, they can also commonly occur during sobriety as a result of traumatic experiences, particularly when the person suffers from post-traumatic stress disorder. 
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- A comparison of involuntary autobiographical memory retrievals | https://onlinelibrary.wiley.com/doi/abs/10.1002/acp.1264
- Memory in Posttraumatic Stress Disorder: Properties of voluntary and involuntary, traumatic and non-traumatic autobiographical memories in people with and without PTSD symptoms | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2597428/