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Now, in eLife, Eleanor Maguire of University College London (UCL) and colleagues – including Goffredina Spanò as first author – report that the dreams of four amnesia patients lacking a hippocampal memory system do not have the richness of detail found in most dreams ( Spanò et al., 2020). As a result, patients without a hippocampus find it difficult to imagine scenes that are coherent, possibly because the hippocampus is responsible for combining different elements of memory into a spatially coherent whole. Recent work in the cognitive neurosciences has established that the hippocampus, in addition to being involved in the formation of memories, is also part of a brain system that is involved in using memory to construct novel imagined scenarios and simulate possible future events ( Hassabis et al., 2007 Hassabis and Maguire, 2009 Schacter and Addis, 2007). However, studies dating back to the 1960s have suggested that patients with a damaged hippocampus still dream ( Torda, 1969a Torda, 1969b Solms, 2014) and, somewhat amazingly, such patients can have dreams involving recent experiences of which they have no conscious memory ( Stickgold et al., 2000)!īut are the dreams of patients with damage to hippocampus truly ‘normal’? Or alternatively, might such damage, while not preventing dreams, alter the form in which they are expressed? Indeed, there is reason to think that the hippocampus supports crucial aspects of dream construction beyond the simple insertion of memories. Given all this, one might guess that dreams are created by those regions of the brain responsible for memory. Although these dreams are rarely a faithful replication of any one memory, fragments of various recent experiences intermingle with other memories (usually related remote and semantic memories) to create a novel dream. How does our brain accomplish this? It has long been suspected that the hippocampus contributes to dreaming, in part due to its close association with memory: according to one estimate, about half of all dreams contain at least one element originating from a specific experience while the subject was awake ( Fosse et al., 2003). Our most vivid dreams are a remarkable replication of reality, combining disparate objects, actions and perceptions into a richly detailed hallucinatory experience.