Déjà-rêvé: Prior dreams induced by direct electrical brain stimulation

Abstract Background Epileptic patients sometimes report experiential phenomena related to a previous dream they had during seizures or electrical brain stimulation (EBS). This has been alluded to in the literature as “deja-reve” (“already dreamed”). However, there is no neuroscientific evidence to support its existence and this concept is commonly mixed up with deja-vu. We hypothesized that deja-reve would be a specific entity, i.e., different from other experiential phenomena reported in epileptic patients, induced by EBS of specific brain areas. Methods We collected all experiential phenomena related to dreams induced by electrical brain stimulations (EBS) in our epileptic patients (2003–2015) and in a review of the literature. The content of these deja-reve and the location of EBS were analyzed. Results We collected 7 deja-reve in our database and 35 from the literature, which corresponds to an estimated prevalence of 0.3‰ of all EBS-inducing deja-reve. Deja-reve is a generic term for three distinct entities: it can be the recollection of a specific dream (“episodic-like”), reminiscence of a vague dream (“familiarity-like”) or experiences in which the subject feels like they are dreaming (literally “a dreamy state”). EBS-inducing “episodic-like” and “familiarity-like” deja-reve were mostly located in the medial temporal lobes. “Dreamy states” were induced by less specific EBS areas although still related to the temporal lobes. Conclusions This study demonstrates that deja-reve is a heterogeneous entity that is different from deja-vu, the historical “dreamy state” definition and other experiential phenomena. This may be relevant for clinical practice as it points to temporal lobe dysfunction and could be valuable for studying the neural substrates of dreams.