What dreaming can reveal about cognitive and brain functions during sleep? A lexico-statistical analysis of dream reports

Abstract

Multidimensional statistical procedures were used to analyze three corpuses of dream reports on the basis of their word content, automatically and without any a priori coding of their meaning. The analyses revealed that the same clusters of dream reports were found consistently in all three datasets. Each cluster of dream content was characterized by a specific predominant cognitive category such as recent memory, visuo-spatial processing, verbal activity, reasoning, or emotions. In addition, the analysis of a 15-months dream diary from the same individual showed that the proportion of different clusters of dreams remained stable over time. We also show that the identification of these well-defined and common cognitive characteristics in dream reports could provide important insights into the processing of information within specialized brain regions during sleep. In conclusion, dream reports contain valuable information about the cognitive processes and brain functions that participate to their generation.