Story structure in verbal reports of mental sleep experience after awakening in REM sleep.

Four night reports obtained after awakening in rapid eye movement (REM) sleep and their corresponding morning reports were collected from 20 subjects in an experimental night. All of the reports were analyzed using a slightly modified version of Mandler and Johnson's story grammar. Values for a series of indicators were compared with respect to the factors "moment of reporting" (at night/in the morning) and "order of reporting" (first/second/third/fourth report). Story-like organization seems to be a feature of dream production and not merely due to reconstructive effects in recall: values of no indicator significantly differ in night and morning reports. The more extensive thematic progression and the increasing complexity in reports over the first half of the night show that the effectiveness of the system of dream production varies in different periods of REM sleep. These findings, while strengthening the view of a multilevel character of the system of dream production, still generate the problem of the direction of activation (bottom-up or top-down) of this system.