Fig. 1.

Line tracking during lucid REM sleep dreaming in a single participant. a Enlarged section showing LRLR eye movement signals and smooth tracking task as recorded in the horizontal EOG (HEOG). Upon awakening, the subject reported becoming lucid in the dream, making a LRLR signal (1), fully extending his right thumb, and tracking his thumb nail as he slowly swung his arm horizontally from center to approximately 30° left, back through center to 30° right, and finally leftward back to center. While tracking to the right, he noticed moving his head slightly in the direction of tracking both rightward and leftward as he reversed motion back to the center (2). He marked the end of the smooth tracking task (estimated 10 s) with a second LRLR signal (3). Having completed the task, he spent the remainder of his lucid dream exploring the dream environment, waking approximately 60 s later. See Supplementary Note 1 “Report of line tracking task” for the report associated with this figure. b Six channels of physiological data (HEOG, vertical EOG (VEOG), skin potential response (SPR)), occipital EEG bandpass filtered for alpha (OZ (8–12 Hz)), H-reflex amplitude (a measure of spinal reflex excitability) (upward black triangles mark H-reflex STIM), and electromyogram (EMG)) are shown during an initial period of wakefulness, REM period onset (REMP onset), transition to lucid REM sleep and awakening. Suppression of EMG and H-reflex amplitude along with reduced alpha in EEG confirm that the participant remained in uninterrupted REM sleep during lucid dreaming, including LRLR signals and during completion of the slow tracking task. Lucid dream onset is localized by the autonomic nervous system surprise response (scalp skin potential response (SPR; black asterisk)) before the LRLR signal