title: Can we still dream when the mind is blank? Sleep and dream mentations in auto-activation deficit.
abstract: Bilateral damage to the basal ganglia causes auto-activation deficit, a neuropsychological syndrome characterized by striking apathy, with a loss of self-driven behaviour that is partially reversible with external stimulation. Some patients with auto-activation deficit also experience a mental emptiness, which is defined as an absence of any self-reported thoughts. We asked whether this deficit in spontaneous activation of mental processing may be reversed during REM sleep, when dreaming activity is potentially elicited by bottom-up brainstem stimulation on the cortex. Sleep and video monitoring over two nights and cognitive tests were performed on 13 patients with auto-activation deficit secondary to bilateral striato-pallidal lesions and 13 healthy subjects. Dream mentations were collected from home diaries and after forced awakenings in non-REM and REM sleep. The home diaries were blindly analysed for length, complexity and bizarreness. A mental blank during wakefulness was complete in six patients and partial in one patient. Four (31%) patients with auto-activation deficit (versus 92% of control subjects) reported mentations when awakened from REM sleep, even when they demonstrated a mental blank during the daytime (n = 2). However, the patients' dream reports were infrequent, short, devoid of any bizarre or emotional elements and tended to be less complex than the dream mentations of control subjects. The sleep duration, continuity and stages were similar between the groups, except for a striking absence of sleep spindles in 6 of 13 patients with auto-activation deficit, despite an intact thalamus. The presence of spontaneous dreams in REM sleep in the absence of thoughts during wakefulness in patients with auto-activation deficit supports the idea that simple dream imagery is generated by brainstem stimulation and is sent to the sensory cortex. However, the lack of complexity in these dream mentations suggests that the full dreaming process (scenario, emotions, etc.) require these sensations to be interpreted by higher-order cortical areas. The absence of sleep spindles in localized lesions in the basal ganglia highlights the role of the pallidum and striatum in spindling activity during non-REM sleep.
authors.affiliation: 1 Sleep Disorders Unit, Pitié-Salpêtrière Hospital, AP-HP, Paris 6 University, Paris, France.
authors.forename: Smaranda
authors.initials: S
authors.lastname: Leu-Semenescu
authors.forename: Ginevra
authors.initials: G
authors.lastname: Uguccioni
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Golmard
authors.forename: Virginie
authors.initials: V
authors.lastname: Czernecki
authors.forename: Jerome
authors.initials: J
authors.lastname: Yelnik
authors.forename: Bruno
authors.initials: B
authors.lastname: Dubois
authors.forename: Baudouin
authors.initials: B
authors.lastname: Forgeot d'Arc
authors.forename: David
authors.initials: D
authors.lastname: Grabli
authors.forename: Richard
authors.initials: R
authors.lastname: Levy
authors.forename: Isabelle
authors.initials: I
authors.lastname: Arnulf
mesh_terms: D000328:Adult; D000368:Aged; D057565:Apathy / Q000502:physiology; D001479:Basal Ganglia / Q000503:physiopathology; D004325:Dreams / Q000502:physiology*; D004644:Emotions / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008606:Mental Processes / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology; D008875:Middle Aged; D012894:Sleep Stages / Q000502:physiology*; D012893:Sleep Wake Disorders / Q000503:physiopathology*; D014851:Wakefulness / Q000502:physiology
keywords: apathy; basal ganglia, anoxic lesions; dream; spindles