Intrusions of a drowsy mind: neural markers of phenomenological unpredictability

Abstract

The transition from a relaxed to a drowsy state of mind is often accompanied by hypnagogic experiences: most commonly, perceptual imagery, but also linguistic intrusions, i.e., the sudden emergence of unpredictable anomalies in the stream of inner speech. This study has sought to describe the contents of such intrusions, to verify their association with the progression of sleep onset, and to investigate the electroencephalographic processes associated with linguistic intrusions as opposed to more common hypnagogic perceptual imagery. A single participant attended 10 experimental sessions in the EEG laboratory, where he was allowed to drift into a drowsy state of mind, while maintaining metacognition of his own experiences. Once a linguistic intrusion or a noticeable perceptual image occurred, the participant pressed a button and reported it verbally. An increase in the EEG-defined depth of drowsiness as assessed by the Hori system of sleep onset was observed in the last 20 s before a button press. Likewise, EEG Dimension of Activation values decreased before the button press, indicating that the occurrence of cognitively incongruous experiences coincides with the rapid change of EEG predictability patterns. EEG hemispheric asymmetry analysis showed that linguistic intrusions had a higher alpha and gamma power in the left hemisphere electrodes, whereas perceptual imagery reports were associated with a higher beta power over the right hemisphere. These findings indicate that the modality as well as the incongruence of drowsiness-related hypnagogic experiences is strongly associated with distinct EEG signatures in this participant. Sleep onset may provide a unique possibility to study the neural mechanisms accompanying the fragmentation of the stream of consciousness in healthy individuals.

In your phase: Neural phase synchronisation underlies visual imagery of faces

“…A classical experimental approach for studying endogenous changes in the EEG related to internal fluctuations during cognitive tasks is to analyze the EEG window before the onset of motor responses when participants report internal changes. For instance, this approach has been used for studying neural signatures of bistable awareness (Britz, Landis, & Michel, 2009; Canales-Johnson et al, 2019; Parkkonen, Andersson, Hämäläinen, & Hari, 2008), binocular rivalry (Doesburg, Kitajo, & Ward, 2005) and intrusions of consciousness (Noreika et al, 2015). Following the same rationale, but this time for the analysis of visually imagined faces, we computed ongoing EEG activity preceding the onset of each response (button press), i.e.…”

Dormio

“…EEG and fMRI work has shown that the same hypofrontality underlying creative flexibility while awake is also common to the early stages of sleep [37], [14]. REM sleep has been shown to enhance the integration of unassociated information for creative problem solving [29], [10]. Hypofrontality in sleep thus provides possibilities for creative idea generation in hypnagogia, if novel thoughts can be captured.…”

“…By popular account, thinkers August Kekulé, Thomas Edison and Nikola Tesla all regularly napped with a steel ball in hand: As they lost consciousness and muscle control, they were jolted awake suddenly as it fell to the floor below [42]. A dive into the humanities reveals use of this technique by artists as well, from Nabokov to Mozart to Poe [24], [29]. Artists and scientists alike used this crude but fascinating technique to awaken during sleep onset, unearthing creative inspiration found in fragmented dreams on the threshold between drowsy stage 1 sleep and fully unconscious stage 2 [28].…”

“…Artists and scientists alike used this crude but fascinating technique to awaken during sleep onset, unearthing creative inspiration found in fragmented dreams on the threshold between drowsy stage 1 sleep and fully unconscious stage 2 [28]. This semi-conscious state, called Hypnagogia, is characterized by phenomenological unpredictability: visual and kinesthetic hallucinations, spontaneous words, distorted perception of space and time, awareness of sleep onset and loss of sense of self have all been reported [29], [25]. Unlike other dream states allowing for awareness, namely REM-state lucid dreaming, Hypnagogia is a typical stage of circadian rhythm, extremely common across subjects and requiring no training [29].…”

“…This semi-conscious state, called Hypnagogia, is characterized by phenomenological unpredictability: visual and kinesthetic hallucinations, spontaneous words, distorted perception of space and time, awareness of sleep onset and loss of sense of self have all been reported [29], [25]. Unlike other dream states allowing for awareness, namely REM-state lucid dreaming, Hypnagogia is a typical stage of circadian rhythm, extremely common across subjects and requiring no training [29]. The system described in this paper, Dormio, offers an interface to this liminal state of mind: We present results suggesting feasibility of dream interfacing as well as overall satisfaction and comfort with the system.…”