Neural dynamics necessary and sufficient for transition into pre-sleep induced by EEG neurofeedback.
The transition from being fully awake to pre-sleep occurs daily just before falling asleep; thus its disturbance might be detrimental. Yet, the neuronal correlates of the transition remain unclear, mainly due to the difficulty in capturing its inherent dynamics. We used an EEG theta/alpha neurofeedback to rapidly induce the transition into pre-sleep and simultaneous fMRI to reveal state-dependent neural activity. The relaxed mental state was verified by the corresponding enhancement in the parasympathetic response. Neurofeedback sessions were categorized as successful or unsuccessful, based on the known EEG signature of theta power increases over alpha, temporally marked as a distinct "crossover" point. The fMRI activation was considered before and after this point. During successful transition into pre-sleep the period before the crossover was signified by alpha modulation that corresponded to decreased fMRI activity mainly in sensory gating related regions (e.g. medial thalamus). In parallel, although not sufficient for the transition, theta modulation corresponded with increased activity in limbic and autonomic control regions (e.g. hippocampus, cerebellum vermis, respectively). The post-crossover period was designated by alpha modulation further corresponding to reduced fMRI activity within the anterior salience network (e.g. anterior cingulate cortex, anterior insula), and in contrast theta modulation corresponded to the increased variance in the posterior salience network (e.g. posterior insula, posterior cingulate cortex). Our findings portray multi-level neural dynamics underlying the mental transition from awake to pre-sleep. To initiate the transition, decreased activity was required in external monitoring regions, and to sustain the transition, opposition between the anterior and posterior parts of the salience network was needed, reflecting shifting from extra- to intrapersonal based processing, respectively.
Department of Psychology, Tel Aviv University, Tel Aviv 6997801, Israel; Functional Brain Center, Wohl Institute for Advanced Imaging, Tel-Aviv Sourasky Medical Center, Tel Aviv 6423906, Israel.
Sivan
S
Kinreich
Functional Brain Center, Wohl Institute for Advanced Imaging, Tel-Aviv Sourasky Medical Center, Tel Aviv 6423906, Israel.
Ilana
I
Podlipsky
School of Computer Science, Tel Aviv University, Tel Aviv 6997801, Israel.
Shahar
S
Jamshy
School of Computer Science, Tel Aviv University, Tel Aviv 6997801, Israel.
Nathan
N
Intrator
Department of Psychology, Tel Aviv University, Tel Aviv 6997801, Israel; Department of Physiology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel; Functional Brain Center, Wohl Institute for Advanced Imaging, Tel-Aviv Sourasky Medical Center, Tel Aviv 6423906, Israel. Electronic address: hendlert@gmail.com.
Talma
T
Hendler
D000328:Adult; D000513:Alpha Rhythm / Q000502:physiology; D004569:Electroencephalography / Q000379:methods*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D058765:Neurofeedback / Q000379:methods*; D012890:Sleep / Q000502:physiology*; D012894:Sleep Stages / Q000502:physiology*; D013826:Theta Rhythm / Q000502:physiology; D055815:Young Adult
EEG neurofeedback; External and internal awareness; Salience network; Sleep onset; Thalamus; fMRI