Ultra-slow mechanical stimulation of olfactory epithelium modulates consciousness by slowing cerebral rhythms in humans.

The coupling between respiration and neural activity within olfactory areas and hippocampus has recently been unambiguously demonstrated, its neurophysiological basis sustained by the well-assessed mechanical sensitivity of the olfactory epithelium. We herein hypothesize that this coupling reverberates to the whole brain, possibly modulating the subject's behavior and state of consciousness. The olfactory epithelium of 12 healthy subjects was stimulated with periodical odorless air-delivery (frequency 0.05 Hz, 8 s on, 12 off). Cortical electrical activity (High Density-EEG) and perceived state of consciousness have been studied. The stimulation induced i) an enhancement of delta-theta EEG activity over the whole cortex mainly involving the Limbic System and Default Mode Network structures, ii) a reversal of the overall information flow directionality from wake-like postero-anterior to NREM sleep-like antero-posterior, iii) the perception of having experienced an Altered State of Consciousness. These findings could shed further light via a neurophenomenological approach on the links between respiration, cerebral activity and subjective experience, suggesting a plausible neurophysiological basis for interpreting altered states of consciousness induced by respiration-based meditative practices.

Brain connectivity is altered by extreme physical exercise during non-REM sleep and wakefulness: indications from EEG and fMRI studies.

Brain connectivity is associated to behavioral states (e.g. wake, sleep) and modified by physical activity although, to date, it is not clear which components (e.g. hypothalamus-pituitary-adrenal axis hormones, cytokines) associated to the exercise are involved. In this pilot study, we used extreme exercise (UltraTriathlon) as a model to investigate physical-activity-related changes of brain connectivity. We studied post-race brain synchronization during wakefulness and sleep as well as possible correlations between exercise-related cytokines/hormones and synchronization features. For wakefulness, global synchronization was evaluated by estimating from fMRI data (12 athletes) the brain global connectivity (GC). GC increased in several brain regions, mainly related to sensory-motor activity, emotional modulation and response to stress that may foster rapid exchange of information across regions, and reflect post-race internally-focused mental activity or disengagement from previous motor programs. No significant correlations between cytokines/hormones and GC were found. For sleep (8 athletes), synchronization was evaluated by estimating the local-(cortical) and global-related (thalamo- cortical) EEG features associated to the phenomenon of Sleep Slow Oscillations (SSO) of NREM sleep. Results showed that: power of fast rhythms in the baseline preceding the SSO increased in midline and parietal regions; amplitude and duration of SSOs increased, mainly in posterior areas; sigma modulation in the SSO up state decreased. In the post race, IL-10 positively correlated with fast rhythms baseline, SSO rate and positive slope; IL-1ra and cortisol inversely correlated with SSO duration; TNF-α and C-reactive protein positively correlated with fast rhythm modulation in the SSO up state. Sleep results suggest that: arousal during sleep, estimated by baseline fast rhythms, is increased; SSO may be sustained by cortical excitability, linked to anti-inflammatory markers (IL-10); thalamo-cortical entrainment, (sigma modulation), is impaired in athletes with higher inflammatory markers.

Metacognitive beliefs relate specifically to sleep quality in primary insomnia: a pilot study.

OBJECTIVE: To identify whether metacognitive aspects are a specific mental pattern of primary insomnia (PI) or an aspecific correlate of sleep alterations. METHODS: Sleep quality (Pittsburgh Sleep Quality Index: PSQI), anxiety (Self-rating Anxiety State: SAS), depression (Beck Depression Inventory: BDI) and metacognition (Metacognitions Questionnaire - Insomnia: MCQ-I) were evaluated in 24 PI patients, 13 snorers and 17 healthy controls. Rank-transformed PSQI, BDI, SAS and MCQ-I scores were submitted to one-way analysis of variance with group as a between-factor. PSQI was submitted to three-way analysis of covariance (ANCOVA) with MCQ-I, BDI or SAS as covariate and group as a between-factor. Post-hoc analyses were conducted using pairwise comparisons with Sidak correction. RESULTS: As expected, PSQI scores significantly differentiated the three groups, one from another: PI had highest scores followed by snorers and healthy controls. PI subjects had MCQ-I scores significantly higher than those of snorers and healthy controls; no difference between the latter groups was found. The ANCOVA on PSQI with MCQ-I as a covariate abolished the difference in sleep quality between PI and snorers, whereas covarying for BDI or SAS left the differences in sleep quality between the groups unchanged. CONCLUSION: These preliminary results lead to two main conclusions: (i) metacognitive aspects are more prominent in PI when compared to snorers and healthy controls; (ii) MCQI shows higher sensitivity in defining PI patients, with respect to PSQI. If these findings are confirmed and expanded by further studies, the development of a specific metacognitive model of primary insomnia may be warranted.