Alterations of sleep initiation in NREM parasomnia after sleep deprivation - A multimodal pilot study.

Objectives: NREM parasomnias also known as disorders of arousal (DOA) are characterised by abnormal motor and autonomic activation during arousals primarily from slow wave sleep. Dissociative state between sleep and wake is likely responsible for clinical symptoms of DOA. We therefore investigated potential dissociation outside of parasomnic events by using simultaneous 256-channel EEG (hdEEG) and functional magnetic resonance imaging (fMRI). Methods: Eight DOA patients (3 women, mean age = 27.8; SD = 4.2) and 8 gender and age matched healthy volunteers (3 women, mean age = 26,5; SD = 4.0) were included into the study. They underwent 30-32 h of sleep deprivation followed by hdEEG and fMRI recording. We determined 2 conditions: falling asleep (FA) and arousal (A), that occurred outside of deep sleep and/or parasomnic event. We used multimodal approach using data obtained from EEG, fMRI and EEG-fMRI integration approach. Results: DOA patients showed increase in delta and beta activity over postcentral gyrus and cuneus during awakening period. This group expressed increased connectivity between motor cortex and cingulate during arousals unrelated to parasomnic events in the beta frequency band. They also showed lower connectivity between different portions of cingulum. In contrast, the greater connectivity was found between thalamus and some cortical areas, such as occipital cortex. Conclusion: Our findings suggest a complex alteration in falling asleep and arousal mechanisms at both subcortical and cortical levels in response to sleep deprivation. As this alteration is present also outside of slow wave sleep and/or parasomnic episodes we believe this could be a trait factor of DOA.

Subanesthetic dose of ketamine decreases prefrontal theta cordance in healthy volunteers: implications for antidepressant effect.

BACKGROUND: Theta cordance is a novel quantitative electroencephalography (QEEG) measure that correlates with cerebral perfusion. A series of clinical studies has demonstrated that the prefrontal theta cordance value decreases after 1 week of treatment in responders to antidepressants and that this effect precedes clinical improvement. Ketamine, a non-competitive antagonist of N-methyl-D-aspartate (NMDA) receptors, has a unique rapid antidepressant effect but its influence on theta cordance is unknown. METHOD: In a double-blind, cross-over, placebo-controlled experiment we studied the acute effect of ketamine (0.54 mg/kg within 30 min) on theta cordance in a group of 20 healthy volunteers. RESULTS: Ketamine infusion induced a decrease in prefrontal theta cordance and an increase in the central region theta cordance after 10 and 30 min. The change in prefrontal theta cordance correlated with ketamine and norketamine blood levels after 10 min of ketamine infusion. CONCLUSIONS: Our data indicate that ketamine infusion immediately induces changes similar to those that monoamineric-based antidepressants induce gradually. The reduction in theta cordance could be a marker and a predictor of the fast-acting antidepressant effect of ketamine, a hypothesis that could be tested in depressive patients treated with ketamine.

EEG abnormalities in dementia reflect the parietal lobe syndrome.

The aim of this study was to investigate to what extent the examination of regional syndromes can improve EEG diagnostics in dementia. The study was based on 77 patients, aged between 47 and 83 years, with a dementia disease in accordance with the DSM-III-R criteria. The clinical examination was refined using a so-called stepwise clinical status analysis to estimate the occurrence and intensity of the parietal lobe syndrome, the frontal lobe syndrome, the subcortical syndrome and the less-regionalised global syndrome. In the same time period, the patients were examined electroencephalographically and the recordings were assessed both visually and by means of spectrum analysis. It was found that the intensity of the parietal lobe syndrome was correlated more strongly to the EEG slow activity as compared to the other regional syndromes. Thus, it can be expected that the EEG will be most valuable in the early-onset type of Alzheimer's disease, in which the parietal syndrome is dominant, giving information regarding the degree of dementia and suggesting a possible interference with depression. The results of the study can probably explain some discrepancies between the EEG findings and the results of clinical examination in other forms of dementia.