Showing papers on "Delta wave published in 2004"

Lack of delta waves and sleep disturbances during non-rapid eye movement sleep in mice lacking α1G-subunit of T-type calcium channels

Abstract: T-type calcium channels have been implicated as a pacemaker for brain rhythms during sleep but their contribution to behavioral states of sleep has been relatively uncertain. Here, we found that mice lacking alpha1(G) T-type Ca(2+) channels showed a loss of the thalamic delta (1-4 Hz) waves and a reduction of sleep spindles (7-14 Hz), whereas slow ( 16 sec compared with the wild-type, whereas no difference was seen in BAs of <16 sec between the two genotypes. These results are consistent with the previous idea of the distinct nature of delta oscillations and sleep spindles from cortically generated slow waves. These results also suggest that the alpha1(G)-subunit of T-type calcium channels plays a critical role in the genesis of thalamocortical oscillations and contributes to the modulation of sleep states and the transition between NREM sleep and wake states.

Functional MRI during sleep: BOLD signal decreases and their electrophysiological correlates

Abstract: Prominent local decreases in blood oxygenation level (BOLD) can be observed by functional magnetic resonance imaging (fMRI) upon acoustic stimulation during sleep. The goal of this study was to further characterize this BOLD signal decrease with respect to corresponding neurophysiological phenomena using a simultaneous electroencephalography (EEG)/fMRI approach in sleeping human subjects. Healthy volunteers were subjected to acoustic stimulation during non-rapid eye movement (NREM) sleep. On the basis of statistical parametric maps, the correlations between the fMRI response (both amplitude and extent of the BOLD response) and the concomittant changes in the EEG (delta power and K-complexes) were calculated. Amplitude and extent of the stimulus-induced negative BOLD effect correlated positively with measures of EEG synchronization, namely an increase in the number of K-complexes and EEG delta power. Stimulus-induced BOLD decreases were most prominent during light (stage 2) NREM sleep and disappeared during slow wave sleep, indicating an influence of the baseline degree of hyperpolarization. Our observations provide first evidence that 'negative' BOLD signal changes during human sleep are associated with electrophysiological indicators of altered neuronal activity. Increased number of K-complexes and delta power reflecting hyperpolarization suggests true cortical deactivation upon stimulus presentation. This sleep stage-dependent deactivation might serve to protect the brain from arousing stimuli, particularly during the light phases of sleep shortly after sleep onset.

The neuroanatomy of sleep. Considerations on the role of the thalamus in sleep and a proposal for a caudorostral organization

Abstract: This review synthetizes the most important historical contributions in sleep anatomy and the pioneer discoveries in sleep medicine in the light of our clinical observations in Fatal Familial Insomnia (FFI), a genetic prion disease. Together with Morvan?s chorea and Delirium Tremens, FFI is characterized by inability to sleep with severeloss of sleep spindles and delta sleep, with preserved presleep behaviour and abnormal REM sleep, associated with motor and autonomic overactivation. We labelled this pattern as Agrypnia Excitata (AE). AE is due to dysfunction in thalamolimbic circuits, which emphasizes the key role of the thalamus in sleep physiology and indicates that the anatomo-functional substrate of stage 1 non-REM sleep differs from that generating slow-wave-sleep (SWS, spindle and delta activity). Accordingly, the sleep-wake cycle in man should be conceptualized as consisting of 5 different behavioural and electrophysiological distinct states: active wakefulness, quiet wakefulness, drowsiness (or stage 1 non-REM), SWS (which incorporates spindle and delta sleep) and REM sleep. An intricate neuronal network extending from the caudal brainstem to the forebrain controls these different wake and sleep behaviours with several, at least three distinct generators.

Case report Subclinical rhythmic electrographic discharge of adults (SREDA) in REM sleep

Abstract: We describe the first reported case of subclinical rhythmic electrographic discharge of adults (SREDA) during rapid eye movement (REM) sleep. This 48-year-old man, with a history of witnessed apneic spells, was sent for a baseline polysomnogram. Besides demonstrating obstructive sleep apnea, his study showed the occurrence of paroxysmal delta waves evolving into a theta frequency during REM sleep. A repeat polysomnogram with 16-channel electroencephalography confirmed SREDA in the bilateral temporal/parietal regions during REM sleep. This uncommon paroxysmal electrographic pattern should not be mistaken for seizure activity and is now recognized to occur in all stages of sleep, including REM. q 2003 Elsevier B.V. All rights reserved.