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The neurobiology of sleep
Published in Philip N. Murphy, The Routledge International Handbook of Psychobiology, 2018
Roman Rutka, Sonia Pellissier, Pascal Hot
The last two stages of NREM sleep are the deepest. Although NREM-3 and NREM-4 were initially thought of as different mechanisms, they do not differ markedly in terms of their EEG characteristics and function, and so are now considered as a single stage. NREM-3 and NREM-4 are characterized by the predominance of slow waves in the delta band (i.e., between 0.5 and 4 Hz), and therefore both are referred to as slow-wave sleep (SWS, Figure 24.1). The results of neuroimaging studies suggest that the delta rhythm comes from several pacemakers. Firstly, the slowest oscillations (below 1 Hz) are generated by cortical neurons and glial cells, whereas the faster oscillations (between 1 Hz and 4 Hz) result from spontaneous discharges by thalamocortical and pyramidal neurons. During NREM sleep, cholinergic activity progressively decreases in the brainstem and thus prompts the occurrence of spindles and SWS. Figure 24.1 shows electroencephalograms that are representative of wakefulness and each sleep stage.
Diagnostic testing and ominous causes of headache
Published in Stephen D. Silberstein, Richard B. Upton, Peter J. Goadsby, Headache in Clinical Practice, 2018
Stephen D. Silberstein, Richard B. Upton, Peter J. Goadsby
The EEG is a non-invasive and relatively low-cost study. It lacks specificity and sensitivity, however, and while it reveals different rates of abnormality in headache sub-types, it is not helpful in distinguishing between subtypes (Figure 4.1). Between 12% and 15% of healthy adults who have no history of head injury, seizures, headaches, or other neurological diseases have nonspecific EEG abnormalities.7 Earlier studies have reported EEG abnormalities in migraine. Slater8 found posterior quadrant, bilateral but asymmetric, slow-wave abnormalities in 82 of 184 migraine patients. He also observed abnormal responses to photic stimulation and hyperventilation. He concluded that migraine causes a disorder of cerebral functioning that produces EEG changes. Smyth and Winter9 found that 43% of 202 migraineurs had abnormal interjetai records, with slowing in either the theta or delta range. The incidence of delta rhythm was related to headache severity, disease duration and a positive family history of migraine. Lauritzen et al10 found no EEG abnormalities on hyperventilation or photic stimulation, during attacks or interictally, in 11 patients with migraine without aura or in eight of 10 patients with migraine with aura. Two patients who had migraine with aura had frontal slowing between and during attacks. While the interictal EEG may reveal diffuse or focal abnormalities to be more common in migraineurs, there is no migraine-specific pattern. The American Academy of Neurology (AAN) has reviewed the use of EEG in headache diagnosis and found that many studies suffer from major flaws.11 These include referral bias (studies not population-based) and poor controls (studies usually uncontrolled and, when controlled, not age- or sex-matched). The studies are frequently non-blinded and have high intraobserver variability. In addition, archaic criteria for normalcy are employed (patterns originally considered abnormal are now considered normal, e.g. posterior slow waves of youth).
ENTRIES A–Z
Published in Philip Winn, Dictionary of Biological Psychology, 2003
The slow-wave activity that occurs during slow-wave sleep corresponds to a different mode of neuronal discharge than that during wakefulness by neurons in the THALAMUS and CEREBRAL CORTEX. Whereas thalamo-cortical neurons fire in a TONIC, repetitive mode during waking, they fire in a PHASIC, bursting mode (see TONIC- PHASIC) during slow-wave sleep. The frequency of this bursting varies with spindles, delta and the slow oscillation. The rhythm of the bursting is determined in part by intrinsic properties of the individual neurons and also by properties of the thalamo- cortical-thalamic network (see THALAMUS). Thus certain cells in the circuit drive certain frequencies of the NETWORK OSCILLATION. The thalamocortical relay neurons and cortico-thalamic feedback neurons contain the excitatory neurotransmitter, GLUTAMATE. GABAERGIC neurons are inserted between the cortico-thalamic and thalamo-cortical neurons in a shell-like nucleus surrounding the thalamus and termed the THALAMIC RETICULAR NUCLEUS (due to its net-like appearance similar to, but not to be confused with, the RETICULAR FORMATION of the BRAINSTEM). The GABAergic thalamic reticular neurons discharge in bursts in association with spindles in the early stages of slow wave sleep and accordingly both inhibit and entrain the thalamo- cortical neurons onto which they project into first a spindle then a delta rhythm riding on the slow oscillation. Though entrained (see ENTRAINMENT) in the rhythmic discharge, the thalamo-cortical neurons become progressively hyperpolarized and inhibited, giving rise to fewer and fewer spikes per burst with the progression into slow wave sleep. Transmission through the thalamus, which occurs with high fidelity during waking, is accordingly progressively decreased during slow-wave sleep. The afferent gateway to the cerebral cortex thus progressively closes during this state. In addition, the non-specific thalamo-cortical projection system is also being inhibited, blocking the widespread cortical activation produced by this system during wakefulness. This thalamic inhibition may thus underlie the decrease in sensory awareness and loss of CONSCIOUSNESS that occur during slow-wave sleep.
An assistive technology program for enabling five adolescents emerging from a minimally conscious state to engage in communication, occupation, and leisure opportunities
Published in Developmental Neurorehabilitation, 2022
Fabrizio Stasolla, Alessandro O. Caffò, Sara Bottiroli, Donatella Ciarmoli
The coma duration for Christine was 2 weeks. She first emerged in a vegetative state and subsequently improved into a minimally conscious state. Her CT evidenced a lesion in the thalamus (i.e., posterior region) and in the nucleus pallidus. Functional magnetic resonance (fMRI) demonstrated ventricular enlargement and cortical atrophy. The EEG activity outlined a medium diffuse voltage with delta rhythm. Auditory assessment carried out through event-related brain potentials demonstrated a P300 wave of reduced amplitude contingently to the presentation of familiar voices. She presented with spastic tetraplegia, lack of speech, and minimal head and trunk control. Christine was provided with a urinary catheter. She was capable of “Yes” and “NO” responses correctly produced through a prolonged eye blinking versus a double blinking. Her total score on the JFK-CRS-R was 15 with partial scores of 2 on arousal, auditory, oromotor/verbal, and communication subscales, 3 on visual and 4 on motor subscales, respectively.
Electroencephalographic changes using virtual reality program: technical note
Published in Neurological Research, 2018
Síria Monyelle Silva de Oliveira, Candice Simões Pimenta de Medeiros, Thaiana Barbosa Ferreira Pacheco, Nathalia Priscilla Oliveira Silva Bessa, Fernanda Gabrielle Mendonça Silva, Nathália Stéphany Araújo Tavares, Isabelle Ananda Oliveira Rego, Tania Fernandes Campos, Fabrícia Azevedo da Costa Cavalcanti
Each electrical signal is registered synchronously in terms of frequency and is known as brain rhythms: delta (0.5–4 Hz), theta (4–8 Hz), alpha (8–13 Hz), beta (13–30 Hz), and gamma (Above 30 Hz) [2]. The delta rhythm is related to a coma state, deep sleep, newborns, and some brain dysfunction. Theta rhythm is generally observed in states of deep meditation, relaxation, and automated activities. Alpha rhythm is associated with mild states of alertness, meditation and alertness with closed eyes. The beta rhythm is observed in alert states, mental effort, decision-making and external information processing. Finally, gamma rhythm is associated with information processing, voluntary movements, and attention control [1,2].
Physiological Monitoring to Enhance Clinical Hypnosis and Psychotherapy
Published in International Journal of Clinical and Experimental Hypnosis, 2020
The delta rhythm ranges from 0.5 to 3.5 Hz. Delta is the dominant frequency from ages 1 to 2 and is associated in adults with deep sleep and brain pathology such as traumatic injury, tumors, lesions, and learning disability.