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Consciousness among delta waves: a paradox?
- Source :
- Brain : a journal of neurology. 144(8)
- Publication Year :
- 2020
-
Abstract
- A common observation in EEG research is that consciousness vanishes with the appearance of delta (1–4 Hz) waves, particularly when those waves are high amplitude. High amplitude delta oscillations are frequently observed in states of diminished consciousness, including slow wave sleep, anaesthesia, generalized epileptic seizures, and disorders of consciousness, such as coma and the vegetative state. This strong correlation between loss of consciousness and high amplitude delta oscillations is thought to stem from the widespread cortical deactivation that occurs during the ‘down states’ or troughs of these slow oscillations. Recently, however, many studies have reported the presence of prominent delta activity during conscious states, which casts doubt on the hypothesis that high amplitude delta oscillations are an indicator of unconsciousness. These studies include work in Angelman syndrome, epilepsy, behavioural responsiveness during propofol anaesthesia, postoperative delirium, and states of dissociation from the environment such as dreaming and powerful psychedelic states. The foregoing studies complement an older, yet largely unacknowledged, body of literature that has documented awake, conscious patients with high amplitude delta oscillations in clinical reports from Rett syndrome, Lennox-Gastaut syndrome, schizophrenia, mitochondrial diseases, hepatic encephalopathy, and non-convulsive status epilepticus. At the same time, a largely parallel body of recent work has reported convincing evidence that the complexity or entropy of EEG and magnetoencephalographic signals strongly relates to an individual’s level of consciousness. Having reviewed this literature, we discuss plausible mechanisms that would resolve the seeming contradiction between high amplitude delta oscillations and consciousness. We also consider implications concerning theories of consciousness, such as integrated information theory and the entropic brain hypothesis. Finally, we conclude that false inferences of unconscious states can be best avoided by examining measures of electrophysiological complexity in addition to spectral power.
- Subjects :
- 0301 basic medicine
Electromagnetic theories of consciousness
Consciousness
media_common.quotation_subject
Disorders of consciousness
Unconsciousness
Electroencephalography
03 medical and health sciences
0302 clinical medicine
Level of consciousness
medicine
Humans
Slow-wave sleep
media_common
Epilepsy
medicine.diagnostic_test
Brain
medicine.disease
Delta wave
030104 developmental biology
Delta Rhythm
Neurology (clinical)
medicine.symptom
Psychology
Neuroscience
030217 neurology & neurosurgery
Subjects
Details
- ISSN :
- 14602156
- Volume :
- 144
- Issue :
- 8
- Database :
- OpenAIRE
- Journal :
- Brain : a journal of neurology
- Accession number :
- edsair.doi.dedup.....861e2192d12c9073cb20b473da5ce5ca