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Hypnagogia

Definition and Terminology: – Hypnagogia defined as the onset of sleep, contrasted with hypnopompia for waking up. – Various terms proposed for hypnagogia. – Threshold […]

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Definition and Terminology:
– Hypnagogia defined as the onset of sleep, contrasted with hypnopompia for waking up.
– Various terms proposed for hypnagogia.
– Threshold consciousness describes the mental state towards sleep or wakefulness.
– Transition brief but can be extended by sleep disturbance.
– Term ‘hypnagogic’ introduced by Alfred Maury in 1848, from Greek words ύπνος (hypnos) and αγωγός (agōgos).
– Term ‘hypnopompic’ coined by Frederic Myers in 1904, with the word-ending from the Greek word pompos.
– Hypnopompic refers to waking up.

Signs and Symptoms:
– Transition to/from sleep may have sensory experiences.
– Sensory experiences range from vague to vivid hallucinations.
– Sensory features include phosphenes, lines, and geometrical patterns.
– Hypnagogic imagery differs from dreams proper.
– Vivid hypnagogic visuals described in literature.
– Vivid and elaborate hypnagogic visuals noted in works of Marquis d’Hervey Saint Denys.

Physiology and Characteristics:
– Hypnagogia associated with stage 1 of NREM sleep.
– Pre-sleep alpha waves can trigger hypnagogic experiences.
– Short flashes of dreamlike imagery correlate with drops in alpha EEG activity.
– EEG power spectra of hypnagogic images resemble those of REM sleep and relaxed wakefulness.
– Sleep onset hypnagogia distinct from wakefulness and sleep.

Daydreaming and Waking Reveries:
– Microsleep can occur at any point in the wakefulness-sleep cycle.
– Sleep deprivation can lead to impaired cognition and amnesia.
– Regular meditation may help freeze the hypnagogic process at later stages.
– Hypnagogic states can be influenced by external objects.
– Respiratory pattern changes and muscle activity decrease in the hypnagogic state.

History and Research:
– Early references to hypnagogia found in writings of Aristotle and others.
– Romanticism renewed interest in the subjective experience of sleep edges.
– Serious scientific inquiry began in the 19th century.
– Research on hypnagogia has seen a revival in the later 20th century.
– Self-observation was the primary tool of early researchers; questionnaires and experimental studies have supplemented this.
– Techniques like sleep manipulation and interruption help study hypnagogia.

Hypnagogia (Wikipedia)

Hypnagogia is the transitional state from wakefulness to sleep, also defined as the waning state of consciousness during the onset of sleep. Its opposite state is described as hypnopompia – the transitional state from sleep into wakefulness. Mental phenomena that may occur during this "threshold consciousness" phase include hypnagogic hallucinations, lucid dreaming, and sleep paralysis.

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