Processing of semantic incongruency at the onset of sleep: An auditory N400 evoked potential study.
International journal of psychophysiology : official journal of the International Organization of Psychophysiology June 1, 2023 Sarah Diezig, Melissa Spaar, Simone Denzer et al.
The ability to organize self-generated thought into coherent, meaningful semantic representations is a central aspect of human cognition and undergoes regular alterations throughout the day. To investigate whether changes in semantic processing might explain the loss of coherence, logic, and voluntary control over thinking typically accompanying the transition to sleep, N400 evoked potentials were recorded from 44 healthy subjects. Auditory word pairs with varying semantic distance were presented while subjects were allowed to fall asleep. Semantic distance reliably elicited an N400, and lower wakefulness levels were associated with increased frontal negativity. Contrary to the initial hypothesis, the results showed an increased N400 effect with decreasing wakefulness, suggesting that semantic processes alone may not explain diminished thought control during sleep onset.