Frontiers in Psychology
April 23, 2021
Arnfinn Aamodt, André Sevenius Nilsen, Benjamin Thürer et al.
24 citations
Signal diversity in EEG recordings, measured by Lempel-Ziv complexity and other metrics, decreases with deeper non-REM sleep stages, consistent with theories linking consciousness to complex cortical dynamics. However, signal diversity did not significantly differ between dreaming and non-dreaming periods within the same sleep stage. A positive correlation was found between Lempel-Ziv complexity over the posterior cortex and the thought-perceptual quality of dream contents, suggesting that specific aspects of dream experience may relate to local cortical signal diversity.
Neuroscience of consciousness
January 1, 2024
André Sevenius Nilsen, Alessandro Arena, Johan F Storm
10 citations
In rats under propofol, sevoflurane, and ketamine anesthesia, the perturbational complexity index (PCI) and two spontaneous EEG measures—Lempel-Ziv complexity (LZ) and geometric integrated information (ΦG)—best distinguished awake from anesthetized states for propofol and sevoflurane. However, PCI was anti-correlated with spontaneous measures of integrated information, which increased during propofol and sevoflurane anesthesia, contrary to expectations. The divergence suggests anesthesia disrupts global cortico-cortical information transfer, while spontaneous activity suggests the opposite, possibly due to suppressed encoding specificity or driving subcortical projections. Perturbation-based and spontaneous measures may be complementary for studying altered consciousness.
Brain sciences
September 13, 2024
André Sevenius Nilsen, Johan Frederik Storm, Bjørn Erik Juel
Measures of consciousness based on signal diversity of spontaneous or perturbed EEG are not affected by cognitive load, whereas the P300b event-related potential is. In 12 participants, EEG was recorded during passive attention to sensory stimuli and during a demanding working memory task. The P300b, which reflects conscious awareness of auditory deviance, was significantly reduced by the concurrent memory task. In contrast, several signal diversity measures, including the perturbational complexity index, were unchanged. These findings suggest that signal diversity measures may remain reliable for assessing consciousness in clinical settings where attention, sensory processing, or command following are impaired.