Exploring effects of anesthesia on complexity, differentiation, and integrated information in rat EEG
Published in Neuroscience of Consciousness, 2024
Animal models are indispensable for mechanistic consciousness research, yet most validated EEG-based consciousness measures have been developed and tested exclusively in humans. This study applies a suite of such measures to rats undergoing anesthesia with three pharmacologically distinct agents: propofol, sevoflurane, and ketamine.
The perturbational complexity index (PCI)—which quantifies causal integration and differentiation in response to direct cortical perturbation—reliably declined during propofol and sevoflurane anesthesia. Spontaneous signal diversity measures (Lempel-Ziv complexity) similarly decreased, consistent with predictions from leading theories. However, geometric integrated information (ΦG), a mathematically defined approximation of IIT’s Φ, showed a paradoxical increase under propofol and sevoflurane, and an anti-correlation with LZC.
Ketamine, which is known to produce dissociative and potentially experience-preserving effects in humans, showed no significant change on any spontaneous measure tested. The divergence between measure families suggests they may be sensitive to different dimensions of neural organization—and that perturbation-based and spontaneous measures are best understood as complementary rather than redundant tools. The results also inform the translation of consciousness research paradigms from human to non-human models.
Recommended citation: Sevenius Nilsen A, Arena A, Storm JF. (2024). "Exploring effects of anesthesia on complexity, differentiation, and integrated information in rat EEG." Neuroscience of Consciousness. 2024(1):niae021. https://doi.org/10.1093/nc/niae021
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