Anesthesia’s Neural Signature Spans Hundreds of Millions of Years of Evolution

General anesthetics are among the most remarkable tools in modern medicine. Within seconds of administration, a patient who was awake, aware, and conversant is plunged into a state of profound unresponsiveness, and upon withdrawal of the drug, consciousness returns. What makes this even more striking is that anesthetic drugs do not act only on humans. They render insects immobile, sedate fish, quiet the nervous systems of worms, and induce reversible unresponsiveness in rodents and non-human primates. The fact that compounds as chemically diverse as propofol, sevoflurane, and ketamine appear to work across species separated by hundreds of millions of years of evolution raises a deep question: is there a common neural signature of the transition from wakefulness to anesthesia that transcends the anatomical differences among species?

A landmark study by Luppi and colleagues, published in Nature Neuroscience and analyzed in a News & Views commentary by George A. Mashour and Zirui Huang of the University of Michigan, now provides compelling evidence that the answer is yes. The researchers identified a conserved dynamic signature of anesthesia that persists across the animal kingdom, suggesting that the mechanisms by which anesthetics abolish consciousness are not idiosyncratic to particular brains but reflect fundamental principles of how neural systems organize activity. The finding carries implications not only for anesthesiology but also for the scientific study of consciousness itself, and for how we think about the evolutionary history of the sleeping, waking, and oblivion states that all animals share.

To appreciate the significance of this work, it helps to recall what is already known about how anesthetics act on the brain. Despite their varied molecular targets, ranging from GABA receptors to NMDA receptors to potassium channels, most general anesthetics produce convergent effects on large-scale neural dynamics. In humans, the onset of anesthesia is associated with a characteristic shift in electroencephalographic activity: slow, high-amplitude oscillations emerge, coherent alpha rhythms appear over frontal regions, and the complex, differentiated patterns of activity that typify the awake brain give way to more stereotyped, synchronized dynamics. Crucially, the capacity of the brain to integrate information across distributed cortical networks collapses. Studies using the perturbational complexity index, developed by Casali and colleagues, demonstrated that the brain’s response to direct stimulation becomes locally confined and mechanically simple under anesthesia, in contrast to the rich, widespread, and differentiated responses seen during wakefulness and dreaming.

Previous work has also shown that anesthesia does not simply shut the brain down. Rather, it fragments neural communication. Functional imaging and electrophysiological studies in humans and in animal models, including work by Lewis and colleagues on the transitions into and out of unconsciousness, and by Uhrig and colleagues in monkeys, have revealed that anesthetic-induced unconsciousness involves a breakdown of the brain’s ability to sustain stable, integrated networks. Information continues to be processed in isolated pockets of cortex, but the global integration that appears to underpin conscious experience is disrupted. This framework, articulated by Mashour and colleagues in a 2020 Neuron review, holds that consciousness depends on the joint capacity of the brain to differentiate information locally and integrate it globally, and that anesthetics work by severing that integration.

What remained uncertain was whether these dynamic principles apply beyond the mammalian brain. The human cortex is a six-layered structure with elaborate areal specialization; the insect brain is a compact arrangement of ganglia; the nematode nervous system contains a few hundred neurons. If anesthetics abolish behavior in all of these organisms, do they do so through the same dynamical route, or through entirely different mechanisms that merely converge on the same behavioral outcome? This question touches on one of the oldest debates in neuroscience: whether consciousness, and the mechanisms that regulate it, are evolutionarily conserved or independently evolved. The phrase used by Mashour and Huang in their commentary, the oblivion of species, captures the poignancy of the question. Anesthesia erases experience in every animal to which it is administered, but does it erase experience in the same way in each of them?

Luppi and colleagues addressed this question with a cross-species analysis of neural dynamics during the transitions between wakefulness and anesthesia. By examining how neural activity changes as animals of different species move into and out of anesthetic-induced unresponsiveness, the researchers searched for features of the dynamics that are preserved despite vast anatomical divergence. Their central finding is that such a signature exists. The transitions into anesthesia are marked by common changes in the organization of neural activity, a dynamic fingerprint of oblivion that is conserved across evolutionary lineages. This suggests that the relevant target of general anesthetics is not a particular brain region, receptor type, or anatomical circuit unique to mammals, but rather a set of dynamical properties that nervous systems share by virtue of their common functional architecture.

The significance of a conserved dynamic signature is difficult to overstate. It implies that the relationship between neural dynamics and behavioral state is not an accident of mammalian cortical organization but a general property of neural systems. It also provides a principled basis for using animal models to study anesthesia and unconsciousness. If the dynamic signature of anesthesia is conserved, then findings in rodents, flies, or worms can speak to mechanisms that are likely operative in humans, provided the comparison is made at the level of dynamics rather than anatomy. This aligns with a growing movement in consciousness science, reflected in work such as the 2023 PLoS Computational Biology paper by Albantakis and colleagues, to identify principled, species-independent measures of the capacity for integrated experience rather than relying on structural proxies that inevitably favor one lineage over another.

The study also resonates with earlier hints in the literature. John and colleagues reported in 2001 that loss and recovery of consciousness, whether induced by anesthesia or occurring in other states, is associated with convergent changes in neural activity patterns. Lee and colleagues showed in 2013 that different anesthetic agents produce convergent disruptions of frontal-parietal networks in the human brain. More recently, Eisen and colleagues reported in Cell Reports in 2026 further evidence bearing on cross-species comparisons of anesthetic action, and Jang, Mashour, Hudetz, and Huang demonstrated in Nature Communications in 2024 that the temporal complexity of neural activity carries information about states of consciousness. The new work by Luppi and colleagues unifies these threads by demonstrating that the convergence is not merely agent-specific or species-specific but evolutionarily deep, spanning lineages whose last common ancestors lived hundreds of millions of years ago.

For clinical medicine, the implications are substantial. Anesthetic monitoring in humans currently relies on processed EEG indices that capture some, but not all, of the dynamic features of unconsciousness, and cases of intraoperative awareness and excessively deep anesthesia remain a clinical challenge. If the conserved dynamic signature identified by Luppi and colleagues can be measured reliably at the bedside, it could yield biomarkers of anesthetic depth that are grounded in the fundamental dynamics of neural systems rather than in species- or drug-specific signatures. Casey and colleagues explored related questions in the British Journal of Anaesthesia in 2024, underscoring the growing interest in dynamic, principled measures of brain state during anesthesia. A biomarker rooted in evolutionarily conserved dynamics would be robust across anesthetic classes and could improve both safety and precision in the operating room.

For the science of consciousness, the study reframes the question of which animals are capable of subjective experience. If the dynamics that anesthetics disrupt to produce oblivion are shared across species, then the substrates of consciousness, or at least the substrates of the state transitions that govern consciousness, are likely shared as well. This does not settle the question of which species are conscious, but it shifts the burden of evidence. It suggests that the appropriate objects of comparison are dynamical organization and informational capacity, not the presence of a six-layered cortex. As Mashour and Huang observe in their commentary, the oblivion that anesthesia induces in every species may be the mirror image of a form of neural organization that every species shares. In revealing a conserved dynamic signature of anesthesia, Luppi and colleagues have not only illuminated how anesthetics work; they have offered a glimpse of what may be the deepest common ground of the conscious brain, a ground that predates the divergence of the species and endures, hidden, beneath the astonishing diversity of animal minds.

Subject of Research: Conserved cross-species neural dynamics of anesthetic-induced loss of consciousness

Article Title: Conserved neural dynamics of anesthesia and the oblivion of species

Article References: Mashour, G. A., & Huang, Z. (2026). Conserved neural dynamics of anesthesia and the oblivion of species. Nature Neuroscience. https://doi.org/10.1038/s41593-026-02399-6

Image Credits: AI Generated

DOI: 10.1038/s41593-026-02399-6

Keywords: anesthesia, consciousness, neural dynamics, evolution, cross-species, biomarkers, electroencephalography, neural integration, unresponsiveness, Nature Neuroscience, Mashour, Luppi