General anaesthesia reduces the uniqueness of brain connectivity across individuals and across species

Abstract

The human brain is characterised by idiosyncratic patterns of spontaneous thought, rendering each brain uniquely identifiable from its neural activity. However, deep general anaesthesia suppresses subjective experience. Does it also suppress what makes each brain unique? Here we used functional MRI under the effects of the general anaesthetics sevoflurane and propofol to determine whether anaesthetic-induced unconsciousness diminishes the uniqueness of the human brain: both with respect to the brains of other individuals, and the brains of another species. We report that under anaesthesia individual brains become less self-similar and less distinguishable from each other. Loss of distinctiveness is highly organised: it co-localises with the archetypal sensory-association axis, correlating with genetic and morphometric markers of phylogenetic differences between humans and other primates. This effect is more evident at greater anaesthetic depths, reproducible across sevoflurane and propofol, and reversed upon recovery. Providing convergent evidence, we show that under anaesthesia the functional connectivity of the human brain becomes more similar to the macaque brain. Finally, anaesthesia diminishes the match between spontaneous brain activity and meta-analytic brain patterns aggregated from the NeuroSynth engine. Collectively, the present results reveal that anaesthetised human brains are not only less distinguishable from each other, but also less distinguishable from the brains of other primates, with specifically human-expanded regions being the most affected by anaesthesia.

Multimodal identification of the mouse brain using simultaneous Ca2+imaging and fMRI

“…Similarly, it is likely that our use of anesthesia reduced our observed ID rates given recent work in anesthetized human subjects 41 . This is notable given that the majority of fMRI studies in rodents use anesthesia, and that differences in resting-state fMRI signals between awake and anesthetized mice have not been extensively characterized (see 42 for a recent systematic review).…”

Individual variability in neural representations of mind-wandering

“…Our findings may even suggest that functional connectivity ‘fingerprints’ (i.e., individual-specific, state-independent patterns 73 ) are driven by tendencies to engage in certain forms of thought, which could be conceptualized as ‘thought fingerprints.’ Support for this idea comes from a recent study demonstrating that when spontaneous thoughts were abolished due to deep general anaesthesia, functional connectivity patterns became less inter-individually distinguishable. 79 People often report certain patterns of thought that are relatively stable 80 (despite influence of context 81 ), which may imply that during resting states, thought trajectories tend to ‘default’ toward recurring patterns that an individual is predisposed to experiencing. These considerations promote the idea that resting-state fMRI interpretability may be enhanced through incorporating annotations of experiences.…”

“…The amount of times that a subject responded to each option for a given probe question was counted across all mind-wandering events. This yielded a vector of counts for each subject and for each probe question, where each element in the vector was a count of responses from a subject to a particular option for a probe question (e.g., [142,79,8] is the count vector of responses from subject 1 to probe question "Perspective" tallying the counts to options "First person", "Third person", and "Not sure", respectively). The distance between two subjects for a probe question was compared by taking the Euclidean distance (i.e., square root of the sum of squared differences) between the respective count vectors.…”

Individual variability in neural representations of mind-wandering

“…Our findings may even suggest that functional connectivity 'fingerprints' (i.e., individualspecific, state-independent patterns (Finn et al, 2015)) are driven by tendencies to engage in certain forms of thought, which could be conceptualized as 'thought fingerprints.' Support for this idea comes from a recent study demonstrating that when spontaneous thoughts were abolished due to deep general anaesthesia, functional connectivity patterns became less inter-individually distinguishable (Luppi et al, 2023). People often report certain patterns of thought that are relatively stable (Ho et al, 2020) (despite influence of context (Mulholland et al, 2023)), which may imply that during resting states, thought trajectories tend to 'default' toward recurring patterns that an individual is predisposed to experiencing.…”