Evan Accatino ’25, Health Sciences, 22S
Figure 1: When children are placed under general anesthesia, they enter a state in which brain activity remains relatively constant. This finding was not observed in anesthetized adults.
Image Source: Wikimedia Commons
Daily human life is characterized by a continuous cycling between periods of wakefulness and periods of rest. When we’re awake, conscious, and attentive to our surroundings, the state of the brain is constantly changing to monitor novelty in the world around us. The wakeful brain alternates between various patterns of neuronal activity to ensure that the task of maintaining homeostasis is completed efficiently. In contrast, when the brain enters an induced state of unconsciousness (i.e., when general anesthesia is administered) it is severely limited in its ability to move among attentive states.
In a 2020 study, Kreuzer et al. of the University of Munich compared the unconscious brain activity of anesthetized adults and children. An electroencephalogram (EEG) was used to measure functional signaling between cortical brain regions of study participants. As has been previously observed, the authors of the study found that general anesthesia in children and teenagers (8 to 16 years old) enhanced connectivity between frontal and prefrontal brain regions. It was further concluded that over the entire time period that an anesthetic was administered, the brains of young children adhered to a small number of nearly identical EEG patterns (Kreuzer et al., 2020). Thus, general anesthesia forced the brains of young participants into a state of “rigid” functionality where only a handful of active states could be achieved. The time that a child spent in each respective brain state depended on the stability of signaling in the state as well as the level of external stimuli required to shift the brain to a new pattern of communication .
This finding differed from adult study samples who were found to switch between many markedly different patterns of brain signaling every few minutes (Sleigh, 2022). Kreuzer et al. rationalize that the transitions between these patterns are quite abrupt, and that the brains of children are not yet functionally equipped to make these jumps (2020). A child’s brain is constantly undergoing vast amounts of structural change; there is also a significant decrease in gray matter. Taken together, these factors seem to explain differences in the unconscious brain activity of children and adults, though the exact neural mechanisms underlying these processes are not yet known.
Taken together, these findings suggest that anesthesia induces a single stable brain state in children but many possible different brain states in adults. The difficulty that children experience in shifting between various states is likely caused by insufficient strength of external stimuli that are responsible for causing these changes. For the first time, this research provides an important insight into difference that exist in the unconscious activity of still-developing human brains. These findings suggest that the unconscious brain activity of children is far more limited than it is in adults.
References
Anesthesia – the noun project.svg. Wikimedia Commons. (n.d.). Retrieved May 13, 2022, from https://commons.wikimedia.org/wiki/File:Anesthesia_-_The_Noun_Project.svg
Kreuzer, M., Stern, M. A., Hight, D., Berger, S., Schneider, G., Sleigh, J. W., & García, P. S. (2020). Spectral and entropic features are altered by age in the electroencephalogram in patients under Sevoflurane Anesthesia. Anesthesiology, 132(5), 1003–1016. https://doi.org/10.1097/aln.0000000000003182
Sleigh, J. W. (2022). Stuck in a rut: Anesthetic Brain Dynamics in the young. Anesthesiology. https://doi.org/10.1097/aln.0000000000004252