The point of criticality that the brain reaches when it performs at its highest level is a state of balance between stability and flexibility. In this state, the brain is able to efficiently process information, make connections between different areas, and quickly adapt to changes in its environment.
At this point, the brain's neurons and their connections become synchronized or desynchronized depending on the level of input they receive, which allows for efficient processing of information. This synchronization and desynchronization can be compared to the way a flock of birds or a school of fish moves in unison, responding to changes in the environment. This state of criticality is thought to be related to the brain's ability to rapidly switch between different modes of operation and to dynamically reorganize its functional connections. This flexibility allows the brain to respond quickly and effectively to new information and challenges. Overall, the point of criticality that the brain reaches when it performs at its highest level is a delicate balance between stability and flexibility that enables efficient processing of information and rapid adaptation to changes in the environment.
The brain is a complex system, and there is still much to be learned about how it functions at its highest potential. However, some researchers have proposed that the brain operates most effectively when it is in a state of "criticality" - a state that is balanced between order and chaos.
In this state, the brain is able to quickly adapt and respond to changes in its environment. It is also able to efficiently process information and make connections between seemingly unrelated ideas. This idea is based on the principle of self-organized criticality, which suggests that many natural systems, including the brain, organize themselves to operate at the boundary between order and chaos. This is because this critical state allows for a balance between stability and flexibility, enabling the system to be both resilient and adaptive. In the brain, this state of criticality is thought to be related to the activity of neurons and their connections, which can become synchronized or desynchronized depending on the level of input they receive. When there is a balance between synchronization and desynchronization, the brain is able to efficiently process information and make connections between different areas. Overall, the idea that the brain operates most effectively at the critical point between order and chaos is still a topic of ongoing research and debate. However, it does suggest that there may be certain conditions or activities that can help promote this state of criticality, such as exposure to novel experiences, engagement in challenging tasks, and regular exercise.
Criticality is the singular state of complex systems poised at the brink of a phase transition between order and randomness. Such systems display remarkable information-processing capabilities, evoking the compelling hypothesis that the brain may itself be critical. source 
The past 25 years have seen a strong increase in the number of publications related to criticality in different areas of neuroscience. The potential of criticality to explain various brain properties, including optimal information processing, has made it an increasingly exciting area of investigation for neuroscientists.
Recent reviews on this topic, sometimes termed brain criticality, make brief mention of clinical applications of these findings to several neurological disorders such as epilepsy, neurodegenerative disease, and neonatal hypoxia.
Other clinically relevant domains – including anesthesia, sleep medicine, developmental-behavioural pediatrics, and psychiatry – are seldom discussed in review papers of brain criticality. Thorough assessments of these application areas and their relevance for clinicians have also yet to be published.
In this scoping review, studies of brain criticality involving human data of all ages are evaluated for their current and future clinical relevance. To make the results of these studies understandable to a more clinical audience, a review of the key concepts behind criticality (e.g., phase transitions, long-range temporal correlation, self-organized criticality, power laws, branching processes) precedes the discussion of human clinical studies. Open questions and forthcoming areas of investigation are also considered. source
In computational and theoretical models, criticality optimizes certain features of learning, including optimal information capacity and transmission (Shew et al., 2011; Shew and Plenz, 2013; Del Papa et al., 2017). Important aspects of human learning, including cognition and attention, have been analyzed through the lens of criticality (see Table 5). Studies on attention-deficit hypersensitivity disorder (ADHD) and autism, in which features of neurotypical cognition and attention are disrupted, are few in number but appear promising.
A recent resting-state fMRI study of neurotypical adults with a range of IQ scores found that high fluid intelligence is associated with proximity to a critical phase transition in a spin-glass model (Ezaki et al., 2020). This finding was consistent with previous work suggesting near-criticality as perhaps optimal for learning (Gisiger et al., 2014). From an EEG study of healthy university students learning organic chemistry, it is also known that a lower power-law exponent of the fractal component of EEG signals correlates with higher learning gains during a computerized learning task under EEG (Bongers et al., 2019). While this latter study makes no claims regarding criticality, one can infer that the scale-free behavior of neurons matters for the acquisition of complex new knowledge.
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