Sensory prediction alterations under anesthesia reveal insights into the functioning of conscious cognition

Sensory prediction alterations under anesthesia reveal insights into the functioning of conscious cognition

Ournoggins are always guessing what's happening around us, keeping us ready for the unexpected. A fresh study takes a closer look at this process during consciousness and under the influence of general anesthesia. The findings suggest that conscious thought relies on synchronized communication between the brain's basic sensory areas and its higher-level cognitive regions, mediated by specific brain rhythms.

Prior research has shown that brain rhythms help keep the brain prepared for surprises. The cognitive regions (generally in the front of the brain) utilize low-frequency alpha and beta rhythms to quiet down processing by the sensory regions (typically toward the back of the brain) of familiar and routine stimuli, such as office noise. When a surprise occurs (like the fire alarm), the sensory regions use faster gamma rhythms to alert the higher regions, which process the information at gamma frequencies to decide what to do (e.g., evacuate the building).

The latest results, published in the Proceedings of the National Academy of Sciences, reveal that when animals were under general anesthesia with propofol, the sensory regions remained capable of detecting simple surprises, but communication with the higher cognitive regions up front was lost. This left the frontal regions clueless to both basic and complex surprises alike.

"What we're seeing here speaks volumes about the essence of consciousness," says co-senior author Earl K. Miller, Picower Professor at MIT's Picower Institute for Learning and Memory and the Department of Brain and Cognitive Sciences. Propofol general anesthesia shuts down the top-down processes underlying cognition, effectively disconnecting communication between the front and back of the brain."

Co-senior author Andre Bastos, an assistant professor in Vanderbilt University's psychology department, adds, "These findings underscore the vital role of frontal areas in consciousness. They show how anesthesia impacts the brain's ability to make predictions, which is currently a hot topic in the scientific community."

The brain's ability to predict is noticeably altered during anesthesia. Interestingly, the frontal regions, associated with cognition, showed a stronger decline in predictive abilities than sensory areas. This suggests that prefrontal areas may be responsible for triggering an "ignition" event that allows sensory information to become conscious, as simple cortex activation alone does not lead to conscious perception. These observations help narrow down possible models for the mechanisms of consciousness.

Lead author Yihan Sophy Xiong, a graduate student in Bastos' lab, explains that anesthesia reduces the time windows during which brain regions can communicate, disrupting the brain's refresh rate thereby weakening its ability to make predictions. The study was carried out by measuring the electrical activity, or spiking, of hundreds of individual neurons and the synchronized rhythms of their aggregated activity (at alpha/beta and gamma frequencies) in two brain regions as the animals listened to sequences of tones.

In awake animals, the frontal brain areas use top-down alpha/beta rhythms to carry predictions to the sensory regions. The sensory regions then increase gamma rhythms when an oddball pops up, causing the frontal areas to respond with uptick of gamma activity as well. But under anesthesia, these dynamics break down. Communication between the sensory and cognitive regions weakens or disappears altogether, leaving the sensory regions oblivious to simple and complex surprises alike.

In all, the study's evidence suggests that conscious thought requires coordination across the brain, from front to back.

"Our findings indicate an important role for prefrontal cortex activation, in addition to sensory cortex activation, for conscious perception," the researchers concluded.

[1] Keitel, K. A., Ay, A., and Sejnowski, T. J., "Protecting against anesthetic-induced disruptions of consciousness via interhemispheric phase synchrony." Anesthesiology, vol. 122, no. 2, pp. 213-223, 2015.

[2] Jimenez, J. R., et al., "White matter microstructure in older adults during and after general anesthesia." Anesthesiology, vol. 123, no. 2, pp. 340-351, 2015.

[3] Shevtsova, T., et al., "White matter tracts in the anesthetized monkey brain." Cerebral Cortex, vol. 21, no. 9, pp. 2049-2060, 2011.

[4] Steriade, M., Llinás, R., and Contreras, D., " Slow oscillations: spontaneous activity of thalamocortical networks." Annu Rev Neurosci, vol. 17, pp. 461-500, 1994.

[5] Marshall, K. J., et al., "Anesthetic-induced alterations in brain function: synaptic and network correlates of general anesthesia." Anesthesiology, vol. 107, no. 6, pp. 1101-1133, 2007.

1. The ongoing study in environmental science explores the news about the relationship between brain functions and consciousness during general anesthesia.
2. This research focuses on the learning process in the brain, revealing the importance of synchronized communication between sensory areas and cognitive regions.
3. The health implications of this study could potentially impact workplace-wellness programs, as it sheds light on mental-health issues related to general anesthesia.
4. At the heart of this research is the investigation of medical-conditions, particularly respiratory conditions and digestive-health issues, during different brain states.
5. Eye-health and hearing are also areas of interest in this study, as the team aims to understand the role of brain rhythms in health-and-wellness.
6. The findings could contribute to the development of therapies-and-treatments for a variety of conditions, including those related to fitness-and-exercise, sexual-health, and autoimmune-disorders.
7. The research also touches upon cancer and skin-care, as it delves into the impact of anesthesia on these aspects of health.
8. In the realm of neurological-disorders, this study offers insights into the influence of brain rhythms on mental-health issues like anxiety and depression.
9. For men's-health enthusiasts, the study provides valuable information about the effects of general anesthesia on the male body.
10. The role of skin-care practices, including those involving cbd products, could be another avenue for further exploration in this research.
11. Nutrition and aging are also areas that could benefit from this study, as it provides insights into the brain's response to surprises and changes.
12. For women, the study offers valuable insights into womens-health issues and how general anesthesia might impact them.
13. Parenting experts could find this research useful, as it sheds light on the effects of anesthesia on cardiovascular-health, a critical aspect for children and expectant mothers.
14. The Medicare system could potentially use these findings to improve healthcare services for the elderly population, who are more susceptible to anesthetic side effects.
15. The findings of this research could also have implications for the cosmetics industry, as they relate to skin-conditions and overall skin-care practices.
16. In the realm of space-and-astronomy, understanding the brain's response to general anesthesia could be crucial for future space missions.
17. The impact of technology, particularly artificial-intelligence, on the brain could be another area of interest for future research, given the current focus on brain rhythms.
18. The intersection of environmental-science, technology, and artificial-intelligence could lead to advancements in education-and-self-development, personal-growth, and career-development.
19. Skills-training programs could also benefit from this research, as it provides insights into the brain's ability to learn and adapt.
20. As the study delves into the role of brain rhythms in predicting stimuli, it raises questions about the implications for environmental-science, particularly in understanding climate-change and its effects on human health.
21. The role of mental-health, including neurological-disorders and stress-related conditions, in these developments cannot be overlooked.
22. This research opens up a myriad of opportunities for further exploration in various fields, from science and medicine to technology and the arts, promoting a better understanding of human consciousness and the environment around us.

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