The nature of consciousness. How consciousness arises and disappears
Every time I take a shower, wash dishes, or walk somewhere, my brain passively scrolls through various scenarios. It’s completely normal to imagine yourself on the surface of Jupiter or run through the “wow, how would I respond to him in a conversation!” scenario over and over again. Moreover, such predictive thinking is the basis for survival. Our brains are constantly working to make predictions about what is happening around us in order to account for possible surprises. However, what is the nature of such a connection?
Not so long ago, our brain was compared to a computer, and the work of consciousness was metaphorically described as the work of an operating system. There is also a theory that our consciousness is a by-product of the brain, like the roar of an engine. However, our consciousness is much closer to the sound of a symphony. And its key factor is the synchronization of all musicians, they are also the neurons of the brain, for a single and harmonious composition. They talk about strings, maintenance of musical instruments and neuron playing techniques materials from our community. Subscribe so you don't miss the latest articles!
Anesthesia and the nature of consciousness
New research sheds light on how consciousness arises during wakefulness, and what exactly happens in the brain as it changes and loss of consciousnessin particular when a person is under general anesthesia.
The results of the study supported the idea that the phenomenon of consciousness is generated by synchronized communication, which occurs in a certain rhythm of the brain in certain frequency ranges, between basic sensory and higher order cognitive areas of the brain.
Former research group members at the Picower Institute for Learning and Memory at MIT and Vanderbilt University describedhow such rhythms allow the brain to remain ready to respond to environmental factors.
How the brain deals with unpredictable events
When sensory areas detect something unexpected, such as a blaring fire alarm, they use faster gamma rhythms to report the threat to higher cognitive areas. And the cognitive areas process this information at gamma frequencies to decide what to do. For example, move towards the exit of the building.
The new findings, published Oct. 7 in the Proceedings of the National Academy of Sciences, show that when the animals were under general anesthesia induced by propofol, the sensory region retained the ability to detect unexpected stimuli, but connections to a higher cognitive region at the front of the brain were lost. The disruption of the connection rendered this area unable to participate in the feedback regulation of the sensory area. Because of this, the animal was immune to both simple and more complex unexpected factors.
What we are doing here speaks to the nature of consciousness. General anesthesia with propofol deactivates the connection between processes that underlie cognition. Essentially, the substance shuts down communication between the front and back of the brain.
Earl K. Miller, a professor at the Picower Institute and co-author of the study.
Study co-author Andre Bastos, an assistant professor of psychology at Vanderbilt University and a former member of Miller's lab at MIT, added that the study's findings highlight the key role of frontal regions in shaping and supporting performance. pure consciousness.
The findings are especially important given new scientific interest in the mechanisms of consciousness and how consciousness relates to the brain's ability to form predictions.
Study co-author Andre Bastos
Brain function and the ability to predict
The brain's ability to predict spontaneously changes during anesthesia. Interestingly, the most active suppression was in the front part of the brain, namely the areas associated with cognition. In turn, sensory areas resisted anesthesia much more effectively.
This suggests that prefrontal areas help initiate an event that transforms sensory information into conscious information. Activation of the sensory cortex does not by itself lead to conscious perception. These observations help us narrow down the range of potentially working models of the mechanisms of consciousness. In the waking brain, brain waves give neurons short periods of time to fire optimally. They set, so to speak, the “refresh rate” of the brain.” This refresh rate helps organize different areas of the brain for effective communication.
Yihan Sophie Xiong, a graduate student in Bastos's lab, led the study.
Anesthesia slows down the frequency of communication, which narrows the time windows for brain regions to communicate, making communication less effective. Disorganization between neurons increases. And the ability to predict behavior weakens.
Deviations in patterns
To conduct the study, neuroscientists measured the electrical signals, or “bursts,” of hundreds of individual neurons, and also tracked the coordinated rhythms of their combined activity at alpha/beta and gamma frequencies. Activity was monitored in two areas of the animals' cerebral cortex as they listened to specific sequences of tones.
Sometimes the sequences would sound like they were all using the same note and the overall picture would look like “AAAAA”. Sometimes a factor of randomness or “local oddity” was specified, such as AAAAB. But sometimes the accident was more complex or “globally strange” in nature. For example, after a series of AAAAB patterns, suddenly an AAAAA pattern followed, which violated the global but not the local pattern.
Previous studies have suggested that a sensory area, in this case the temporoparietal area, or Tpt, can independently detect local oddities. Detection of more complex global changes requires the participation of a higher order region, in this case the FEF region was responsible for this.
Delving into the Nature of Consciousness
Animals heard sequences of tones both while awake and under propofol anesthesia. There were no surprises or abnormalities in the waking state. The researchers confirmed that descending alpha/beta rhythms from the FEF conveyed a predictive pattern to the Tpt, and as a result, the Tpt increased activity at the gamma level when an unusual signal appeared, causing the FEF, and the prefrontal cortex, to also respond with bursts of gamma activity.
Thus, our results indicate an important role for prefrontal cortex activation in addition to sensory cortex activation for conscious perception.
From research materials.
However, through a series of measurements and analyses, scientists were able to see that this dynamic breaks down after the animals lose their condition. objective consciousness. With the same propofol, spike activity was generally reduced, but when a locally unusual stimulus appeared, Tpt spikes increased activity commensurately, but FEF spikes did not maintain this activity, as occurs during wakefulness.
Meanwhile, when a global strange object appeared during wakefulness, the researchers could use software to “decode” its image among neurons in the FEF and prefrontal cortex, another area focused on cognitive understanding of the world.
They could also decode local changes in Tpt. But under anesthesia, the decoder could not reliably recognize local or global abnormalities in the FEF or prefrontal cortex.
Moreover, when scientists compared the rhythms between the awake and unconscious states, they found stark differences. When the animals were awake, gamma activity in both Tpt and FEF increased in response to an anomalous local stimulus, and alpha/beta rhythms decreased. Stable stimulation increased alpha/beta rhythms. But when the animals lost consciousness, the increase in gamma rhythms from the local stimulus was even greater in Tpt than when the animal was awake.
Overall, these studies suggest that our consciousness is not the product of any special part of the brain, but is born in the process of communication between completely different areas of the cerebral cortex, from the front to the back.
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