Cortical Integration

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April 9, 2017 – MCAT CARS Passage

Question: What is your summary of the author’s main ideas. Post your own answer in the comments before reading those made by others.

The question of whether the human consciousness is subjective or objective is largely philosophical. But the line between consciousness and unconsciousness is a bit easier to measure. In a new study of how anesthetic drugs affect the brain, researchers suggest that our experience of reality is the product of a delicate balance of connectivity between neurons—too much or too little and consciousness slips away.

“It’s a very nice study,” says neuroscientist Melanie Boly at the University of Wisconsin, Madison, who was not involved in the work. “The conclusions that they draw are justified.”

Previous studies of the brain have revealed the importance of “cortical integration” in maintaining consciousness, meaning that the brain must process and combine multiple inputs from different senses at once. Our experience of an orange, for example, is made up of sight, smell, taste, touch, and the recollection of our previous experiences with the fruit. The brain merges all of these inputs—photons, aromatic molecules, etc.—into our subjective experience of the object in that moment.

“There is new meaning created by the interaction of things,” says Enzo Tagliazucchi, a physicist at the Institute for Medical Psychology in Kiel, Germany. Consciousness ascribes meaning to the pattern of photons hitting your retina, thus differentiating you from a digital camera. Although the brain still receives these data when we lose consciousness, no coherent sense of reality can be assembled.

In order to look for the signature of consciousness in the brain, Tagliazucchi and his colleagues used a drug called propofol—an anesthetic drug used in surgery—to induce loss of consciousness in participants while they were inside a functional magnetic resonance imaging (fMRI) machine’s scanner. fMRI works by tracking blood flow in the brain, which can be used as a real-time proxy for electrical activity when neurons fire. The team recorded data from 12 participants in states of wakefulness, ongoing sedation, unconsciousness, and recovery.

The results, published online today in the Journal of the Royal Society Interface, show that brain activity varies widely between conscious and unconscious states. The difference may come down to how the brain “explores the space of its own possible configurations,” Tagliazucchi says.

During wakeful consciousness, participants’ brains generated “a flurry of ever-changing activity,” and the fMRI showed a multitude of overlapping networks activating as the brain integrated its surroundings and generated a moment to moment “flow of consciousness.” After the propofol kicked in, brain networks had reduced connectivity and much less variability over time. The brain seemed to be stuck in a rut—using the same pathways over and over again.

The results suggest that, in the brain, there is an optimal level of connectivity between neurons that creates the maximum number of possible pathways. If each neuron can be thought of as a node in the network, consciousness might result from exploring the network as thoroughly as possible. But the most diverse networks—the ones with the largest possible number of arrangements—don’t necessarily have the maximum amount of neuronal connectivity.

If every neuron in the brain were directly connected to every other neuron, however, the brain would become too homogenous, and one signal would become indistinguishable from the next, Tagliazucchi explains. “They all fire or they all stay quiet.” Instead, consciousness might emerge from a careful balancing that causes the brain to “explore” the maximum number of unique pathways to generate meaning, he says. The researchers call this balance point “a critical point.”

“[It’s] like cars exploring the streets of the city,” Tagliazucchi says. “If the cars move always in the same restrictive manner, if they move from point A to point B and back, at the end of the day you don’t really understand the city. But if the cars are thorough explorers and go through all possible parts of the city, you get a map that’s very close to the actual map of the city. At the critical point, the cars are exploring the streets in the optimal way.”

Unlike cars, though, the flow of electricity through our brains is not driven by some sentient force with will or intent. And, in fact, what causes the brain to move between states of consciousness and unconsciousness—to and from the critical point—remains unknown. “If you’re in a critical point, the brain is really chaotic,” Boly says. “If you’re far from there, it’s too monotonous or stable.”

That stability could explain what makes it hard to wake people from a coma. Tagliazucchi hopes that by understanding where the critical points lie, and how they’re maintained, we might eventually rouse coma patients from unconscious states, coaxing the brain to begin exploring its streets in just the right way.

Adapted from Sciencemag.

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This was an article on Psychology.

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Jack Westin
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30 Comments


  1. MI: brain activity = different b/w consciousness and unconsciousnes + former = activity involving variable networks (RTA: Tagliazucchi)

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  2. Consciousness is a marriage between objective data collection and subjective assignments of meaning. Researchers using fMRI while patients were both awake and sedated found striking differences in the activity of cortical networks. The awake patients displayed a furry of activation of different, overlapping networks, sedated patients showed far more stable, monotonous network activity. The team defined “critical point” as the maximum number of possible neural pathways the brain could exploit during the awake state.

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  3. Scientists are tracking the neuronal difference between a conscious and unconscious brain to try and find a solution for comatose patients

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  4. cortical integration = important for maintaining consciousness = ascribes meaning
    brain activities vary between conscious and unconscious states (Tagliazucchi study findings)
    consciousness = balance that enables brain to explore max # of unique pathways to generate meaning + driven force is unclear + need more understanding on the critical point

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  5. consciousness = balanced neuron connectivity = changing activity, critical point = chaotic RTA (Boly) drugs = loss of consciousness,

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  6. MIP: Many aspects of consciousness, research proves these aspects to be useful.

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  7. MIP: merge multiple sense inputs –> subjective experience; optimal love of connectivity exists + diversity = max connectivity

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  8. critical point = optimal connectivity

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  9. Scientist research on the critical point of best connectivity between Conscious and unconscious.

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  10. MIP: Conscious/ unconscious differ ; critical pt = brain balance uncon/con

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  11. Consciousness = balance; understand more might help patients in a coma

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  12. consciousness is a delicate balance. hopefully can help understand coma patients better

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  13. consciousness = many networks + critical point

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  14. Brain activity varies between the state of consciousness and unconsciousness, mainly due to the number of pathways utilized for brain activity between those two states. The cause for consciousness and unconsciousness is unclear, but can be utilized for our benefit if we can unlock the mystery.

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  15. MI: Con/Uncon related to number of neural connections in brain, critical point = balance for max number of pathways in brain

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  16. Consciousness = brain activity + balance + critical point + help coma patients.

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  17. Multiple pathways=imp. to consciousness
    Conscious and unconscious states= varied
    Critical point= imp. consciousness

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  18. conscious = meaning, optimal pathway, cortical integration vs. unconscious = monotony, stability. RTA: Tagliazucchi

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  19. consciousness determined by neuron connections; CI allows for meaning; critical point = change/flux of connections, and allows for consciousness (but unknown what causes CP)

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  20. MIP: Consciousness involves a critical point where there is maximal exploration; tone = neutral

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  21. Study=difference b/w conscious and unconscious states. Consciousness = optimal level of connectivity + maximum number of unique pathways = critical point

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  22. researchers explore unconsciousness vs consciousness states
    consciousness hits critical points = optimal connectivity & max pathways

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  23. unconscious brain =/= conscious brain = more research needed to understand difference
    conscious brain=unique and optimal connections to generate meaning = critical point

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  24. Critical point = max connectivity +flow unknown +ex. car

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  25. Brain: C+ UC state= critical point= derived from exploration of diff networks

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  26. consciousness= human quality+ more integrated brain activity
    maximal exploration of connectivity, rather than maximal connectivity, determines strength of consciousness
    critical point= best balance point of neuronal activation. method of reaching this stage could help coma patients

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  27. Cons vs unc= easier to measure (CW) (boyl)

    Cons vs uncon=diferent + cons= High connectivity with uniqueness

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  28. knowledge of critical point is useful; optimal connectivity =/= max number of connections

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  29. This passage discusses the topic of consciousness and unconsciousness by describing recent studies. The passage describes how consciousness can be related to a “critical point” or different neural pathways that are used to stream reality, while unconsciousness is more stable. In the end, future research will try to further understand this concept to wake people up from comas.

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  30. MIP: Conscious vs unconscious=balance of connectivity; cortical integration=combining multiple inputs; AU: neutral

    Reply

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