Posts tagged consciousness
Articles and news from the latest research reports.
Common Brain Processes of Anesthetic-Induced Unconsciousness Identified
A study from the June issue of Anesthesiology found feedback from the front region of the brain is a crucial building block for consciousness and that its disruption is associated with unconsciousness when the anesthetics ketamine, propofol or sevoflurane are administered.
Brain centers and mechanisms of consciousness have not been well understood, resulting in a need for better monitors of consciousness during anesthesia. In addition, how anesthetics with different structures and pharmacological properties can generate unconsciousness has been a persistent question in anesthesiology since the beginning of the field in the mid-19th century.
A team of researchers from the University of Michigan, Ann Arbor, Mich., and Asan Medical Center, Seoul, South Korea, conducted a brain wave (electroencephalographic, or EEG) study of the front and back regions of the brain in 30 surgical patients who received intravenous ketamine. They compared the results of this study to the EEG data collected from 18 surgical patients who received either intravenous propofol or inhaled sevoflurane in a previous study. These three anesthetics, known to act on different parts of the brain and produce different EEG patterns, had the same effect of disrupting communication in the brain.
“Understanding a commonality among the actions of these diverse drugs could lead to a more comprehensive theory of how general anesthetics induce unconsciousness,” said study author George Mashour, M.D., Ph.D., assistant professor and associate chair for faculty affairs, Department of Anesthesiology, University of Michigan. “Our research shows that studying general anesthesia from the perspective of consciousness may be a fruitful approach and create new avenues for further investigation of anesthetic mechanisms and monitoring.”
An accompanying editorial by Jamie W. Sleigh, M.D., professor of anaesthesiology and intensive care, Department of Anaesthesia, University of Auckland, Hamilton, New Zealand, supported the study’s ability to better understand the neurobiology of consciousness.
“If the study’s findings are confirmed by subsequent work, the paper will achieve landmark status,” said Dr. Sleigh. “The study not only sheds light on the phenomenon of general anesthesia, but also how it is necessary for certain regions of the brain to communicate accurately with one another for consciousness to emerge.”
In addition, Dr. Sleigh recognized the study’s potential to lead to the development of better depth-of-anesthesia monitors that work for all general anesthetics.
(Image: Shutterstock)
The brain has been traditionally viewed as a deterministic machine where certain inputs give rise to certain outputs. However, there is a growing body of work that suggests this is not the case. The high importance of initial inputs suggests that the brain may be working in the realms of chaos, with small changes in initial inputs leading to the production of strange attractors. This may also be reflected in the physical structure of the brain which may also be fractal. EEG data is a good place to look for the underlying patterns of chaos in the brain since it samples many millions of neurons simultaneously. Several studies have arrived at a fractal dimension of between 5 and 8 for human EEG data. This suggests that the brain operates in a higher dimension than the 4 of traditional space-time. These extra dimensions suggest that quantum gravity may play a role in generating consciousness.
(Image courtesy: Kookmin University)
Babies develop conscious perception from five months of age
Infants develop the ability to consciously process their environment as early as five months of age, according to a study published in the journal Science.
The team of French and Danish researchers, led by neuroscientist Sid Kouider, discovered a signal in the nervous system of infants that reliably identifies the beginning of visual consciousness, or the ability to see something and recall that you have seen it.
The team set out believing infants had the capacity for conscious reflection, but they had to overcome the barrier that babies could not report their thoughts.
They used electroencephalography (EEG) to record electrical activity in the brains of 80 infants aged five, 12 and 15 months while they were shown pictures of faces and random patterns for a fraction of a second.
When adults are aware of a stimulus, their brains show a two-stage pattern of activity. When they see a moving object, the sensors in the vision centre of the brain activate with a spike of activity.
The signal then moves from the back of the brain to the prefrontal cortex, which deals with higher-level cognition. This is known as the late slow wave.
Conscious awareness begins after the second stage of neural activity reaches a specific threshold.
The new study found this two-stage pattern of brain activity was present in the three groups of infants, though it was weaker and more drawn out in the five-month-olds.
The researchers say neurological markers of visual consciousness may help paediatricians better manage infant pain and anaesthesia.
But they note the research does not provide direct proof of consciousness. “Indeed, it is a genuine philosophical problem whether such a proof can ever be obtained from purely neurophsysiological data,” the paper said.
Professor Louise Newman, Director of the Centre for Developmental Psychiatry & Psychology at Monash University, said the study was novel in its ability to measure the way very young brains register stimuli.
But five months should not be seen as a fixed point at which infants start to process information, she said.
“Although this group has studied five months and up, my suspicion would be that if we had different techniques, young infants – from birth on – would show the capacity of registering these sorts of stimuli.
“Infants are born with quite sophisticated capacities to observe, respond to and interact with the environment, particularly the social environment,” she said.
“Very soon after birth, infants will maintain gaze with their parents or parent: they’ve got quite sophisticated visual tracking capacity from an early age.”
Professor Newman, who has undertaken behavioural studies in two- to four-month olds, said young infant brains were extremely sensitive to their mother’s emotional reaction.
“They learn that ‘if I do this, or if I smile or signal in this way, this is what usually happens’. If you manipulate that so they don’t get that response, they’re very sensitive to that and they show signs that it’s very aversive to them.”
How the brain loses and regains consciousness
Study reveals brain patterns produced by a general anesthesia drug; work could help doctors better monitor patients.
Since the mid-1800s, doctors have used drugs to induce general anesthesia in patients undergoing surgery. Despite their widespread use, little is known about how these drugs create such a profound loss of consciousness.
In a new study that tracked brain activity in human volunteers over a two-hour period as they lost and regained consciousness, researchers from MIT and Massachusetts General Hospital (MGH) have identified distinctive brain patterns associated with different stages of general anesthesia. The findings shed light on how one commonly used anesthesia drug exerts its effects, and could help doctors better monitor patients during surgery and prevent rare cases of patients waking up during operations.
Anesthesiologists now rely on a monitoring system that takes electroencephalogram (EEG) information and combines it into a single number between zero and 100. However, that index actually obscures the information that would be most useful, according to the authors of the new study, which appears in the Proceedings of the National Academy of Sciences the week of March 4.
“When anesthesiologists are taking care of someone in the operating room, they can use the information in this article to make sure that someone is unconscious, and they can have a specific idea of when the person may be regaining consciousness,” says senior author Emery Brown, an MIT professor of brain and cognitive sciences and health sciences and technology and an anesthesiologist at MGH.
We know when we’re being lazy thinkers
New study shows that human thinkers are conscious cognitive misers
Are we intellectually lazy? Yes we are, but we do know when we take the easy way out, according to a new study by Wim De Neys and colleagues, from the CNRS in France. Contrary to what psychologists believe, we are aware that we occasionally answer easier questions rather than the more complex ones we were asked, and we are also less confident about our answers when we do. The work is published online in Springer’s journal Psychonomic Bulletin & Review.
Research to date on human thinking suggests that our judgment is often biased because we are intellectually lazy, or so-called cognitive misers. We intuitively substitute hard questions for easier ones. What is less clear is whether or not we realize that we are doing this and notice our mistake.
Using an adaptation of the standard ‘bat-and-ball’ problem, the researchers explored this phenomenon. The typical ‘bat-and-ball’ problem is as follows: a bat and ball together cost $1.10. The bat costs $1 more than the ball. How much does the ball cost? The intuitive answer that immediately springs to mind is 10 cents. However, the correct response is 5 cents.
The authors developed a control version of this problem, without the relative statement that triggers the substitution of a hard question for an easier one: A magazine and a banana together cost $2.90. The magazine costs $2. How much does the banana cost?A total of 248 French university students were asked to solve each version of the problem. Once they had written down their answers, they were asked to indicate how confident they were that their answer was correct.
Only 21 percent of the participants managed to solve the standard problem (bat/ball) correctly. In contrast, the control version (magazine/banana) was solved correctly by 98 percent of the participants. In addition, those who gave the wrong answer to the standard problem were much less confident of their answer to the standard problem than they were of their answer to the control version. In other words, they were not completely oblivious to the questionable nature of their wrong answer. The key reason seems to be that reasoners tend to minimize cognitive effort and stick to intuitive processing.
The authors comment: “Although we might be cognitive misers, we are not happy fools who blindly answer erroneous questions without realizing it.”
Indeed, although people appear to unconsciously substitute hard questions for easier ones, in reality, they are less foolish than psychologists might believe because they do know they are doing it.
Sleep and dreaming: The how, where and why
Within a few hours of reading this you will lose consciousness and slip into a strange twilight world. Where does your mind go during that altered state – or more accurately states – we call sleep? And what is so vital about it that we must spend a third of our lives sleeping? In these articles, we review the latest ideas on why we sleep and look at new ways to enhance its benefits.
Your Unconscious Brain Can Do Math, Process Language
The unconscious brain may not be able to ace an SAT test, but new research suggests that it can handle more complex language processing and arithmetic tasks than anyone has previously believed. According to these findings, just published in the Proceedings of the National Academy of Sciences, we may be blithely unaware of all the hard work the unconscious brain is doing.
In their experiments, researchers from Hebrew University in Israel used a cutting-edge “masking” technique to keep their test subjects from consciously perceiving certain stimuli. With this technique, known as continuous flash suppression, the researchers show a rapidly changing series of colorful patterns to just one of the subject’s eyes. The bright patterns dominate the subject’s awareness to such an extent that when researchers show less flashy material to the other eye (like words or equations), it takes several seconds before the brain consciously registers it.
This masking technique is “a game changer in the study of the unconscious,” the scientists write, “because unlike all previous methods, it gives unconscious processes ample time to engage with and operate on subliminal stimuli.”
To study the unconscious brain’s ability to process language, the researchers subliminally showed the subject short phrases that made variable amounts of sense: For example, subjects might see the phrase “I ironed coffee” or “I ironed clothes.” The researchers gradually turned up the contrast between the phrase and its background, and measured how long it took for the phrase to “pop” into the subject’s conscious awareness. As the nonsensical phrases popped sooner, the researchers hypothesize that the unconscious brain processed the sentence, found it surprising and odd, and quickly passed it along to the conscious brain for further examination.
To determine the unconscious brain’s mathematical abilities, the researchers presented a simple subtraction or addition equation (for example, “9 − 3 − 4 = “) to a subject, but took it away before it could pop into consciousness. Then they stopped the masking pattern and displayed a single number, asking the viewer to pronounce the number as soon as it registered. When the number was the answer to the subtraction equation (for example, “2”), the subject was quicker to pronounce it. The researchers argue that the viewer was “primed” to respond to that number because the unconscious brain had solved the equation. Oddly, they didn’t find the same clear effect with easier addition equations.
(Source: spectrum.ieee.org)
Brain-damaged man ‘aware’ of scientists’ questions
A crash victim thought to have been in a vegetative state for more than a decade has used the power of thought to tell scientists he is not in pain.
Canadian Scott Routley, from London, Ontario, communicated with researchers via a brain scan, proving that he is conscious and aware. It is the first time such a severely brain-damaged patient has been able to provide clinically relevant information to doctors.
British neuroscientist Professor Adrian Owen, who leads the research team at the Brain and Mind Institute of Western Ontario, said: “Scott has been able to show he has a conscious, thinking mind. We have scanned him several times and his pattern of brain activity shows he is clearly choosing to answer our questions. We believe he knows who and where he is.”
Prof Owen was speaking on a BBC Panorama programme to be broadcast on Tuesday night.
Inside the unconscious brain
A new study from MIT and Massachusetts General Hospital (MGH) reveals, for the first time, what happens inside the brain as patients lose consciousness during anesthesia.
By monitoring brain activity as patients were given a common anesthetic, the researchers were able to identify a distinctive brain activity pattern that marked the loss of consciousness. This pattern, characterized by very slow oscillation, corresponds to a breakdown of communication between different brain regions, each of which experiences short bursts of activity interrupted by longer silences.
“Within a small area, things can look pretty normal, but because of this periodic silencing, everything gets interrupted every few hundred milliseconds, and that prevents any communication,” says Laura Lewis, a graduate student in MIT’s Department of Brain and Cognitive Sciences (BCS) and one of the lead authors of a paper describing the findings in the Proceedings of the National Academy of Sciences this week.
This pattern may help anesthesiologists to better monitor patients as they receive anesthesia, preventing rare cases where patients awaken during surgery or stop breathing after excessive doses of anesthesia drugs.
The idea of an untethered consciousness is something we can understand, even when we don’t suppose it is found in nature.