Posts tagged brain activity
Articles and news from the latest research reports.
Study examines how brain ‘reboots’ itself to consciousness after anesthesia
One of the great mysteries of anesthesia is how patients can be temporarily rendered completely unresponsive during surgery and then wake up again, with all their memories and skills intact.
A new study by Dr. Andrew Hudson, an assistant professor of anesthesiology at the David Geffen School of Medicine at UCLA, and colleagues provides important clues about the processes used by structurally normal brains to navigate from unconsciousness back to consciousness. Their findings are currently available in the early online edition of Proceedings of the National Academy of Sciences.
Previous research has shown that the anesthetized brain is not “silent” under surgical levels of anesthesia but experiences certain patterns of activity, and it spontaneously changes its activity patterns over time, Hudson said.
For the current study, the research team recorded the brain’s electrical activity in a rodent model that had been administered the inhaled anesthesia isoflurane by placing electrodes in several brain areas associated with arousal and consciousness. They then slowly decreased the amount of anesthesia, as is done with patients in the operating room, monitoring how the electrical activity in the brain changed and looking for common activity patterns across all the study subjects.
The researchers found that the brain activity occurred in discrete clumps, or clusters, and that the brain did not jump between all of the clusters uniformly.
A small number of activity patterns consistently occurred in the anesthetized rodents, Hudson noted. The patterns depended on how much anesthesia the subject was receiving, and the brain would jump spontaneously from one activity pattern to another. A few activity patterns served as “hubs” on the way back to consciousness, connecting activity patterns consistent with deeper anesthesia to those observed under lighter anesthesia.
"Recovery from anesthesia, is not simply the result of the anesthetic ‘wearing off’ but also of the brain finding its way back through a maze of possible activity states to those that allow conscious experience," Hudson said. "Put simply, the brain reboots itself."
The study suggests a new way to think about the human brain under anesthesia and could encourage physicians to reexamine how they approach monitoring anesthesia in the operating room. Additionally, if the results are applicable to other disorders of consciousness — such as coma or minimally conscious states — doctors may be better able to predict functional recovery from brain injuries by looking at the spontaneously occurring jumps in brain activity.
In addition, this work provides some constraints for theories about how the brain leads to consciousness itself, Hudson said.
Going forward, the UCLA researchers will test other anesthetic agents to determine if they produce similar characteristic brain activity patterns with “hub” states. They also hope to better characterize how the brain jumps between patterns.
Portable brain-mapping device allows researchers to ‘see’ where memory fails student veterans
UT Arlington researchers have successfully used a portable brain-mapping device to show limited prefrontal cortex activity among student veterans with Post Traumatic Stress Disorder when they were asked to recall information from simple memorization tasks.
The study by bioengineering professor Hanli Liu and Alexa Smith-Osborne, an associate professor of social work, and two other collaborators was published in the May 2014 edition of NeuroImage: Clinical. The team used functional near infrared spectroscopy to map brain activity responses during cognitive activities related to digit learning and memory retrial.
Smith-Osborne has used the findings to guide treatment recommendations for some veterans through her work as principal investigator for UT Arlington’s Student Veteran Project, which offers free services to veterans who are undergraduates or who are considering returning to college.
“When we retest those student veterans after we’ve provided therapy and interventions, they’ve shown marked improvement,” Smith-Osborne said. “The fNIRS data have shown improvement in brain functions and responses after the student veterans have undergone treatment.”
Liu said this type of brain imaging allows us to “see” which brain region or regions fail to memorize or recall learned knowledge in student veterans with PTSD.
“It also shows how PTSD can affect the way we learn and our ability to recall information, so this new way of brain imaging advances our understanding of PTSD.” Liu said.
This study is multi-disciplinary, associating objective brain imaging with neurological disorders and social work.
While UT Arlington bioengineering faculty associate Fenghua Tian is the primary author assisted by bioengineering graduate research assistant Amarnath Yennu, collaborators of the study include UT Austin psychology professor Francisco Gonzalez-Lima and psychology professor Carol North with UT Southwestern Medical Center and the Veterans Administration North Texas Health Care System.
Khosrow Behbehani, dean of the UT Arlington College of Engineering, said this collaborative research is “allowing the researchers to objectively measure the changes in the level of oxygen in the brain and relate them to some of the brain functions that may have been adversely affected by trauma or stress.”
Numerous neuropsychological studies have linked learning dysfunctions – such as memory loss, attention deficits and learning disabilities – with PTSD.
The new study involved 16 combat veterans previously diagnosed with PTSD who were experiencing distress and functional impairment affecting cognitive and related academic performance. The veterans were directed to perform a series of number-ordering tasks on a computer while researchers monitored their brain activity through near infrared spectroscopy, a noninvasive neuroimaging technology.
The research found that participants with PTSD experienced significant difficulty recalling the given digits compared with a control group. This deficiency is closely associated with dysfunction of a portion in the right frontal cortex. The team also determined that near infrared spectroscopy was an effective tool for measuring cognitive dysfunction associated with PTSD.
With that information, Smith-Osborne said mental healthcare providers could customize a treatment plan best suited for that individual.
“It’s not a one-size-fits-all treatment plan but a concentrated effort to tailor the treatment based on where that person is on the learning scale,” Smith-Osborne said.
Smith-Osborne and Liu hope that their research results lead to better and more comprehensive care for veterans and a better college education.
(Source: uta.edu)
Clever Suppression in the Brain
The hippocampus is a small structure in the brains of mammals that plays a crucial role in processing input from our senses and allows perceptions to be stored as memories. Nerve cells that inhibit the activity of other cells have now been shown to play a much larger and more complex role in these processes than previously assumed. Teams led by Prof. Dr. Marlene Bartos from the Cluster of Excellence BrainLinks-BrainTools at the University of Freiburg and Prof. Dr. Imre Vida from the Cluster of Excellence NeuroCure at the hospital Charité in Berlin report these findings in the current issue of the Journal of Neuroscience.
(Image caption: Three different cell types in the hippocampus (BC, HCP, and HIPP) were previously known to have different morphologies (top). New research shows that they respond to electrical stimulation (black traces) by inhibiting other nerve cells in very different patterns (bottom), allowing for more powerful information processing. Credit: BrainLinks-BrainTools)
In their study, the scientists investigated how special types of so-called interneurons build connections with each other within the hippocampus and how their function influences the network of nerve cells as a whole. Interneurons do not prompt other nerve cells to become active but, on the contrary, inhibit them. This kind of suppression plays an important role in brain activity in general. Information processing would not be possible otherwise, because a brain in which all nerve cells are active at the same time is effectively put out of order.
The hippocampus is home to a variety of different inhibitory cells, which were known so far to differ greatly in their form and function. But up to now it has been generally assumed that their actual influence on the activity of the brain structure they belong to is rather small. By combining several different experimental methods, Bartos, Vida, and their teams succeeded in showing that these cells are actually able to strongly interfere with the activity and the timing of activity patterns within the hippocampus. Moreover, the various possible combinations of connections between these different cell types show markedly different characteristics in their function. This makes the inhibition within the hippocampus much more flexible and versatile than previously assumed. The team of scientists suspects that this also makes the capability to process information within the hippocampus much bigger. The results published in this study are from experiments conducted in acute slice preparations of the hippocampus. Up next for the researchers will be the task of verifying these results within the actual brain.
(Source: pr.uni-freiburg.de)
To recover consciousness, brain activity passes through newly detected states
Anesthesia makes otherwise painful procedures possible by derailing a conscious brain, rendering it incapable of sensing or responding to a surgeon’s knife. But little research exists on what happens when the drugs wear off.
(Image caption: Unconscious states. New findings suggest the anesthetized brain must pass through certain ‘way stations’ on the path back to consciousness. Above, the prevalence of particular clusters of brain activity states as recorded in rats that had been administered an anesthetic. The longest appear in red and the shortest in yellow and green.)
“I always found it remarkable that someone can recover from anesthesia, not only that you blink your eyes and can walk around, but you return to being yourself. So if you learned how to do something on Sunday and on Monday, you have surgery, and you wake up and you still know how to do it,” says Alexander Proekt, a visiting fellow in Don Pfaff’s Laboratory of Neurobiology and Behavior at Rockefeller University and an anesthesiologist at Weill Cornell Medical College. “It seemed like there ought to be some kind of guide or path for the system to follow.”
The obvious explanation is that as the anesthetic washes out of the body, electrical activity in the brain gradually returns to its conscious patterns. However, new research by Proekt and colleagues suggests the trip back is not so simple.
“Using statistical analysis, our research shows that the recovery from deep anesthesia is not a smooth, linear process. Instead, there are dynamic ‘way stations’ or states of activity the brain must temporarily occupy on the way to full recovery,” Pfaff says. “These results have implications for understanding how someone’s ability to recover consciousness can be disrupted by, for example, brain injury.”
Proekt, along with former postdoc Andrew Hudson, now an assistant professor in anesthesiology at the University of California, Los Angeles, and Diany Paola Calderon, a research associate in the lab, put rats “under” using the common medical and veterinary anesthetic isoflurane. As the rats recovered, the team monitored the electrical potential outside neurons, known as local field potentials (LFPs), in particular parts of the brain known, from previous elecrophysiological and pharmacological studies, to be associated with wakefulness and anesthesia. These recordings gave them a sensitive handle on the activities of whole groups of neurons in particular parts of the thalamus and cortex.
In the awake brain, of both humans and rats, neurons generate electrical voltage that oscillates. Many of these oscillations together form a signal that appears as a squiggly line on a recording of brain activity, such as an LFP. When someone is asleep, under anesthesia, or in a coma, these oscillations occur more slowly, or at a low frequency. When he or she is awake, they speed up. The researchers examined the recordings from the rats’ brains to figure out how the electrical activity in these regions changed as they moved from anesthetized to awake.
“Recordings from each animal wound up having particular features that spontaneously appeared, suggesting their brain activity was abruptly transitioning through particular states,” Hudson says. “We analyzed the probability of a brain jumping from one state to another, and we found that certain states act as hubs through which the brain must pass to continue on its way to consciousness.” While the electrical activity in all the rats’ brains passed through these hubs, the precise path back to consciousness was not the same each time, the team reports today in the Proceedings of the National Academy of Sciences.
“These results suggest there is indeed an intrinsic way in which the unconscious brain finds its way back to consciousness. The anesthetic is just a tool for severely reducing brain activity in a way in which we can control,” Hudson says.
In other scenarios, including coma caused by brain injury or neurological disease, the disruption to brain activity cannot be controlled, making these states much more difficult to study. However, the team’s results may help explain what is going on in these cases. “Maybe a pathway has shut down, or a brain structure that was key for full consciousness is no longer working. We don’t know yet, but our results suggest the possibility that under certain circumstances, someone may be theoretically capable of returning to consciousness but, due to the inability to transition through the hubs we have identified, his or her brain is unable to navigate the way back,” Calderon says.
(Source: newswire.rockefeller.edu)
Does ‘free will’ stem from brain noise?
Our ability to make choices — and sometimes mistakes — might arise from random fluctuations in the brain’s background electrical noise, according to a recent study from the Center for Mind and Brain at the University of California, Davis.
"How do we behave independently of cause and effect?" said Jesse Bengson, a postdoctoral researcher at the center and first author on the paper. "This shows how arbitrary states in the brain can influence apparently voluntary decisions."
The brain has a normal level of “background noise,” Bengson said, as electrical activity patterns fluctuate across the brain. In the new study, decisions could be predicted based on the pattern of brain activity immediately before a decision was made.
Bengson sat volunteers in front of a screen and told them to fix their attention on the center, while using electroencephalography, or EEG, to record their brains’ electrical activity. The volunteers were instructed to make a decision to look either to the left or to the right when a cue symbol appeared on screen, and then to report their decision.
The cue to look left or right appeared at random intervals, so the volunteers could not consciously or unconsciously prepare for it.
The brain has a normal level of “background noise,” Bengson said, as electrical activity patterns fluctuate across the brain. The researchers found that the pattern of activity in the second or so before the cue symbol appeared — before the volunteers could know they were going to make a decision — could predict the likely outcome of the decision.
"The state of the brain right before presentation of the cue determines whether you will attend to the left or to the right," Bengson said.
The experiment builds on a famous 1970s experiment by Benjamin Libet, a psychologist at UCSF who was later affiliated with the UC Davis Center for Neuroscience.
Libet also measured brain electrical activity immediately before a volunteer made a decision to press a switch in response to a visual signal. He found brain activity immediately before the volunteer reported deciding to press the switch.
The new results build on Libet’s finding, because they provide a model for how brain activity could precede decision, Bengson said. Additionally, Libet had to rely on when volunteers said they made their decision. In the new experiment, the random timing means that “we know people aren’t making the decision in advance,” Bengson said.
Libet’s experiment raised questions of free will — if our brain is preparing to act before we know we are going to act, how do we make a conscious decision to act? The new work, though, shows how “brain noise” might actually create the opening for free will, Bengson said.
"It inserts a random effect that allows us to be freed from simple cause and effect," he said.
The work, which was funded by the National Institutes of Health, was published online in the Journal of Cognitive Neuroscience.
Finding the perfect balance — regulating brain activity to improve attention
Researchers from The University of Nottingham have found that balanced activity in the brain’s prefrontal cortex is necessary for attention.
The research helps to make sense of attention deficits in people suffering from cognitive disorders — like schizophrenia — who often find it hard to sustain their attention. This has a significant effect on many aspects of their lives, including the ability to follow conversations, drive a car and hold down a job.
Activity in a healthy brain is controlled by inhibitory signals between neurons. The research shows that disrupting this healthy inhibition may be just as bad for attention as reducing neuron firing. It is often assumed that increasing brain activity has cognitive benefits, but the findings show that this is not always the case.
The research was carried out by a team in the University’s School of Psychology and involved inhibiting or disinhibiting the prefrontal cortex in rats and monitoring the effect. The researchers found that both of these extremes resulted in attentional deficits and that the ability to pay attention required an appropriate balance where neuron-firing was kept within a certain range.
Schizophrenia and attention deficits
Studies of the brain in people with schizophrenia suggest aberrant neuron-firing in the prefrontal cortex. There is evidence that neuron firing in this part of the brain is often too high or too low.
Dr Tobias Bast, who led the study together with first author Dr Marie Pezze, said: “The implication of our findings is that the abnormalities we see in the prefrontal cortex of schizophrenia patients, for example, are indeed a plausible cause of the attention deficit these patients have.
“It also means that if we want to treat this pharmacologically, we can’t just boost activity of the prefrontal cortex or inactivate it, because that would actually result in an impairment. What we need to do is look at restoring balance of activity through drugs which keep the activity within a certain range.”
Cognitive deficits associated with schizophrenia
In people with schizophrenia, cognitive deficits — such as problems with attention — are less striking than other issues associated with the disorder, such as hallucinations, but are nevertheless a major problem.
Dr Bast said: “Initially people focused on the so-called ‘psychotic symptoms’, including hallucinations and delusions, so that’s what probably comes to mind when you think of schizophrenia. They have been in the fore because they have been so striking and that’s why referrals are made. But these can be treated, at least in a large proportion of patients, by using anti-psychotic medication, which we have had since the late 1950s.
“The problem is that unfortunately anti-psychotic drugs don’t improve cognitive deficits which are very debilitating, affecting many aspects of the patients’ lives. Cognitive deficits are a big problem and something that is currently not treated so finding something that helps this is really important.”
Researchers use rhythmic brain activity to track memories in progress
University of Oregon researchers have tapped the rhythm of memories as they occur in near real time in the human brain.
Using electroencephalogram (EEG) electrodes attached to the scalps of 25 student subjects, a UO team led by psychology doctoral student David E. Anderson captured synchronized neural activity while they held a held a simple oriented bar located within a circle in short-term memory. The team, by monitoring these alpha rhythms, was able to decode the precise angle of the bar the subjects were locking onto and use that brain activity to predict which individuals could store memories with the highest quality or precision.
The findings are detailed in the May 28 issue of the Journal of Neuroscience. A color image illustrating how the item in memory was tracked by rhythmic brain activity in the alpha frequency band (8 to 12 beats per second) is on the journal’s cover page to showcase the research.
Although past research has decoded thoughts via brain activity, standard approaches are expensive and limited in their ability to track fast-moving mental representations, said Edward Awh, a professor in the UO’s Department of Psychology and Institute of Neuroscience. The new findings show that EEG measures of synchronized neural activity can precisely track the contents of memory at almost the speed of thought, he said.
"These findings provide strong evidence that these electrical oscillations in the alpha frequency band play a key role in a person’s ability to store a limited number of items in working memory," Awh said. “By identifying particular rhythms that are important to memory, we’re getting closer to understanding the low-level building blocks of this really limited cognitive ability. If this rhythm is what allows people to hold things in mind, then understanding how that rhythm is generated — and what restricts the number of things that can be represented — may provide insights into the basic capacity limits of the mind.”
The findings emerged from a basic research project led by Awh and co-author Edward K. Vogel — funded by the National Institutes of Health — that seeks to understand the limits of storing information. “It turns out that it’s quite restricted,” Awh said. “People can only think about a couple of things at a time, and they miss things that would seem to be extremely obvious and memorable if that limited set of resources is diverted elsewhere.”
Past work, mainly using functional magnetic resonance imaging (fMRI), has established that brain activity can track the content of memory. EEG, however, provides a much less expensive approach and can track mental activity with much a higher temporal resolution of about one-tenth of a second compared to about five seconds with fMRI.
"With EEG we get a fine-grained measure of the precise contents of memory, while benefitting from the superior temporal resolution of electrophysiological measures," Awh said. “This EEG approach is a powerful new tool for tracking and decoding mental representations with high temporal resolution. It should provide us with new insights into how rhythmic brain activity supports core memory processes.”
Hypnosis extends restorative slow-wave sleep
Deep sleep promotes our well-being, improves our memory and strengthens the body’s defences. Zurich and Fribourg researchers demonstrate how restorative SWS can also be increased without medication – using hypnosis.
Sleeping well is a crucial factor contributing to our physical and mental restoration. SWS in particular has a positive impact for instance on memory and the functioning of the immune system. During periods of SWS, growth hormones are secreted, cell repair is promoted and the defence system is stimulated. If you feel sick or have had a hard working day, you often simply want to get some good, deep sleep. A wish that you can’t influence through your own will – so the widely held preconception.
Sleep researchers from the Universities of Zurich and Fribourg now prove the opposite. In a study that has now been published in the scientific journal “Sleep”, they have demonstrated that hypnosis has a positive impact on the quality of sleep, to a surprising extent. “It opens up new, promising opportunities for improving the quality of sleep without drugs”, says biopsychologist Björn Rasch who heads the study at the Psychological Institute of the University of Zurich in conjunction with the “Sleep and Learning” project*.
Brain waves – an indicator of sleep quality
Hypnosis is a method that can influence processes which are very difficult to control voluntarily. Patients with sleep disturbances can indeed be successfully treated with hypnotherapy. However, up to now it hadn’t been proven that this can lead to an objectively measurable change in sleep. To objectively measure sleep, electrical brain activity is recorded using an electroencephalogram (EEG). The characteristic feature of slow-wave sleep, which is deemed to have high restorative capacity, is a very even and slow oscillation in electrical brain activity.
70 healthy young women took part in the UZH study. They came to the sleep laboratory for a 90-minute midday nap. Before falling asleep they listened to a special 13-minute slow-wave sleep hypnosis tape over loudspeakers, developed by hypnotherapist Professor Angelika Schlarb, a sleep specialist, or to a neutral spoken text. At the beginning of the experiment the subjects were divided into highly suggestible and low suggestible groups using a standard procedure (Harvard Group Scale of Hypnotic Susceptibility). Around half of the population is moderately suggestible. With this method women achieve on average higher values for hypnotic susceptibility than men. Nevertheless, the researchers expect the same positive effects on sleep for highly suggestible men.
Slow-wave sleep increased by 80 percent
In their study, sleep researchers Maren Cordi and Björn Rasch were able to prove that highly suggestible women experienced 80 percent more slow-wave sleep after listening to the hypnosis tape compared with sleep after listening to the neutral text. In parallel, time spent awake was reduced by around one-third. In contrast to highly suggestible women, low suggestible female participants did not benefit as much from hypnosis. With additional control experiments the psychologists confirmed that the beneficial impact of hypnosis on slow-wave sleep could be attributed to the hypnotic suggestion to “sleep deeper” and could not be reduced to mere expectancy effects.
According to psychologist Maren Cordi “the results may be of major importance for patients with sleep problems and for older adults. In contrast to many sleep-inducing drugs, hypnosis has no adverse side effects”. Basically, everyone who responds to hypnosis could benefit from improved sleep through hypnosis.
* The project “Sleep and Learning” is headed by Professor Björn Rasch from the University of Fribourg and conducted at the Universities of Zurich and Fribourg. The project is financed by the Swiss National Fund and the University of Zurich (main area of clinical research “Sleep and Health”). The goal of the project is to identify psychological and neurophysiological mechanisms underlying the positive role of sleep for our memory and mental health.
(Source: mediadesk.uzh.ch)
A ‘hands-on’ approach could help babies develop spatial awareness
A study from the Department of Psychology published today found:
- Changes in the way the brain processes touch in the first year of life
- Babies start keeping track of their hands are when their arms move around from 8 months
- Crossing the hands confuses the mind in young babies
- The way we perceive touch in the outside world develops in the first year of life
The research, from Goldsmiths’ InfantLab, suggested that babies’ tactile experiences could be important for developing their sense of place in the world around them.
The InfantLab research team carried out their study on 66 babies aged from six to ten months old.
Babies felt harmless ‘buzzes’ on their arms
In the study, babies felt little tactile ‘buzzes’ on their hands first with their arms in an uncrossed position and then in a crossed position, while their brain activity was recorded through an EEG (electroencephalography) sensor net.
This is one of the first pieces of research to focus on the development of ‘touch perception’, which is crucial for investigating how babies learn to perceive how their own bodies fit into the world around them.
Dr Andy Bremner, InfantLab Director, explained: “We discovered that it takes time for babies to build up good mechanisms for perceiving how they fit into the outside world. Specifically, early on they do not appear to perceive the ways in which the body changes when their limbs, in this case their arms, move around.”
Dr Silvia Rigato, researcher on the project, commented: “The vast majority of previous studies on infant perception has focussed on what babies perceive of a visual environment on a screen and out of reach, giving us a picture of what babies can do and understand when in couch potato mode.”
“Our research has taken this a step further. As adults we need good maps of where our bodies and limbs are in order to be able to act and move around competently. It seems these take time to develop in the first year, and we didn’t know that before.”
The full research paper ‘The neural basis of somatosensory remapping develops in human infancy’ was published in the journal Current Biology.
The claustrum’s proposed role in consciousness is supported by the effect and target localization of Salvia divinorum
This article brings together three findings and ideas relevant for the understanding of human consciousness: (I) Crick’s and Koch’s theory that the claustrum is a “conductor of consciousness” crucial for subjective conscious experience. (II) Subjective reports of the consciousness-altering effects the plant Salvia divinorum, whose primary active ingredient is salvinorin A, a κ-opioid receptor agonist. (III) The high density of κ-opioid receptors in the claustrum. Fact III suggests that the consciousness-altering effects of S. divinorum/salvinorin A (II) are due to a κ-opioid receptor mediated inhibition of primarily the claustrum and, additionally, the deep layers of the cortex, mainly in prefrontal areas. Consistent with Crick and Koch’s theory that the claustrum plays a key role in consciousness (I), the subjective effects of S. divinorum indicate that salvia disrupts certain facets of consciousness much more than the largely serotonergic hallucinogen lysergic acid diethylamide (LSD). Based on this data and on the relevant literature, we suggest that the claustrum does indeed serve as a conductor for certain aspects of higher-order integration of brain activity, while integration of auditory and visual signals relies more on coordination by other areas including parietal cortex and the pulvinar.