Posts tagged neuroscience
Articles and news from the latest research reports.
Heavy Drinking in Middle Age May Speed Memory Loss by up to Six Years in Men
Middle-aged men who drink more than 36 grams of alcohol, or two and a half US drinks per day, may speed their memory loss by up to six years later on, according to a study published in the January 15, 2014, online issue of Neurology®, the medical journal of the American Academy of Neurology. On the other hand, the study found no differences in memory and executive function in men who do not drink, former drinkers and light or moderate drinkers. Executive function deals with attention and reasoning skills in achieving a goal.
“Much of the research evidence about drinking and a relationship to memory and executive function is based on older populations,” said study author Séverine Sabia, PhD, of the University College London in the United Kingdom. “Our study focused on middle-aged participants and suggests that heavy drinking is associated with faster decline in all areas of cognitive function in men.”
The study involved 5,054 men and 2,099 women whose drinking habits were assessed three times over 10 years. A drink was considered wine, beer or liquor. Then, when the participants were an average age of 56, they took their first memory and executive function test. The tests were repeated twice over the next 10 years.
The study found that there were no differences in memory and executive function decline between men who did not drink and those who were light or moderate drinkers—those who drank less than 20 grams, or less than two US drinks per day. Heavy drinkers showed memory and executive function declines between one-and-a-half to six years faster than those who had fewer drinks per day.
More Than Meets the Eye
Many studies suggest that pushing your brain to multitask — writing emails, for instance, while watching the day’s latest news and eating breakfast — leads to poorer performance and lower productivity. But for at least one everyday task — visual sampling (the act of picking up bits of visual information through short glances) — multitasking is not a problem for the brain. A collaboration between researchers at the UC Santa Barbara and the University of Bristol in the UK has shown that during visual sampling, the brain can handle various visual functions simultaneously.
“We might not realize it, but human vision is rather limited,” said Miguel Eckstein, professor in the Department of Psychological and Brain Sciences at UCSB. “We only see clearly in a small region around our specific focus.” Eckstein’s study, “Foveal analysis and peripheral selection during active visual sampling,” appears in the early Proceedings of the National Academy of Sciences Plus edition.
Head injuries triple long-term risk of early death
Survivors of traumatic brain injuries (TBI) are three times more likely to die prematurely than the general population, often from suicide or fatal injuries, finds an Oxford University-led study.
A TBI is a blow to the head that leads to a skull fracture, internal bleeding, loss of consciousness for longer than an hour or a combination of these symptoms. Michael Schumacher’s recent skiing injury is an example of a TBI. Concussions, sometimes called mild TBIs, do not present with these symptoms and were analysed separately in this study.
Researchers examined Swedish medical records going back 41 years covering 218,300 TBI survivors, 150,513 siblings of TBI survivors and over two million control cases matched by sex and age from the general population. The work was carried out by researchers at Oxford University and the Karolinska Institute in Stockholm.
'We found that people who survive six months after TBI remain three times more likely to die prematurely than the control population and 2.6 times more likely to die than unaffected siblings,' said study leader Dr Seena Fazel, a Wellcome Trust Senior Research Fellow in Oxford University's Department of Psychiatry. 'Looking at siblings who did not suffer TBIs allows us to control for genetic factors and early upbringing, so it is striking to see that the effect remains strong even after controlling for these.'
The results, published in the journal JAMA Psychiatry, show that TBI survivors who also have a history of substance abuse or psychiatric disorders are at highest risk of premature death. Premature deaths were defined as before age 56. The main causes of premature death in TBI survivors are suicide and fatal injuries such as car accidents and falls.
'TBI survivors are more than twice as likely to kill themselves as unaffected siblings, many of whom were diagnosed with psychiatric disorders after their TBI,' said Dr Fazel. 'Current guidelines do not recommend assessments of mental health or suicide risk in TBI patients, instead focusing on short-term survival. Looking at these findings, it may make more sense to treat some TBI patients as suffering from a chronic problem requiring longer term management just like epilepsy or diabetes. TBI survivors should be monitored carefully for signs of depression, substance abuse and other psychiatric disorders, which are all treatable conditions.'
The exact reasons for the increased risk of premature death are unknown but may involve damage to the parts of the brain responsible for judgement, decision making and risk taking. TBI survivors are three times more likely to die from fatal injuries which may be a result of impaired judgement or reactions.
'This study highlights the important and as yet unanswered question of why TBI survivors are more likely to die young, but it may be that serious brain trauma has lasting effects on people's judgement,' suggests Dr Fazel. 'People who have survived the acute effects of TBI should be more informed about these risks and how to reduce their impact.'
'When treating traumatic brain injuries focus is placed on immediate treatment and recovery of patients,' says Dr John Williams, Head of Neuroscience and Mental Health at the Wellcome Trust. 'This new finding offers important insight into the longer-term impact of TBIs on the brain and their effect on survival later in life. We hope that further research into understanding which parts of the brain are responsible will help improve future management programmes and reduce the potential for premature death.'
Even relatively minor brain injuries, concussions, had a significant impact on early mortality. People with concussion were found to be twice as likely to die prematurely as the control population, with suicide and fatal injuries as the main causes of death. This raises issues surrounding concussions in a wide range of sports, from American football, rugby and soccer to baseball and cricket.
(Source: ox.ac.uk)
Speech means using both sides of our brain
We use both sides of our brain for speech, a finding by researchers at New York University and NYU Langone Medical Center that alters previous conceptions about neurological activity. The results, which appear in the journal Nature, also offer insights into addressing speech-related inhibitions caused by stroke or injury and lay the groundwork for better rehabilitation methods.
“Our findings upend what has been universally accepted in the scientific community—that we use only one side of our brains for speech,” says Bijan Pesaran, an associate professor in NYU’s Center for Neural Science and the study’s senior author. “In addition, now that we have a firmer understanding of how speech is generated, our work toward finding remedies for speech afflictions is much better informed.”
Many in the scientific community have posited that both speech and language are lateralized—that is, we use only one side of our brains for speech, which involves listening and speaking, and language, which involves constructing and understanding sentences. However, the conclusions pertaining to speech generally stem from studies that rely on indirect measurements of brain activity, raising questions about characterizing speech as lateralized.
To address this matter, the researchers directly examined the connection between speech and the neurological process.
Specifically, the study relied on data collected at NYU ECoG, a center where brain activity is recorded directly from patients implanted with specialized electrodes placed directly inside and on the surface of the brain while the patients are performing sensory and cognitive tasks. Here, the researchers examined brain functions of patients suffering from epilepsy by using methods that coincided with their medical treatment.
“Recordings directly from the human brain are a rare opportunity,” says Thomas Thesen, director of the NYU ECoG Center and co-author of the study.
“As such, they offer unparalleled spatial and temporal resolution over other imaging technologies to help us achieve a better understanding of complex and uniquely human brain functions, such as language,” adds Thesen, an assistant professor at NYU Langone.
In their examination, the researchers tested the parts of the brain that were used during speech. Here, the study’s subjects were asked to repeat two “non-words”—“kig” and “pob.” Using non-words as a prompt to gauge neurological activity, the researchers were able to isolate speech from language.
An analysis of brain activity as patients engaged in speech tasks showed that both sides of the brain were used—that is, speech is, in fact, bi-lateral.
“Now that we have greater insights into the connection between the brain and speech, we can begin to develop new ways to aid those trying to regain the ability to speak after a stroke or injuries resulting in brain damage,” observes Pesaran. “With this greater understanding of the speech process, we can retool rehabilitation methods in ways that isolate speech recovery and that don’t involve language.”
(Source: nyu.edu)
Senses of sight and sound separated in children with autism
Like watching a foreign movie that was badly dubbed, children with autism spectrum disorders (ASD) have trouble integrating simultaneous information from their eyes and their ears, according to a Vanderbilt study published today in The Journal of Neuroscience.
The study, led by Mark Wallace, Ph.D., director of the Vanderbilt Brain Institute, is the first to illustrate the link and strongly suggests that deficits in the sensory building blocks for language and communication can ultimately hamper social and communication skills in children with autism.
“There is a huge amount of effort and energy going into the treatment of children with autism, virtually none of it is based on a strong empirical foundation tied to sensory function,” Wallace said. “If we can fix this deficit in early sensory function then maybe we can see benefits in language and communication and social interactions.”
And the findings could have much broader applications because sensory functioning is also changed in developmental disabilities such as dyslexia and schizophrenia, Wallace said.
In the study, Vanderbilt researchers compared 32 typically developing children ages 6-18 years old with 32 high-functioning children with autism, matching the groups in virtually every possible way including IQ.
Study participants worked through a battery of different tasks, largely all computer generated. Researchers used different types of audiovisual stimuli such as simple flashes and beeps, more complex environmental stimuli like a hammer hitting a nail, and speech stimuli, and asked the participants to tell them whether the visual and auditory events happened at the same time.
The study found that children with autism have an enlargement in something known as the temporal binding window (TBW), meaning the brain has trouble associating visual and auditory events that happen within a certain period of time.
“Children with autism have difficulty processing simultaneous input from audio and visual channels. That is, they have trouble integrating simultaneous information from their eyes and their ears,” said co-author Stephen Camarata, Ph.D., professor of Hearing and Speech Sciences. “It is like they are watching a foreign movie that was badly dubbed, the auditory and visual signals do not match in their brains.”
A second part of the study found that children with autism also showed weaknesses in how strongly they “bound” or associated audiovisual speech stimuli.
“One of the classic pictures of children with autism is they have their hands over their ears,” Wallace said. “We believe that one reason for this may be that they are trying to compensate for their changes in sensory function by simply looking at one sense at a time. This may be a strategy to minimize the confusion between the senses.”
Wallace noted that the recently-released Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, (DSM-5), which serves as a universal authority for psychiatric diagnosis, now acknowledges sensory processing as a core deficit in autism.
Breast cancer spreads to brain by masquerading as neurons
Often, several years can pass between the time a breast cancer patient successfully goes into remission and a related brain tumor develops. During that time, the breast cancer cells somehow hide, escaping detection as they grow and develop. Now City of Hope researchers have found out how.
Breast cancer cells disguise themselves as neurons, becoming “cellular chameleons,” the scientists found. This allows them to slip undetected into the brain and, from there, develop into tumors.
The discovery is being heralded as “a tremendous advance in breast cancer research.”
Although breast cancer is a very curable disease – with more than 95 percent of women with early-stage disease surviving after five years – breast cancer that metastasizes to the brain is difficult to fight. In fact, only about 20 percent of patients survive a year after diagnosis.
"There remains a paucity of public awareness about cancer’s relentless endgame," said Rahul Jandial, M.D., Ph.D., a City of Hope neurosurgeon who headed the breast-cancer-and-brain-tumor study, published online ahead of print this week in the Proceedings of the National Academy of Sciences.
"Cancer kills by spreading. In fact, 90 percent of all cancer mortality is from metastasis," Jandial said. "The most dreaded location for cancer to spread is the brain. As we have become better at keeping cancer at bay with drugs such as Herceptin, women are fortunately living longer. In this hard-fought life extension, brain metastases are being unmasked as the next battleground for extending the lives of women with breast cancer."
He added: “I have personally seen my neurosurgery clinic undergo a sharp rise in women with brain metastases years – and even decades – after their initial diagnosis.”
Jandial and other City of Hope scientists wanted to explore how breast cancer cells cross the blood-brain barrier – a separation of the blood circulating in the body from fluid in the brain – without being destroyed by the immune system.
“If, by chance, a malignant breast cancer cell swimming in the bloodstream crossed into the brain, how would it survive in a completely new, foreign habitat?” said Jandial in a recent interview with New Scientist.
Jandial and his team’s hypothesis: Given that the brain is rich in many brain-specific types of chemicals and proteins, perhaps breast cancer cells that could exploit these resources by assuming similar properties would be the most likely to flourish. These cancer cells could deceive the immune system by blending in with the neurons, neurotransmitters, other types of proteins, cells and chemicals.
Taking samples from brain tumors resulting from breast cancer, Jandial and his team found that the breast cancer cells were exploiting the brain’s most abundant chemical as a fuel source. This chemical, GABA, is a neurotransmitter used for communication between neurons.
When compared to cells from nonmetastatic breast cancer, the metastasized cells expressed a receptor for GABA, as well as for a protein that draws the transmitter into cells. This allowed the cancer cells to essentially masquerade as neurons.”Breast cancer cells can be cellular chameleons (or masquerade as neurons) and spread to the brain,” Jandial said.
Jandial says that further study is required to better understand the mechanisms that allow the cancer cells to achieve this disguise. He hopes that ultimately, unmasking these disguised invaders will result in new therapies.
In Dyslexia, Less Brain Tissue Not to Blame for Reading Difficulties
In people with dyslexia, less gray matter in the brain has been linked to reading disabilities, but now new evidence suggests this is a consequence of poorer reading experiences and not the root cause of the disorder.
It has been assumed that the difference in the amount of gray matter might, in part, explain why dyslexic children have difficulties correctly and fluently mapping the sounds in words to their written counterparts during reading. But this assumption of causality has now been turned on its head.
The findings from anatomical brain studies conducted at Georgetown University Medical Center (GUMC) in the Center for the Study of Learning led by neuroscientist Guinevere Eden, DPhil, were published online today in The Journal of Neuroscience.
The study compared a group of dyslexic children with two different control groups: an age-matched group included in most previous studies, and a group of younger children who were matched at the same reading level as the children with dyslexia.
“This kind of approach allows us to control for both age as well as reading experience,” explains Eden, a professor of pediatrics at GUMC. “If the differences in brain anatomy in dyslexia were seen in comparison with both control groups, it would have suggested that reduced gray matter reflects an underlying cause of the reading deficit. But that’s not what we observed.”
The dyslexic groups showed less gray matter compared with a control group matched by age, consistent with previous findings. However, the result was not replicated when a control group matched by reading level was used as the comparison group with the dyslexics.
“This suggests that the anatomical differences reported in left hemisphere language processing regions appear to be a consequence of reading experience as opposed to a cause of dyslexia,” says Anthony Krafnick, PhD, lead author of the publication. “These results have an impact on how we interpret the previous anatomical literature on dyslexia and it suggests the use of anatomical MRI would not be a suitable way to identify children with dyslexia,” he says.
The work also helps to determine the fine line between experience-induced changes in the brain and differences that are the cause of cognitive impairment. For example, it is known from studies in illiterate people who attain reading skills as adults that this type of learning induces growth of brain matter. Similar learning-induced changes in typical readers may result in discrepancies between them and their dyslexic peers, who have not enjoyed the same reading experiences and thus have not undergone similar changes in brain structure.
Brain Structure Shows Who is Most Sensitive to Pain
Everybody feels pain differently, and brain structure may hold the clue to these differences.
In a study published in the current online issue of the journal Pain, scientists at Wake Forest Baptist Medical Center have shown that the brain’s structure is related to how intensely people perceive pain.
“We found that individual differences in the amount of grey matter in certain regions of the brain are related to how sensitive different people are to pain,” said Robert Coghill, Ph.D., professor of neurobiology and anatomy at Wake Forest Baptist and senior author of the study.
The brain is made up of both grey and white matter. Grey matter processes information much like a computer, while white matter coordinates communications between the different regions of the brain.
The research team investigated the relationship between the amount of grey matter and individual differences in pain sensitivity in 116 healthy volunteers. Pain sensitivity was tested by having participants rate the intensity of their pain when a small spot of skin on their arm or leg was heated to 120 degrees Fahrenheit. After pain sensitivity testing, participants underwent MRI scans that recorded images of their brain structure.
“Subjects with higher pain intensity ratings had less grey matter in brain regions that contribute to internal thoughts and control of attention,” said Nichole Emerson, B.S., a graduate student in the Coghill lab and first author of the study. These regions include the posterior cingulate cortex, precuneus and areas of the posterior parietal cortex, she said.
The posterior cingulate cortex and precuneus are part of the default mode network, a set of connected brain regions that are associated with the free-flowing thoughts that people have while they are daydreaming.
“Default mode activity may compete with brain activity that generates an experience of pain, such that individuals with high default mode activity would have reduced sensitivity to pain,” Coghill said.
Areas of the posterior parietal cortex play an important role in attention. Individuals who can best keep their attention focused may also be best at keeping pain under control, Coghill said.
“These kinds of structural differences can provide a foundation for the development of better tools for the diagnosis, classification, treatment and even prevention of pain,” he said.
Short circuit in molecular switch intensifies pain
Pain functions as an important alarm signal. It alerts us to potential bodily harm – a hot or sharp object, for example – and motivates us to withdraw from damaging situations. At the cellular level, pain involves the stimulation of a network of pain nerves spread through the skin, mucosa and bodily organs.
Embedded in the cell wall surrounding these nerves are ion channels. These tiny, microscopic pathways respond to stimuli such as extreme cold or heat, mechanical pressure or harmful chemicals. When ion channels open, an electrical signal is created, transmitted to the brain, and interpreted as pain.
In previous research, the team of KU Leuven researchers led by Professor Thomas Voets (Laboratory of Ion Channel Research) and Professor Joris Vriens (Laboratory of Obstetrics and Experimental Gynaecology) discovered that a particular ion channel – TRPM3 – acts as a molecular fire detector: the ion channel detects heat and the hormone pregnenolone sulfate, a precursor to the sex hormones estrogen and testosterone and a trigger for pain and inflammation. In the present study, the researchers were looking for TRPM3 inhibitors that could potentially be used as painkillers.
Short circuit
Surprisingly, their results show that a number of drugs meant as painkillers actually increased pain in mice tested in the study, says Professor Voets: “Normally, when the ion channel is closed, no electrical signal is sent to the brain and therefore no pain is detected. But we found that pain can indeed occur despite a closed ion channel. How? A short circuit in the ion channel. When short-circuiting occurs, the electrical signal effected by a stimulus does not follow the normal pathway through the central pore of the ion channel. Instead, it navigates an alternative path through the surrounding material. This ‘electrical leak’ activates the pain nerves, thus increasing the sensation of pain. This may explain the pain-enhancing side effects of some drugs – such as clotrimazole, a common remedy for yeast infections that often causes unpleasant side effects such as irritation and burning sensations.”
“It is striking that short circuits in the ion channel only occur at high hormone levels. This could explain why some patients experience these side effects while others do not,” says Professor Voets. The researchers hope this new knowledge about TRPM3-dependent pain will contribute to the development of new painkillers with fewer painful side effects.
Recall of stressful events caught in pictures
The study is of patients with conversion disorder (what Freud would have called Hysteria), which is still a very common disorder though rarely discussed or researched today.
“Freud started his whole theory by arguing that patients with hysteria repressed their memories of traumatic events and that this led to their developing their symptoms (of paralysis, for example) - what he called ‘conversion,” said Professor Richard Kanaan from the Department of Psychiatry, University of Melbourne and Austin Health.
“The world has pretty much given up on that theory largely because they thought it couldn’t be tested,” he said.
Published recently in the Journal of the American Medical Association, Psychiatry, the fMRI findings support Freud’s theories for the first time in over a century.
Researchers first painstakingly identified what they thought were the traumatic events that led to them becoming sick using the Life Events and Difficulties Schedule (LEDS) as a guide. This is a well-known psychological measurement for assessing life stress levels and experience.
“We got our patients to remember the traumatic events while we scanned their brains. Results showed something that looked like it could be them repressing their memories and possibly what could be them developing symptoms in response.”
“While it is still a preliminary study, in the history of psychiatry as a science it is potentially a significant breakthrough,” he said.