Category: Brain Injury

 Silent strokes, which have no immediate symptoms but could cause long-term cognitive and learning deficits, occur in a significant number of severely anemic children, especially those with sickle cell disease, according to research presented at the American Stroke Association's International Stroke Conference 2011.

One-quarter to one-third of children with sickle cell disease have evidence of silent strokes in their brains, according to Michael M. Dowling, M.D., Ph.D., lead author of the study and assistant professor of pediatrics and neurology at the University of Texas Southwestern Medical Center in Dallas.

"These are 5- to 10-year-old children who have brains that look like the brains of 80-year-olds," Dowling said. "These strokes are called 'silent' because they don't cause you to be weak on one side or have any obvious neurologic symptoms. But they can lead to poor academic performance and severe cognitive impairments."

Sickle cell disease is a blood disorder characterized by low levels of hemoglobin, the iron-containing component of red blood cells that carries oxygen. Low hemoglobin causes anemia. In sickle cell disease, the blood cells are misshapen (sickle-shaped) and may form clots or block blood vessels. About 10 percent of children with sickle cell disease suffer a stroke. Blood transfusions can reduce the high risk of repeat strokes.

Dowling and colleagues hypothesized that silent strokes occur during severe anemia and may be detectable by MRI. They used MRI on the brains of 52 hospitalized children 2- to 19-years-old at Children's Medical Center Dallas with hemoglobin concentrations dropping below 5.5 g/dL. They compared severely anemic children with sickle cell disease to a group of children without sickle cell disease who had hemoglobin levels below 5.5 g/dL.

They identified silent strokes in about 20 percent of the children with sickle cell disease who were experiencing acute anemia. They also saw evidence of silent strokes, though not as often, in severely anemic children who didn't have sickle cell disease.

The many reasons, besides sickle cell disease, why children could have anemia include trauma, surgery, iron deficiency or cancer such as leukemia.

"These are brain injuries that go unnoticed by doctors, unless the children have testing with a special MRI," he said. "We looked at every child who went to the hospital for a 30-month period and identified about 400 children that came in with hemoglobin below 5.5 g/dL. That represented about 12 percent of the admissions for sickle cell disease and about 1 percent of the total admissions to Children's Medical Center."

The findings suggest that children with or without sickle cell disease who have acute anemia could be suffering undetected brain damage. The researchers suggest that all children with severe anemia need careful examination for silent strokes.

Improved recognition and timely transfusion to increase blood hemoglobin levels could prevent permanent brain damage in children with silent strokes, according to the study.

Future studies should look at larger groups of children for longer periods to better understand the impact of acute anemia on children, Dowling said.

Co-authors are: Charles T. Quinn, M.D., M.S; Patricia Plumb, R.N., M.S.N.; Zora R. Rogers, M.D.; Nancy Rollins, M.D.; Korgun Koral, M.D.; Robert Barber, Ph.D. and George R Buchanan, M.D.

Medical researchers from The University of Texas Health Science Center at Houston (UTHealth) presented new research results at the American Heart Association International Stroke Conference that demonstrated how MultiStem®, a novel stem cell therapy being developed by Athersys, Inc. provided multiple benefits when administered in preclinical models of ischemic stroke. The study, conducted by leading researchers from the Department of Neurology at the UTHealth Medical School working in collaboration with scientists at Athersys, illustrated the potential benefits of MultiStem therapy for treating stroke. Researchers observed that intravenous administration of MultiStem one day after a stroke reduced inflammatory damage in the brain and resulted in a significant improvement in motor skills.

"We are seeing a paradigm shift in the way some types of stem cells may enhance recovery from stroke," said Sean I. Savitz, M.D., principal investigator and associate professor of neurology at UTHealth. "The stem cells may actually exert some of their effects on other organs such as the spleen. The spleen seems to play an important role in some neurological disorders by contributing, for example, to ongoing inflammation and brain injury after stroke. We're finding these stem cells are working on dampening inflammation involving the spleen."

According to the American Heart Association, approximately 800,000 individuals suffer a stroke each year in the United States, and an estimated 2 million individuals suffer a stroke each year in the U.S., Japan, and major European countries combined. Approximately 85% of strokes are ischemic, meaning they are caused by a blockage of blood flow in the brain, which occurs as a result of a clot or "thrombus." Currently there is only one FDA-approved drug therapy for the treatment of ischemic stroke, the thrombolytic tPA, which helps to dissolve the flow-impeding blood clot. However, tPA must be administered within several hours from when the stroke has occurred in order to be effective. Due to its limited window, only about 5% of all patients who could potentially benefit from therapy with tPA actually receive treatment. Given the lack of effective therapies, many patients who suffer a stroke require extensive physical therapy or experience significant or permanent disability, and as a result, must receive long-term institutional care or be cared for by a family member. As a consequence of an aging population, recent forecasts from the American Heart Association project that the prevalence of stroke will increase by 25% in the next 20 years, and the total estimated annual cost for treating and caring for stroke survivors will skyrocket from $64 billion in 2010 to $140 billion in 2030, representing a substantial increase in cost to the national healthcare system.

In the rat model of stroke used in the study, animals that received treatment with MultiStem showed statistically significant improvement in motor skills relative to animals that received placebo, and also showed reduced cell death, reduction of inflammatory cytokines and an increase in anti-inflammatory cytokines. Interestingly, researchers found that animals treated with placebo showed a reduction in spleen size and an increase in inflammatory cytokines in the blood, whereas animals that were treated with MultiStem showed normal spleen size and increased levels of anti-inflammatory cytokines in the blood. The spleen is believed to play a significant role in promoting and sustaining the inflammation that can result in substantial long-term damage following brain injury.

"Ischemic stroke represents an enormous clinical, economic and social burden that is expected to increase dramatically in the years ahead as a result of an aging population, and the corresponding increase in the number of individuals that are susceptible to all forms of cardiovascular disease," said Gil Van Bokkelen, Chairman and Chief Executive Officer of Athersys. "MultiStem appears to have profound effects in multiple neurological injury models, by reducing inflammation, protecting at-risk brain tissue, and promoting tissue repair. If we can develop new, more effective therapies that meaningfully extend the treatment window for stroke victims, we can improve clinical care, reduce long-term health care costs, and improve the quality of life for millions of people."

Whether or not you're fond of Indian, Southeast Asian and Middle Eastern food, stroke researchers at Cedars-Sinai Medical Center think you may become a fan of one of their key spices.

The scientists created a new molecule from curcumin, a chemical component of the golden-colored spice turmeric, and found in laboratory experiments that it affects mechanisms that protect and help regenerate brain cells after stroke. Research scientist Paul A. Lapchak, Ph.D., director of Translational Research in the Department of Neurology at Cedars-Sinai Medical Center, is presenting these findings at the American Heart Association International Stroke Conference in Los Angeles.

Only one drug is now approved for ischemic stroke, which occurs when a clot blocks blood flow to the brain. Commonly called a "clot-busting drug," tissue plasminogen activator (tPA) is injected intravenously to dissolve clots and reinstate blood flow. If blood and oxygen are restored in time, consequences of the stroke, such as speech, memory, movement and other impairments, may be reduced.

The new curcumin-hybrid compound — CNB-001 — does not attack clots but instead repairs stroke damage at the molecular level that feed and support the all-important brain cells, neurons.

Curcumin has been studied for its potential to treat brain injury and disease, and while the substance itself looks promising, it has several drawbacks, especially as an emergency stroke treatment, which must be quick to be effective: It is not well absorbed in the body, fails to reach its target in high concentrations, becomes depleted quickly, and is blocked from entering the brain by a natural protective mechanism called the blood-brain barrier.

"CNB-001 has many of the same benefits of curcumin but appears to be a better choice of compound for acute stroke because it crosses the blood-brain barrier, is quickly distributed in the brain, and moderates several critical mechanisms involved in neuronal survival," Lapchak says, adding that he and his colleagues expect the new drug to move to human clinical trials soon.

When brain tissue is deprived of blood and oxygen, a cascading series of interrelated events triggers at the molecular level, breaking down the normal electrical and chemical "signaling pathways" responsible for nourishing and supporting neurons. The environment quickly becomes toxic, killing brain cells and destroying their support structures.

Theoretically, interrupting these harmful events and restoring normal pathway function could prevent cell death and the memory and behavioral deficits that result, but it will take a cocktail of drugs or a drug capable of targeting many mechanisms to correct the many pathways damaged by stroke, Lapchak says. CNB-001protects brain cells from damage by repairing four major pathways. One mechanism also plays a major role in the growth and survival of neurons.

The drug reduced stroke-caused "motor deficits" — problems of muscle and movement control — in this laboratory study. It was effective when administered up to an hour after stroke, which correlates with about three hours in humans, the same time frame for which tPA is currently approved.

Lapchak and colleagues at the Salk Institute for Biological Studies used the same laboratory rabbit model to mimic human stroke that earlier researchers had employed before the clot-busting drug tPA entered clinical trials. Patrick D. Lyden, M.D., chairman of Cedars-Sinai's Department of Neurology, helped lead a major trial that resulted in the Food and Drug Administration's 1996 approval of tPA, still considered the stroke treatment gold standard.

Those who cook Indian, Thai, Malay and Persian dishes know turmeric well for its zesty flavor, use in curries and for the rich color it imparts to food. Turmeric also has a long history of use in Ayurvedic and Chinese traditional medicine.

Grants from the National Institute of Neurological Disorders and Stroke, part of the National Institutes of Health, supported the CNB-001 study (NS060685 to PAL).

Motorcycle helmets, long known to dramatically reduce the number of brain injuries and deaths from crashes, appear to also be associated with a lower risk of cervical spine injury, new research from Johns Hopkins suggests.

"We are debunking a popular myth that wearing a helmet while riding a motorcycle can be detrimental during a motorcycle crash," says study leader Adil H. Haider, M.D., M.P.H., an assistant professor of surgery at the Johns Hopkins University School of Medicine. "Using this new evidence, legislators should revisit the need for mandatory helmet laws. There is no doubt that helmets save lives and reduce head injury. And now we know they are also associated with a decreased risk of cervical spine injury."

For more than two decades, the researchers say, activists lobbying against universal helmet laws have cited a small study suggesting that, in the event of a crash, the weight of a helmet could cause significant torque on the neck that would be devastating to the spine. But results of the new study, published online in the Journal of the American College of Surgeons, shows that helmeted riders were 22 percent less likely to suffer cervical spine injury than those without helmets. The study reviewed and mined the National Trauma Databank, looking through information on more than 40,000 motorcycle collisions between 2002 and 2006.

Even with what researchers say are mountains of evidence that helmets reduce mortality and traumatic brain injury after a collision, many states, including Florida, Pennsylvania and Texas, have over the past 15 years repealed their mandatory helmet use laws after lobbying from motorcycle riders, Haider says. Anti-helmet lobbyists often cite a 25-year-old study which found more spine injuries in helmet wearers. That study, has been criticized by many, including the National Highway Traffic Safety Administration, because of flawed statistical reasoning. "Additionally, helmet technology has significantly improved since that time — now helmets are much lighter but even sturdier and more protective" Haider says.

Forty years ago, Haider says, nearly all states required helmets for motorcyclists of any age in the United States. Today, helmets are mandatory for all riders in only 20 states, Puerto Rico and the District of Columbia.

Motorcycle use has risen sharply over the past 10 years in the United States. Since 1997, motorcycle injuries in the U.S. have increased by roughly 5,000 per year and motorcycle fatalities have nearly doubled, according to the new journal article.

Haider's study, like many others before, found a reduction in risk of traumatic brain injury in helmet wearers (65 percent) and decreased odds of death (37 percent). But the new paper, Haider says, is the strongest evidence yet that helmets significantly reduce cervical spine injury, which can result in paralysis.

Other Johns Hopkins researchers who contributed to this study include Curt Bone; Keshia M. Pollack, Ph.D., M.P.H.; Cassandra Villegas, M.P.H.; Kent Stevens, M.D., M.P.H.; David T. Efron, M.D.; and Elliott R. Haut, M.D.

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Journal Reference:

1. Joseph G. Crompton, Curt Bone, Tolulope Oyetunji, Keshia M. Pollack, Oluwaseyi Bolorunduro, Cassandra Villegas, Kent Stevens, Edward E. Cornwell III, David T. Efron, Elliott R. Haut. Motorcycle Helmets Associated with Lower Risk of Cervical Spine Injury: Debunking the Myth. Journal of the American College of Surgeons, 2011; DOI: 10.1016/j.jamcollsurg.2010.09.032

The number of acute ischemic stroke hospitalizations among middle-aged and older men and women fell between 1994 and 2007, but sharply increased among those under age 35 — including teens and children — according to research presented at the American Stroke Association's International Stroke Conference 2011.

Analysts at the U.S. Centers for Disease Control and Prevention (CDC), reviewing hospitalization data by age and gender, identified declining rates of 51 percent in girls 0-4 years and 25 percent in men and 29 percent in women over 45.

However, the number of ischemic stroke hospitalizations increased 51 percent in males between ages 15 and 34 during the period studied. The rate increased 17 percent in females between 15 and 34.

Among children and teens, they found a 31 percent increase in boys between 5 to 14 years and a 36 percent increase among girls 5 to 14 years.

Among the younger middle-aged set, they found a 47 percent increase among men 35-44 and a 36 percent increase among women 35-44.

"I believe this is the first large study to report these findings, stratified by age and gender," said Xin Tong, M.P.H., a health statistician with the CDC's Division for Heart Disease and Stroke Prevention in Atlanta.

"We cannot link anything in particular to the trend in younger patients, but I believe the role of obesity and hypertension will prompt a big discussion. Unfortunately, right now we can't speculate on the causes."

The unit of analysis was hospitalization, so researchers couldn't draw any firm connections or determine what factors are driving the increase in ischemic stroke cases among the young. Ischemic stroke occurs when blood supply to the brain becomes obstructed, usually by a clot or narrowing of the arteries. The risk of long-term brain damage can be reduced significantly if patients receive the clot-busting tissue plasminogen activator (tPA) within three or four and a half hours after stroke onset.

Hospitals and physicians should be aware of the rising risk of stroke in young people, and the necessity to educate them about stroke symptoms, Tong said.

"Acute ischemic stroke is currently considered something that mostly happens to older people, but awareness of rising rates in the young is important or else tPA and other important stroke treatment may be unnecessarily delayed in younger patients," she said.

Tong said her group is pursuing additional investigation on this subject.

Co-authors are: Elena V. Kuklina, M.D., Ph.D.; Cathleen Gillespie, M.S.; and Mary G. George, M.D., M.S.P.H.

 Older people with late-stage, age-related macular degeneration (AMD) appear to be at increased risk of brain hemorrhage (bleeding stroke), but not stroke caused by brain infarction (blood clot), according to research presented at the American Stroke Association's International Stroke Conference 2011.

"Other studies have found there are more strokes in older individuals with late AMD, but ours is the first to look at the specific types of strokes," said Renske G. Wieberdink, M.D., study researcher and epidemiologist at Erasmus Medical Center in Rotterdam, the Netherlands. "We found the association is with brain hemorrhage, but not brain infarction."

AMD is degeneration of the macula, which is the part of the retina responsible for the sharp, central vision needed to read or drive. Because the macula primarily is affected in AMD, central vision loss may occur. Age-related macular degeneration usually produces a slow, painless loss of vision. Early signs of vision loss from AMD include shadowy areas in your central vision or unusually fuzzy or distorted vision.

Because the number of brain hemorrhages observed in the study was small, the findings will need to be corroborated in a larger group, Wieberdink said.

"These findings should be considered preliminary," she said. "Patients and physicians must be very careful not to over-interpret them. We don't know why there are more brain hemorrhages in these patients or what the relationship with AMD might be. This does not mean that all patients with late-stage AMD will develop brain hemorrhage."

Beginning in 1990, the Rotterdam Study is a prospective, population-based cohort investigation into factors that determine the occurrence of cardiovascular, neurological, ophthalmological, endocrinological and psychiatric diseases in older people.

The researchers tallied stroke incidence among 6,207 participants 55 years and older. All of the participants were stroke-free at the study's outset. AMD was assessed during scheduled eye examinations, and participants with the condition were divided into five different stages of AMD, and whether their condition was wet AMD or dry AMD. Participants were tracked for an average of 13 years. Of the 726 persons who suffered a stroke in that time, 397 were brain infarctions, 59 were brain hemorrhages and the stroke type was not available for 270.

Late AMD (stage 4) was associated with a 56 percent increased risk of any type of stroke. Late AMD, both the dry and the wet form, was strongly associated with more than six times the risk of brain hemorrhage, but not with brain infarction. Early AMD (stages 1-3) did not increase the risk of any stroke. Associations were adjusted for possible confounders, such as diabetes, blood pressure, anti-hypertensive medications, smoking status, body mass index, alcohol use and C-reactive protein levels.

"We cannot yet say if there is a common causal pathway or mechanism of action yet — this association needs to be further investigated," Wieberdink said. "But I don't think it is a causal relationship. It seems more likely that late AMD and brain hemorrhage both result from some as yet unknown common mechanism."

If the findings are replicated, it may be possible to develop some stratification of risk among such patients, Wieberdink said.

Co-authors are: Lintje Ho, M.D.; Kamran Ikram, M.D., Ph.D.; Peter Koudstaal, M.D., Ph.D.; Albert Hofman, M.D., Ph.D.; Hans Vingerling, M.D., Ph.D.; and Monique Breteler, M.D., Ph.D. Author disclosers and funding information are on the abstract.

— Movements become skilled and automatic with practise, so tasks like riding a bicycle can be performed without much attention or mental effort. New research by scientists at Royal Holloway, University of London provides evidence that the cerebellum, a part of the brain used to store memories for skilled movements, could also store memories important for mental skills — such as the rules used to interpret traffic light signals.

The prefrontal cortex, in the frontal lobe, uses problem-solving to establish the correct rules using attention, and the new research raises the possibility that the cerebellum then learns to implement them skilfully with little conscious attention, freeing the prefrontal cortex to direct attention to new problems.

The study, published in the Journal of Neuroscience, reports that brain imaging was used to scan volunteers during learning, and that in a part of the cerebellum known to be connected with the prefrontal cortex, activity changed from one practice trial to the next. The rate of change was faster for rules that became automatic more quickly. After practice, volunteers used simple rules quickly and accurately even when attention drawn away by a 'distractor' task performed at the same time.

Dr Ramnani, from the Department of Psychology at Royal Holloway said: "The study adds to the groundwork for understanding cognitive deficits in patients with cerebellar damage and improving strategies for their rehabilitation. It also raises the possibility that the cerebellum might be used for the skillful, automatic and unconscious use of mathematical and grammatical rules."

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Journal Reference:

1. Joshua H. Balsters and Narender Ramnani. Cerebellar Plasticity and the Automation of First-Order Rules. Journal of Neuroscience, 

 A simple test performed at the sideline of sporting events can accurately detect concussions in athletes, according to a study by researchers at the University of Pennsylvania School of Medicine. Current sideline tests can leave a wide amount a brain function untested following concussion. Penn researchers showed that this simple test was superior to current methods and accurately and reliably identified athletes with head trauma.

The study appears online now in Neurology.

The one-minute test involves the athlete reading single digit numbers displayed on index-sized cards. Any increase (worsening) in the time needed to complete the test suggests a concussion has occurred, particularly if the delay is greater than five seconds compared to the individual's baseline test time.

The test, called the King-Devick test, captures impairments of eye movement, attention, language and other symptoms of impaired brain function. It looks at saccadic and other types of eye movements that are frequently abnormal following a concussion.

"This rapid screening test provides an effective way to detect early signs of concussion, which can improve outcomes and hopefully prevent repetitive concussions," said the study's senior author, Laura Balcer, MD, MSCE, Professor of Neurology, Ophthalmology and Epidemiology at the University of Pennsylvania School of Medicine. "If validated in future studies, this test has the potential to become a standard sideline test for athletes."

While more extensive testing can best capture post-concussion syndrome symptoms, and these tests may be influenced by other factors such as intellectual ability or depression, tests of rapid number naming such as the King-Devick test are objective and capture many aspects of function. This may help coaches and athletic trainers determine whether players should be removed from games or not.

As emphasized by the study's lead author, Kristin Galetta, MS, "Concussion is a complex type of brain injury that is not visible on the routine scans we do of the brain, yet is detectable when we measure important aspects of brain function, such as vision. The K-D test is only one test on the sidelines, though, and the diagnosis of concussion requires a combination of tests and input of medical professionals."

In a study of 39 boxers and MMA fighters, post-fight time test scores were significantly higher (worse) for those who had head trauma during their matches (59.1 ± 7.4 vs 41.0 ± 6.7 seconds, p < 0.0001). Among those with head trauma, fighters who lost consciousness had even higher post-fight scores compared to those who didn't lose consciousness (65.5 ± 2.9 vs 52.7 ± 2.9 seconds, p < 0.0001). Test times improved by more than a second on average for participants who did not have head trauma, while average times for those who suffered head trauma worsened by 11.1 seconds. Fighters who lost consciousness were 18 seconds slower on the test after their bouts.

The study was funded by a grant from the National Eye Institute.

A follow-up study, looking prospectively at college athletes at the University of Pennsylvania, is examining changes in athlete test scores over the course of a season, reliability of retest or tests conducted by different testers such as athletic trainers, and establish test norms and expected ranges of pre-competition scores for this age group. It will also provide large-scale results to further evaluate the effectiveness of the test to identify closed head injury and concussions accurately.

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Journal Reference:

1. K. M. Galetta, J. Barrett, M. Allen, F. Madda, D. Delicata, A. T. Tennant, C. C. Branas, M. G. Maguire, L. V. Messner, S. Devick, S. L. Galetta, L. J. Balcer. The King-Devick test as a determinant of head trauma and concussion in boxers and MMA fighters. Neurology, 2011; DOI: 10.1212/WNL.0b013e31821184c9

Most people who survive a stroke recover some degree of their motor, sensory and cognitive functions over the following months and years. This recovery is commonly believed to reflect a reorganisation of the central nervous system that occurs after brain damage. Now a new study, published in the February 2011 issue of Elsevier's Cortex, sheds further light on the recovery process through its effect on language skills.

For almost all right-handed people and for about 60% of left-handers, damage to the left side of the brain causes a condition known as aphasia, an acute or chronic impairment of language skills. The syndrome is strongly associated with damage to the left hemisphere of the brain; however, there is a long-standing controversy regarding the involvement of parts of the right hemisphere in language functions and their contribution to recovery from aphasia. The majority of experts stress the role of the dominant left side in language recovery, while others argue for a complementary (or compensatory) function of the right hemisphere.

Odelia Elkana, from the Hebrew University, Jerusalem, and colleagues investigated the systematic patterns of reorganisation in the brain's language functions, and their relation to linguistic performance, in patients recovering from childhood brain damage to the left hemisphere. They used functional MRI to detect patterns of brain activity while patients performed various linguistic tasks inside the scanner. The new study focused on a rare group of children whose brain damage had occurred after they had already developed language skills but while the brain was still developing, and therefore most able to reorganise its language functions.

According to the authors, the findings suggest that "recovery is a dynamic, ongoing process, may last for years after onset and is reflected in an increasing proficiency of inter-hemispheric coordination, rather than just in an increase of activation in one side or the other. Therefore, the role of each hemisphere in the recovery process is not only dependent on the stage of recovery (acute, sub-acute or chronic stage), but also within each of these stages it may continuously change over time."

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Journal Reference:

1. Odelia Elkana, Ram Frost, Uri Kramer, Dafna Ben-Bashat, Talma Hendler, David Schmidt, Avraham Schweiger. Cerebral reorganization as a function of linguistic recovery in children: An fMRI study. Cortex, 2011; 47 (2): 202 DOI: 10.1016/j.cortex.2009.12.003

 — Wouldn't life be easy if everything happened as we anticipated? In reality, our brains are able to adapt to the unexpected using an inbuilt network that makes predictions about the world and monitors how those predictions turn out. An area at the front of the brain, called the orbitofrontal cortex, plays a central role and studies have shown that patients with damage to this area confuse memories with reality and continue to anticipate events that are no longer likely to happen.

The brain's ability to react adaptively, becomes crucial for survival, when faced with potential dangers, such as snakes and spiders, so to what extent does the harmfulness of an anticipated outcome affect our brain's event monitoring system? Not at all, reveals a new study published in the February 2011 issue of Elsevier's Cortex: the processes are the same, regardless how scary the anticipated event.

The team of researchers, supervised by Prof. Armin Schnider of the University Hospitals of Geneva in Switzerland, recorded functional magnetic resonance images (fMRI) while healthy volunteers performed a task in which they repeatedly saw a pair of faces and had to predict on which face a target was about to appear. The target could be a simple black disk (neutral stimulus) or a spider (potentially harmful stimulus). The researchers found a strong activation of the brain's visual areas whenever the spider appeared. However, irrespective of whether the disk or the spider was the target, its unexpected absence activated a cerebral network including the orbitofrontal cortex.

The findings show that, while the potential harmfulness of an event strongly affects brain responses, it does not influence the way the brain reacts when the expected event does not occur. The study supports the notion that the orbitofrontal cortex is "at the centre of a specific cerebral network which functions as a generic outcome monitoring system," says Louis Nahum, the first author of the study. "This capacity is probably as old in evolution as the instinctive reaction to threatening stimuli; its failure deprives the brain of the ability to remain in phase with reality," notes Armin Schnider.

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Journal Reference:

1. Louis Nahum, Stéphane R. Simon, David Sander, François Lazeyras, Armin Schnider. Neural response to the behaviorally relevant absence of anticipated outcomes and the presentation of potentially harmful stimuli: A human fMRI study. Cortex, 2011; 47 (2): 191 DOI: 10.1016/j.cortex.2009.11.007r its staff.