Posts tagged cognitive deficits
Articles and news from the latest research reports.
Brain May Never Fully Recover from Exposure to Paint, Glue, Degreasers
People who are exposed to paint, glue or degreaser fumes at work may experience memory and thinking problems in retirement, decades after their exposure, according to a study published in the May 13, 2014, print issue of Neurology®, the medical journal of the American Academy of Neurology.
“Our findings are particularly important because exposure to solvents is very common, even in industrialized countries like the United States.” said study author Erika L. Sabbath, ScD, of Harvard School of Public Health in Boston. “Solvents pose a real risk to the present and future cognitive health of workers, and as retirement ages go up, the length of time that people are exposed is going up, too.”
The study involved 2,143 retirees from the French national utility company. Researchers assessed the workers’ lifetime exposure to chlorinated solvents, petroleum solvents, and benzene, including the timing of last exposure and lifetime dosage. Benzene is used to make plastics, rubber, dye, detergents and other synthetic materials. Chlorinated solvents can be found in dry cleaning solutions, engine cleaners, paint removers and degreasers. Petroleum solvents are used in carpet glue, furniture polishes, paint, paint thinner and varnish. Of the participants, 26 percent were exposed to benzene, 33 percent to chlorinated solvents and 25 percent to petroleum solvents.
Participants took eight tests of their memory and thinking skills an average of 10 years after they had retired, when they were an average age of 66. A total of 59 percent of the participants had impairment on one to three of the eight tests; 23 percent had impairment on four or more tests; 18 percent had no impaired scores.
The average lifetime solvent exposure was determined based on historical company records, and the participants were categorized as having no exposure, moderate exposure if they had less than the average and high exposure if they had higher than the average. They were also divided by when the last exposure occurred, with those last exposed from 12 to 30 years prior to the testing considered as recent exposure and those last exposed 31 to 50 years prior considered as more distant exposure.
The research found that people with high, recent exposure to solvents were at greatest risk for memory and thinking deficits. For example, those with high, recent exposure to chlorinated solvents were 65 percent more likely to have impaired scores on tests of memory and visual attention and task switching than those who were not exposed to solvents. The results remained the same after accounting for factors such as education level, age, smoking and alcohol consumption.
“The people with high exposure within the last 12 to 30 years showed impairment in almost all areas of memory and thinking, including those not usually associated with solvent exposure,” Sabbath said. “But what was really striking was that we also saw some cognitive problems in those who had been highly exposed much longer ago, up to 50 years before testing. This suggests that time may not fully lessen the effect of solvent exposure on some memory and cognitive skills when lifetime exposure is high.”
Sabbath said the results may have implications for policies on workplace solvent exposure limits. “Of course, the first goal is protecting the cognitive health of individual workers. But protecting workers from exposure could also benefit organizations, payers, and society by reducing workers’ post-retirement health care costs and enabling them to work longer,” said Sabbath. “That said, retired workers who have had prolonged exposure to solvents during their career may benefit from regular cognitive screening to catch problems early, screening and treatment for heart problems that can affect cognitive health, or mentally stimulating activities like learning new skills.”
Marijuana use in adolescence may cause permanent brain abnormalities
Regular marijuana use in adolescence, but not adulthood, may permanently impair brain function and cognition, and may increase the risk of developing serious psychiatric disorders such as schizophrenia, according to a recent study from the University of Maryland School of Medicine. Researchers hope that the study, published in Neuropsychopharmacology — a publication of the journal Nature – will help to shed light on the potential long-term effects of marijuana use, particularly as lawmakers in Maryland and elsewhere contemplate legalizing the drug.
"Over the past 20 years, there has been a major controversy about the long-term effects of marijuana, with some evidence that use in adolescence could be damaging," says the study’s senior author Asaf Keller, Ph.D., Professor of Anatomy and Neurobiology at the University of Maryland School of Medicine. "Previous research has shown that children who started using marijuana before the age of 16 are at greater risk of permanent cognitive deficits, and have a significantly higher incidence of psychiatric disorders such as schizophrenia. There likely is a genetic susceptibility, and then you add marijuana during adolescence and it becomes the trigger."
"Adolescence is the critical period during which marijuana use can be damaging," says the study’s lead author, Sylvina Mullins Raver, a Ph.D. candidate in the Program in Neuroscience in the Department of Anatomy and Neurobiology at the University of Maryland School of Medicine. "We wanted to identify the biological underpinnings and determine whether there is a real, permanent health risk to marijuana use."
The scientists — including co-author Sarah Paige Haughwout, a research technician in Dr. Keller’s laboratory — began by examining cortical oscillations in mice. Cortical oscillations are patterns of the activity of neurons in the brain and are believed to underlie the brain’s various functions. These oscillations are very abnormal in schizophrenia and in other psychiatric disorders. The scientists exposed young mice to very low doses of the active ingredient in marijuana for 20 days, and then allowed them to return to their siblings and develop normally.
"In the adult mice exposed to marijuana ingredients in adolescence, we found that cortical oscillations were grossly altered, and they exhibited impaired cognitive abilities," says Ms. Raver. "We also found impaired cognitive behavioral performance in those mice. The striking finding is that, even though the mice were exposed to very low drug doses, and only for a brief period during adolescence, their brain abnormalities persisted into adulthood."
The scientists repeated the experiment, this time administering marijuana ingredients to adult mice that had never been exposed to the drug before. Their cortical oscillations and ability to perform cognitive behavioral tasks remained normal, indicating that it was only drug exposure during the critical period of adolescence that impaired cognition through this mechanism. The researchers took the next step in their studies, trying to pinpoint the mechanisms underlying these changes and the time period in which they occur.
"We looked at the different regions of the brain," says Dr. Keller. "The back of the brain develops first, and the frontal parts of the brain develop during adolescence. We found that the frontal cortex is much more affected by the drugs during adolescence. This is the area of the brain controls executive functions such as planning and impulse control. It is also the area most affected in schizophrenia."
Dr. Keller’s team believes that the results have indications for humans as well. They will continue to study the underlying mechanisms that cause these changes in cortical oscillations. “The purpose of studying these mechanisms is to see whether we can reverse these effects,” says Dr. Keller. “We are hoping we will learn more about schizophrenia and other psychiatric disorders, which are complicated conditions. These cognitive symptoms are not affected by medication, but they might be affected by controlling these cortical oscillations.”
Reseachers from Bochum and Warwick suggest consequences for planning school lessons
Large numbers of preterm born babies will place new demands on education system
About 15 million, i.e., more than ten per cent of all babies worldwide are born preterm every year; that is before the 37th week of pregnancy – and the numbers are rising due to improvements in neonatal medicine and demographic changes. Recent studies suggest that delivery at any gestation other than full term (39 to 41 weeks gestational age) may impair brain development, rendering survivors at risk for adverse neuro-cognitive outcomes. Considering that 50 per cent of children are born before the 39th week of pregnancy, even small increases in cognitive impairments may have large effects on a population level. “As the total number of children born preterm increases there will be parallel increases in special education needs placing new demands on the education system,” Julia Jäkel and her colleagues say. To date, uncertainties remain regarding the nature and underlying causes of learning difficulties in preterm children. The new cognitive workload model now reconciles previous inconsistent findings on the relationship of gestational age and cognitive performance.
Cognitive deficits of children born preterm depend on the workload of the task
The research team tested 1326 children, born between weeks 23 and 41 of pregnancy, at an age of eight years. Data were collected as part of the prospective Bavarian Longitudinal Study. The children took part in a range of cognitive tests with varying workload. High workload tasks require the simultaneous integration of different sources of information, thereby placing high demands on the so called working memory. The results: The higher the workload and the shorter the pregnancy duration, the larger were the cognitive performance deficits. Deficits were disproportionally higher for children born before the 34th week of pregnancy compared with children born after week 33. Being born preterm specifically affected the ability to solve high workload tasks, whereas lower workload tasks were largely unaffected.
Results are relevant for cognitive follow-ups and planning of school lessons
According to the researchers, these results should be taken into account for routine cognitive follow-ups of preterm children as well as for planning school lessons. “New studies suggest that computerized training can improve working memory capacity,” Prof Dieter Wolke from Warwick says. “In addition, educational interventions could be developed in which information is not presented simultaneously to preterm children but more slowly and sequentially to promote academic attainment.”
Skulls of early humans carry telltale signs of inbreeding
Buried for 100,000 years at Xujiayao in the Nihewan Basin of northern China, the recovered skull pieces of an early human exhibit a now-rare congenital deformation that indicates inbreeding might well have been common among our ancestors, new research from the Chinese Academy of Sciences and Washington University in St. Louis suggests.
The skull, known as Xujiayao 11, has an unusual perforation through the top of the brain case — an enlarged parietal foramen (EPF) or “hole in the skull” — that is consistent with modern humans diagnosed with a rare genetic mutation in the homeobox genes ALX4 on chromosome 11 and MSX2 on chromosome 5.
These specific genetic mutations interfere with bone formation and prevent the closure of small holes in the back of the prenatal braincase, a process that is normally completed within the first five months of fetal development. It occurs in about one out of every 25,000 modern human births.
Although this genetic abnormality is sometimes associated with cognitive deficits, the older adult age of Xujiayao 11 suggests that any such deficits in this individual were minor.
Traces of genetic abnormalities, such as EPF, are seen unusually often in the skulls of Pleistocene humans, from early Homo erectus to the end of the Paleolithic.
"The probability of finding one of these abnormalities in the small available sample of human fossils is very low, and the cumulative probability of finding so many is exceedingly small," suggests study co-author Erik Trinkaus, the Mary Tileston Hemenway Professor of Anthropology in Arts & Sciences at Washington University in St. Louis.
"The presence of the Xujiayao and other Pleistocene human abnormalities therefore suggests unusual population dynamics, most likely from high levels of inbreeding and local population instability." It therefore provides a background for understanding populational and cultural dynamics through much of human evolution.
Veterans with mild traumatic brain injury have brain abnormalities
Mild traumatic brain injury (TBI), including concussion, is one of the most common types of neurological disorder, affecting approximately 1.3 million Americans annually.
It has received more attention recently because of its frequency and impact among two groups of patients: professional athletes, especially football players; and soldiers returning from mid-east conflicts with blast-related TBI. An estimated 10 to 20 percent of the more than 2 million U.S. soldiers deployed in Iraq or Afghanistan have experienced TBI.
A recent study by psychiatrists from the Iowa City VA Medical Center and University of Iowa Health Care finds that soldiers returning from Iraq and Afghanistan with mild TBI have measurable abnormalities in the white matter of their brains when compared to returning veterans who have not experienced TBI. These abnormalities appear to be related to the severity of the injury and are related to cognitive deficits. The findings were published online in December in the American Journal of Psychiatry.
Cognitive deficits from concussions still present after two months
The ability to focus and switch tasks readily amid distractions was compromised for up to two months following brain concussions suffered by high school athletes, according to a study at the University of Oregon.
Research team members, in an interview, said the discovery suggests that some athletes may need longer recovery periods than current practices dictate to lower the risk of subsequent concussions. Conventional wisdom, said lead author David Howell, a graduate student in the UO Department of Human Physiology, says that typical recovery from concussion takes seven to 10 days.
"The differences we detected may be a matter of milliseconds between a concussed person and a control subject, but as far as brain time goes that difference for a linebacker returning to competition too soon could mean the difference between another injury or successfully preparing to safely tackle an oncoming running back," Howell said.
The findings are based on cognitive exercises used five times over the two months with a pair of sensitive computer-based measuring tools — the attentional network test and the task-switching test. The study focused on the effects of concussions to the frontal region of the brain, which is responsible for working, or short-term, memory and executive function, said Li-Shan Chou, professor of human physiology and director of the UO Motion Analysis Laboratory.
The study was published online ahead of print by Medicine & Science in Sports & Exercise, the official journal of the American College of Sports Medicine.