Posts tagged brain plasticity
Articles and news from the latest research reports.
Alternative pathways let right and left communicate in early split brains
During the last century, many patients have undergone a variety of brain surgeries in an attempt to alleviate all sorts of psychiatric maladies, from hysteria and depression (mainly in women) to schizophrenia and epilepsy. Early on, doctors believed that psychiatric patients suffered from aberrant wiring among different brain areas and that cutting the connections between these areas would help patients regain normal brain circuits as well as their mental health. For instance, since the 1940s, several patients with intractable epilepsy have been treated with callosotomy, a surgical procedure that severs part or most of the corpus callosum. Curiously, some individuals are already born without the corpus callosum, a condition known as callosal dysgenesis (CD).
In 1968, the neurobiologist Roger Sperry confirmed that both callosotomized and CD patients have either absent or massively diminished connections between brain hemispheres. However, these two types of patients show a paradoxical difference concerning the transfer of information between the two sides of their brains. While typical callosotomized patients suffer from a disconnection syndrome in which there is minor or no communication between the left and right brain hemispheres, in CD patients, the two hemispheres are in fact able to communicate with each other.
For instance, when an unseen object is held in the right hand and thus recognized by the left hemisphere, both callosotomized and CD individuals can easily name that object verbally, because it is the left hemisphere that most often dominates verbal language. However, when an object is held in the left hand and thus recognized by the right hemisphere, callosotomized patients fail to verbally name the object because the missing corpus callosum prevents the right hemisphere from communicating with the left hemisphere. Conversely, CD patients have no difficulties in naming an unseen object regardless of the hand holding it.
The observation that the corpus callosum is the main connector between brain hemispheres earned Roger Sperry the Nobel Prize in 1981, but his own paradoxical discovery that CD patients do not present the classical disconnection syndrome observed in callosotomized patients remained unexplained until now.
In an article entitled “Structural and functional brain rewiring clarifies preserved inter-hemisphere transfer in humans born without the corpus callosum” and published in the Proceedings of the National Academy of Sciences (PNAS), a group of scientists from Rio de Janeiro and Oxford puts an end to Sperry’s paradox.
Previous work had led to the hypothesis that a defect in callosal formation would cause the brains of CD patients to create alternative pathways early on in life, but little was known about these potential pathways. The group led by Fernanda Tovar-Moll and Roberto Lent at the D’Or Institute for Research and Education and the Institute of Biomedical Sciences in Rio de Janeiro, Brazil, tested the brains of patients with CD using state of the art functional neuroimaging methods. The researchers were able to identify, morphologically describe and establish the function of two alternative pathways that help compensate for the lack of the corpus callosum. These pathways enable the transfer of complex tactile information between hemispheres, an ability missing in surgically callosotomized patients. Furthermore, by comparing six CD patients with 12 normal individuals, the group was able to demonstrate that CD patients present tactile recognition abilities similar to those observed in controls, indicating a functional role for these newly discovered brain pathways.
The authors believe that the development of alternative pathways results from the brain’s ability for long-distance plasticity and occurs in the utero during embryo development, which indicates that connections formed in the human brain early in development can be greatly modified, and most likely by environmental or genetic factors.
These findings will change the way we perceive the mechanisms of brain plasticity and may pave the way for a better understanding of a number of human disorders resulting from abnormal neuronal connections during embryonic development.
Research Shows Strategic Thinking Strengthens Intellectual Capacity
Strategy-based cognitive training has the potential to enhance cognitive performance and spill over to real-life benefit according to a data-driven perspective article by the Center for BrainHealth at The University of Texas at Dallas published in the open-access journal Frontiers in Systems Neuroscience. The research-based perspective highlights cognitive, neural and real-life changes measured in randomized clinical trials that compared a gist-reasoning strategy-training program to memory training in populations ranging from teenagers to healthy older adults, individuals with brain injury to those at-risk for Alzheimer’s disease.
“Our brains are wired to be inspired,” said Dr. Sandra Bond Chapman, founder and chief director of the Center for BrainHeath and Dee Wyly Distinguished University Chair at The University of Texas at Dallas. “One of the key differences in our studies from other interventional research aimed at improving cognitive abilities is that we did not focus on specific cognitive functions such as speed of processing, memory, or learning isolated new skills. Instead, the gist reasoning training program encouraged use of a common set of multi-dimensional thinking strategies to synthesize information and elimination of toxic habits that impair efficient brain performance.”
The training across the studies was short, ranging from 8 to 12 sessions delivered over one to two months in 45 to 60 minute time periods. The protocol focused on three cognitive strategies — strategic attention, integrated reasoning and innovation. These strategies are hierarchical in nature and can be broadly applied to most complex daily life mental activities.
At a basic level, research participants were encouraged to filter competing information that is irrelevant and focus only on important information. At more advanced levels, participants were instructed to generate interpretations, themes or generalized statements from information they were wanting or needing to read, for example. Each strategy built on previous strategies and research participants were challenged to integrate all steps when tackling mental activities both inside and outside of training.
“Cognitive gains were documented in trained areas such as abstracting, reasoning, and innovating,” said Chapman. “And benefits also spilled over to untrained areas such as memory for facts, planning, and problem solving. What’s exciting about this work is that in randomized trials comparing gist reasoning training to memory training, we found that it was not learning new information that engaged widespread brain networks and elevated cognitive performance, but rather actually deeper processing of information and using that information in new ways that augmented brain performance.
Strengthening intellectual capacity is no longer science fiction; what used to seem improbable is now in the realm of reality.”
Positive physical changes within the brain and cognitive improvement across populations in response to strategy-based mental training demonstrate the neuro-regenerative potential of the brain.
“The ability to recognize, synthesize and create the essence of complex ideas and problems to solve are fundamental skills for academic, occupational and real-life success,” Chapman said. “The capacity to enhance cognition and complex neural networks in health, after injury or disease diagnosis will have major implications to preventing, diagnosing and treating cognitive decline and enhancing cognitive performance in youth to prepare them for an unknown future and in middle age to older adults who want to remain mentally robust.”
Touching the brain
By examining the sense of touch in stroke patients, a University of Delaware cognitive psychologist has found evidence that the brains of these individuals may be highly plastic even years after being damaged.
The research is published in the March 6 edition of the journal Current Biology, in an article written by Jared Medina, assistant professor of psychology at UD, and Brenda Rapp of Johns Hopkins University’s Department of Cognitive Science. The findings, which are focused on patients who lost the sense of touch in their hands after a stroke, also have potential implications for other impairments caused by brain damage, Medina said.
“Our lab is interested in how the brain represents the body, not just in the sense of touch,” he said. “That involves a lot of different areas of the brain.”
For decades, scientists have been mapping the brain to determine which areas control certain functions, from movement to emotion to memory. In terms of representing the sense of touch, researchers know which specific parts of the brain are associated with representing specific parts of the body, Medina said.
Those scientists also know that, following the brain damage a stroke causes, patients often regain some of what they initially lost due to that damage.
“Even if every neuron has been killed in the part of the brain that represents touch on the hand, that doesn’t mean that you’re never going to feel anything on your hand again,” Medina said. “We’ve known that isn’t the case because the map can reorganize. The brain can change due to injury.”
But what the new research by Medina and Rapp found is that the brains of those stroke patients may change much more easily than the undamaged brains of healthy people — what they call “hyper-lability.”
The researchers worked with people who had had strokes in the past that affected their ability to localize touch. Each research participant, without being able to see his hand, was touched on the wrist and then on the fingertips. When asked to pinpoint the second touch, the stroke patients reported sensing the touch farther down their finger, toward the wrist, rather than in its actual location.
Medina says that likely occurs because the neural map in the brain is shifting based on the earlier wrist touch — a phenomenon termed “experience-dependent plasticity.”
“Now what’s interesting about this is that when you and I [who haven’t had a stroke] are touched on the wrist, then the fingertips, we don’t have these changes that the brain-damaged individuals do,” he said. “This provides the counterintuitive finding that the maps in brain-damaged individuals are actually much more plastic than in you and me.”
Hyper-plasticity has positive and negative implications, he said.
“On the positive side, this plasticity may potentially be harnessed in rehabilitation to improve function” after a stroke or various other types of brain injury, Medina said. But, he added, the brain may also be so plastic in those cases that changes aren’t stable, creating additional problems.
That’s what he expects additional research to address.
“Now that we’ve found that these maps are more plastic than we thought, can certain strategies help the map become more stable and more accurate again? That’s one of the next questions, and we can only answer it by continuing to learn more about how the mind works.”
(Source: udel.edu)
Vision restored with total darkness
Restoring vision might sometimes be as simple as turning out the lights. That’s according to a study reported on February 14 in Current Biology, a Cell Press publication, in which researchers examined kittens with a visual impairment known as amblyopia before and after they spent 10 days in complete darkness.
Researchers Kevin Duffy and Donald Mitchell of Dalhousie University in Canada believe that exposure to darkness causes some parts of the visual system to revert to an early stage in development, when there is greater flexibility.
"There may be ways to increase brain plasticity and recover from disorders such as amblyopia without drug intervention," Duffy says. "Immersion in total darkness seems to reset the visual brain to enable remarkable recovery."
Amblyopia affects about four percent of the general population and is thought to develop when the two eyes do not see equally well in early life, as the connections from the eyes to visual areas in the brain are still being refined. Left untreated, that imbalance of vision can lead to permanent vision loss.
In the new study, the researchers examined kittens with amblyopia induced by experimentally depriving them of visual input to one eye. After those animals were plunged into darkness, their vision made a profound and rapid recovery. Further examination suggested that the restoration of vision depends on the loss of neurofilaments that hold the visual system in place. With those stabilizing elements gone, the visual system becomes free to correct itself.
Darkness therapy holds promise for the treatment of children with amblyopia, the researchers say, but don’t try this at home. They think that the darkness must be absolute to work, with no stray light at any time. It is also important to address the original cause of the amblyopia first, and to ensure that a period of darkness will not harm an individual’s good eye.
The researchers are still working out just how much darkness is required, and for how long. Regardless, they say it is unlikely that a drug could ever adequately mimic the effects of darkness that they’ve seen.
"The advantage of a simple nonpharmacological sensory manipulation, such as a period of darkness, is that it may initiate changes in a constellation of molecules in a beneficial temporal order and in appropriate brain regions," they write.
Musical Training as a Framework for Brain Plasticity: Behavior, Function, and Structure
Musical training has emerged as a useful framework for the investigation of training-related plasticity in the human brain. Learning to play an instrument is a highly complex task that involves the interaction of several modalities and higher-order cognitive functions and that results in behavioral, structural, and functional changes on time scales ranging from days to years. While early work focused on comparison of musical experts and novices, more recently an increasing number of controlled training studies provide clear experimental evidence for training effects. Here, we review research investigating brain plasticity induced by musical training, highlight common patterns and possible underlying mechanisms of such plasticity, and integrate these studies with findings and models for mechanisms of plasticity in other domains.