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Engage multiple layers to rebuild a brain

The researchers placed mice in a dark box and trained them to search for a nearby object with their whiskers. When the mice detected the object, they pulled a lever with their paw to dispense water as a reward. Conventional wisdom argued that this kind of detection task depends almost entirely on a functioning sensory cortex — in this case, the barrel cortex. To confirm this was true, the researchers used laser light to temporarily turn off barrel-cortex cells, a popular technique known as optogenetics. As expected, animals had difficulty whisking while the cells were turned off. And when the team then permanently removed their barrel cortex, the animals could not perform the task the next day. But on day two, the animals’ performance suddenly recovered to original levels. “This came as a huge surprise, since it suggested that tactile sensation, such as whisker-based touch, may not completely rely on the cortex,” said Dr. Hong. “These findings challenge the commonly held, cortex-centric view of how the brain drives touch perception.”

Fundamental Rule of Brain Plasticity Discovered - Neuroscience News

Our brains are famously flexible, or “plastic,” because neurons can do new things by forging new or stronger connections with other neurons. But if some connections strengthen, neuroscientists have reasoned, neurons must compensate lest they become overwhelmed with input. In a new study in Science, researchers at the Picower Institute for Learning and Memory at MIT demonstrate for the first time how this balance is struck: when one connection, called a synapse, strengthens, immediately neighboring synapses weaken based on the action of a crucial protein called Arc. Senior author Mriganka Sur said he was excited but not surprised that his team discovered a simple, fundamental rule at the core of such a complex system as the brain, where 100 billion neurons each have thousands of ever-changing synapses. He likens it to how a massive school of fish can suddenly change direction, en masse, so long as the lead fish turns and every other fish obeys the simple rule of following the fish right in front of it.

Reduced hippocampal volume observed in currently but not previously depressed older adults

By analyzing MRI brain scans, Calati and her colleagues observed hippocampal volume reduction in currently depressed participants compared to the healthy control group. But they found no significant difference between those with a history of past, but not current, depression and the healthy controls. “When we compared the three groups, we found left posterior hippocampal volume reduction in currently depressed individuals when compared to healthy subjects. This reduction was not present when we compared past depressed subjects to healthy controls,” Calati explained.

Birth of new neurons in the human hippocampus ends in childhood: Adult 'neurogenesis,' observed in other species, appears not to occur in humans -- ScienceDaily

The researchers found plentiful evidence of neurogenesis in the dentate gyrus during prenatal brain development and in newborns, observing an average of 1,618 young neurons per square millimeter of brain tissue at the time of birth. But the number of newborn cells sharply declined in samples obtained during early infancy: dentate gyrus samples from year-old infants contained fivefold fewer new neurons than was seen in samples from newborn infants. The decline continued into childhood, with the number of new neurons declining by 23-fold between one and seven years of age, followed by a further fivefold decrease by 13 years, at which point neurons also appeared more mature than those seen in samples from younger brains. The authors observed only about 2.4 new cells per square millimeter of DG tissue in early adolescence, and found no evidence of newborn neurons in any of the 17 adult post-mortem DG samples or in surgically extracted tissue samples from 12 adult patients with epilepsy.

The Roles of BDNF in the Pathophysiology of Major Depression and in Antidepressant Treatment

Animal studies have demonstrated that stress reduces BDNF expression or activity in the hippocampus and that this reduction can be prevented by treatment with antidepressant drugs. A similar change in BDNF activity occurs in the brain of patients with major depression disorder (MDD). Recently, clinical studies have indicated that serum or plasma BDNF levels are decreased in untreated MDD patients. Antidepressant treatment for at least four weeks can restore the decreased BDNF function up to the normal value. Therefore, MDD is associated with impaired neuronal plasticity. Suicidal behavior can be a consequence of severe impaired neuronal plasticity in the brain. Antidepressant treatment promotes increased BDNF activity as well as several forms of neuronal plasticity, including neurogenesis, synaptogenesis and neuronal maturation. BDNF could also play an important role in the modulation of neuronal networks. Such a neuronal plastic change can positively influence mood or recover depressed mood.

A new path into bipolar disorder comes to light -- ScienceDaily

One type of protein produced by IEGs is the so-called Early Growth Response (EGR) proteins, which translate environmental influence into long-term changes in the brain. These proteins are found throughout the brain and are highly produced in response to environmental changes such as stressful stimuli and sleep deprivation. Without the action played out by these proteins, brain cells and the brain itself cannot appropriately respond to the many stimuli that are constantly received from the environment. Effective neuronal plasticity also depends on neurotrophins, which are regulatory factors that promote development and survival of brain cells. Brain-derived neurotrophic factor (BDNF) is the neurotrophin mostly found in the brain. It has been extensively investigated in BD patients and has been suggested as a hallmark of BD. Indeed, some studies have shown that the levels of BDNF in the serum of BD patients are reduced whenever patients undergo a period of depression, hypomania, or mania. Other studies have shown that regardless of mood state, BD patients present reduced levels of BDNF. Overall, changes in BDNF levels seem to be a characteristic found in BD patients that may contribute to the pathophysiology of the disease.

Brain halves increase communication to compensate for aging, study finds -- ScienceDaily

"This study provides an explicit test of some controversial ideas about how the brain reorganizes as we age," said lead author Simon Davis, PhD. "These results suggest that the aging brain maintains healthy cognitive function by increasing bilateral communication." Simon Davis and colleagues used a brain stimulation technique known as transcranial magnetic stimulation (TMS) to modulate brain activity of healthy older adults while they performed a memory task. When researchers applied TMS at a frequency that depressed activity in one memory region in the left hemisphere, communication increased with the same region in the right hemisphere, suggesting the right hemisphere was compensating to help with the task. In contrast, when the same prefrontal site was excited, communication was increased only in the local network of regions in the left hemisphere. This suggested that communication between the hemispheres is a deliberate process that occurs on an "as needed" basis.

Brains of one-handed people suggest new organization theory -- ScienceDaily

"We found that the traditional hand area" -- which, Makin notes, takes up a rather sizable portion of the brain -- "gets used up by a multitude of body parts in congenital one-handers. Interestingly, these body parts that get to benefit from increased representation in the freed-up brain territory are those used by the one-handers in daily life to substitute for their missing-hand function -- say when having to open a bottle of water." Whether Makin's theory on brain organization corresponding to function instead of body parts pans out or not, the findings reveal remarkable brain plasticity. Her hope is to find a way to encourage the brain to represent and control artificial body parts, such as a prosthetic arm, using the brain area that would have controlled the missing hand.

Brain 'rewires' itself to enhance other senses in blind people -- ScienceDaily

"Our results demonstrate that the structural and functional neuroplastic brain changes occurring as a result of early ocular blindness may be more widespread than initially thought," said lead author Corinna M. Bauer, Ph.D., a scientist at Schepens Eye Research Institute of Mass. Eye and Ear and an instructor of ophthalmology at Harvard Medical School. "We observed significant changes not only in the occipital cortex (where vision is processed), but also areas implicated in memory, language processing, and sensory motor functions." The researchers used MRI multimodal brain imaging techniques (specifically, diffusion-based and resting state imaging) to reveal these changes in a group of 12 subjects with early blindness (those born with or who have acquired profound blindness prior to the age of three), and they compared the scans to a group of 16 normally sighted subjects (all subjects were of the same age range). On the scans of those with early blindness, the team observed structural and functional connectivity changes, including evidence of enhanced connections, sending information back and forth between areas of the brain that they did not observe in the normally sighted group. These connections that appear to be unique in those with profound blindness suggest that the brain "rewires" itself in the absence of visual information to boost other senses. This is possible through the process of neuroplasticity, or the ability of our brains to naturally adapt to our experiences.

Satnavs 'switch off' parts of the brain: Using a satnav to get to your destination 'switches off' parts of the brain that would otherwise be used to simulate different routes -- ScienceDaily

When volunteers navigated manually, their hippocampus and prefrontal cortex had spikes of activity when volunteers entered new streets. This brain activity was greater when the number of options to choose from increased, but no additional activity was detected when people followed satnav instructions. "Entering a junction such as Seven Dials in London, where seven streets meet, would enhance activity in the hippocampus, whereas a dead-end would drive down its activity. If you are having a hard time navigating the mass of streets in a city, you are likely putting high demands on your hippocampus and prefrontal cortex," explains senior author Dr Hugo Spiers (UCL Experimental Psychology). "Our results fit with models in which the hippocampus simulates journeys on future possible paths while the prefrontal cortex helps us to plan which ones will get us to our destination. When we have technology telling us which way to go, however, these parts of the brain simply don't respond to the street network. In that sense our brain has switched off its interest in the streets around us."

How aerobic exercise enhances neuroplasticity in the brain

A brief but intense period of aerobic exercise immediately reduces GABA, the main inhibitory neurotransmitter in the brain. GABA play an important role in regulating the brain’s capacity to undergo change or neuroplasticity. We observed reduced excitability of GABA-mediated networks in the motor cortex, which may explain findings from previous studies where enhanced neuroplasticity is observed after aerobic exercise. Our findings may have implications for individuals after stroke, where GABA is a promising target for promoting neuroplasticity to promote recovery of motor function.

Running + challenges lead to neurogenisis

Voluntary physical exercise (wheel running, RUN) and environmental enrichment both stimulate adult hippocampal neurogenesis but do so by different mechanisms. RUN induces precursor cell proliferation, whereas ENR exerts a survival-promoting effect on newborn cells. In addition, continued RUN prevented the physiologically occurring age-related decline in precursor cell in the dentate gyrus but did not lead to a corresponding increase in net neurogenesis. We hypothesized that in the absence of appropriate cognitive stimuli the potential for neurogenesis could not be realized but that an increased potential by proliferating precursor cells due to RUN could actually lead to more adult neurogenesis if an appropriate survival-promoting stimulus follows the exercise. We thus asked whether a sequential combination of RUN and ENR (RUNENR) would show additive effects that are distinct from the application of either paradigm alone. We found that the effects of 10 days of RUN followed by 35 days of ENR were additive in that the combined stimulation yielded an approximately 30% greater increase in new neurons than either stimulus alone, which also increased neurogenesis.

Perceptually relevant remapping of human somatotopy in 24 hours. - PubMed - NCBI

Experience-dependent reorganisation of functional maps in the cerebral cortex is well described in the primary sensory cortices. However, there is relatively little evidence for such cortical reorganisation over the short-term. Using human somatosensory cortex as a model, we investigated the effects of a 24-hour gluing manipulation in which the right index and right middle fingers (digits 2 & 3) were adjoined with surgical glue. Somatotopic representations, assessed with two 7 tesla fMRI protocols, revealed rapid off-target reorganisation in the non-manipulated fingers following gluing, with the representation of the ring finger (digit 4) shifted towards the little finger (digit 5) and away from the middle finger (digit 3). These shifts were also evident in two behavioural tasks conducted in an independent cohort, showing reduced sensitivity for discriminating the temporal order of stimuli to the ring and little fingers, and increased substitution errors across this pair on a speeded reaction time task.

How hearing loss can change the way nerve cells are wired -- ScienceDaily

In mice whose ears were blocked, cells in the auditory nerve started to use their supplies of neurotransmitter more freely. They depleted their reserves of these chemicals rapidly each time a new auditory signal came in, and they decreased the amount of space within the cells that housed sac-like structures called vesicles -- biological storage tanks where neurotransmitter chemicals are kept. "When it's quiet, the demands on the auditory nerve cells are not as great," Xu-Friedman says. "So it makes sense that you would see these changes: You no longer need as much neurotransmitter, so why invest in a lot of storage? If you're not that active, you don't need a big gas tank. And you're not as afraid to use up what you have. This is one plausible explanation for what we observed." The changes in cellular structure and behavior were the opposite of what Xu-Friedman team's saw in a previous study that placed mice in a consistently noisy environment. In that project -- faced with an unusually high level of noise -- the mice's auditory nerve cells started to economize their resources, conserving supplies of neurotransmitter while increasing the storage capacity for the chemicals. "It looks like these effects are two sides of the same coin, and they might be the first hints of a general rule that nerve cells regulate their connections based on how active they are," Xu-Friedman says.

How physical exercise aids in stroke recovery: Engaging in voluntary physical exercise helps protects the brain it from the damaging effects of a stroke, shown in mice -- ScienceDaily

In order to do this, Kalogeraki and her co-authors used a standard test to assess the brain's 'plasticity' -- its ability to change the way it activates in response to an experience. When the visual input of one eye is compromised for a couple of days, then the part of the brain that processes visual information gets preferentially activated by the other, open eye. The brain's ability to change eye dominance (called ocular dominance plasticity) is age-related, being most pronounced in juvenile animals and completely absent in older mice that have been raised without any stimulation. As well as confirming existing knowledge about the anti-aging effects of voluntary physical exercise -- older mice that exercised retained the ability to change eye dominance in comparison to those that didn't -- the study also revealed some exciting new findings. Those mice that had free-access to a running wheel were able to maintain ocular dominance plasticity after suffering a stroke, compared to those that didn't. "We found that mice with free access to a running wheel throughout their life preserved a more juvenile brain into adulthood and were able to prevent the negative effects of a stroke," reveals Kalogeraki. That was not all -- in addition, the researchers observed that exercise could even be used therapeutically after suffering a stroke. "We also found that mice with no previous access to a running wheel showed an equally positive recovery if voluntary exercise started after a stroke had occurred," adds Dr. Justyna Pielecka-Fortuna, co-author of the study.

Stress and hippocampus

New research now shows that even a brief period of stress can cause the hippocampus to start shrinking.This shrinking of the hippocampus -- a change in the brain's structure -- actually precedes the onset of a change in behaviour, namely, the loss of memory.

Changes in brain connectivity protect against developing bipolar disorder -- ScienceDaily

"The ability of the siblings to rewire their brain networks means they have adaptive neuroplasticity that may help them avoid the disease even though they still carry the genetic scar of bipolar disorder when they process emotional information," said Sophia Frangou, MD, PhD, Professor of Psychiatry at the Icahn School of Medicine at Mount Sinai and lead author of the study. Dr. Frangou's ongoing research uses neuroimaging to study how differences in brain wiring can either increase or decrease the likelihood of developing mental health problems.

Newly discovered windows of brain plasticity may help stress-related disorders -- ScienceDaily

"Even after a long period of chronic stress, the brain retains the ability to change and adapt. In experiments with mice, we discovered the mechanism that alters expression of key glutamate-controlling genes to make windows of stress-related neuroplasticity--and potential recovery--possible," says senior author Bruce McEwen, Alfred E. Mirsky Professor, and head of the Harold and Margaret Milliken Hatch Laboratory of Neuroendocrinology. Glutamate is a chemical signal implicated in stress-related disorders, including depression. "This sensitive window could provide an opportunity for treatment, when the brain is most responsive to efforts to restore neural circuitry in the affected areas," he adds.

Adjustment in mouse whiskers

A mouse that loses one whisker becomes more sensitive to his remaining whiskers, because neurons in the touch-related cortical region rewire to receive inputs from the spared whiskers. When scientists recorded neural activity before and after trimming a mouse whisker, they found that it was the less active neurons that became more sensitive to spared whiskers.8