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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