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Exercise and memory mechanisms

Mice were given cocaine injections over four days in special chambers with a distinctive floor texture to produce a drug association with that environment. The animals were then housed for 30 days in cages, some of which included a running wheel. The researchers found that mice that exercised on these wheels had lower levels of brain peptides related to myelin, a substance that is thought to help fix memories in place. Re-exposure to the cocaine-associated environment affected running and sedentary mice differently: Compared with sedentary mice, the animals with running wheels showed a reduced preference for the cocaine-associated environment. In addition, the brains of re-exposed runners contained higher levels of hemoglobin-derived peptides, some of which are involved in cell signaling in the brain. Meanwhile, peptides derived from actin decreased in the brains of re-exposed sedentary mice. Actin is involved in learning and memory and is implicated in drug seeking. The researchers say these findings related to peptide changes will help to identify biomarkers for drug dependence and relapse.

Running triggers brain repair and extends life in mouse model - Medical News Today

The researchers allowed some of the mice the opportunity to run by installing a wheel into their cages. Surprisingly, the mice given the opportunity to run lived more than 12 months (a relatively normal lifespan for a mouse). On top of their extended lives, the running mice also put on more weight and achieved a better sense of balance, compared with their less active siblings. "We saw that the existing neurons became better insulated and more stable. This means that the unhealthy neurons worked better and the previously damaged circuits in the brain became stronger and more functional." Dr. Matías Alvarez-Saavedra, lead author However, these changes were reversed if the opportunity to exercise was taken away. Once the running wheel was removed, the symptoms returned, and their lives were once more cut short.

Odds are good that risky gambling choices are influenced by a single brain connection -- ScienceDaily

Using that technique, called diffusion-weighted MRI, Knutson and graduate student Josiah Leong found a tract that directly connects the anterior insula and nucleus accumbens -- something that had been seen before in animals but never in humans. What's more, they found that the thicker the sheath of fatty tissue insulating the bundle -- an indicator of the strength of the connection -- the more cautious the study participants' decisions were in a gambling test. The neuronal connection appears to be a conduit for the more cautious brain region to dampen activity in the more enthusiastic region. "Most people love the small chance of a huge win," Knutson said. "But people vary. Some people really, really like it. But people who have a stronger connection don't like it as much."
Meanwhile, in times of doubt, take inspiration in one last distinction of the teen brain—a final key to both its clumsiness and its remarkable adaptability. This is the prolonged plasticity of those late-developing frontal areas as they slowly mature. As noted earlier, these areas are the last to lay down the fatty myelin insulation—the brain's white matter—that speeds transmission. And at first glance this seems like bad news: If we need these areas for the complex task of entering the world, why aren't they running at full speed when the challenges are most daunting? The answer is that speed comes at the price of flexibility. While a myelin coating greatly accelerates an axon's bandwidth, it also inhibits the growth of new branches from the axon. According to Douglas Fields, an NIH neuroscientist who has spent years studying myelin, "This makes the period when a brain area lays down myelin a sort of crucial period of learning—the wiring is getting upgraded, but once that's done, it's harder to change."