Brain and Behavior

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The Trouble With Brain Science
On July 7, hundreds of neuroscientists from all over the world issued an open letter to the European Commission, claiming that its $1.6 billion Human Brain Project, intended to build a computer simulation of the human brain, is "overly narrow" and not "well conceived." Some have called the project "radically premature." Gary Marcus, a psychologist writing in the New York Times, says the controversy is a reminder that "scientists are not only far from a comprehensive explanation of how the brain works," but also "not even in agreement about the best way to study it, or what questions we should be asking."
    Marcus notes that neither the Human Brain Project nor the U.S.'s Brain Initiative (see p 48) has grappled with the often ignored question: What would a good theory of the brain actually look like? Partly, he says, this is due to the fact that biology is incredibly complex, the product of countless evolutionary accidents. Neuroscience, he says, is still waiting for a bridge comparable to the discovery of DNA, "which allowed us to understand how genetic information could be represented in a physical structure." Such a breakthrough might, for example, allow us to understand the relationship between circuits of neurons and thought. Marcus thinks both projects should allocate some of their funds to spanning this conceptual chasm. New York Times, July 11, 2014.

Omega-3 Promotes Development of Neural Networks
According to a study with rhesus monkeys at Oregon Health & Science University, eating a diet rich in omega-3 fatty acids encourages highly connected brains with well organized neural networks. The monkeys were fed the diet until they were 17-19 years old, after their mothers had been given the same diet during gestation. Compared to omega-3 deficient monkeys, they had strong connectivity in visual pathways and greater connections in brain networks for higher-level processing, attention, and cognition.
    The study has important implications for human brain development, but it also represents the first time scientists have been able to image the interactions of multiple brain networks in monkeys. A future possibility is studying monkeys to see if deficits in various networks are accompanied by behavioral patterns resembling those of humans with conditions such as attention deficit hyperactivity disorder and autism. Journal of Neuroscience Vol 34, 2065-2074.


Early Antibiotics Alter Gut Microbes and Obesity Proneness
One influence on weight gain is the balance of microbes in the gut; Firmicutes contribute to obesity, while Bacteriodetes appear to have a protective function. Now we have learned that the gut microbiota is influenced by environmental events occuring during an early developmental window. Noting that early low doses of antibiotics make pigs and chickens grow faster and put on more fat, Martin Blaser and his team at New York University gave mice small amounts of penicillin during either the first four or eight weeks of life. The treatment reduced the numbers of some bacteria, including lactobacilli, one of the Firmicutes, but this effect disappeared after a couple of weeks.
     However, 10 weeks later treated mice given a high-fat diet began gaining weight rapidly; this was especially true of females, which gained twice as much body fat as untreated females eating the same diet. Treatment had no effect on mice confined to a low-fat diet, nor on mice receiving antibiotics when they were older.
    To demonstrate that the obesity resulted from gut bacteria rather than direct effects of the penicillin, microbes from the obese mice were transferred to mice previously kept bacteria-free; these mice also began to gain weight on a high-fat diet. The antibiotic regimen isn't quite like what human infants would receive and the human microbiota differs from that of mice, but the study does point up the sensitivity of the weight regulation system, particularly the gut microbiota, to environmental influences. Cell, Vol 158, 705-721.

Why Do Teenage Boys Engage in Risky Behavior?
It is well known that teenage boys seem to be drawn to risky pursuits, a characteristic often linked to a still-developing prefrontal cortex. The journal Developmental Neuroscience devoted its entire July, 2014, issue to 19 studies that looked at the question from the perspectives of psychology, neurochemistry, brain imaging, clinical neuroscience, and neurobiology. The articles cover brain development, drug abuse, and prenatal drug exposure. Highlights include:
• The limbic system of teenage boys reacts to threat markedly more than that of adult men.
• Brain activity measures show very little response to the threat of punishment, but hypersensitivity to the possibility of large gains from gambling.
    The table of contents, with links to all the abstracts and some full-text articles, can be accessed here. (This summary is based on an article at sciencedaily.com.)

Youthful Blood Plasma Will Be Used to Treat Alzheimer's
Starting in October, 2014, Stanford School of Medicine will begin experimental treatments of people with mild to moderate Alzheimer's using blood plasma donated by volunteers under the age of 30. The reason for trying this intriguing approach is its track record in the physical rejuvenation of old mice.
    For example, young blood returns the liver and skeletal stem cells of old mice to a more youthful state, helping them repair injured muscles as well as young mice (Nature, Vol 433, 760-764). A study in which blood from young mice reversed heart decline in aging mice identified a protein in the blood called growth differentiation factor 11 that contributed to the effect and possibly accounted for it (Cell, Vol 153, 828-839). Levels of this protein decline as both mice and humans age, but injection of GDF11 increases the numbers of blood vessels and stem cells in the brain. A Stanford University team found that treatment of aged mice increased synaptic plasticity and the density of dendritic spines in the hippocampus. In addition, it improved age-impaired fear conditioning and spatial learning (Nature Medicine, Vol 20, 659-663).
    Following a single transfusion of donor blood, the Stanford team conducting the human trial will assess the volunteers' cognitive functioning for several days. Then they will continue their monitoring for a few months to see if family and friends see any differences. Obviously, they're hoping the results will be every bit as impressive as those with mice have been. New Scientist, August 20, 2014.