Jolting the brain into better math skills: Last week, we had electric currents to the brain inducing flashbacks. This week, the same sort of jolt to a different area of the brain gives us... better math skills? So it seems, at least provided the wires are hooked up properly. The technique, transcranial direct current stimulation, can send a current of one orientation or the other to a specific area of the brain. Depending on the current's orientation, this either stimulates or slows down neural activity in that area.

The researchers performed this stimulation to the parietal lobe, which has been associated with mathematical reasoning, and then trained subjects on a math system that involved artificial symbols for a span of six days. With the right orientation, the subjects showed improved performance relative to the baseline; swap the wires, and they did worse. The currents seemed to have no effect on the consolidation of what was learned, since the improved understanding of the artificial math system lasted for at least six months.

Boa constrictors can squeeze out the males when producing young: Or, as the press release put it, "Main squeeze not needed for boa mom." Parthenogenesis has been observed in a number of species, which can do without a male by producing eggs that develop into viable adults without fertilization. In this case, a female boa was found to produce viable offspring without fertilization that were genetically distinct from their mom. The authors suggest that the egg nucleus fused with one of the other sets of chromosomes that are normally discarded during the process of meiosis.

Evolution driven by religion, at least in fish: The religion in this case is a pre-Columbian ritual that takes place annually in Mexico, where participants go to a cave and place a toxin in the water to harvest some of the fish that live there. The ceremony has now been going on for long enough that the fish at the site of the ritual have evolved increased resistance to the toxin compared to those living elsewhere in the same cave. Presumably, if this continues long enough, the ritual may come to an end simply because the fish no longer feel any effects of the toxin.

An unrecognized menace for hospital costs: Removing foreign objects that are swallowed is apparently fairly expensive for hospitals, since it can involve general anesthesia and the use of endoscopic hardware. Presumably, most of them are accidental, but a search of eight years' worth of one hospital's records has pulled out over 300 cases of intentionally ingested objects. The surprise (to me at least), is that all these cases occurred in just 33 patients, who racked up $2,018,073 in medical expenses. The authors say that these 33 individuals had psychiatric disorders, and suggest that focusing on treating those issues could pay off in the long run.

Planting the seeds of lower crime: There are all sorts of ideas on how environments influence crime rates, some of which (like elimination of graffiti) have been turned into public policy. Two US Forest Service employees, however, have found an unexpected influence: the number and types of trees in the area. The authors registered the trees present near 2,813 homes, and then correlated that with the crimes that occurred there over a two-year period. Having trees helped reduce crime rates, but only if they were tall; "Smaller, view-obstructing trees are associated with increased crime," the authors note. They suggest that a tree acts a bit like a clean, graffiti-free wall, and signals that the home is well cared for.

Double the drugs means trouble: Lots of drug therapies rely on the fact that two drugs that have distinct mechanisms of action can be more effective than a single drug alone. When it comes to the flu, though, combining the two most popular antivirals (tamiflu/oseltamivir and relenza/zanamivir) actually makes matters worse. The protection offered by the combo was no better than that from zanamivir alone, and actually worse than relying on oseltamivir. The study was double blind and placebo controlled, so it looks pretty good.