Gambling Fever Starts in Brain
An abnormal craving for pleasurable stimulation, combined with a lack of impulse control, may explain why some people become pathological gamblers, a German study suggests.
Scientists have long theorized that some people get addicted to drugs because their brains are relatively unreactive to dopamine, a brain chemical that offers most people a constant, low-level sense of reward. Hungry for the positive signals that others get from routine activities, these people turn to dopamine-stimulating drugs such as cocaine, the theory goes.
To see if similar abnormalities might explain why 1 percent to 2 percent of adults end up essentially addicted to gambling, Christian Buchel of University Hospital Hamburg-Eppendorf conducted brain scans on 12 pathological gamblers (people whose relationships, finances and social status are negatively affected by their gambling) and compared them with 12 healthy counterparts. The scans tracked brain activity while the participants played a computer gambling game programmed to create a string of wins and losses.
Compared with the controls, the pathological gamblers showed a lower level of activity in the ventral striatum, the dopamine-producing brain region that provides the pleasure in winning, suggesting gamblers remain unsatisfied even when winning. The scans also showed decreased activation of the ventrolateral prefrontal cortex -- the brain's "superego," which keeps people from acting impulsively.
The findings, reported in yesterday's online edition of Nature Neuroscience, suggest that pathological gamblers are predisposed to their long nights at the slots.
It's possible, said Buchel, that at least some of the brain differences are the result -- rather than the cause -- of so much gambling. Sorting that out will require long-term studies -- a difficult proposition, he said, because pathological gamblers tend not to show up for study appointments.
-- Rick Weiss
Rats Distinguish Languages
The ability to recognize patterns in the sound of speech is considered fundamental to the development of spoken language. Only two species of mammals, humans and tamarin monkeys, were known to possess this ability -- until now.
New research has identified a surprising third -- rats.
Juan M. Toro of the Parc Cientific of Barcelona in Spain and colleagues studied 16 rats, training them to press a lever when they heard a synthesized five-second sentence in Dutch or Japanese.
The rats could differentiate between sentences in Dutch or Japanese, pressing the lever only when they were played a sentence in the language in which they had been trained. The rats trained in Japanese, for example, did not press the lever when they were played the same sentence in Dutch.
In addition, the animals appeared able to transfer their familiarity with the patterns of the language they had been trained in to new sentences -- pressing the lever when they were played sentences in that language even if they had never heard them before.
"It was striking to find that rats can track certain information that seems to be so important in language development in humans," Toro said.
The rats were, however, not as adept as humans, who are able to discern the same sentence when spoken by different individuals, something rats were less able to do.
The research shows "which abilities that humans use for language are shared with other animals and which are uniquely human."
-- Rob Stein
Predators Picky About Food
Different plants are rich in different nutrients, so many plant-eating animals must alter their diets day to day to balance their intake of proteins, oils and minerals. By contrast, scientists have long thought, prey animals are so nutritionally rich that carnivorous predators need not worry about what to eat. Their challenge is just to catch something, period.
Not so, suggests new research by a team of scientists from Europe, Israel, New Zealand and Australia, who tested the supposition in predatory insects and spiders.
The team limited the diets of carnivorous beetles, hunting wolf spiders and web-building desert spiders to make them deficient in either protein or fat. Then they offered the predators prey especially rich in one or the other nutrient. The beetle and the wolf spider preferentially dined on the food best able to correct their deficiency, the team found. And although the web-builder had no choice about what landed in its web, it showed a surprising capacity to selectively absorb the particular nutrients it needed most.
The research does not explain how these predators sense and select the nutrients they need. But the findings should force a rethinking of standard ecological models of predator behavior, the team wrote in Friday's issue of the journal Science.
-- Rick Weiss
