Intermittent fasting significantly increases neurogenesis in mice—even more than calorie restriction does. The finding is particularly interesting because the calorie-restricted mice and the fasting rats were eating the same number of calories. All that differed was the timing. Mice who fasted every other day had much more neurogenesis than rats who were on a constant calorie-restricted diet.

Another researcher, Tarique Perera of Columbia, presented compelling new data about antidepressant and neurogenesis. Other scientists have previously noted associations between antidepressant use and elevated rates of neurogenesis—Perera’s work strengthened this association considerably. Working with a macaque model of depression, Perera showed, unsurprisingly, that administering Prozac reversed the symptoms of depression. But when he gave the monkeys Prozac and then prevented neurogenesis by administering low doses of radiation to the temporal lobe, the anti-depressant was no longer effective. A simple and cool demonstration. There’s definitely more to be found there.

Finally, Sebastien Couillard-Despres discussed his interesting work on neurogenesis and aging. We know that the rate of neurogenesis gradually decreases as animals age. Couillard-Despres gave Prozac to 100, 200, and 400-day old mice (roughly corresponding to humans 15, 30, and 60 years old). She found that the mice of all ages had similar rates of proliferation of new neurons, but in these neurons had much higher rates of maturation and survival in the youngest mice. It’s a big step toward helping untangle the relationship between aging and neurogenesis.

Some fascinating presentations this afternoon on corollary discharge. Corollary discharge is the brain’s mechanism for distinguishing between self-generated and external stimuli. It helps the brain disregard sensations that are generated by our bodies own movements. For instance, when we view a painting, our eyes are constantly moving across it. Yet, the painting appears stable. For that, we can thank corollary discharge—the messages the brain’s motor centers send the sensory processing areas, warning them about upcoming movements. These messages allow the sensory centers to anticipate the sensory ramifications of the body’s movements and essentially tune them out. (One of today’s speakers provided the following brilliant analogy for corollary discharge: It’s as if the motor cortex is sending the body an e-mail telling it how to move and cc-ing the sensory cortex to keep it apprised of impending movements.)

In any case, today’s symposium had two highlights. The first was a presentation by Berthold Hedwig, who studied corollary discharge in the auditory systems of crickets. In order to attract mates, male crickets rub their wings together, generating loud songs. The songs are so loud, in fact, that the males, who are forced to listen to their own songs continuously, should be deafened by them. But they’re not—thanks to corollary discharge. Scientists in Hedwig’s lab discovered that when a male cricket sings, his motor system sends a signal, via one specific type of neuron, to his auditory pathway. This signal inhibits the auditory neurons, reducing their response to the cricket’s own sound. Interestingly, they also found that these signals are generated even when a cricket engages in “silent singing”—which occurs when a male has one of his wings removed, rendering him unable to create sounds.

Turning now to corollary discharge in humans…Judith Ford spoke about her research on the role that corollary discharge dysfunction may play in schizophrenia. Since corollary discharge provides a way for the brain to distinguish between self-generated and external stimuli, it’s logical that disruptions of this system might be associated with the hallucinations and delusions associated with schizophrenia. Ford’s results support this notion. She measured brain activity in schizophrenics and non-schizophrenics as they spoke aloud. Schizophrenics showed significantly less evidence of corollary discharge—their motor systems did not seem to be preparing their auditory systems for the sounds they were about to speak. Such impairments could help explain schizophrenics’ inability to distinguish between the internal and external, and Ford is continuing to test and expand upon this intriguing idea.

My other favorite symposium of the day was the one on “the new neuroimmunology.” For years, many scientists thought that neurons were the only cells in the body that didn’t express appreciable amounts of immune system molecules. Now, we know that’s not true, and it looks as though proteins of the immune system have surprising, important, and unique roles in the brain. I’m too tired and jet-lagged to go into the details, but if you’re interested, you should check out the work of Carla Shatz, who is providing compelling evidence that immune proteins expressed by neurons influence synaptic plasticity, and Lisa Boulanger, who is studying whether the immune proteins expressed in the brain may play a role in disease, particularly autism and schizophrenia. Neuroimmunology seems sure to yield some important new insights in the years to come.

The conference isn’t even half over yet, so stay tuned.

The meeting kicked off today with its annual “Dialogues Between Neuroscience in Society” talk, which is traditionally given by someone who’s not a neuroscientist. (In previous years, this talk has been given by Frank Gehry and the Dalai Lama.) This year, we heard from Jeff Hawkins, the computer scientist and entrepreneur who founded Palm Computing, Handspring, and, most recently, Numenta.

Hawkins, the author of On Intelligence, spoke about his effort to create intelligent machines by building computers that more closely mimic the workings of the brain. Artificial intelligence is a decades-old goal that has turned out to be more even more challenging than the experts once imagined. The root of the difficulty, Hawkins says, is that an intelligent machine must have an extraordinary amount of information about the world. We haven’t the foggiest idea about how to go about collecting all the necessary information, let alone how to program it into a machine. But humans manage to get all that data into their own heads. And by figuring out how, Hawkins believes, we can train computers to do it, too.

Hawkins’s theory is that the central feature of intelligence is the ability to predict. The brain’s neocortex, as Hawkins explains it, stores and transmits information using vertical hierarchies—with low-level sensory data converging on higher and higher processing centers. When the highest levels have interpreted the data, they pass that information back down the chain, helping the brain predict what it might sense next. Now, Hawkins and the scientists at Numenta are trying to create computers that process information in this hierarchical way (rather than linearly, as they do now), enabling them to learn, generalize, and predict.

The details of this effort have been covered widely (see here, here, and here), and Hawkins was at his most interesting when speculated about the more distant future. If we can build these machines—and Hawkins acknowledges that it is an if—what might we be able to do with them? There’s no reason we should limit ourselves to merely trying to duplicate human capabilities, Hawkins says. Once we’ve created machines that use hierarchical processing, we could design them to be bigger or faster than the human brain. Or design machines that can become intelligent about sensory data that humans can’t even detect. For instance, we could create systems that can learn about, interpret, and predict barometric pressure or other weather and climate data. Or scientists could play around with the settings and designs, making the computers better or worse at generalizing, for instance. This sort of tinkering could reveal important new insights about the brain itself. And thus, we come full circle.

Back tomorrow with more from the conference.

This Wednesday, the world will officially creep closer to nuclear apocalypse, according to the Doomsday Clock maintained by the Bulletin of Atomic Scientists.

The symbolic Doomsday Clock counts down the minutes to midnight, which represents the moment of global disaster. The Clock is currently set at seven minutes to midnight and will, presumably, move forward on Wednesday.

“The major new step reflects growing concerns about a ‘Second Nuclear Age’ marked by grave threats, including: nuclear ambitions in Iran and North Korea, unsecured nuclear materials in Russia and elsewhere, the continuing ‘launch-ready’ status of 2,000 of the 25,000 nuclear weapons held by the U.S. and Russia, escalating terrorism, and new pressure from climate change for expanded civilian nuclear power that could increase proliferation risks,” says a Bulletin press release.

The Bulletin of Atomic Scientists was founded in 1945 by Manhattan Project scientists worried about nuclear weaponry and war. Two years later, the Bulletin created the Clock. Its hands have moved 17 times since then, most recently in 2002, when they moved two minutes closer to midnight. The Clock has been set as late as two minutes to midnight–in 1953 after the U.S. and the Soviet Union conducted hydrogen bomb tests.

The decision to move the hands of the Clock this week was made by the Bulletin‘s boards of directors and sponsors, a group that includes 18 Nobel Laureates. But why does it seem unlikely that the consensus of a group of scientists—even Nobel-prize winning ones—will have much of an impact on U.S. nuclear policy? (Hint: see President George W. Bush’s positions on global warming, air pollution, and sex education, for starters.) And given that worries about a nuclear Iran and North Korea are poised to escalate, the Bulletin better leave itself some room to keep moving that minute hand forward.

Image © iStockphoto.com

Utility = E x V / Γ D

Where utility is the desirability of a task, E is the expectancy someone has of succeeding at it, V is the task’s value, Γ (the Greek letter gamma) is the task’s immediacy, and D is an individual’s sensitivity to delay. (The formula does not, alas, seem to account for such factors as the likelihood of being e-mailed a YouTube video during attempts to complete the task.)

Steel’s research also revealed that (surprise!) most people are doomed to fail when it comes to keeping New Year’s resolutions and that perfectionism may not be the root cause of procrastination.

Steel’s meta-analysis, published in the current issue of the American Psychological Association’s Psychological Bulletin, is based on a synthesis of nearly 700 other works on procrastination. And it only took him 10 years to finish it.

Image © iStockphoto.com