Memories are unreliable, at least for humans.

According to MIT scientist (and Nobel Prize winner) Susumu Tonegawa, as quoted in Scientific American, only humans have false memories.

“Humans are the most amazing, imaginative animals,” he said. “We are thinking. Lots of things are going on. Humans are recording what happens and passing it on.”

An imperfect memory, Tonegawa said, may be the price we pay for the imagination and creativity that makes us human.

The phenomenon of humans’ false memory is well-documented—in many court cases, defendants have been found guilty on testimony from witnesses and victims who were sure of their recollections, but DNA evidence later overturned the conviction.

But now, Tonegawa and his colleagues have succeeded in also creating false memories in mice, hoping to further understand where and how these fake memories are made in the human brain.

Memories are stored in networks of neurons that form memory traces for each experience we have. Scientists call these traces engrams, and can identify the cells that make up part of an engram for a specific memory and reactivate it with a technology called optogenetics.

Using optogenetics, Tonegawa’s research team started the experiment by putting mice in a chamber and recording their memories of that chamber. The chamber was harmless and pleasant enough that the mice felt comfortable exploring the space. The next day, the researchers moved the mice into a different chamber, stimulating the memory of the previous chamber. The scientists also lightly shocked the rodents’ feet.

On the third day, the mice were placed back into the first chamber. They now froze in fear, even though they had never been shocked there. A false memory had been incepted—the mice feared the memory of the first chamber because when the shock was given in the second, they were reliving the memory of being in the first.

The team discovered they could both implant false memories and that the neurological traces of these false memories are identical in nature to those of authentic memories. “Whether it’s a false or genuine memory, the brain’s neural mechanism underlying the recall of the memory is the same,” says Tonegawa.

The MIT team is now planning further studies of how memories can be distorted in the brain.

The study is published in the current edition of Science.

Image: Steve Ramirez and Xu Liu

But what about creatures that are blind?

If you haven’t already, meet the eastern or common mole, Scalopus aquaticus. In addition to being cute in a kind of creepy way, these mammals are blind and have teeny ears. But they are remarkably good at finding their prey.

Ken Catania, a neurobiologist at Vanderbilt who studies animal sensory systems (he’s one of the researchers responsible for the sensitive alligator study we covered in Science in Action) decided to investigate the mole’s sense of smell.

He didn’t think the moles smelled in stereo—in fact, just the opposite. “I came at this as a skeptic. I thought the moles’ nostrils were too close together to effectively detect odor gradients.” But he’s a scientist—he needed evidence to support his assumption.

To test the theory of stereo smell, he created a radial arena with food wells spaced around the 180-degree circle with the entrance for the mole located at the center. He then ran a number of trials with pieces of earthworm placed randomly in different food wells.

When the mole first entered the arena, it moved its nose back and forth as it sniffed. Then, it seemed to zero in on the food source, moving in a direct path. This was pretty remarkable, and made Catania reconsider the idea of stereo sniffing.

“It was amazing. They found the food in less than five seconds and went directly to the right food well almost every time,” Catania said. “They have a hyper-sensitive sense of smell.”

Catania then blocked one of the moles’ nostrils with a small plastic tube. When their left nostrils were blocked, the moles’ paths consistently veered off to the right, and when their right nostrils were blocked, they consistently veered to the left. They still found the food but it took them significantly longer to do so.

Voilà! Stereo-smelling! (A video of the trials demonstrates this very clearly.)

Catania proved himself wrong and published his findings this week in Nature Communications.

What about the rest of us mammals? Do we smell in stereo?

“The fact that moles use stereo odor cues to locate food suggests other mammals that rely heavily on their sense of smell, like dogs and pigs might also have this ability,” Catania says. But as for humans, he remains skeptical. I guess stereo- vision and hearing is enough…

Image: Ken Catania

The findings may help explain why mammals evolved such large and complex brains, which in some cases ballooned 10 times larger than relative body size. The authors reconstructed fossils of two Early Jurassic Period small shrew-like pre-mammals – Morganuocodon and Hadrocodium—using a medical imaging technique called X-ray computed tomography or CT.

The 3D images gave the researchers a magnified, inside view of the brain and nasal cavities of the fossils. The team observed that the nasal cavity and related smell regions were enlarged in the pre-mammal fossils, along with areas of the brain that process olfactory information. Both characteristics indicate an improved sense of smell in pre-mammals.

“Now we have a much better idea of the historical sequence of events and of the relative importance of the different sensory systems in the early evolution of mammals. It paints a much more vivid picture of what the ancestral mammal was like and how it behaved, and of our own ancestry,” says lead author Tim Rowe, of the University of Texas.

In fact, comparing the mammal brain endocasts with fossils of other groups, like those of primitive reptiles called cynodonts, revealed that the brains of the Morganuocodon and the Hadrocodium were almost 50 percent larger than the brains of mammal precursors.

Nature News reports that

With this foundation in place, later mammals could have siphoned off some of those resources for colour vision, echolocation and even, in the case of the platypus, the ability to sense electric currents.

Rowe says this is just step one. “Now that we have a general picture of the brain in mammals ancestrally, we plan to explore the subsequent diversification of the brain and sensory systems as mammals evolved and diversified. This will unlock new secrets about how huge brains and extreme sensory adaptations evolved in mammals… It is all very exciting!”

Image: Matt Colbert, Univ. of Texas at Austin

Earth

The Gulf oil spill—the number of gallons spilled and the controversy surrounding the damage seems to top many lists this year. Nature even named Jane Lubchenco, head of NOAA, its newsmaker of the year for how she handled the crisis.

Natural disasters often took the front page in 2010 with the Haitian earthquake and the eruption of Eyjafjallajökull topping many lists. The hard-to-pronounce Icelandic volcano also made many of the best science images of the year lists.

DiscoveryNews ends the year on a positive note with “How Humans Helped the Earth in 2010,” a slide show with text concerning recent strides in alternative energy, species and habitat conservation efforts and individual efforts to go green (electric cars, white roofs and saving energy).

For more environmental news of the year, New Scientist’s Short Sharp Science has a great review and the Nature Conservancy has a best/worst list on its site.

Life

Teeny, modified life stole the spotlight this year—the J. Craig Venter Institute’s so-called “synthetic cell” and GFAJ-1—the bacteria that incorporates arsenic into its DNA—or so NASA scientists claimed.  Science writer Carl Zimmer discredited the arsenic bacteria paper on Slate; NASA author Felisa Wolfe-Simon defended herself in Science. Fun stuff!

The spread of pesky bedbugs was number six in Discover’s “Top 100 Science Stories of 2010.”

Nature’s great article this past summer on eradicating mosquitoes was among its readers’ top choices of the year.

Looking for something a little bigger and less controversial? New Scientist has “The coolest animals of 2010,” which includes a scorpion-eating bat and a fly thought to be extinct for over 160 years!

NPR found it was a very good year for Neanderthals—their genome was sequenced, brain examined and diet expanded.

Remarkably, the Census of Marine Life tops the BP oil spill in the Deep Type Flow blog’s biggest marine science stories of the year for its sheer numbers:

…over 500 research expeditions covering every ocean, over 2,500 scientists and the discovery of over 6,000 species new to science and published in over 2600 peer-reviewed papers.

Space

ScienceNow’s most popular story of all time, not just 2010, was “Does Our Universe Live Inside a Wormhole?” A wonderful theory that we also covered last spring.

Exoplanets, in part thanks to the Kepler mission, were all over the news this year—whether it had to do with size, atmosphere or number within a star system. Discover’s interview with local exoplanet hunter (and California Academy of Sciences Fellow) Geoff Marcy made number 11(!) on their 100 top stories list.

A little closer to home, Jupiter’s missing stripe and Neptune’s tale of cannibalism are included in New Scientist’s most popular space stories of 2010.

Our Moon and Saturn’s moons made news throughout the year and the top lists on Universe Today and Wired this week.

Universe Today also included SDO’s new views of the sun in their top stories list. Stunning!

Hubble celebrated its 20^th year in space this year by taking even more beautiful images. Several are included in Bad Astronomy’s “Top 14 Astronomy Pictures of 2010.”

Technology

Electric cars and NASA’s new foray into commercial spacecraft are included in Scientific American’s top ten stories of the year.

The Large Hadron Collider was very busy this year, and topped many lists. Another machine at CERN made news (and also topped Nature’s readers’ choice list) when it was able to capture antimatter for a sixth of a second!

Graphene not only garnered a Nobel Prize this year, the material (and it’s potential) also made news and top science lists of the year.

DiscoveryNews put plastics on their 2010 list—whether its finding new ways of removing plastic from the oceans or engineering smarter plastics.

What was your favorite science story of the year? Share with us by adding it to the comment section below!

Image by Les Stone, International Bird Rescue Research Center/Wikipedia

The amygdala is a small, almond-shaped structure in the brain. We have two, one on each side of the brain, and researchers understand they play a large part in our emotions. The amygdala can vary in volume from 2.5 cubic millimeters to twice that size.

Researchers have known for some time that the size of non-human primates’ amygdalae depends on the social circles of the particular species. The larger the amygdala, the more social the primate. That lead the authors of a new paper in Nature Neuroscience to wonder if the same could be true of humans.

Using magnetic resonance imaging, the researchers studied 58 healthy humans’ brains—focusing on the amygdala and the hippocampus, another emotional area of the brain. They also had the subjects fill out surveys about their social lives—their number of friends and the groups to which they belonged.

While researchers detected no variations in the hippocampus, they found that the volume of both amygdalae was greater for those people with more robust social lives. The researchers also measured “happiness”—things like life support and social satisfaction—to make sure it wasn’t something else causing the larger-sized amygdalae. Sure enough, the volume of the amygdala did not correlate with other social variables.

While scientists can see that the relationship between the amygdala and social groups exists, they don’t know which causes the other. Do larger social circles increase the amygdala’s size, or does a larger amygdala naturally lead the person to larger social groups? With all of the current brain research underway, we may soon find out which comes first.

Images are generated by Life Science Databases (LSDB)

Human brains vs. Neanderthal brains

German and French researchers compared CT scans of human and Neanderthals at various growth stages and published their results in Current Biology. The brains in each species started out the same size and shape, but as each grew, their shapes changed. Both begin elongated, but human brains become more round and globular. Despite having similarly large brains, according to Science Now:

The differences suggest that Neandertals did not see the world the same way we do and may not have been as adept at language or forming complex social networks.

Human brains vs Chimpanzee brains

Excitingly, the same researchers had another similar study published last Friday. Using the same scanning techniques, they compared chimp and human brains at different ages. Unlike the Neanderthals, even at birth, the brain shape is different and in fact, according to the paper, “there is no overlap between the two species throughout ontogeny.” In addition, “the shape changes associated with this early “globularization phase” are unique to humans.”

Another study published last week in PLoS Genetics explains a by-product of this brain uniqueness—a weaker immune system. It all has to do with a type of white blood cells called natural killer cells, or NK cells. NK cells are crucial in fighting disease in both chimpanzees and humans, but they do a better job in chimps— chimps are not susceptible to diseases like HIV and malaria.

Human NK cells seem to have evolved differently. NPR had a great story on the research this week.

The kind of NK cells that are good for getting lots of blood to the developing fetus are not as good for dealing with infection, and vice versa.

And whereas the chimpanzees develop the cells good for infections,

The human system, on the other hand, seems to be optimized for getting lots of blood to the developing fetus so our big brains can grow the way they’re supposed to.

More Human Brain

Finally, how about two items that are good for the brain? A study published in PLoS One yesterday shows that the video game Tetris may reduce Post-Traumatic Stress flashbacks.  And Jonah Lehrer, one of our favorite neuroscience writers, has a great blog post in Wired today about the pleasure we get from preparing our own meals.

Image from Science- Credit: (baby skulls, L) P. Gunz et al., Current Biology, 20 (9 November 2010); (Adult skulls) Philipp Gunz/MPI EVA Leipzig

Where’s the Plastic?

While there’s been much coverage of plastic in the Pacific Ocean, the actual amount of garbage in the Great Pacific Garbage Patch remains a mystery. In addition, we’ve heard little of the garbage in the Atlantic. This week researchers published an article in Science quantifying the amount of plastic garbage in the Atlantic. And their results were surprising. From New Scientist:

The amount of floating plastic trapped in a north Atlantic current system hasn’t got any bigger in 22 years, despite more and more plastic being thrown away.

(New Scientist also has a great video on the process of collecting the plastics.)

So where is it? That seems to be a mystery, even to the researchers. An article in Science reports:

That suggests that either people are keeping their trash on land or plastic is going to some unknown destination in the sea.

It may also just be too small to catch.

Where’s the Oil? Still There

Not surprisingly, scientists are reporting that despite a NOAA report saying that almost three-quarters of the oil released in the Gulf is gone, the oil actually still exists.

In late June, scientists followed a plume of oil that was a mile long and 650 feet thick as it traveled southwest of the blown well. It was average as these plumes go, but, as Wired reports so well:

its behavior may give some indication of what is happening elsewhere…

…the results suggest that lots of oil is still in the Gulf, and will be there for a long time.

Their study, focusing on the microbes breaking down the oil, was also published in Science. Other researchers from the University of Georgia are also stating that the oil is still there.

Athletic Brain

Ever since Malcolm Gladwell published his great article about brain damage in football players in the New Yorker last fall, there’s been a lot to read and watch on the subject. This week the New York Times reported that Lou Gehrig may not have had Lou Gehrig’s disease (!)—but perhaps his illness was a result of concussions (and other brain trauma), much like the football players who receive hit after hit to the head.

Also, writing in Discover this week, one of our favorite science writers, Carl Zimmer, went inside the brain to find out what happens to the neurons of a linebacker.

Happy reading. Let us know what other science news sparked your interest this week.

Now you can add invertebrates to the list. Researchers from the University of Maryland are using crayfish to unravel the brain activity involved in human decisions. Their work was published online yesterday in the Proceedings of the Royal Society B.

“Matching individual neurons to the decision making processes in the human brain is simply impractical for now,” explains University of Maryland psychologist Jens Herberholz, PhD, the study’s senior author.

“History has shown that findings made in the invertebrate nervous systems often translate to more complex organisms. It’s unlikely to be exactly the same, but it can inform our understanding of the human brain, nonetheless.”

Using a simple model and a non-invasive method that allowed the crustaceans to move freely, the researchers offered juvenile Louisiana Red Swamp crayfish a simultaneous threat and reward: ahead lay the scent of food, but also the apparent approach of a predator.

In some cases, the “predator” (actually a shadow) appeared to be moving swiftly, in others slowly. To up the ante, the researchers also varied the intensity of the odor of food.

The crayfish would either escape or play dead depending on the threat or the nearness of the food. To make a quick escape, the crayfish flip their tails and swim backwards, an action preceded by a strong, measurable electric neural impulse. If the predator (shadow) seemed to be moving too fast, the crayfish would freeze. Each decisive action took only a matter of milliseconds and the specially designed tanks could non-invasively pick up and record these electrical signals.

Don’t you wish most of your decision-making could happen in milliseconds and was that simple?

Their study is possibly the first to isolate individual neurons involved in value-based decisions. Currently, there’s no direct way to do this with a human brain. (To gain insight on the areas of the human brain involved in decision-making, watch the Science in Action video here.)

Image credit: David D. Yager/Jens Herberholz

Two research articles published online yesterday in Nature publications follow mice research in two behavioral directions—one in father-child bonding and one on exhibiting pain—that may help humans in the future.

Neuroscientists in Calgary found that male mice that were allowed to nuzzle with their infant offspring were able to recognize those offspring as adults. According to Science Now, “That recognition correlates with new neuron growth in dad’s brain, the team reports online today in Nature Neuroscience. When Mak and Weiss injected a marker that tags newly formed neurons into the fathers just after their pups were born, they found up to 40% more new neurons in… mice that had nuzzled their pups.

“The results suggest that in mice, and perhaps in humans, young babies and dads bond biologically in ways that can last a lifetime.”

Other scientists in Canada studied facial expressions in mice, looking for signs of pain. They discovered that when subjected to moderate pain stimuli, mice showed discomfort through facial expressions in the same way humans do. (Watch Science in Action’s story about human facial expressions here.)

Their study, published online May 9 in the journal Nature Methods, also details the development of a Mouse Grimace Scale that could inform better treatments for humans and improve conditions for lab animals.

Continuing experiments in the lab will investigate whether the scale works equally well in other species, whether drugs given to mice after surgical procedures work well at their commonly prescribed doses, and whether mice can respond to the facial pain cues of other mice.

Creative Commons image by George Shuklin