To help you prepare for the Society for Neuroscience's annual conference, New Scientist looks back at some of the news stories we have covered in 2011
Sleeping enhances memory – but only the important stuff (01 February 2011)
While we doze, our brain busily squirrels away memories. But not just any memories. During sleep, the brain specifically preserves nuggets of thought it previously tagged as important.
Jan Born of the University of Tübingen in Germany asked 191 adults to perform different memory tasks, such as learning word-pairs. Half were told to expect a test on the task nine hours later, while the others were told they would have a different kind of task. During the interval, some members of each group were allowed to sleep.
Participants who went to bed anticipating a post-nap quiz recalled 12 per cent more word pairs than those who slept with no expectation of a test. Furthermore, those anticipating a test also experienced more slow-wave sleep, known to be linked to memory consolidation.
Sleep did not significantly improve memory by itself; participants who were not anticipating a test performed as badly as one another, regardless of whether or not they'd had a nap before the exam.
The results improve our understanding of sleep, says Born."There is an active memory process during sleep that selects certain memories and puts them in long-term storage."
Boosted heat-shock proteins may fight Alzheimer's (10 April 2011)
Symptoms of Alzheimer's disease in mice have been eased by extra supplies of"heat shock" proteins, which re-fold or dispose of proteins implicated in the disease. Tohru Mizushima of Kumamoto University, Japan, used mice bred to mimic Alzheimer's symptoms. Half the mice were also engineered to make extra supplies of heat-shock protein (HSP) 70 in their brains.
Postmortems showed the brains of the HSP70-boosted mice to be free of the beta-amyloid plaques that clog the brains of people with Alzheimer's. That's because the boosted mice produced normal – rather than high – levels of the amyloid precursor proteins from which plaques are made.
Car braking system taps directly into the brain (01 August 2011)
A mind-reading device that taps into a driver's brain can recognize and act on the brain signals to stop the car precious milliseconds before the signals become leg movements.
With colleagues, Stefan Haufe from the Berlin Institute of Technology wired 18 volunteers to an EEG headset and asked them to drive at 100 km/h in a car simulator, closely following the car in front.
The EEG measured patterns of brain activity as drivers were forced to brake suddenly. It recorded three distinct patterns, which the team was able to use to detect the intention to brake before the driver moved, says Benjamin Blankertz, also at TU Berlin, who co-led the study. Sensors on the drivers'legs to monitor muscle tension provided another way to confirm the intention to brake.
The system reliably triggered the braking system 130 milliseconds sooner than the driver touched the pedal. At 100 km/h, that reduces the stopping distance by the length of a small car – potentially enough to prevent an accident.
Brain's synaptic pruning continues into your 20s (17 August 2011)
The synaptic pruning that helps sculpt the adolescent brain into its adult form continues to weed out weak neural connections throughout our 20s. As children, we overproduce the connections – synapses – between brain cells. During puberty, the body snips away some synapses while allowing others to strengthen. Over a few years, the number of synapses roughly halves and the adult brain emerges.
Or so we thought. Pasko Rakic at Yale University and colleagues at the University of Zagreb, Croatia, and the VU University Medical Center in Amsterdam, the Netherlands, have now found that the brains of adults in their 20s are still subject to synaptic pruning.
Rakic's team analyzed postmortem tissue from a brain region called the prefrontal cortex (PFC) in 32 people aged between one week and 91 years. Specifically, they calculated the density of dendritic spines that facilitate communication with other neurons through a synapse.
As expected, Rakic's team found that spine density increased rapidly during infancy, reaching a peak before the ninth birthday. It then began to fall away as pruning began. Intriguingly, though, spine density did not plateau after adolescence, as might have been expected, but continued to fall gradually until the late 20s. Rakic says the result could be good news for those hoping to gain new skills in their third decade. The period of pruning is associated with a heightened ability to learn – whether that is in picking up language skills or understanding new concepts, he says.
Habits form when brainwaves slow down (28 September 2011)
Habits may be difficult to change, but at least we now have an insight into how they form.
When a group of neurons fire simultaneously, the activity appears as a brainwave. Different brainwave frequencies are linked to different tasks in the brain. To track how brainwaves change during learning, Ann Graybiel and Mark Howe at the Massachusetts Institute of Technology used electrodes to analyse brainwaves in the ventromedial striatum of rats that were being taught to navigate a maze.
As the rats were learning the task, their brain activity showed bursts of fast gamma waves. Once the rats mastered the task, their brainwaves slowed to almost a quarter of their initial frequency, becoming beta waves. Graybiel's team suspects this transition reflects the point at which learning becomes habit.
Bernard Balleine , a neuroscientist at the University of Sydney, Australia, says the slower brainwaves may be the brain weeding out excess activity to refine behaviour.
Brain tweak turns wimpy mice into dominant leaders (05 October 2011)
Dominant mice can be humbled and wimps made mighty by altering the strength of electrical connections in their brains. The work may reveal mechanisms that dictate social standing in people.
Crucial brain connections directing a mouse's place in the social hierarchy sit in the medial prefrontal cortex. To investigate the mPFC's role in social ranking, Hailan Hu and her colleagues at the Institute of Neuroscience in Shanghai first worked out the hierarchy within a group of mice through challenges between pairs in tubes. When the mice came face to face, the subordinate animal would back out of the tube.
The team then injected a virus into some of the mice that inserts a gene into mPFC neurons. The gene amplifies transmission of electrical signals – a key step in strengthening connections. When the tests were repeated, previously subordinate mice that had received the virus became dominant. Likewise, implanting a gene that reduced the strength of connections caused previously dominant mice to become subordinate.
Hu says that the strengthened connections probably enable mice to exert more control over anger, emotion and aggression.
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