Study: Why students shouldn't stay up all night

This study explains why students should not pull all-nighters to study.

Memory neurons lull us to sleep in order to consolidate what we've learned, say researchers from Brandeis University, who advise students against pulling all-nighters to prepare for tests.

Knowing that sleep, memory and learning are deeply intertwined, the Brandeis team set out to find out whether memory is consolidated during sleep simply because the brain happens to be at rest or whether those neurons provoke sleep in order to do their job.

In the study, which was published in the journal eLife, the researchers focused on a specific group of neurons called the dorsal paired medial (DPM), which are well known to implant memories in fruit flies.

In what's thought to be a first-of-its-kind observation, the flies slept more when the DPM neurons were activated, yet continued to buzz about when these neurons were switched off.

As these neurons start to convert short-term memory to long-term memory, they do their best to make sure you stay sleeping and actually hinder wakefulness, according to the study.

In the case of the fruit flies, the part of their brain in charge of memory and learning — called the mushroom body — The is also what determines wakefulness and, consequently, it's where the DPM are housed.

"It's almost as if that section of the mushroom body were saying 'hey, stay awake and learn this,'" says co-author Bethany Christmann, a graduate student at Brandeis. "Then, after a while, the DPM neurons start signaling to suppress that section, as if to say 'you're going to need sleep if you want to remember this later.'"

Christmann points out that knowing how sleep, memory and learning work together in the fruit fly brain can help researchers know what to look for when working with human participants.

"Eventually, it could help us figure out how sleep or memory is affected when things go wrong, as in the case of insomnia or memory disorders," she says.

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Head impacts lead to lower test scores

A new study shows that non-concussion head impacts can result in lower test scores and brain changes over time.

Repeated blows to the head during a season of contact sports may cause changes in the brain's white matter and affect cognitive abilities even if none of the impacts resulted in a concussion, according to a study published today in the journalNeurology.

Using a form of magnetic resonance imaging, or MRI, researchers at the Indiana University School of Medicine and the Geisel School of Medicine at Dartmouth College found significant differences in brain white matter of varsity football and hockey players compared with a group of noncontact-sport athletes following one season of competition. White matter is composed primarily of axons, the long fibers that transmit signals between neurons.

"The contact sports and noncontact-sports groups differed, and the number of times the contact sports participants were hit, and the magnitude of the hits they sustained, were correlated with changes in the white matter measures," said Thomas W. McAllister, M.D., chair of the IU Department of Psychiatry.

"In addition, there was a group of contact sports athletes who didn't do as well as predicted on tests of learning and memory at the end of the season, and we found that the amount of change in the white matter measures was greater in this group," Dr. McAllister said.

The study was conducted while Dr. McAllister was Millennium Professor of Psychiatry at Dartmouth.

"This study raises the question of whether we should look not only at concussions but also the number of times athletes receive blows to the head and the magnitude of those blows, whether or not they are diagnosed with a concussion," Dr. McAllister said.

Two groups of Dartmouth athletes were studied: 80 football and ice hockey players in the contact sports group, and 79 athletes drawn from such noncontact sports as track, crew and Nordic skiing. The football and hockey players wore helmets equipped with accelerometers, which enabled the researchers to compile the number and severity of impacts to their heads. Players who sustained a concussion during the season were not included in the analysis.

The athletes were administered a form of MRI test known as diffusion tensor imaging, which is used to measure the integrity of the white matter. They were also given the California Verbal Learning Test II, a measure of verbal learning and memory.

The study did not find "large-scale, systematic differences" in the brain scan measures at the end of the season, which the authors found "somewhat reassuring" and consistent with the fact that thousands of individuals have played contact sports for many years without developing progressive neurodegenerative disorders.

However, the results do suggest that some athletes may be more susceptible to repeated head impacts that do not involve concussions, although much more research would be necessary to determine how to identify those athletes.

More work would also be necessary to determine whether the effects of the head impacts are long-lasting or permanent, and whether they are cumulative.

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Irregular bedtimes can limit a child's brain power

By looking at how children scored on tests, researchers show that children who go to sleep at irregular times score lower on exams than children with regular bedtimes.

Going to bed at different times every night appears to reduce children's brainpower, a new British study suggests.

The research included 11,000 children in the United Kingdom whose family routines, including bedtimes, were recorded when they were aged 3, 5 and 7. At age 7, the children were given tests to assess their math and reading skills and spatial awareness.

Irregular bedtimes were most common at age 3, when around one in five children went to bed at varying times. By the age of 7, more than half the children went to bed regularly between 7:30 p.m. and 8:30 p.m.

At age 7, girls who had irregular bedtimes had lower scores on all three tests than girls with regular bedtimes. This was not the case among 7-year-old boys, according to the study, which was published online in the Journal of Epidemiology and Community Health.

Irregular bedtimes at age 5 were not associated with poorer brainpower in girls or boys at age 7. But irregular bedtimes at age 3 were associated with lower scores in reading, math and spatial awareness in both genders, suggesting that around the age of 3 could be a sensitive period for the development of mental skills.

The impact of irregular bedtimes seemed to be cumulative. Girls who never had regular bedtimes at ages 3, 5 and 7 had significantly lower reading, math and spatial-awareness scores than girls who had consistent bedtimes. The impact was the same in boys, but at any two of the three ages.

Irregular bedtimes could disrupt natural body rhythms and cause sleep deprivation, harming children's ability to acquire and retain information, the researchers said.

"Early child development has profound influences on health and well-being across the life course," said study author Amanda Sacker, from the department of epidemiology and public health at University College London. "Therefore, reduced or disrupted sleep -- especially if it occurs at key times in development -- could have important impacts on health throughout life."

While the study found an apparent connection between irregular bedtimes and reduced mental acuity, it did not prove cause-and-effect.

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