Brain networks come 'online' during adolescence to prepare teenagers for adult life

Brain networks come 'online' during adolescence to prepare teenagers for adult life

January 29, 2020

Science Daily/University of Cambridge

New brain networks come 'online' during adolescence, allowing teenagers to develop more complex adult social skills, but potentially putting them at increased risk of mental illness, according to new research published in the Proceedings of the National Academy of Sciences (PNAS).

Adolescence is a time of major change in life, with increasing social and cognitive skills and independence, but also increased risk of mental illness. While it is clear that these changes in the mind must reflect developmental changes in the brain, it has been unclear how exactly the function of the human brain matures as people grow up from children to young adults.

A team based in the University of Cambridge and University College London has published a major new research study that helps us understand more clearly the development of the adolescent brain.

The study collected functional magnetic resonance imaging (fMRI) data on brain activity from 298 healthy young people, aged 14-25 years, each scanned on one to three occasions about 6 to 12 months apart. In each scanning session, the participants lay quietly in the scanner so that the researchers could analyse the pattern of connections between different brain regions while the brain was in a resting state.

The team discovered that the functional connectivity of the human brain -- in other words, how different regions of the brain 'talk' to each other -- changes in two main ways during adolescence.

The brain regions that are important for vision, movement, and other basic faculties were strongly connected at the age of 14 and became even more strongly connected by the age of 25. This was called a 'conservative' pattern of change, as areas of the brain that were rich in connections at the start of adolescence become even richer during the transition to adulthood.

However, the brain regions that are important for more advanced social skills, such as being able to imagine how someone else is thinking or feeling (so-called theory of mind), showed a very different pattern of change. In these regions, connections were redistributed over the course of adolescence: connections that were initially weak became stronger, and connections that were initially strong became weaker. This was called a 'disruptive' pattern of change, as areas that were poor in their connections became richer, and areas that were rich became poorer.

By comparing the fMRI results to other data on the brain, the researchers found that the network of regions that showed the disruptive pattern of change during adolescence had high levels of metabolic activity typically associated with active re-modelling of connections between nerve cells.

Dr Petra Vértes, joint senior author of the paper and a Fellow of the mental health research charity MQ, said: "From the results of these brain scans, it appears that the acquisition of new, more adult skills during adolescence depends on the active, disruptive formation of new connections between brain regions, bringing new brain networks 'online' for the first time to deliver advanced social and other skills as people grow older."

Professor Ed Bullmore, joint senior author of the paper and head of the Department of Psychiatry at Cambridge, said: "We know that depression, anxiety and other mental health disorders often occur for the first time in adolescence -- but we don't know why. These results show us that active re-modelling of brain networks is ongoing during the teenage years and deeper understanding of brain development could lead to deeper understanding of the causes of mental illness in young people."

Measuring functional connectivity in the brain presents particular challenges, as Dr František Váša, who led the study as a Gates Cambridge Trust PhD Scholar, and is now at King's College London, explained.

"Studying brain functional connectivity with fMRI is tricky as even the slightest head movement can corrupt the data -- this is especially problematic when studying adolescent development as younger people find it harder to keep still during the scan," he said. "Here, we used three different approaches for removing signatures of head movement from the data, and obtained consistent results, which made us confident that our conclusions are not related to head movement, but to developmental changes in the adolescent brain."

The study was supported by the Wellcome Trust.

https://www.sciencedaily.com/releases/2020/01/200129104705.htm

Teens sleep longer, are more alert for homework when school starts later

Middle and high schoolers felt less sleepy and more engaged in academics

June 7, 2019

Science Daily/American Academy of Sleep Medicine

Preliminary findings from a new study of middle school and high school students suggest that they got more sleep and were less likely to feel too sleepy to do homework after their district changed to later school start times.

In fall 2017, the Cherry Creek School District in Greenwood Village, Colorado, delayed school start times for middle school by 50 minutes (changing from 8 a.m. to 8:50 a.m.) and for high school by 70 minutes (changing from 7:10 a.m. to 8:20 a.m.). Results show that one year after the change, self-reported sleep on school nights was 31 minutes longer among middle school students and 48 minutes longer among high school students.

"Biological changes in the circadian rhythm, or internal clock, during puberty prevents teens from falling asleep early enough to get sufficient sleep when faced with early school start times," said principal investigator Lisa J. Meltzer, Ph.D., an associate professor of pediatrics at National Jewish Health in Denver, Colorado. "This study provides additional support that delaying middle and high school start times results in increased sleep duration for adolescents due to later wake times."

The American Academy of Sleep Medicine recommends that middle schools and high schools should start at 8:30 a.m. or later to support teen health, alertness and safety. However, a previous data analysis by the Centers for Disease Control and Prevention found that only 14% of high schools and 19% of middle schools started at 8:30 a.m. or later.

The study involved more than 15,000 students in grades 6-11 who completed online surveys during school hours before the start time change in spring 2017 (n=15,700) and after the start time change in spring 2018 (n=18,607). The survey included questions asking about weekday and weekend bedtime, wake time and total sleep time; sleepiness during homework; and academic engagement.

The study also found that the percentage of students who reported feeling too sleepy to do their homework declined after the school start time delay from 46% to 35% among middle school students and from 71% to 56% among high school students. Scores on a measure of academic engagement were significantly higher after the start time change for both middle school and high school students.

"The study findings are important because getting enough sleep is critical for adolescent development, physical health, mood, and academic success," said Meltzer.

CCSD Superintendent Dr. Scott Siegfried said that the study supports firsthand feedback he's received from students across the 108-square-mile district.

"I don't know how many of our high school students have come up to me and said, 'This has changed my life for the better.' They've told me they're getting up to an hour of additional sleep before school starts," Siegfried said. "That extra sleep makes a real difference in terms of health and wellness. The input from our students and the numbers from this landmark study point to the same conclusion: The change in our start times has been a positive step and benefited our students' everyday routines."

The research abstract was published recently in an online supplement of the journal Sleep and will be presented Wednesday, June 12, in San Antonio at SLEEP 2019, the 33rd annual meeting of the Associated Professional Sleep Societies LLC (APSS), which is a joint venture of the American Academy of Sleep Medicine and the Sleep Research Society.

Meltzer is also the senior author of another abstract from this study, "Impact of Changing School Start Times on Teachers/Staff," which found significant benefits of later school start times for middle and high school teachers and school-based staff. They reported increased sleep duration due to later wake times, as well as improvements in daytime functioning.

"This is the first large study to examine the impact of healthy school start times on teachers and staff," said Meltzer. "It is important to consider that this policy change, critical for the health and well-being of students, also impacts other members of the school community."

https://www.sciencedaily.com/releases/2019/06/190607113825.htm