How brain maturation changes uninhibited teens to self-controlled adults

March 16, 2016 by Christopher Packham report
brain
White matter fiber architecture of the brain. Credit: Human Connectome Project.

(Medical Xpress)—One of the biggest problems in the U.S. justice system is the expanding number of states that treat teens as adults for certain crimes. While harsh treatment of adolescents might generate votes for tough-on-crime policies and candidates, an increasing amount of neurological research strongly suggests that the brain function of teens is vastly different than adult brains, and that impulsivity in adolescents is largely unavoidable.

However, little is yet known about the physiological development of prefrontal neurons after puberty. In the past, it's been established that the ability to resist impulsive responses matures after puberty, but neurologists want to know how this maps to changes in the brain. Recently, a collaborative of U.S. researchers published the results of a longitudinal study in the Proceedings of the National Academy of Sciences that tracked the neuronal responses of monkeys as they transitioned from puberty to adulthood, comparing brain activity at different stages of development.

Puberty begins in monkeys around 3.5 years of age, and they reach sexual maturity at around five years old. This corresponds to the human ages of approximately 11 years and 16 years, respectively. The researchers made neurophysiological recordings with a group of monkeys trained in an antisaccade task—meaning that they were trained not to look at a particular visual stimulus. They were tested once in and again as adults.

The researchers demonstrate that behavioral response inhibition to the stimulus significantly improved in adulthood. "Performance benefits were observed for all types of errors, including the ability to resist making an eye movement toward the cue," the authors write. But this finding came with one surprising conclusion: "This enhanced control was not achieved through a general slowing of reaction times in the adult stage; to the contrary, adult monkeys needed less time to process the cue and plan a correct saccade."

In the adults, the researchers observed an increase in baseline neural activity, even before the appearance of a cue. This was a significant finding, because low levels of baseline activity—as observed in adolescents—are predictive of errors. The researchers believe that this baseline neural activity is related to the preparation of a response, which is critical to inhibitory control.

The researchers report increased activity of purely visual neurons, and activity associated with vector inversion in the lateral intraparietal area, writing, "It is likely that this change between stages is associated with the neural representation of the goal through processes such as shifting of attention and vector inversion, which correspond to the encoding of a spatial location away from the stimulus." Furthermore, they observed that neurons in the exhibited vector-inversion behavior away from the stimulus without imposing a delay on response time.

The researchers note that their results leave open the possibility that neurophysiological changes may also occur in areas outside the prefrontal cortex that could also contribute to the improved responses of the adult monkeys, but which were not within the scope of the study.

Explore further: Childhood's end: ADHD, autism and schizophrenia tied to stronger inhibitory interactions in adolescent prefrontal cortex

More information: Behavioral response inhibition and maturation of goal representation in prefrontal cortex after puberty. PNAS 2016 ; published ahead of print March 7, 2016, DOI: 10.1073/pnas.1518147113

Abstract
Executive functions including behavioral response inhibition mature after puberty, in tandem with structural changes in the prefrontal cortex. Little is known about how activity of prefrontal neurons relates to this profound cognitive development. To examine this, we tracked neuronal responses of the prefrontal cortex in monkeys as they transitioned from puberty into adulthood and compared activity at different developmental stages. Performance of the antisaccade task greatly improved in this period. Among neural mechanisms that could facilitate it, reduction of stimulus-driven activity, increased saccadic activity, or enhanced representation of the opposing goal location, only the latter was evident in adulthood. Greatly accentuated in adults, this neural correlate of vector inversion may be a prerequisite to the formation of a motor plan to look away from the stimulus. Our results suggest that the prefrontal mechanisms that underlie mature performance on the antisaccade task are more strongly associated with forming an alternative plan of action than with suppressing the neural impact of the prepotent stimulus.

Related Stories

Childhood's end: ADHD, autism and schizophrenia tied to stronger inhibitory interactions in adolescent prefrontal cortex

March 14, 2014
(Medical Xpress)—Key cognitive functions such as working memory (which combines temporary storage and manipulation of information) and executive function (a set of mental processes that helps connect past experience with ...

How we keep track of what matters

February 23, 2016
When watching basketball, we are easily able to keep track of the ball while also making frequent eye and head movements to look at the different players. Neuroscientists Tao Yao, Stefan Treue and B. Suresh Krishna from the ...

Waking up the visual system

October 3, 2014
The ways that neurons in the brain respond to a given stimulus depends on whether an organism is asleep, drowsy, awake, paying careful attention or ignoring the stimulus. However, while the properties of neural circuits in ...

Researchers get a look at neural networks supporting working memory

August 21, 2015
(Medical Xpress)—Translating stored information into behaviorally appropriate responses is a pretty fundamental brain activity, supporting biological, social and survival behaviors. Researchers have long believed that the ...

Brain study finds that practice doesn't always make perfect

March 10, 2016
Even our most practiced movements are imperfect. When pro basketball players shoot free throws, they need to release the ball the same way every time. But they still miss game-winning shots.

Study explains why mistakes slow us down, but not necessarily for the better

January 21, 2016
Taking more time to make decisions after a mistake arises from a mixture of adaptive neural mechanisms that improve the accuracy and maladaptive mechanisms that reduce it, neuroscientists at New York University have found. ...

Recommended for you

'Residual echo' of ancient humans in scans may hold clues to mental disorders

July 26, 2017
Researchers at the National Institute of Mental Health (NIMH) have produced the first direct evidence that parts of our brains implicated in mental disorders may be shaped by a "residual echo" from our ancient past. The more ...

Laser used to reawaken lost memories in mice with Alzheimer's disease

July 26, 2017
(Medical Xpress)—A team of researchers at Columbia University has found that applying a laser to the part of a mouse brain used for memory storage caused the mice to recall memories lost due to a mouse version of Alzheimer's ...

Cognitive cross-training enhances learning, study finds

July 25, 2017
Just as athletes cross-train to improve physical skills, those wanting to enhance cognitive skills can benefit from multiple ways of exercising the brain, according to a comprehensive new study from University of Illinois ...

Brain disease seen in most football players in large report

July 25, 2017
Research on 202 former football players found evidence of a brain disease linked to repeated head blows in nearly all of them, from athletes in the National Football League, college and even high school.

Zebrafish study reveals clues to healing spinal cord injuries

July 25, 2017
Fresh insights into how zebrafish repair their nerve connections could hold clues to new therapies for people with spinal cord injuries.

Lutein may counter cognitive aging, study finds

July 25, 2017
Spinach and kale are favorites of those looking to stay physically fit, but they also could keep consumers cognitively fit, according to a new study from University of Illinois researchers.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

brahmix
1 / 5 (1) Mar 17, 2016
Crime: is it a lack of self control or a failure to adhere to law?

In the world today, where parents are forced to talk to delinquents, can one not expect that the under-developed pre-frontal cortex will not learn the basic cause-and-effect of lawlessness?
This is a manufactured tragedy - California dreaming while the world dies screaming (adlib, ole' Maiden).
Self-control is not a natural eventuality - it is learned. Good culture, good manners, lawfulness - these are products, not of neurons mapping themselves, but by being taught what is Good through good example and consequences to own actions as a very young child- the lessons force the neural path, not the other way around.
So, in short: lack of self control is proof positive of criminality - i.e. a social deviance that is detrimental to society in terms of peace, security and well being.
Frank Hubert, in his wonderful book: 'Dune', linked the lack of self-control to the lack of humanity (Gom Jabbar).

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.