It's normal for kids to want to learn all about sex, especially during puberty and adolescence when reproduction becomes the brain's top priority. For this we can thank the specifics of teen-brain development.
Think of an adolescent jungle primate watching another band with such fascination that he (or she, in some species) leaves his companions, and endures the slings and arrows of being without allies at the bottom of another troop's pecking order—all for a chance to get it on with exotic hotties in the future. The things our genes do to guarantee genetic diversity!
Now, fast-forward to a young guy discovering the mind-boggling novelty of Internet erotica:
I started looking at Internet porn when I was 11. I immediately became hooked, and spent hours daily viewing porn. Simply seeing a pair of exposed breasts was enough to get me off. But desensitization soon kicked in, and I began developing fetishes to get the same hit from porn. It started out with different ethnicities, then lesbians, then watersports, then scat/beastiality/BDSM/tranny, and then any combination of the above to create the sickest porn imaginable. I can remember sitting in school fantasizing about sick porn that I could search for that night.
What is it about the adolescent brain that makes this guy's experience not unusual? Answer: During adolescence a temporary neurological imbalance develops. The "sex, drugs and rock & roll" part of the brain is in overdrive. The "let's give this some thought" part is still under construction, and won't reach maturity until adulthood.
This recipe for impulsive and risky behavior rearranges other adolescent-mammal brains too. It is evolution's way of driving the brash independence many young mammals need as they seek mates and carve out territories. In the brain's cost-benefit analysis, the scale is tipping heavily in the direction of possible rewards.
There's a kicker though. The capacity of our teen to wire up new sexual associations mushrooms around 11 or 12 when billions of new neural connections (synapses) create endless possibilities. However, by adulthood his brain must prune his neural circuitry to leave him with a manageable assortment of choices. By his twenties, he may not exactly be stuck with the sexual proclivities he falls into during adolescence, but they can be like deep ruts in his brain—not easy to ignore or reconfigure.
Sexual-cue exposure matters more during adolescence than at any other time in life. Now, add to this incendiary reality the lighter fluid of today's off-the-wall erotica available at the tap of a finger. Is it any surprise that some teens wire semi-permanently to constant cyber novelty instead of potential mates? Or wire their sexual responsiveness to things that are unrelated to their sexual orientation? Or manage to desensitize their brains—and spiral into porn addiction?
Incidentally, are you a guy remembering your own adolescence—and how you could never climax enough during those years? Perhaps you're supposing that Internet porn would have been a splendid innovation. If so, read these two articles: Porn, Novelty and the Coolidge Effect and Porn Then and Now: Welcome to Brain Training. Porn, its content, the way it's delivered, and its potential effects on the brain have changed radically. For today's users, more orgasm can lead to less satisfaction.
When we dug into the brain research on adolescents, we were astonished at how malleable teen brains are. Radical changes in the sexual environment hit them hardest. Here are four vulnerabilities unique to teen brains:
1. Much stronger "Go get it!" signals
The reward circuitry is the core of all drives (including libido), emotions, likes, dislikes, motivation...and addiction. In adolescence, sex hormones propel this ancient circuitry into a window of hyperactivity, which subsides by the early twenties. As journalist David Dobbs explains.
We all like new and exciting things, but we never value them more highly than we do during adolescence. Here we hit a high in what behavioral scientists call sensation seeking: the hunt for the neural buzz, the jolt of the unusual or unexpected. ... This love of the thrill peaks at around age 15.
The brain's sensitivity to dopamine, the "Gotta get it!" neurochemical crests, which spurs novelty-seeking, overrides executive control, and helps consolidate learning and habits.
In fact, teen brains respond to anything perceived as exciting with twice to four times the reward-circuitry activation of adults thanks to their extra dopamine sensitivity and bigger spikes of dopamine. Both novelty and searching/seeking spike dopamine in all human brains, but cyber erotica's endless possibilities prove an irresistible lure for many teens.
The first time I looked at those hot pictures the feeling seemed to be out of this world, just ineffable. Suddenly I knew there was something worth living for, everything else was just boring, everyday life. I fled to this artificial drug: porn and masturbation. It was not unusual to watch porn for hours a day.
"Ineffable?" Yes. Teens are more likely to register sexual arousal, and other highs, as transcendental, memorable experiences. That is why you can still recall the shimmering details of that first centerfold. But there's more evidence of hypersensitivity to thrills. (Click chart to enlarge.)
Alas, their heightened sensitivity to reward automatically renders teens more susceptible to addiction than if they encountered the same thrills later in life.
2. Decreased sensitivity to aversion
Having spent Friday night playing "World of Warcraft" until 4AM, while washing down eight slices of pizza and a bag of Dorritos with a six-pack of Mountain Dew, our hero is ready to do it all again come Saturday night. Research shows that teens are less deterred by symptoms of excess. Aversion is a reward-circuitry function, and teens can handle more wattage before their circuits overload
Ever wonder why Slasher + Teens (sex)2 = Summer Box-Office Hit? It all comes down to the marvels of the brain. No wonder porn images that adults find shocking, "eeeew," or violent, register as abnormally exciting to teens. Also keep in mind that teens are less able to take other people's feelings into account (even bad actors).
When I was 14/15 I encountered [transexual] porn while surfing the Internet. I still remember the graphic nature of the advert. Something just snapped in my pubescent brain. All the straight and lesbian porn I had watched for several years seemed ordinary. My heart started racing. My head was thumping, and the fear of getting caught...not just watching porn, but watching what some could consider not exactly 100% straight porn...made it all the more memorable. I remember crying after I finished. I didn't know what came over me. I was so terrified I wanted to curl up into a ball in my bedroom. But I didn't stop watching it. I was still attracted to girls, but with the [transexual] porn, I could orgasm quicker.
3. Weaker "Stop!" signals
The sex hormones that initiate teen sensitivity to thrills unfortunately do nothing to speed up development of their brain's self-control center. A teen brain is like a new car with a Ferrari engine and Ford Pinto brakes.
At puberty, an extremely reactive "accelerator" comes online: the brain's emotion-motivation mechanism, or reward circuitry, located below the rational cortex. It overpowers the "brakes," the brain's "CEO" or prefrontal cortex in the forehead, which won't fully mature for a decade. The latter assesses risk, thinks ahead, chooses priorities, allocates attention and controls impulses.
Meanwhile, teens often base their choices on their emotional impulses as opposed to reasoning or planning. Later, as the prefrontal cortex matures, there will be fewer "I can't believe he did that" moments. Teens make sounder judgments and modulate mood, plan and remember more effectively.
In the meantime, teens have trouble perceiving the consequences of "going for it." Again, this is no accident. Daredevil tendencies during adolescence serve species that must take risks then to strike out on their own or find mates. In the case of adolescent humans, evolution has simply not had time to adapt to the hazards of recreational drugs, fast cars, or excessive consumption of junk food, online gaming or Internet porn. That's why we have the Darwin Awards.
4. Extreme neuronal growth followed by pruning
Human brains go through two stages of dramatic neuronal growth: one in utero and throughout the first several months of life, the other between the ages of 10 and 13— just when most boys (and now, many girls) begin to look at Internet porn. Ideally, during this critical developmental period, we humans are exposed to age-appropriate sexual behavior. We learn how to flirt and connect with potential partners.
This second burst of neuronal activity entails first multiplication and then subtraction of neural connections. No wonder mood swings are a hallmark of adolescence! Together, genes and environment sculpt the clay of a teen's frontal cortex. As use-it-or-lose-it proceeds, the brain reorganizes and fine-tunes itself:
The cortex prunes away little used circuits, while strengthening well worn neural pathways. Nerve cell axons in favored pathways become better insulated with myelin, increasing the speed of nerve impulses. Little branches that receive messages (called dendrites) grow like vines to better hear the incoming signal. The connections between axons and dendrite (synapses) multiply on strong circuits and vanish on weaker ones. In the end you have memories, skills, habits, preferences and ways of coping that stand the test of time. (ibid., Dobbs, emphasis added)
In less glowing terms, we restrict our options—without realizing how critical our choices were during our final, pubescent, neuronal growth spurt. According to researcher Jay Giedd, (See this talk - Brain Evolution and the Digital Revolution, by Jay Giedd )
If a teen is doing music or sports or academics, those are the cells and connections that will be hardwired. If they're lying on the couch or playing video games or MTV [or Internet porn], those are the cells and connections that are going to survive.
This is one reason why polls asking teens how Internet porn use is affecting them are unlikely to reveal the extent of porn's effects. Kids who have never masturbated without porn have no idea how it is affecting them. (It's like asking them, "How has being male affected you?") They have nothing to compare with. Keep in mind that older porn users often do not connect their porn-related symptoms with heavy porn use—even when they develop porn-induced sexual dysfunction (PISD). Porn always seems like the "cure," because even if they can't get it up for sex, they can usually get it up if they watch enough extreme porn. Can we expect teens to figure it out?
Same problem with asking them about porn's effects on mood. Users always "feel better" when using, even if the more they use, the worse they feel overall. So why would porn be seen as the problem? Moreover, when users try to quit, they sometimes face weeks of severe withdrawal symptoms, so controlling use can be mistaken for the problem instead of the solution.
Fact is, most heavy users who are going to hit a wall from excess, don't do so until their twenties—just about the time their reward circuitry has curtailed its hypersensitivity. For example, by adulthood, dopamine receptors in the reward circuitry gradually decrease by a third or a half. Now, thrills aren't as thrilling, and the consequences of excess are more disconcerting. Once nature's foot is off the reward accelerator, it's time for a hunter-gatherer to settle down and raise some youngins.
Meanwhile, the adolescent brain is ripe for a perfect storm as the genetically driven hunt for novelty and the unexpected collides with the endless erotica of the Internet. Hypnotic Web-surfing—requiring no effort but scrolling and fapping—replaces leaving one's tribe to search the savanna for fertile mates.
When I was 18, I had sex for the first time. When she said she was "down all the way", I ran to the nearest store to pick up condoms like I had the Reaper chasing me. After the deed, my thoughts were, "Hmm...it didn't feel that much different from masturbation, and it required a hell of a lot more work! Meh, I'll stick to porn and not bother with a girlfriend."
Another guy responded,
My thoughts EXACTLY. Just back pain, muscle strain, breathlessness, sweatiness and performance anxiety. MUCH less stress to just crack one off, plus you got your own 'Iron Fist' that gets you off better than that real vagina. Not only that, you always get a 'good visual' with a 'porn girlfriend.' You can see all those beautiful body contours in perfect lighting, breasts n' butts n' thighs look glorious, and *always* visible. In real life that's rarely the case. The first time I did it, I didn't truly enjoy it (even though we both came a lot). My first time should've felt like a TRIUMPH, given how 'successful' it was, but it felt artificial. It was then I KNEW there was perhaps something a tad wrong. The sex in my *mind* always seemed sexy and enjoyable. The *real* sex I had was primarily industrial and unexciting. Not good.
Today's teens sometimes wire their arousal to Internet porn's unnaturally intense, synthetic stimuli for as long as a decade before they try to connect with real partners. (See pages of self-reports of adolescent porn use.) The situation is even more precarious if a teen's innocent pursuit of jollies has led to more fundamental brain changes, i.e., addiction. Again, teens are more susceptible to addiction than adults, due to their hyperactive reward circuitry and immature executive control.
More important, while glued to his screen(s), a young guy is not learning courtship skills and or spending time around real potential mates—the very tasks for which mammalian adolescence evolved. His brain is not wiring his sexual pleasure to flirting, pheromones or three-dimensional partners of normal proportions providing ordinary simulation. In days gone by, nervous young men fumbled through one-on-one, vanilla sex for a bit before graduating to the kama sutra. Now, a 17-year old virgin envisions his first time with his first love as involving two of her friends, handcuffs, strap-on gear and a massive amount of lube.
Nor will our hero be able to explain to a future sweetheart his apparent lack of ardor, his fading erection and condom mishaps, or his frantic attempts to stay hard by fantasizing about watching someone have sex. He doesn't have a clue why he isn't responding, or how to go about repairing the damage. Nor do his peers.
I'm really afraid that since all my brain knows is watching porn (these are really the only two sexual encounters I've ever had, and they're both complete failures) that I've messed up my brain soooooo much that I'll never get better. I mean, all my sexual experiences from my youth are from porn. For the most formative years of my life, I've only ever orgasmed to porn. That's all my brain knows. Will I ever be able to get it up with a normal woman? Will I ever be attracted to a normal woman the way I am to those pixels on the computer screen? I'm really afraid that I've messed up myself for good. Can I change?
Alas, many mates are too confused or hurt to hang around in such a disheartening situation. Resulting performance anxiety makes our hero's situation worse. Could this explain why 36 percent of young Japanese guys and 20 percent of young Frenchmen have no interest in real partners? Or why abstinence rates in the States are increasing?
Today, a 13-year old's sexual pathways are chiseled by hardcore porn, multiple windows, and constant clicking. In contrast, Dad's matured to Sally next door and his fertile imagination. At first, we were astonished to see some older porn addicts recover from PISD (porn-induced sexual dysfunction) more quickly than young ones. Is it because thirty- and forty-somethings had well established brain pathways relating to connections with real partners from pre-Internet days? Please watch this September 2015 TEDx talk by a young man who need extra time and relearning/rewiring to overcome porn-induced ED and anorgasmia:
The good news is that brains retain some plasticity even after teen years. When a guy stops using synthetic sexual cues (or fantasizing to them) for 2-3 months, his brain's recovering reward circuitry begins to 'look around' for the sexual cues it evolved to find. After all, its top priority is passing on genes, so it wants action. Gradually it wires the neuronal circuitry for natural cues more strongly to the brain's pleasure center. The girl next door looks more interesting.
Said a 21-year old guy three months after giving up porn/masturbation:
I remember saying to my girlfriend, during my very worst days of porn use and porn-related erectile dysfunction, that it didn't feel like I'd had sex yet. She didn't really understand, and I couldn't explain myself. But last night, OMG it felt so good. I could feel everything, and it was great. My penile sensitivity has increased loads. For the first time in my life, it feels like I've lost my virginity.
[Early twenties] Day 43 now, I am definitely seeing a girl as the source of my arousal now, rather than seeing her as an image that I can store up for later use. I see a hot girl now and think 'That's what I want', and try to take steps to meet her. It's been a gradual flipping of the switch. I'm probably about 90% there, but I can remember being 10%, 20% etc.
Today, average young Westerners are feverishly cultivating neuronal connections between all manner of Internet porn and their sexual response. No longer can we take for granted that teen arousal arises from some mysterious, individual, unchanging, core sexual identity. Thanks to the teen brain's incessant quest for novelty to relieve its owner's ever present boredom, some teens manage to wire in sexual tastes that cause them to doubt their fundamental sexual orientation.
Adolescence is a unique period of brain development. In the right environment, it's highly functional and adaptive. No matter how keen hunter-gatherer teens were to seek thrills, they were also like bumper-car drivers. They had few opportunities to wire their sexual responsiveness to anything beyond the neighboring hotties.
The brains of today's kids are equally eager, yet they're titillated with abnormally stimulating erotica that pushes all their buttons: passion for novelty, delight in shocking things, potential for overriding normal satiety, and desire for sexual instruction with "adult" cachet.
Adults tend to assume that Internet porn use is harmless because "porn has been around a long time." But how many males born, say, in 1960 started daily porn use circa 1973? Especially the hard-core, endlessly novel porn available now?
Today's kids can't necessarily stop themselves:
For years, like since I was 11-years old, I have been looking at porn and masturbating. I just can't resist it and I do it too much now. I wanna stop it now. I'm 15 years old and wanna stop it because I think it's affecting my social life, relationships, and school grades. How do I stop?
Adults also often assume kids will naturally leave impulsive behaviors behind at adulthood. Indeed, studies suggest that college-age kids do tend to outgrow binge drinking, pot use, etc. However, Internet porn habits may prove to be different. Did the young adults who outgrow substance abuse start their daily drinking/pot use at age 11?
[Age 35] When I was in my early teens and my mum would take us to the library, I'd sneak off to find an erotic novel. Just the talk/description of a woman would get me going. God, how I long for those days again LOL. Today, you can get 'maxed out' on porn. In the early stages it was a novelty and hard to get hold off. Over the last few years, porn is always on tap. Now it's a necessity rather than a thrill/reward. How sad is that? I have no moral objection to porn. In fact quite the opposite, but when you get to my state, it's no longer a positive, just a huge negative. A big, fat anchor around my neck.
Remember, learning to binge drink or get high isn't the brains' prime evolutionary imperative; reproduction is. Food habits may be a better analogy. Do 22-year olds suddenly change their habitual food choices? Now that junk foods are ubiquitous, 4 out of 5 adult Americans are overweight, and nearly half of those obese (i.e., hooked on food). Do they change their ingrained sexual tastes? Perhaps not unless they hit the wall of PISD.
Obviously, watching Internet porn from an early age does not mean the user will end up a deviant, or more sexually active, or more violent toward partners—although some may believe it's normal for sex partners to relish "facials" while having every orifice filled with objects. Tragically, however, a percentage of users will end up addicted, and that percentage may be higher than we think, given the rates of Internet addiction already affecting adolescents (6-18%, depending upon whether Italy, China or Hungary did the research).
For many, the lingering effects of heavy Internet porn use are likely to be analogous to effects on online gamers. Overstimulation leaves the brain with a need for intense stimulation (unless it is consciously restored to normal sensitivity). Other activities seem boring in comparison. In this short TED talk, The Demise of Guys? famous psychologist Philip Zimbardo describes the ill effects of widespread "arousal addiction."
Such effects impact relationships. Constant novelty is one of the prime reasons Internet porn is a superstimulus for the brain. Erotic training that relies on novelty as aphrodisiac can condition users such that familiar partners quickly lose their luster—confining users affected to shallow hook-ups. Also, the non-climax aspects of sex (skin-to-skin contact, kissing, comforting stroking, playful behavior, etc.) may be too unfamiliar and subtle to register as deliciously rewarding. Unfortunately, these are the very behaviors that soothe the brain and help couples strengthen their bonds.
First guy - Perhaps it is the easiness and comfort of just sitting in front of my computer jerking to images that I don't have to please. I can go at my own pace and not have to worry about them. Having a real girl in my bed kind of distracts me.
Second guy - I don't use porn, but going through my history of images, I realize that I sometimes look at thousands of images in an hour. I'm looking for that right girl or image that [gets me to climax]. Porn is not what's desensitizing my sexual responsiveness; I think my huge Internet harem is.
Maybe no one should be turned loose on the planet today without thorough education about the brain's reward circuitry and its unique vulnerabilities during adolescence. That's when it's bombarded by junk food, drugs, video games, i-Phones and online erotica. Why not teach kids the simplified science behind the potential effects of extreme stimuli on the brain? (Watch Things You Didn't Know About Porn, for possible concepts suitable for 10-13-year olds.)
Today, adolescents can (and do) wire up their brains to random erotic caricatures that their ancestors never imagined, let alone viewed intently for years before mating. Users may know that porn's cartoonish 2-D stimuli are nearly as unreal as Santa. Yet those who inadvertently wire their ability to climax to gonzo porn themes are sometimes horrified. Many are afraid to ask for help because they think they are hopeless perverts. Some are even suicidal.
Advisers who don't understand the difference between fundamental sexual orientation and randomly acquired, plastic tastes can increase an adolescent's angst. Sadly, few experts yet know enough about brain plasticity to help kids rewire, which results in some sorry advice. (see - Young Porn Users Need Longer To Recover Their Mojo)
As pubescent brains are going to start wiring up sexual tastes anyway, give kids the facts and explicit information they are seeking—without the implausible scenarios porn makers must rely on to lure viewers whose brains have grown numb to subtler sexual pleasures. Teach kids the difference between sexual orientation and sexual tastes, and how the two can slip out of sync with habitual use of extreme stimulation. Also, teach them the behavioral-addiction signs to watch for, and how to reverse those changes.
[Age 17 arrived with weak erections, and was still showing limited signs of erectile health on Day 50 of no porn/masturbation] Day 76: Feeling great, way happier and more energetic and way more libido. My morning wood this morning was ridiculous—it literally wouldn't go down for like 20 minutes even standing up! I'm gonna give it 90 days so I've done a full 3 months and then I should be completely back to normal and ready to try and find a partner. So relieved this actually works.
I'm 27 and I have a science and medical education, and I strongly believe that this brain-plasticity viewpoint about Internet porn needs to get out there. We're losing the opportunity to educate young men who are suffering from physiological problems within their brains. Basically, I wish I had learned about this 15 years ago.
For more information:
Today there is a lively and provocative discussion about adolescent pornography access and even addiction to pornography. It was generated by a first email sent by a professional colleague who wrote of a young man in his early 20's who recently told her "on-line porn is the scourge of my generation of young men."
He described his addiction with online porn and the ensuing isolation and loneliness he felt and the impact it has on his "expectations of relationships."
The professional feedback bemoans the fact that there is really no good research into this growing phenomenon much less sound or tested advice on how to advise parents or patients on this and many of the other issues that arise from "growing up online." How do we even ask the questions in the right way in order to get at the answers? What constitutes addiction anyway? How do we measure that? What can we do if we uncover it?
There were some answers from the world of research into gaming addiction which is already being considered for the Diagnostic and Statistical Manual (the bible of psychiatric diagnosis). Some warning signs might be:
November 15th, 2011 in Neuroscience
A new study suggests that sex during adolescence can have lasting negative effects on the body and mood well into adulthood, most likely because the activity occurs when the nervous system is still developing.
While the research used laboratory animals, the findings provide information that may be applicable to understanding human sexual development.
Researchers paired adult female hamsters with male hamsters when the males were 40 days old, the equivalent of a human's mid-adolescence. They found that these male animals with an early-life sexual experience later showed more signs of depressive-like behaviors as well as lower body mass, smaller reproductive tissues and changes to cells in the brain than did hamsters that were first exposed to sex later in life or to no sex at all.
Among the cell changes observed in the animals that had sex during adolescence were higher levels of expression of a gene associated with inflammation in their brain tissue and less complex cellular structures in key signaling areas of the brain.
They also showed signs of a stronger immune response to a sensitivity test, suggesting their immune systems were in a heightened state of readiness even without the presence of infection - a potential sign of an autoimmune problem.
The combination of physiologic responses in adulthood don't necessarily cause harm, but do suggest that sexual activity during the nervous system's development might be interpreted by the body as a stressor, researchers say.
"Having a sexual experience during this time point, early in life, is not without consequence," said John Morris, a co-author of the study and a doctoral student in psychology at Ohio State University. "It could be affecting males' susceptibility to symptoms of depression, and could also expose males to some increase in inflammation in adulthood."
Morris presented the research Tuesday (11/15) at the Society for Neuroscience annual meeting in Washington, D.C. He conducted the study with Zachary Weil, research assistant professor, and Randy Nelson, professor and chair, both from Ohio State's Department of Neuroscience.
Previous research has most often examined the effects of adolescent sex on young women, and for ethical reasons must be done in humans as retrospective explorations of behavior. The Ohio State scientists used hamsters, which have physiologic similarities to humans, to learn specifically how the body responds to sexual activity early in life.
"There is a time in nervous system development when things are changing very rapidly, and part of those changes are preparations for adult reproductive behaviors and physiology," Weil said. "There is a possibility that environmental experiences and signals could have amplified effects if they occur before the nervous system has settled down into adulthood."
The scientists worked with five groups of male hamsters: two groups that had sex at age 40 days and were assessed at 40 days and 80 days after exposure to sex, two groups that had adult sex at age 80 days and were assessed at the same time intervals, and hamsters that had no sexual experience. Male hamsters reach puberty at age 21 days.
The researchers placed the adolescent and adult males in environments with in-heat female hamsters for six hours and recorded their encounters to ensure that sexual activity occurred.
The animals were subjected to a variety of tests when they all had reached adulthood. They were placed in mazes with options to explore open areas or hide in isolation; those that chose not to explore were showing signs of anxiety. Animals placed in water showed signs of depressive-like behavior if they stopped swimming vigorously.
"Both groups of sexually active hamsters showed an increase in anxiety-like behavior compared to the control group, but the increase in a depressive-like response was specific to the adolescent sexually paired group," Morris said.
A test of immune system sensitivity suggested that the hamsters with adolescent sexual experiences were at risk for excess inflammation as part of an enhanced immune response. In addition, these same hamsters had higher levels of a pro-inflammatory cytokine called interleukin-1, or IL-1, in their brain tissue than did the other hamsters. IL-1 is one of several chemical messengers that cause inflammation, most often to fight infection or repair injury; when it circulates without an infection to fight, the body experiences excess inflammation.
This elevated gene expression was seen in areas of the brain known not to reach maturity until well into adulthood - including the amygdala, prefrontal cortex, hippocampus and striatum. In some of these same areas of the brain, animals with adolescent sexual experience also showed less complexity in the dendrites, the branching segments from nerve cells that house the synapses, which carry signals to the brain from the rest of the body.
Without further research, the scientists don't know exactly what these brain differences mean. But because they are seen most prominently in the animals that were exposed to sex in adolescence, the scientists say, there is a clear association with that activity. "Sex is doing something physiological that these cells are interpreting and responding to with shorter dendrites," Weil said.
Finally, the hamsters that had adolescent sex had a smaller total body mass as well as a decrease in accessory reproductive tissue, including the seminal vesicles, vas deferens and epididymis, as adults.
"This suggests to us that maybe this process is causing the animals to have a maladaptive response reproductively, as well," Morris said.
Provided by The Ohio State University
"Adolescent sex linked to adult body, mood troubles, in animal study." November 15th, 2011.
Nodes of the adolescent brain's structural network coloured by how much they change between 14 and 24 years of age. The size of the nodes represent how well connected they are and halfway through the movie the smallest nodes are removed and only the hubs remain. The edges that are added in are the strongest connections between these hub regions and represent the brain's rich club. Credit: Kirstie Whitaker
[Comment: Would teens show greater reward response in the case of social and sexual rewards perhaps?]
Scientists have uncovered a unique feature of the adolescent brain that enriches teens' ability to learn and form memories: the coordinated activity of two distinct brain regions. This observation, which stands in contrast to the adult brain, may be related to teens' oft-derided affinity for reward-seeking behavior. These findings suggest that such behavior is not necessarily detrimental, but instead may be a critical feature of adolescence and the maturing brain.
The results of this research were published today in Neuron.
"Studies of the adolescent brain often focus on the negative effects of teens' reward-seeking behavior. However, we hypothesized that this tendency may be tied to better learning," said Daphna Shohamy, PhD, a principal investigator at Columbia's Mortimer B. Zuckerman Mind Brain Behavior Institute and associate professor of psychology at Columbia. "Using a combination of learning tasks and brain imaging in teens and adults, we identified patterns of brain activity in adolescents that support learning—serving to guide them successfully into adulthood."
For this study, which involved 41 teens and 31 adults, the authors initially focused on a brain region called the striatum. Previous research has shown that the striatum coordinates many aspects of higher brain function, from planning to decision making. But it is most well-known for its role in something called reinforcement learning.
"In simplest terms, reinforcement learning is making a guess, being told whether you're right or wrong, and using that information to make a better guess next time," said Juliet Davidow, PhD, the paper's first author, who completed this research while earning her doctorate in psychology at Columbia and is now a postdoctoral fellow at Harvard University.
For example, imagine you are given a series of cards with numbers on them and are asked to guess the next number in the sequence.
"If you guess right, the striatum shows activity that corresponds to that positive feedback, thus reinforcing your choice," Dr. Davidow explained. "Essentially, it is a reward signal that helps the brain learn how to repeat the successful choice again."
Because of teens' inclination toward reward-seeking behavior, the researchers proposed that this age group would outpace adults in terms of reinforcement learning by showing a greater affinity for rewards. This hypothesis was confirmed after asking both groups to perform a series of learning tasks.
To see what was happening in the brain, Dr. Shohamy teamed up with Adriana Galván, PhD. Dr. Galván, who is an associate professor of psychology and faculty member of the Brain Research Institute at the University of California, Los Angeles, is an expert in brain imaging in teenagers. Together, they scanned the brains of each participant with functional magnetic resonance imaging (fMRI) while they were performing the learning tasks. The authors hypothesized that the teens' superior abilities were due to a hyperactive striatum.
"But surprisingly, when we compared the brains of teens to those of adults, we found no difference in reward-related striatal activity between the two groups," said Dr. Davidow. "We discovered that the difference between adults and teens lay not in the striatum but in a nearby region: the hippocampus."
The hippocampus is the brain's memory headquarters. And while important for storing memories of events, places or individuals, it is not typically related to reinforcement learning. But in this study, the authors' fMRI analysis revealed an uptick in hippocampal activity for teens—but not adults—during reinforcement learning. Moreover, that activity seemed to be tightly coordinated with activity in the striatum.
To investigate this connection, the researchers slipped in random and irrelevant pictures of objects into the learning tasks, such as a globe or a pencil. The images—which had no bearing on whether the participants guessed right or wrong—served as a kind of background noise during the tasks. When asked later on, both adults and teens remembered seeing some of the objects, but not others. However, only in the teens was the memory of the objects associated with reinforcement learning, an observation that was related to connectivity between the hippocampus and striatum in the teen brain.
"What we can take from these results isn't that teens necessarily have better memory, in general, but rather the way in which they remember is different," said Dr. Shohamy, who is also a member of Columbia's Kavli Institute for Brain Science. "By connecting two things that aren't intrinsically connected, the adolescent brain may be trying to build a richer understanding of its surroundings during an important stage in life."
Indeed, studies have shown that adolescence is a pivotal time when powerful memories are formed, which the authors argue could be due to this enhanced connectivity between the hippocampus and striatum.
"Broadly speaking, adolescence is a time when teens begin to develop their independence," said Dr. Shohamy. "What more could a brain need to do during this period than jump into learning overdrive? It may be that the uniqueness of the teen brain may drive not only how they learn, but how they use information to prime themselves for adulthood."
More information: This paper is titled: "An upside to reward sensitivity: The hippocampus supports enhanced reinforcement learning in adolescence." DOI: 10.1016/j.neuron.2016.08.031 ,
Provided by: Columbia University