We all know that adolescence is that high peak in life where we feel completely invincible and are open to try many things; this is why adolescence is also known as the “experimental stage.” Adolescents are easily influenced by their peers and sometimes fall subject to drug abuse and it is a period marked by intense vulnerability. One of the most common abuses is smoking in which about 30% of adolescents that experiment with it become established smokers. Everyone knows that smoking can cause several types of cancers, but did you know that adolescent smokers also risk damaging their cognition and attention span?
Cognition
What exactly is cognition and how is it possible that smoking can have such negative effects on it? Cognition is a broad term that refers to thinking, remembering, judging, knowing, and problem-solving. Imagination and perception are also higher-level functions of the brain categorized under cognitive behaviors.
This diagram provides a quick overview of how cognition works:
The Prefrontal Cortex
The brain has a very intricate way of communication. Nerves constantly send signals back and forth across the brain and to the rest of the body. What researchers have found is that when exposing the body to nicotine, a stimulant found in tobacco products, during adolescence there is interference and the signals are not quite making it to their terminals. This in turn causes problems with attention span and other areas associated with the prefrontal cortex. The prefrontal cortex, or PFC, is the area of the brain responsible for personality, decision making, social behavior, and cognitive behaviors.
Here’s a video that shows how important the PFC is during the adolescence stage and how it continues developing up until the mid-twenties.
As odd as it may sound, nicotine exposure during adolescence does impair the way you think, how much attention you pay, and even how you behave. Since the nerves do not receive the signals under the influence of nicotine, normal brain function is not possible and communication is reduced.
The Experiment
Researchers at VU University in Amsterdam conducted an experiment on three groups of rats. One group was given nicotine treatments from the start of the adolescence and the other was given a simple saline solution. The third group was given nicotine only during adulthood. The experiment was conducted on rats because their brain functions are consistent with those of the human brain, therefore the results could easily be applied to humans as well. Prior to the exposure of nicotine, the adolescent rats experienced “normal adolescent” behavior. It’s kind of an entertaining thought to see rats making impulsive decisions and falling for “peer pressure.”
Remember how the brain communicates? The brain uses nerves to transmit signals - you can think of them as messengers. These messengers are constantly communicating with other messengers in order to process different actions such as moving an arm or mental processes such as thinking. In order to successfully send a message there must be a terminal receptor that receives the final signal. Inside these terminal receptors are metabotropic glutamate receptors (mGluR2). Try saying that ten times fast! The receptors are responsible for controlling excess glutamate, a chemical that plays an important role in learning and memory, release.
What researchers found in the experiment was that nicotine was severely decreasing mGluR2 which led to deficits in cognitive behaviors. The decrease in mGluR2 can be seen in the wider gaps between each interval in which the rats were stimulated (Fig. B). These tests were conducted after the adolescent rats were taken of their treatments (approximately five weeks before they reached adulthood) in order to see the full effect that nicotine had on their cognition.
During this abstinence, researchers noticed that impulsive behaviors were still present but so were other problems: the rats were having many issues with their attention spans. When compared to the rats only exposed to nicotine during adulthood the results were extremely different. The adult rats were only experiencing some behavioral changes unlike the adolescent rats that were losing their minds. Since the PFC is still developing during adolescence, alterations made to it can lead to negative results in adulthood. The alterations in mGluR2 were significant enough to make an impact because the receptors are directly linked to cognitive behaviors, so disturbances during development can only end with irreversible consequences in the future. Does this mean that smoking in adulthood is “better” than smoking during adolescence? Not necessarily, but this shows how vulnerable the stage of adolescence can be. Because adolescence is a major stage in human development, bad habits that start early often lead to dire consequences.
The Results
Researchers found that nicotine did in fact lower mGluR2 activity which caused the cognitive disturbances simply because the signals were not being received. Nicotine served as a barrier in adolescent rats and the results included increase in impulsivity, impaired attention span, and other defects in cognitive behaviors. When compared to the third group of rats that were only treated with nicotine during adulthood, the adolescent rats were showing lasting effects that the adult rats were not.
One important thing to note is that when researchers increased mGluR2 levels in the adolescent rats the symptoms were not expressed as much, but this was not a “cure” because they still showed poor cognitive activity in adulthood.
Moral of the story for adolescents, think before you choose to be a part of the 30% "experimenters" that become smokers so that maybe you can still have the ability to think, focus, and remember when you are an adult.
Reference
Mansvelder, Pattij, Spijker. “Lasting synaptic changes underlie attention deficits caused by nicotine exposure during adolescence.” Nature Neuroscience: Brief Communication doi:10.1038/nn.2770 (2011): n. pag. Web. 20 March 2011.
Interesting Links
http://www.landesbioscience.com/curie/chapter/683/
http://www.psychologytoday.com/blog/the-skeptical-brain/201012/attention-and-the-hemispheres
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