Driving and DNA

BDNF Gene Linked to Poor Motor Skills
November 13, 2009 If you've ever wondered why that moron in front of you can't drive, maybe it's because of his DNA. Scientists recently used a steering wheel and some brain scans to show how a person's DNA can affect his or her motor skills. They found that a single difference in the BDNF gene is linked to poor driving. About 30% of people have at least one copy of the Met version of BDNF, whereas 70% have two copies of the Val version. Using a driving test, scientists found that people with Met tended to make more mistakes and had a worse memory. The results make sense given that a good memory (like how far to turn the wheel) is important for good driving.

Hopefully this driver has
two Val versions of
the BDNF gene.
In a separate test, scientists looked at the brains of people as they learned a new motor skill (when to push a button). Of course the scientists didn't open up the subjects' heads and have a peek. Instead they used an fMRI machine to look at the motor regions of the brain. The scientists found that Met and Val people's brains worked differently. This part of the Val people's brains was much more active compared to the Met people. Both this and the driving result suggest that which version of the BDNF gene a person has affects how that person learns. And maybe how they drive a car. Does this mean if a person has the Met version that he or she is doomed to more accidents? Stop the bus. First of all, this study does not directly address the relationship between BDNF and accident rates. Accidents happen for many reasons and this study only tests how well a person steers a car. It doesn't test for all of the behaviors that have been associated with increased accident rates: speeding, texting while driving, driving under the influence. The authors themselves admit that the study has its flaws. They point out that DNA differences can have different effects on different people. Age, race, and behavior can play a role. In fact, the Met version of BDNF has been shown to affect a person's mood, attention, and anxiety. Also, it has more of an effect in Caucasian people. The study group was mostly young Caucasians. More studies on older, ethnically diverse groups need to be done. So nobody should even think about using these results to decide insurance rates.
Driving and Memory
There are different types of memory. One, called episodic, was already linked to the Val/Met difference in the BDNF gene. What is episodic memory? It's the ability to recall when and where life events happened. Do you remember what you did on your birthday last year? You just used your episodic memory. But Steven Cramer's group was curious about a different type: motor memory.

Motor memory is used in
all types of sports,
including skateboarding.
Motor memory isn't whether or not you recall how many cylinders a '68 Ford Mustang has. However, it is related to a car -- in some ways. Motor memory is the ability to remember a series of movements. Have you ever practiced sports, handwriting, or typing? If so, you've tried to strengthen your motor memory. A driver has to do many repeated movements, like turn a wheel and press pedals. How hard to turn and how hard to press is stored in a person's motor memory. To see if BDNF and motor memory are connected, Cramer's group conducted two tests on two groups of people. The groups were formed based on the subjects' DNA. One group had a Met version of the BDNF gene (Met group). The second group only had Val copies (Val group). After the tests, scientists compared the two groups to each other. The first test was a driving one. Twenty nine subjects sat in front of a computer monitor with a steering wheel and "drove" along a track on the screen, sort of like Mario Kart. On the first day, scientists measured how well a subject did each of 15 times. They found that both groups learned to drive the course better over time. They all improved the more they drove it. However, the Met group did not improve as much. That suggests that their short term motor memory isn't as strong as in the Val group. A similar observation was made for long term motor memory. Subjects returned four days later to drive the course again. Both groups showed much better driving compared to the first time they drove. However, when scientists compared the last drive on the first day to the first drive four days later, they found a difference. Met group subjects made more errors than they did on the last drive, whereas Val group subjects did not. That suggests that people with the Met version don't retain long term memories quite as well as people with Val. The Met group made more mistakes driving and forgot more than the Val group. But scientists wanted to know what was actually happening in the brains of both groups. So they took a look. Motor Activity in the Brain Instead of dealing with how to drive a motor vehicle, the second test dealt with teaching subjects a motor skill. This time scientists looked directly at the brain activity of a Met group and a Val group during this test. To see the activity, they used an fMRI (functional magnetic resonance imaging) machine. This is a high tech tool that shows where activity is occurring in the brain. Subjects' heads were scanned as they pressed a button. An fMRI of random brain activity. The subjects then "trained" for 25 minutes to improve their motor skills. After the training, their brains were again scanned as they pressed a button while following some instructions. Scientists then looked at how much of the brain was active during the scans and compared the two groups. They saw two differences between the groups. Before the training, the Met group had less activity in the motor regions of their brains. The Val group had more. Additionally, brain activity in the Met group dropped as subjects learned. In the Val group, brain activity increased. Now, these results could mean that the Met group is more efficient at using their brains. Or it could mean that they just don't have as many brain resources to pull from when they are learning motor skills. Cramer's group argues that since the Met group did worse on the driving test, they probably aren't more efficient. They probably dedicate less of their brains to learning motor skills compared to the Val group.

More Information

So what's going on in the Met version? Why does it cause some people to not learn certain motor skills as well? Let's back up a little bit and review what has to go on for BDNF, or any gene, to work correctly. First, genes are instructions for making proteins. Think of genes as a cookbook, instructions for making a dish or dessert. The resulting food is what is doing the work -- making you full. Proteins are the products of genes, and they actually do the work in the cell that needs to be done. But proteins have to be shuttled to the correct spot within the cell to do their jobs. In the case of BDNF, it is secreted out of the cell as a signal to other cells. Think of it as firing a flare gun from the cell to provide other cells with information. BDNF stands for Brain Derived Neurotrophic Factor. Let's break that down. Brain derived means that it's produced and found in the brain. Neurotrophic means that it helps cells in the brain, also known as neurons, grow. BDNF helps neurons grow, connect to each other, and even alter those connections. The brain's ability to form and alter those connections allows it to form memories. The problem with the Met version of BDNF is that BDNF doesn't get shuttled correctly. The protein gets made, but it doesn't efficiently get to the correct spot within the cell. That means that it isn't secreted and can't efficiently do its job, making it harder for memories to be formed. Even though the BDNF gene is linked to a worse memory and steering ability, it's far from an excuse for most bad driving behaviors. Scientists still haven't linked a gene to putting on makeup, shaving, or talking on a phone while driving. Andrew Hellman