How Do Tics Develop in Tourette Syndrome?

Tourette syndrome is a brain dysfunction that leads to involuntary motor tics, such as sniffing, blinking, or clapping. In about 10 percent of cases, it also leads to the spontaneous utterance of taboo words or phrases, known as coprolalia. Until recently, these tics were believed to be the result of a dysfunction primarily in a brain structure known as the basal ganglia—a brain region associated with voluntary motor control, which primarily uses the neurotransmitter gamma-aminobutyric acid (GABA) to function. Recent studies of rat, monkey, and even human brains, however, has suggested that the tics stem from a more complex, system-level dysfunction that involves the cerebellum, the thalamus, and the cortex, which are all connected.

To better explore these brain regions and their influence on Tourette syndrome, Daniele Caligiore, a researcher at the Institute of Cognitive Sciences and Technologies of the Italian National Research Council in Italy, and his colleagues created a computer-simulated model of the neural activity of a brain with Tourette syndrome. The results are published in PLOS Computational Biology.

“The model presented here is a first step of a research agenda aiming at building virtual patients, allowing us to test potential therapies by using computer simulations,” Caligiore tells mental_floss. This method can be performed at low cost, without ethical implications, and, he hopes, help develop “more effective therapeutic protocols, and suggest promising therapeutic interventions.”

Using a computer programming language called Python, Caligiore’s team built an artificial neural network model. In it, each neuron has a behavior that is regulated by mathematical equations. He explains, “Once built, the model works like a computer program—you can run it and observe its behavior.”

Caligiore reproduced the brain activity from monkey studies, published in the Journal of Neuroscience, in which an agent called bicuculline was microinjected into a region of the brain called the sensorimotor striatum that is involved in motor function. The researchers found that this microinjection of bicuculline inhibits GABA, which causes an abnormal release of the neurotransmitter dopamine.

“This excess [dopamine] might cause an abnormal functioning of the basal ganglia-thalamo-cortical circuit, leading to the production of tics,” Caligiore says. The abnormal dopamine release is one necessary condition for a tic, but it's not the only one, he says. “To have a motor tic you need both abnormal dopamine and a background activity in the motor cortex (due to the neural noise) above a threshold.”

In other words, “it is not just a matter of dopamine or just a matter of abnormal cortical activity," he explains. "It is a necessary combination of both.”

Caligiore’s team also found that the cerebellum appeared to influence tic production as well. Their model shows that during a tic, there is abnormal activity in a region of the basal ganglia called the subthalamic nucleus (STN). The STN connects with the cerebellum. “This is a possible reason [for a tic] because there is an abnormal tic-related activity in the cerebellum as well.”

What the computer model shows is that motor tics in Tourette syndrome “are generated by a brain system-level dysfunction, rather than by a single area malfunctioning as traditionally thought.” Studying this interaction between regions “could substantially change our perspective about how these areas interact with each other and with the cortex,” he adds.

Moreover, Caligiore’s team’s computer model is a noninvasive, ethical, and low-cost way to study these brain systems—and it certainly could be the first important step to identify new target areas for future therapies.

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Feeling Anxious? Just a Few Minutes of Meditation Might Help

Some say mindfulness meditation can cure anything. It might make you more compassionate. It can fix your procrastination habit. It could ward off germs and improve health. And it may boost your mental health and reduce stress, anxiety, depression, and pain.

New research suggests that for people with anxiety, mindfulness meditation programs could be beneficial after just one session. According to Michigan Technological University physiologist John Durocher, who presented his work during the annual Experimental Biology meeting in San Diego, California on April 23, meditation may be able to reduce the toll anxiety takes on the heart in just one session.

As part of the study, Durocher and his colleagues asked 14 adults with mild to moderate anxiety to participate in an hour-long guided meditation session that encouraged them to focus on their breathing and awareness of their thoughts.

The week before the meditation session, the researchers had measured the participants' cardiovascular health (through data like heart rate and the blood pressure in the aorta). They evaluated those same markers immediately after the session ended, and again an hour later. They also asked the participants how anxious they felt afterward.

Other studies have looked at the benefits of mindfulness after extended periods, but this one suggests that the effects are immediate. The participants showed significant reduction in anxiety after the single session, an effect that lasted up to a week afterward. The session also reduced stress on their arteries. Mindfulness meditation "could help to reduce stress on organs like the brain and kidneys and help prevent conditions such as high blood pressure," Durocher said in a press statement, helping protect the heart against the negative effects of chronic anxiety.

But other researchers have had a more cautious outlook on mindfulness research in general, and especially on studies as small as this one. In a 2017 article in the journal Perspectives on Psychological Science, a group of 15 different experts warned that mindfulness studies aren't always trustworthy. "Misinformation and poor methodology associated with past studies of mindfulness may lead public consumers to be harmed, misled, and disappointed," they wrote.

But one of the reasons that mindfulness can be so easy to hype is that it is such a low-investment, low-risk treatment. Much like dentists still recommend flossing even though there are few studies demonstrating its effectiveness against gum disease, it’s easy to tell people to meditate. It might work, but if it doesn't, it probably won't hurt you. (It should be said that in rare cases, some people do report having very negative experiences with meditation.) Even if studies have yet to show that it can definitively cure whatever ails you, sitting down and clearing your head for a few minutes probably won't hurt.

Can You 'Hear' These Silent GIFs?

GIFs are silent—otherwise they wouldn't be GIFs. But some people claim to hear distinct noises accompanying certain clips. Check out the GIF below as an example: Do you hear a boom every time the structure hits the ground? If so, you may belong to the 20 to 30 percent of people who experience "visual-evoked auditory response," also known as vEAR.

Researchers from City University London recently published a paper online on the phenomenon in the journal Cortex, the British Psychological Society's Research Digest reports. For their study, they recruited more than 4000 volunteers and 126 paid participants and showed them 24 five-second video clips. Each clip lacked audio, but when asked how they rated the auditory sensation for each video on a scale of 0 to 5, 20 percent of the paid participants rated at least half the videos a 3 or more. The percentage was even higher for the volunteer group.

You can try out the researchers' survey yourself. It takes about 10 minutes.

The likelihood of visual-evoked auditory response, according to the researchers, directly relates to what the subject is looking at. "Some people hear what they see: Car indicator lights, flashing neon shop signs, and people's movements as they walk may all trigger an auditory sensation," they write in the study.

Images packed with meaning, like two cars colliding, are more likely to trigger the auditory illusion. But even more abstract images can produce the effect if they have high levels of something called "motion energy." Motion energy is what you see in the video above when the structure bounces and the camera shakes. It's why a video of a race car driving straight down a road might have less of an auditory impact than a clip of a flickering abstract pattern.

The researchers categorize vEAR as a type of synesthesia, a brain condition in which people's senses are combined. Those with synesthesia might "see" patterns when music plays or "taste" certain colors. Most synesthesia is rare, affecting just 4 percent of the population, but this new study suggests that "hearing motion synesthesia" is much more prevalent.

[h/t BPS Research Digest]


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