Your brain is wired to avoid the gym
In high-income countries, 26 percent of men and 35 percent of women don’t get enough physical activity, but it’s not always for a lack of trying. Many people sign up for gym memberships, and then simply don’t go—even though they’re being charged fees each month.
It’s called the exercise paradox. When you exercise, you know that you’re doing it to be healthier, but the experience can often be unpleasant; it’s exhausting, and requires effort or coordination. This conflict, between reason and affect, can lead to skipping the physical activity altogether. A new study in Neuropsychologia looked at what’s going in people’s brains when they choose between doing nothing and doing something active.
In the study, participants did a task in which they steered an avatar towards pictures of physical activity—and away from pictures of sedentary behavior—and then did the opposite. The people were 32 milliseconds faster at moving away from the sedentary image, “which is considerable for a task like this," says author Boris Cheval, Post-doctoral researcher in Health and Exercise Psychology at the University of Geneva, in a press release.
This is a good thing, right? They wanted to move towards the physical activity. But the researchers also saw that it was more work on their brains to avoid the sedentary behaviors. “The faster avoidance of sedentary behaviors came at the cost of an increased recruitment of brain resources,” author Matthieu Boisgontier, a postdoctoral researcher at the University of British Columbia, tells me. “This suggests an innate attraction to sedentary behaviors.” The brain needs to use more resources to avoid minimizing effort, which represents that oh-so-relatable struggle: “between the desire to do nothing and the physical activity."
The preference for doing nothing may have once helped keep us alive. “Minimizing energy cost gave us an advantage for survival," Boisgontier says. “For instance, it helped us to be more efficient at finding food and escaping predators. In the current pandemic of physical inactivity, this minimization is not helpful, but we need to address it because it is there, in our brain.”
Boisgontier says that if we are aware of this conflict, perhaps we can fight it. For example, if you’re at the gym you can ignore the automatic attraction you have to getting into the elevator and going home—this is just a trick your brain is pulling on you to conserve energy! Perhaps easier said than done, but “whether the brain’s automatic attraction to sedentary behaviors can be retrained is unknown yet,” Boisgontier says. “We need more studies to investigate this, and it will take time.”
This might be why we are deaf to our own footsteps
When you’re out in the world, you hear sounds. Some of the sounds come from you, and some come from other people and objects. Sound obvious? Well maybe you haven’t noticed this bit before: You’re often unaware of the sound of your own footsteps, or the sounds coming from you (unless you’re really paying attention). David Schneider, assistant professor at New York University's Center for Neural Science, wanted to understand how the cells in the brain might work together to make that happen.
In a new study in Nature, he and colleagues put mice into an augmented reality system where they could control the noises the mice heard when they were running around. For a couple of days, the researchers made the mice’s walking make one sound, and then they switched it to another.
When mice were expecting their walking to make one sound, neurons in the auditory cortex, one of the main hearing centers of the brain, stopped responding to it. “It was almost like they were wearing special headphones that could filter out the sound of their own movements,” Schneidersays. “In contrast, when we played an unexpected sound, neurons in their auditory cortex had large responses.”
After the mice had learned to associate a particular sound with their own footsteps, their brains went through a series of changes in order to ignore that sounds, Schneider says. “The connections were changing between a part of their brain important for moving—the motor cortex —and the auditory cortex,” he explains. “The end result was that every time the mouse walked, a group of inhibitory neurons were active to create a photo-negative of the sound the mouse expected, which could cancel out the expected sound when it was heard.”
For mice, this could be important to prevent them from being a predator’s lunch. Their movements can be quite noisy, Schneider says—despite the phrase “quiet as a mouse.” Being able to ignore their own sounds allows them to hear others approaching.
Humans might use this ability for the same purpose: “I probably want to ignore my own footsteps so I can focus on the voice of a person walking next to me,” he says. “And ignoring only the expected sounds of my footsteps allows me to notice when the sounds are unexpected."
This ability to ignore expected sounds could also play into our ability to learn music—by recognizing unexpected errors, or mistakes—or help us learn how to speak. An impairment in this process might be involved in certain disorders, like schizophrenia. Hearing voices is a common symptom of schizophrenia and psychosis, and one theory as to why, Schneider says, is that there might be something wrong in the connection between the motor and auditory cortex. These could be the same connections that they’re looking at in the mice brains. “If the motor cortex starts sending signals in the absence of any actual movement, then this could cause the auditory cortex to become active, leading the perception of phantom voices,” he tells me.
For the moment, they will continue to study this circuitry in healthy mice, and see if it translates it to human brains. “ If that’s the case,” Schneider says. “Then we’d be really interested in trying to understand whether or not this circuitry gets mis-wired in schizophrenia.”
The gut-brain connection might be faster and stronger than we thought
Researchers know that there’s a connection between your gut and your brain—it's how your brain knows, among other things, that the stomach is full or empty. But previously, it was thought that the gut communicated with the brain through hormones: When nutrients hit the stomach, it released hormones, which enter the bloodstream and eventually reach the brain.
But a new study in mice shows there’s another—much faster—mechanism by which the stomach connects to the brain. Diego V. Bohórquez, an assistant professor of medicine at Duke University School of Medicine, had previously found that there are sensory cells in the gut lining that are similar to sensory cells on the tongue or in the nose. In 2015, he published a study showing they these cells, or neuropods, contained nerve endings or synapses—which meant they might connect somehow to the brain.
In his recent study, Bohórquez and his colleagues used mice to show that this connection is there, and it’s fast. They used a virus tagged with green fluorescence, so they could watch it move, and “they were shocked to see the signal cross a single synapse in under 100 milliseconds—that's faster than the blink of an eye,” their press release says.
Bohórquez’s postdoctoral fellow, Maya Kaelbere, then grew sensory gut cells of mice in a dish, alongside neurons. “She saw the neurons crawl along the surface of the dish to connect to the gut cells and begin to fire signals,” the release says. When she added sugar to the mix, the firing increased, which means that the neurotransmitter glutamate might be involved in the process.
Bohórquez says that the existence of a faster way for the gut and the brain to talk to each other makes sense, because “the brain needs to be aware of the food that we ingest,” he tells me. “The speed and specificity brings up the possibility that the brain recognizes not only the amount of food we eat but also the quality of the nutrients—sugars versus proteins, or different properties within sugars.”
Additionally, it may explain why appetite suppressants—which were based on hormonal theories of communication—haven’t worked very well. “Appetite suppressants in the future could be designed to speed or slow down these signals in specific areas of the intestine as opposed to the entire gastrointestinal tract,” he says.
When you give an octopus MDMA they become unusually touchy-feely
Octopuses don’t care much for other octopuses; in general they’re highly solitary animals—from birth they spend their lives alone. So, what would happen if you gave them MDMA, or ecstasy?
Ecstasy releases a flood of neurotransmitters like serotonin, dopamine, and oxytocin, and in people, can lead to feeling euphoria and a sense of intense closeness with others (even if you might not feel that way when you’re not high).
Humans and octopuses are separated by 500 millions years of evolution, and in many ways that’s revealed in the unusual anatomy of the cephalopods: Octopuses are super weird, and have very different brains from humans. In a new study, when researchers at Johns Hopkins gave octopuses MDMA, they saw that the octopuses spent more time with each other, and also touched each other a lot more. “That unusual physical contact between individuals appeared exploratory, not aggressive, in nature,” a press release noted.
If ecstasy affects octopuses in similar ways as it does humans, that means that “ancient neurotransmitter systems are shared across vertebrate and invertebrate species and in many cases enable overlapping functions,” the paper says.
This means that octopuses have receptors for the ecstasy to interact with, and could help reveal how neurotransmitters lead to the creation of social behaviors. Now that we know octopuses are vulnerable to these effects, the researchers plan to compare the DNA of octopuses that have slightly different behaviors. “By comparing the genomes of those species, they hope to gain more insight into the evolution of social behavior,” the release says.
What to read in health and science this week:
Ten translations of care by Mary Wang in Longreads
Mary Wang and her family hide her grandmother’s cancer diagnosis from her.
A yawning gap by Jim Horse in The Psychologist
Why aren’t more researchers studying the mysteries of yawning?
The environment’s new clothes: biodegradable textiles grown from live organisms by Erica Cirino in Scientific American
Fast fashion is clogging up our landfills, but one day our clothes could be biodegradable!
On being an ill woman: a reading list of doctors’ dismissal and disbelief
Eight stories about navigating healthcare as a woman.
Rebooting Becky’s brain by Ingrid Wickelgren in Spectrum
There have only been five people who have received deep brain stimulation for Autism, and Becky was the first. In her case, “the gamble paid off.”
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