The secret to our big brains might be in our gut

Brain tissue is among the most energetically costly in the body, and as a result, larger-brained mammals require more energy to support brain growth and maintenance. Exactly which biological changes allowed human ancestors to meet the very high needs for energy as they evolved larger brains has remained unclear. A new Northwestern University study points to the role of gut microbes, tiny living organisms in our digestive system that help break down food and produce energy.

In a controlled lab experiment, researchers implanted microbes from two large-brain primate species (human and squirrel monkey), and one small-brain primate species (macaque), into mice. Their findings showed the mice with microbes from large-brain primate species produced and used more energy, while those with microbes from the small-brain species stored more energy as fat. The data is the first to show gut microbes from different animal species shape variations in biology between animal species and supports the hypothesis that gut microbes might influence evolution by changing how an animal's body works. The study offers a new perspective on human evolution, particularly the evolution of our large brains. The findings will be published in the journal Microbial Genomics on Dec. 2. Prior studies have compared the influence of genes and the environment on primates with bigger and smallerbrains. However, there are very few studies comparing how different primates use energy. Even less information is available on how metabolism develops in different primate species. "We know the community of microbes living in the large intestine can produce compounds that affect aspects of human biology -- for example, causing changes to metabolism that can lead to insulin resistance and weight gain," said the study's first author Katherine Amato, associate professor of anthropology at Northwestern. "Variation in the gut microbiota is an unexplored mechanism in which primate metabolism could facilitate different brain-energetic requirements," Amato said. After introducing the gut microbes into microbe-free mice, the researchers measured changes in mouse physiology over time, glucose, liver function and other traits. They also measured differences in the types of microbes and the compounds they were producing in each group of mice. The researchers expected to find microbes from different primates would lead to differences in the biology of the mice inoculated with them. They also expected mice with human microbes to have the greatest difference in biology from mice with "While we did see that human-inoculated mice had some differences, the strongest pattern was the difference between large-brained primates (humans and squirrel monkeys) and smaller-brained primates (macaques)," Amato said. The mice given microbes from the humans and squirrel monkeys had similar biology, even though these two larger-brained primate species are not close evolutionary relatives of one another. This suggests something othermicrobes from the other two than shared ancestry -- likely their shared trait of large brains is driving the biological similarities seen in the mice inoculated with their microbes. "These findings suggest that when humans and squirrel monkeys both separately evolved larger brains, their microbial communities changed in similar ways to help provide the necessary energy," Amato said. In future studies, the researchers hope to run the experiment with microbes from additional primate species varying in brain size. They would also like to collect more information on the types of compounds the microbes are producing and gather additional data on the biological traits of the hosts such as immune function and behavior.species.including weight gain, fat percentage, fasting

Scientists monitor brains replaying memories in real time

Brain abstract illustration (stock image).

In a study of epilepsy patients, researchers at the National Institutes of Health monitored the electrical activity of thousands of individual brain cells, called neurons, as patients took memory tests. They found that the firing patterns of the cells that occurred when patients learned a word pair were replayed fractions of a second before they successfully remembered the pair. The study was part of an NIH Clinical Center trial for patients with drug-resistant epilepsy whose seizures cannot be controlled with drugs.

"Memory plays a crucial role in our lives. Just as musical notes are recorded as grooves on a record, it appears that our brains store memories in neural firing patterns that can be replayed over and over again," said Kareem Zaghloul, M.D., Ph.D., a neurosurgeon-researcher at the NIH's National Institute of Neurological Disorders and Stroke (NINDS) and senior author of the study published in Science.

Dr. Zaghloul's team has been recording electrical currents of drug-resistant epilepsy patients temporarily living with surgically implanted electrodes designed to monitor brain activity in the hopes of identifying the source of a patient's seizures. This period also provides an opportunity to study neural activity during memory. In this study, his team examined the activity used to store memories of our past experiences, which scientists call episodic memories.

In 1957, the case of an epilepsy patient H.M. provided a breakthrough in memory research. H.M could not remember new experiences after part of his brain was surgically removed to stop his seizures. Since then, research has pointed to the idea that episodic memories are stored, or encoded, as neural activity patterns that our brains replay when triggered by such things as the whiff of a familiar scent or the riff of a catchy tune. But exactly how this happens was unknown.

Over the past two decades, rodent studies have suggested that the brain may store memories in unique neuronal firing sequences. After joining Dr. Zaghloul's lab, Alex P. Vaz, B.S., an M.D., Ph.D. student at Duke University, Durham, North Carolina, and the leader of this study decided to test this idea in humans.

"We thought that if we looked carefully at the data we had been collecting from patients we might be able to find a link between memory and neuronal firing patterns in humans that is similar to that seen in rodents," said Vaz, a bioengineer who specializes in deciphering the meaning of electrical signals generated by the body.

To do this they analyzed the firing patterns of individual neurons located in the anterior temporal lobe, a brain language center. Currents were recorded as patients sat in front of a screen and were asked to learn word pairs such as "cake" and "fox." The researchers discovered that unique firing patterns of individual neurons were associated with learning each new word pattern. Later, when a patient was shown one of the words, such as "cake," a very similar firing pattern was replayed just milliseconds before the patient correctly recalled the paired word "fox."

"These results suggest that our brains may use distinct sequences of neural spiking activity to store memories and then replay them when we remember a past experience," said Dr. Zaghloul.

Last year, his team showed that electrical waves, called ripples, may emerge in the brain just split seconds before we remember something correctly. In this study, the team discovered a link between the ripples recorded in the anterior temporal lobe and the spiking patterns seen during learning and memory. They also showed that ripples recorded in another area called the medial temporal lobe slightly preceded the replay of firing patterns seen in the anterior temporal lobe during learning.

"Our results support the idea that memories involve coordinated replay of neuronal firing patterns throughout the brain," said Dr. Zaghloul. "Studying how we form and retrieve memories may not only help us understand ourselves but also how neuronal circuits break down in memory disorders."

This study was supported by the NINDS Intramural Research Program and NIH training grants (NS113400, GM007171).

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Materials provided by NIH/National Institute of Neurological Disorders and Stroke. Note: Content may be edited for style and length.

Baby and adult brains 'sync up' during play

Woman and baby playing (stock image).

Have you ever played with a baby and felt a sense of connection, even though they couldn't yet talk to you? New research suggests that you might quite literally be "on the same wavelength," experiencing similar brain activity in the same brain regions.

A team of Princeton researchers has conducted the first study of how baby and adult brains interact during natural play, and they found measurable similarities in their neural activity. In other words, baby and adult brain activity rose and fell together as they shared toys and eye contact. The research was conducted at the Princeton Baby Lab, where University researchers study how babies learn to see, talk and understand the world.

"Previous research has shown that adults' brains sync up when they watch movies and listen to stories, but little is known about how this 'neural synchrony' develops in the first years of life," said Elise Piazza, an associate research scholar in the Princeton Neuroscience Institute (PNI) and the first author on a paper published Dec. 17, 2019, in Psychological Science.

Piazza and her co-authors -- Liat Hasenfratz, an associate research scholar in PNI; Uri Hasson, a professor of psychology and neuroscience; and Casey Lew-Williams, an associate professor of psychology -- posited that neural synchrony has important implications for social development and language learning.

Studying real-life, face-to-face communication between babies and adults is quite difficult. Most past studies of neural coupling, many of which were conducted in Hasson's lab, involved scanning adults' brains with functional magnetic resonance imaging (fMRI), in separate sessions, while the adults lay down and watched movies or listened to stories.

But to study real-time communication, the researchers needed to create a child-friendly method of recording brain activity simultaneously from baby and adult brains. With funding from the Eric and Wendy Schmidt Transformative Technology Grant, the researchers developed a new dual-brain neuroimaging system that uses functional near-infrared spectroscopy (fNIRS), which is highly safe and records oxygenation in the blood as a proxy for neural activity. The setup allowed the researchers to record the neural coordination between babies and an adult while they played with toys, sang songs and read a book.

The same adult interacted with all 42 infants and toddlers who participated in the study. Of those, 21 had to be excluded because they "squirmed excessively," and three others flat-out refused to wear the cap, leaving 18 children, ranging in age from 9 months to 15 months.

The experiment had two portions. In one, the adult experimenter spent five minutes interacting directly with a child -- playing with toys, singing nursery rhymes or reading Goodnight Moon -- while the child sat on their parent's lap. In the other, the experimenter turned to the side and told a story to another adult while the child played quietly with their parent.

The caps collected data from 57 channels of the brain known to be involved in prediction, language processing and understanding other people's perspectives.

When they looked at the data, the researchers found that during the face-to-face sessions, the babies' brains were synchronized with the adult's brain in several areas known to be involved in high-level understanding of the world -- perhaps helping the children decode the overall meaning of a story or analyze the motives of the adult reading to them.

When the adult and infant were turned away from each other and engaging with other people, the coupling between them disappeared.

That fit with researchers' expectations, but the data also had surprises in store. For example, the strongest coupling occurred in the prefrontal cortex, which is involved in learning, planning and executive functioning and was previously thought to be quite underdeveloped during infancy.

"We were also surprised to find that the infant brain was often 'leading' the adult brain by a few seconds, suggesting that babies do not just passively receive input but may guide adults toward the next thing they're going to focus on: which toy to pick up, which words to say," said Lew-Williams, who is a co-director of the Princeton Baby Lab.

"While communicating, the adult and child seem to form a feedback loop," Piazza added. "That is, the adult's brain seemed to predict when the infants would smile, the infants' brains anticipated when the adult would use more 'baby talk,' and both brains tracked joint eye contact and joint attention to toys. So, when a baby and adult play together, their brains influence each other in dynamic ways."

This two-brain approach to neuroscience could open doors to understanding how coupling with caregivers breaks down in atypical development -- such as in children diagnosed with autism -- as well as how educators can optimize their teaching approaches to accommodate children's diverse brains.

The researchers are continuing to investigate how this neural coupling relates to preschoolers' early language learning.

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Materials provided by Princeton University. Original written by Liz Fuller-Wright. Note: Content may be edited for style and length.

Researchers reconstruct spoken words as processed in nonhuman primate brains

Rhesus macaque

A team of Brown University researchers has used a brain-computer interface to reconstruct English words from neural signals recorded in the brains of nonhuman primates. The research, published in the journal Nature Communications Biology, could be a step toward developing brain implants that may help people with hearing loss, the researchers say.

"What we've done is to record the complex patterns of neural excitation in the secondary auditory cortex associated with primates' hearing specific words," said Arto Nurmikko, a professor in Brown's School of Engineering, a research associate in Brown's Carney Institute for Brain Science and senior author of the study. "We then use that neural data to reconstruct the sound of those words with high fidelity.

"The overarching goal is to better understand how sound is processed in the primate brain," Nurmikko added, "which could ultimately lead to new types of neural prosthetics."

The brain systems involved in the initial processing of sound are similar in humans and non-human primates. The first level of processing, which happens in what's called the primary auditory cortex, sorts sounds according to attributes like pitch or tone. The signal then moves to the secondary auditory cortex, where it's processed further. When someone is listening to spoken words, for example, this is where the sounds are classified by phonemes -- the simplest features that enable us to distinguish one word from another. After that, the information is sent to other parts of the brain for the processing that enables human comprehension of speech.

But because that early-stage processing of sound is similar in humans and non-human primates, learning how primates process the words they hear is useful, even though they likely don't understand what those words mean.

For the study, two pea-sized implants with 96-channel microelectrode arrays recorded the activity of neurons while rhesus macaques listened to recordings of individual English words and macaque calls. In this case, the macaques heard fairly simple one- or two-syllable words -- "tree," "good," "north," "cricket" and "program."

The researchers processed the neural recordings using computer algorithms specifically developed to recognize neural patterns associated with particular words. From there, the neural data could be translated back into computer-generated speech. Finally, the team used several metrics to evaluate how closely the reconstructed speech matched the original spoken word that the macaque heard. The research showed the recorded neural data produced high-fidelity reconstructions that were clear to a human listener.

The use of multielectrode arrays to record such complex auditory information was a first, the researchers say.

"Previously, work had gathered data from the secondary auditory cortex with single electrodes, but as far as we know this is the first multielectrode recording from this part of the brain," Nurmikko said. "Essentially we have nearly 200 microscopic listening posts that can give us the richness and higher resolution of data which is required."

One of the goals of the study, for which doctoral student Jihun Lee led the experiments, was to test whether any particular decoding model algorithm performed better than others. The research, in collaboration with Wilson Truccolo, a computational neuroscience expert, showed that recurrent neural networks (RNNs) -- a type of machine learning algorithm often used in computerized language translation -- produced the highest-fidelity reconstructions. The RNNs substantially outperformed more traditional algorithms that have been shown to be effective in decoding neural data from other parts of the brain.

Christopher Heelan, a research associate at Brown and co-lead author of the study, thinks the success of the RNNs comes from their flexibility, which is important in decoding complex auditory information.

"More traditional algorithms used for neural decoding make strong assumptions about how the brain encodes information, and that limits the ability of those algorithms to model the neural data," said Heelan, who developed the computational toolkit for the study. "Neural networks make weaker assumptions and have more parameters allowing them to learn complicated relationships between the neural data and the experimental task."

Ultimately, the researchers hope, this kind of research could aid in developing neural implants the may aid in restoring peoples' hearing.

"The aspirational scenario is that we develop systems that bypass much of the auditory apparatus and go directly into the brain," Nurmikko said. "The same microelectrodes we used to record neural activity in this study may one day be used to deliver small amounts of electrical current in patterns that give people the perception of having heard specific sounds."

The research was supported by the U.S. Defense Advanced Research Projects Agency (N66001-17-C-4013) and a private gift to Brown.

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Materials provided by Brown University. Note: Content may be edited for style and length.

Brains of girls and boys are similar, producing equal math ability

Children with math on blackboard

In 1992, Teen Talk Barbie was released with the controversial voice fragment, "Math class is hard." While the toy's release met with public backlash, this underlying assumption persists, propagating the myth that women do not thrive in science, technology, engineering and mathematic (STEM) fields due to biological deficiencies in math aptitude.

Jessica Cantlon at Carnegie Mellon University led a research team that comprehensively examined the brain development of young boys and girls. Their research shows no gender difference in brain function or math ability. The results of this research are available online in the November 8 issue of the journal Science of Learning.

"Science doesn't align with folk beliefs," said Cantlon, the Ronald J. and Mary Ann Zdrojkowski Professor of Developmental Neuroscience at CMU's Dietrich College of Humanities and Social Sciences and senior author on the paper. "We see that children's brains function similarly regardless of their gender so hopefully we can recalibrate expectations of what children can achieve in mathematics."

Cantlon and her team conducted the first neuroimaging study to evaluate biological gender differences in math aptitude of young children.

Her team used functional MRI to measure the brain activity in 104 young children (3- to 10-years-old; 55 girls) while watching an educational video covering early math topics, like counting and addition. The researchers compared scans from the boys and girls to evaluate brain similarity. In addition, the team examined brain maturity by comparing the children's scans to those taken from a group of adults (63 adults; 25 women) who watched the same math videos.

After numerous statistical comparisons, Cantlon and her team found no difference in the brain development of girls and boys. In addition, the researchers found no difference in how boys and girls processed math skills and were equally engaged while watching the educational videos. Finally, boys' and girls' brain maturity were statistically equivalent when compared to either men or women in the adult group.

"It's not just that boys and girls are using the math network in the same ways but that similarities were evident across the entire brain," said Alyssa Kersey, postdoctoral scholar at the Department of Psychology, University of Chicago and first author on the paper. "This is an important reminder that humans are more similar to each other than we are different."

The researchers also compared the results of the Test of Early Mathematics Ability, a standardized test for 3- to 8-year-old children, from 97 participants (50 girls) to gauge the rate of math development. They found that math ability was equivalent among the children and did not show a difference in gender or with age. Nor did the team find a gender difference between math ability and brain maturity.

This study builds on the team's previous work that found equivalent behavioral performance on a range of mathematics tests between young boys and girls.

Cantlon said she thinks society and culture likely are steering girls and young women away from math and STEM fields. Previous studies show that families spend more time with young boys in play that involves spatial cognition. Many teachers also preferentially spend more time with boys during math class, predicting later math achievement. Finally, children often pick up on cues from their parent's expectations for math abilities.

"Typical socialization can exacerbate small differences between boys and girls that can snowball into how we treat them in science and math," Cantlon said. "We need to be cognizant of these origins to ensure we aren't the ones causing the gender inequities."

This project is focused on early childhood development using a limited set of math tasks. Cantlon wants to continue this work using a broader array of math skills, such as spatial processing and memory, and follow the children over many years.

Cantlon and Kersey were joined by Kelsey Csumitta at the University of Rochester on the study, titled "Gender Similarities in the Brain during Mathematics Development." This research received funding from the National Science Foundation and the National Institutes of Health.

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Materials provided by Carnegie Mellon University. Original written by Stacy Kish. Note: Content may be edited for style and length.