Research Bytes

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Research Bytes

Here is a snapshot of the latest research discoveries from BCS faculty and their research teams. To read the stories in full and to get the latest research news, click the links below.

Distinct brain rhythms and regions help us reason about categories
In a study published in Neuron, BCS Prof Earl Miller (PILM), and his research team show that the ability to categorize items based on straightforward resemblance or abstract similarity arises from the brain’s use of distinct rhythms, at distinct times, in distinct parts of the prefrontal cortex (PFC). Humans have this capability whether the items look patently similar — such as Fuji and McIntosh apples — or they share a more abstract similarity — such as a screwdriver and a drill. Miller says their findings suggest a model of how the brain achieves category abstractions. By precisely describing the frequencies, locations, and timing of brain rhythms that govern categorization, the findings could advance our understanding of some aspects of autism spectrum disorders (ASD), says Miller. —David Orenstein | Picower Institute for Learning and Memory

Distinctive brain pattern helps habits form
Although we may think of routines as a single task, they are usually made up of many smaller actions.  For example, brushing your teeth entails picking up our toothbrush, squeezing toothpaste onto it, and then lifting the brush to our mouth. This process of grouping behaviors together into a single routine is known as “chunking,” but little is known about how the brain groups these behaviors together. Institute Professor and BCS Prof Ann Graybiel (MIBR) and her research team have now found that certain neurons in the brain are responsible for marking the beginning and end of these chunked units of behavior. These neurons, located in the striatum, a brain region highly involved in habit formation, fire at the outset of a learned routine, go quiet while it is carried out, then fire again once the routine has ended. — Anne Trafton | MIT News

Back-and-forth exchanges boost children’s brain response to language
A landmark 1995 study found that children from higher-income families hear about 30 million more words during their first three years of life than children from lower-income families. This “30-million-word gap” correlates with significant differences in tests of vocabulary, language development, and reading comprehension. A study from the laboratory of BCS Prof. John Gabrieli (MIBR), the Grover M. Hermann Professor in Health Sciences and Technology, found that back-and-forth conversations between adults and children are more critical to language development than the word gap. In a study of children between the ages of 4 and 6, they found that differences in the number of “conversational turns” accounted for a large portion of the differences in brain physiology and language skills that they found among the children. This finding applied to children regardless of parental income or education. — Anne Trafton | MIT News

Seeing the brain's electrical activity
Neurons in the brain communicate via rapid electrical impulses that enable the brain to coordinate behavior, sensation, thoughts, and emotion. Scientists who study this electrical activity usually measure these signals with electrodes inserted into the brain, a task that is notoriously difficult and time-consuming. BCS Prof Edward Boyden (MIBR) and his research group have developed a new approach: a light-sensitive protein that can be embedded into neuron membranes, where it emits a fluorescent signal that indicates how much voltage a particular cell is experiencing. This could allow scientists to study how neurons behave, millisecond by millisecond, as the brain performs a particular function. — Anne Trafton | MIT News

Study reveals how the brain tracks objects in motion
Catching a bouncing ball or hitting a ball with a racket requires estimating when the ball will arrive. Neuroscientists have long thought that the brain does this by calculating the speed of the moving object. However, a new study from the laboratory of Mehrdad Jazayeri (MIBR), the Robert A. Swanson Career Development Professor of Life Sciences, shows that the brain’s approach is more complex. The new findings suggest that in addition to tracking speed, the brain incorporates information about the rhythmic patterns of an object’s movement: for example, how long it takes a ball to complete one bounce. They found that people make much more accurate estimates when they have access to information about both the speed of a moving object and the timing of its rhythmic patterns. Anne Trafton | MIT News

Study finds early signatures of the social brain
Humans use an ability known as theory of mind every time they make inferences about someone else’s mental state — what the other person believes, what they want, or why they are feeling happy, angry, or scared. Behavioral studies have suggested that children begin succeeding at a key measure of this ability, known as the false-belief task, around age 4. However, a new study from BCS Prof Rebecca Saxe  and her research group has found that the brain network that controls theory of mind is already formed in children as young as 3. The MIT study is the first to use functional magnetic resonance imaging (fMRI) to scan the brains of young children as they perform a task requiring theory of mind — in this case, watching a short animated movie involving social interactions between two characters. — Anne Trafton | MIT News

Researchers identify important role for gene in 16p11.2 deletion autism
In a new study of one of the most common genetic causes of autism, MIT researchers, led by Mriganka Sur (PILM), the Newton Professor of Neuroscience and director of the Simons Center for the Social Brain at MIT, have identified a molecular mechanism that appears to undermine the ability of neurons in affected mice to properly incorporate changes driven by experience. The findings suggest that a particular gene, MVP, is likely consequential in people with 16p11.2 deletion syndrome. Accounting for up to 1 percent of autism cases, 16p11.2 deletion occurs in people who are missing a small region of DNA near the center of one copy of chromosome 16. For years, scientists have been working to determine exactly how the reduced presence of 29 protein-encoding genes leads to clinical symptoms of the syndrome, such as autism-like behaviors, developmental delay, and intellectual disability. — David Orenstein | Picower Institute for Learning and Memory

Machine-learning system processes sounds like humans do
Using a machine-learning system known as a deep neural network, Josh McDermott, the Frederick A. and Carole J. Middleton Assistant Professor of Neuroscience, and his research group have created the first model that can replicate human performance on auditory tasks such as identifying a musical genre. This model, which consists of many layers of information-processing units that can be trained on huge volumes of data to perform specific tasks, was used by the researchers to shed light on how the human brain may be performing the same tasks. The study also offers evidence that the human auditory cortex is arranged in a hierarchical organization, much like the visual cortex. In this type of arrangement, sensory information passes through successive stages of processing, with basic information processed earlier and more advanced features such as word meaning extracted in later stages. — Anne Trafton | MIT News

Calcium-based MRI sensor enables more sensitive brain imaging
BCS and BE Prof Alan Jasanoff (MIBR) and his research group have developed a new magnetic resonance imaging (MRI) sensor that for monitoring neural activity deep within the brain by tracking calcium ions. Because calcium ions are directly linked to neuronal firing — unlike the changes in blood flow detected by other types of MRI, which provide an indirect signal — this new type of sensing could allow researchers to link specific brain functions to their pattern of neuron activity, and to determine how distant brain regions communicate with each other during particular tasks. In tests in rats, the researchers showed that their calcium sensor can accurately detect changes in neural activity induced by chemical or electrical stimulation, deep within a part of the brain called the striatum. — Anne Trafton | MIT News

Cognitive scientists define critical period for learning language
A great deal of evidence suggests that it is more difficult to learn a new language as an adult than as a child, which has led scientists to propose that there is a “critical period” for language learning. However, the length of this period and its underlying causes remain unknown. A new study out of BCS Prof. Josh Tenenbaum’s lab suggests that children remain very skilled at learning the grammar of a new language much longer than expected — up to the age of 17 or 18. However, the study also found that it is nearly impossible for people to achieve proficiency similar to that of a native speaker unless they start learning a language by the age of 10. The findings are based on an analysis of a grammar quiz taken by nearly 670,000 people, which is by far the largest dataset that anyone has assembled for studying language-learning ability. — Anne Trafton | MIT News

Brain circuit helps us learn by watching others
It’s often said that experience is the best teacher, but the experiences of other people may be even better. If you saw a friend get chased by a neighborhood dog, for instance, you would learn to stay away from the dog without having to undergo that experience yourself. This kind of learning, known as observational learning, offers a major evolutionary advantage, says BCS Prof Kay Tye (PILM). Tye and her colleagues at MIT have now identified the brain circuit that is required for this kind of learning: the anterior cingulate cortex (ACC), which transmits socially-derived information to the basolateral amygdala (BLA), where it assigns predictive value to enable social cognition. —Anne Trafton | MIT News