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How the Brain Learns: Researchers study timing, sensory systems, how regions connect

Garrison

Garrison "Gary" Cottrell, Ph.D.
Department of Computer Science and Engineering
UC San Diego

By Marlene Cimons, National Science Foundation
San Diego, CA, March 9
 -- If a teacher puts out too much new information in the final minutes of a class, students might have trouble “getting” it. If you have a final exam in six weeks, it might be better to study for it now and then again next week, rather than tonight and tomorrow.

“It depends, to some extent, on when you have to remember it,” says Gary Cottrell, a professor in the computer science and engineering department at the University of California at San Diego.  “Cramming the night before a test is okay, but if it’s something you need to know a month from now, spacing between study sessions makes a big difference.”

In other words, timing is everything.

This is the underpinning for the work of the Temporal Dynamics of Learning Center, whose goal is to understand the impact of timing in learning across brain and social systems.

“Time is an understudied variable,” says Cottrell, who directs the center.  “Timing is crucial in learning from the synaptic levels--connections between neurons--to long-time scales, like months and years.”

Learning occurs at any number of levels, among them, synapses and neurons, brain systems, motor behaviors, and in social interactions between teachers and pupils. Every time someone learns a new fact or interacts with another person, timing is a part of how the neurons function, in how sensory systems communicate, and how different regions of the brain connect with each other.

“We think timing can really be exploited to help us understand some of the basic ways in which information is integrated in our brains across a variety of timescales,” Cottrell says. “By understanding how the brain learns, we hope to improve education.”

For example, research shows that the underlying problem for at least some poor readers is their inability to perceive fast acoustic changes in speech sounds (phonemes). This “slow shutter speed” leads to a poor representation of the sound structure of the language, making it difficult for students to acquire the letter-sound correspondence rules for reading, according to Cottrell. 

“We believe that by investigating the temporal dynamics of learning we can change the capacity of children to learn, as well as change the environment to aid in learning,” Cottrell says. “Unfortunately, the study of the role of time and timing has been piecemeal at best; we aim to change that.”

The center, a National Science Foundation Science of Learning Center, began in 2006 and involves 40 researchers from across the United States, Canada and Australia. The scientists cross multiple disciplines, including machine learning, psychology, cognitive science, neuroscience, molecular genetics, biophysics, mathematics and education.

The center is based at the University of California at San Diego, with primary research partners at Rutgers University, University of California at Berkeley, and Vanderbilt University. NSF supports the center with about $3.5 million a year.

Center scientists are studying numerous areas, among them, the activity of synapses, which are structures that allow neurons (nerve cells) to pass electrical or chemical signals to other neurons; and brain systems, including brain waves and regions of the brain involved in forming memories.

In one experiment, for example, center scientists predicted that neurogenesis, or the addition of newly born neurons in the hippocampus, an area of the brain involved in forming and organizing memories, binds new memories together in time.  “They are the cells that group together things that you learned over a few days or weeks,” Cottrell says. 

Furthermore, they found that the hippocampus has “place cells” that are active for specific locations in an environment. In their experiment, the researchers trained rats to explore three distinct environments in the same room, introducing each new environment one of two ways: either spaced over the course of two to three weeks, or presented all at once in a single day. Rats that received training spaced over long periods of time had place cells that were active during exposure only to one of the three contexts, whereas rats trained to all three environments at once had more cells that were active in all three contexts. Reducing the number of newly born cells in the hippocampus also resulted in more cells active in all three contexts.

“We used to think that active cells in this region of the hippocampus would be active in all environments,” Cottrell says. “It turns out that spacing out experiences over time can create cell activity that is dedicated and selective for certain experiences, and that this type of activity is dependent upon newly born cells.”

Furthermore, “importantly, the ability to generate newly born cells increases with enrichment and aerobic exercise,” he adds.

Why is this important for education?  “Perhaps we should think twice before we eliminate physical education and enrichment programs due to financial cutbacks,” says Andrea Chiba, the center’s science director. “These may be very important for continued brain development and critical aspects of learning.”

In another center project, a Rutgers team led by April A. Benasich, professor of neuroscience, is studying the role of gamma waves in the infant brain, and their impact on language development. Gamma waves are fast, high-frequency, rhythmic brain responses that emerge when the brain engages in higher cognitive processes.

Research shows that, in the adult brain, gamma waves bind perceptions, thoughts and memories together. Until recently, however, scientists knew very little about the role of gamma waves in infants.

The Rutgers studies suggest that the power of gamma waves between the ages of 16 months to three years, typically an intense period of cognitive and language development, is an important predictor of later language ability, specifically at ages four and five: the stronger the gamma waves, the greater the likelihood of better language and cognitive skills.

“Infant cognitive ability correlates with power density functions even in an idling brain, that is, a brain not engaged in an active perceptual or cognitive task,” Benasich says. “Thus, the capability to generate higher power in certain frequency ranges at certain crucial developmental periods may well confer an advantage.”

Benasich and her research team looked at “resting” gamma power in the frontal cortex, the “thinking” part of the brain, in children 16, 24 and 36 months old, the time when children rapidly are learning words and what they mean.

After analyzing the babies’ EEG (electroencephalogram, a way to measure brain waves), they found that children with higher language and cognitive abilities had correspondingly higher gamma power than those with poorer scores. Similarly, children with better attention and inhibitory control, the ability to moderate or refrain from behavior when instructed, also had higher gamma power.

“Being able to determine an infant’s level of development could allow for more effective treatment at a critical point in time when the brain is laying down the foundations for cognition and language, and establishing efficient connections for future learning,” Benasich says.

They obtained their measurements by placing a soft bonnet with 62 sensors on the babies’ heads as they sat on their mother’s laps and quietly played. In separate tests, the children were evaluated for their emerging language and cognitive skills. The researchers looked both at children from families with typical language development and those at higher risk for problems because they were born into families with a history of language disorders. The group of children with a family history of language impairments showed lower levels of gamma activity.

Another study, known as the Gamelan Project, has been exploring the role of Balinese music--a style of music that emphasizes synchrony--on cognitive development, in particular, the ability to maintain an attention span. Two center postdoctoral fellows, Alexander Khalil and Victor Minces, are conducting the research.

The first phase of the project already has shown that a child’s ability to synchronize musically in a group setting correlates with his or her ability to focus attention. The team next plans to examine whether intensive music training can improve a child’s attention span.

“Important cognitive skills, such as attentional control, may be closely related to the capacity to maintain rhythmic synchrony within a group, an ability that music trains in unique ways,” Chiba says. 

Cottrell says the idea for the study originated with Khalil’s observation of students in his elementary school music class, where he was teaching Gamelan.  “He had a dozen kids playing instruments, and they were supposed to be doing it exactly in time with each other,” Cottrell says.  “He noticed there were some kids who were having a lot of trouble with this, and they tended to be the kids with ADD (attention deficit disorder).  He wondered whether teaching these kids Gamelan might improve their attention skills in general, so the Gamelan Project was born.”

Other center research includes, among other things, studying whether training autistic children to become “face experts” will improve their social skills; trying to develop robots trained to “read” a student’s facial expressions in order to improve intelligent tutoring systems; and figuring out how brains change as people become experts at perceptual skills, such as scanning for explosives in suitcases.

The scientists believe that a better understanding of the role of time and timing on scales ranging from milliseconds (when brain cells connect) to years (the time it takes to become an expert) potentially could transform education, “giving children a better chance of success in school, and, ultimately, in life,” Cottrell says.

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Jacobs School of Engineering
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