University of Maryland School of Medicine Scientists Identify the First Brain Cells to Respond to Sound

Discovery Could Enable Early Diagnosis of Autism and Other Cognitive Deficits

Some expectant parents play classical music for their unborn babies, hoping to boost their children’s cognitive capacity. While some research supports a link between prenatal sound exposure and improved brain function, scientists had not identified any structures responsible for this link in the developing brain.

A new study by University of Maryland School of Medicine (UMSOM) scientists, along with colleagues from the University of Maryland College Park, is the first to identify a mechanism that could explain an early link between sound input and cognitive function, often called the “Mozart effect.” Working with an animal model, the researchers found that a type of cell in the brain’s primary processing area during early development, long thought to have no role in transmitting sensory information, may conduct such signals after all.

The results, which could have implications for the early diagnosis of autism and other cognitive deficits, were published earlier this week in the Proceedings of the National Academy of Sciences.

“Our work is the first to suggest that very early in brain development, sound becomes an important sense,” said Amal Isaiah, MBBS, DPhil, assistant professor of otorhinolaryngology at UMSOM and one of the principal authors. “It appears that the neurons that respond to sound play a role in the early functional organization of the cortex. This is new, and it is really exciting.”

‌Working with young ferrets, Dr. Isaiah and Patrick Kanold, PhD, a professor of biology at University of Maryland College Park, observed sound-induced nerve impulses in subplate neurons, which help guide the formation of neural circuits in the same way that a scaffolding helps a construction crew erect a new building. This is the first time such impulses have been seen in these neurons. During development, subplate neurons are among the first neurons to form in the cerebral cortex—the outer part of the mammalian brain that controls perception, memory and, in humans, higher functions such as language and abstract reasoning.

The role of subplate neurons is thought to be temporary. Once the brain’s permanent neural circuits form, most subplate neurons disappear. Researchers assumed that subplate neurons had no role in transmitting sensory information, given their transient nature.

‌Scientists had thought that mammalian brains transmit their first sensory signals in response to sound after the thalamus, a large relay center, fully connects to the cerebral cortex. Studies from some mammals demonstrate that the connection of the thalamus and the cortex also coincides with the opening of the ear canals, which allows sounds to activate the inner ear. This timing provided support for the traditional model of when sound processing begins in the brain.

However, researchers had struggled to reconcile this conventional model with observations of sound-induced brain activity much earlier in the developmental process. Until Kanold, senior author of the paper, and his colleagues directly measured the response of subplate neurons to sound, the phenomenon had largely been overlooked.

“Previous research documented brain activity in response to sound during early developmental phases, but it was hard to determine where in the brain these signals were coming from,” Prof. Kanold said. “Our study is the first to measure these signals in an important cell type in the brain, providing important new insights into early sensory development in mammals.”

By identifying a source of early sensory nerve signals, the current study could lead to new ways to diagnose autism and other cognitive deficits that emerge early in development. Early diagnosis is an important first step toward early intervention and treatment.

The next step is to begin studying in more detail how subplate neurons affect brain development. There are many avenues of research: for instance, the researchers say that the neurons might play a role in some cognitive conditions such as autism.

“This collaboration between our school and researchers at College Park has yielded fascinating results,” said E. Albert Reece, MD, PhD, MBA, executive vice president for medical affairs at the University of Maryland, the John Z. and Akiko K. Bowers Distinguished Professor and dean of UMSOM. He is a top expert on pregnancy in diabetes, and has spent much of his career studying the topic. “This is basic research, but it has important potential implications for many child neurodevelopmental disorders. I look forward to seeing with these talented researchers find as their research goes forward in the future.”

About the University of Maryland School of Medicine

Commemorating its 210^th Anniversary, the University of Maryland School of Medicine was chartered in 1807 as the first public medical school in the United States. It continues today as one of the fastest growing, top-tier biomedical research enterprises in the world -- with 43 academic departments, centers, institutes, and programs; and a faculty of more than 3,000 physicians, scientists, and allied health professionals, including members of the National Academy of Sciences, and a distinguished recipient of the Albert E. Lasker Award in Medical Research.  With an operating budget of more than $1 billion, the School of Medicine works closely in partnership with the University of Maryland Medical Center and Medical System to provide research-intensive, academic and clinically-based care for more than 1.2 million patients each year. The School has over 2,500 students, residents, and fellows, and nearly $450 million in extramural funding, with more than half of its academic departments ranked in the top 20 among all public medical schools in the nation in research funding. As one of the seven professional schools that make up the University of Maryland, Baltimore campus, the School of Medicine has a total workforce of nearly 7,000 individuals. The combined School and Medical System (“University of Maryland Medicine”) has a total budget of $5 billion and an economic impact of nearly $15 billion on the state and local community. The School of Medicine faculty, which ranks as the 8^th-highest public medical school in research productivity, is an innovator in translational medicine with 600 active patents and 24 start-up companies. The School works locally, nationally, and globally, with research and treatment facilities in 36 countries around the world. Visit medschool.umaryland.edu/

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• Amal Isaiah, MBBS, DPhil
• Department of Otorhinolaryngology