Research Roundup: Neuroscience of Smell and Sound

When you smell a rose, how does your brain process its fragrance? Does it treat it like a painting, perceiving the fragrance as a momentary snapshot of cellular activity? Or more like a symphony, an evolving ensemble of cells working to capture the scent?

New research from the Del Monte Institute for Neuroscience suggests that both processes play important and interrelated roles. The findings, published in Cell Reports, “reveal a core principle of the nervous system—flexibility in the kinds of calculations the brain makes to represent aspects of the sensory world,” says Krishnan Padmanabhan, an associate professor of neuroscience and corresponding author of the study.

Employing computer simulations, Padmanabhan and lead author Zhen Chen, a PhD student in the Department of Brain and Cognitive Sciences, found that so-called centrifugal fibers, which carry impulses from other parts of the central nervous system to the brain’s olfactory bulb, played a major role in the sense of smell. The fibers acted as a switch, toggling between alternate strategies to efficiently represent smells.

When the centrifugal fibers were in one state, the cells in the piriform cortex—where the perception of an odor forms—relied on the pattern of activity within a given instant in time. When the centrifugal fibers were in the other state, the cells in the piriform cortex improved both the accuracy and the speed with which cells detected and classified the smell by relying on the patterns of brain activity across time.

. . . and the Power of Song
Del Monte Institute neuroscientists are also advancing the understanding of how music is represented in the brain. Samuel Norman-Haignere, an assistant professor of neuroscience and biostatistics and computational biology, coauthored a study identifying neurons in the brain that “light up” to the sound of singing, but do not respond to any other type of music.

The singing-specific area of the brain is located in the temporal lobe, near regions that are selective for speech and music. Norman-Haignere and coauthors from MIT worked with epilepsy patients who had electrodes implanted in their brains in order to localize seizure-related activity as a part of their clinical care. The precision enabled by the electrodes “made it possible to pinpoint this subpopulation of neurons that responds to song,” says Norman-Haignere. “This finding, along with prior findings from our group, give a bird’s-eye view of the organization of the human auditory cortex and suggest that there are different neural populations that selectively respond to particular categories.”

The findings, published in Current Biology, related to both the human olfactory and auditory cortices and have important implications for the improvement of artificial intelligence.

—Kelsie Smith Hayduk

Location Tracking—A Cautionary Tale
If we turn off data tracking on our devices, are we untraceable?

Not necessarily.

“Switching off your location data is not going to entirely help,” says Gourab Ghoshal, an associate professor of physics, mathe- matics, and computer science and the Stephen Biggar ’92 and Elizabeth Asaro ’92 Fellow in Data Science.

In a study published in Nature Communications, Ghoshal and colleagues at four other universities found that even if individual users turned off data tracking, their mobility patterns could still be predicted with surprising accuracy based on data collected from other users.

How? It comes down to what the researchers call a user’s “colocation network.” The network includes people a user knows, such as family members, friends, or coworkers; and people the user does not know but who frequent particular locations at similar times as the user. The latter group might include people working in the same building but with different companies, parents whose children attend the same schools but who are unknown to each other, or people who shop at the same grocery store.

The researchers learned that the movement patterns of people in the first group of a user’s colocation network contain up to 95 percent of the information needed to predict that user’s mobility patterns. Even more surprisingly, they found that the movement patterns of the strangers in the second group could also provide enough information to predict up to 85 percent of the user’s movement.

The ability to predict the locations of individuals or groups can be beneficial in areas such as urban planning and pandemic control, but “we’re offering a cautionary tale,” says Ghoshal.

To protect privacy, “we can’t just tell people to switch off their phones or go off the grid. We need to have dialogues to put in place laws and guidelines that regulate how people collecting your data use it.”

—Lindsey Valich

‘Fracking’ Poses Risks to Infant Health
A new study by Elaine Hill, principal investigator in the Medical Center’s Health and Environmental Economics Lab, links the shale gas industry practice of hydraulic fracturing, known as “fracking,” to poorer infant health outcomes in regions near drilling sites.

The study, which appears in the Journal of Health Economics, is the latest in a series by Hill and Lala Ma of the University of Kentucky that establishes a causal relationship between fracking and diminished public health, the first of which conclusively demonstrated pollution of public water supplies near shale gas drilling sites.

In the most recent study, Hill—who is also an associate professor in the Departments of Public Health Sciences, Economics, and Obstetrics and Gynecology—and Ma examined the geographic expansion of shale gas drilling in Pennsylvania from 2006 to 2015, during which more than 19,000 wells were established in the state. They mapped the location of each new well in relation to groundwater sources that supply public drinking water and linked the information to maternal residences served by those water systems (as evidenced in birth records) and US Geological Service groundwater contamination measures. The data set allowed the researchers to pinpoint infant health outcomes—specifically preterm birth and low birth weight—before, during, and after drilling activity. Preterm birth and low birth weight are associated with a range of negative outcomes, including a higher risk for developing behavioral and social-emotional problems and learning difficulties.

“These findings indicate large social costs of water pollution generated by an emerging industry with little environmental regulation,” says Hill. “Our research reveals that fracking increases regulated contaminants found in drinking water but not enough to trigger regulatory violations. This adds to a growing body of research that supports the reevaluation of existing drinking water policies and possibly the regulation of the shale gas industry.”

—Mark Michaud