Researchers at the University of Minnesota have gained insight into the complex interactions that occur between the ear and brain. They could advance the design of better hearing aids or cochlear implants.
Psychology professor Andrew Oxenham and psychology researchers Magdalena Wojtczak and Anahita Mehta tested volunteers with normal hearing. Each subject was presented with pairs of tones, one low and one high; sometimes the two tones were simultaneous and on the beat, and sometimes one was 50 milliseconds early or late. Using EEG and behavioral activity, researchers monitored whether the brain, or the volunteers’ conscious perception, could pick up timing differences within a pair of tones. They found that if a high flute note comes a little earlier than a bass note, the participant probably wouldn’t notice. But if the bass note came earlier, they would. They also noted that beat didn’t matter. What was important was the order in which the notes were played.
The fact that a low note could come in after a high note without the delay being noticed surprised researchers. Low notes have longer wavelengths, and the cochlea of the inner ear takes longer to respond to them. A low note coming in late, compounding the delay that already exists in the inner ear, should have been noticeable. But the opposite happened. “What we discovered is that the brain seems to compensate for the inner ear’s built-in delay in giving us an accurate report on low notes,” Oxenham explains.
The study is published in the January issue of Proceedings of the National Academy of Sciences.
A study coauthored by Mindy Morales-Williams, a University of Minnesota postdoctoral student in the College of Biological Sciences, found that thousands of lakes in Canada and the United States, including Minnesota, are at risk due to rising chloride levels caused by road salt. The study was the first to examine the impact of road salt on freshwater across a broad geographic region.
Researchers used data from a variety of sources to compile long-term chloride concentrations from 371 lakes across North America. Lakes used in the study had at least a decade worth of chloride data, a low chloride concentration (no brackish lakes), and a surface area greater than about 2.5 acres.
Because rising chloride levels are expected to persist, and even increase, in the coming decades, 14 lakes in the study are expected to surpass levels the Environmental Protection Agency deems necessary to support aquatic life in lakes by the year 2050. Thirteen of those lakes are in Minnesota. Regional models predict that around 7,770 lakes are at risk for increased chloride levels. “This is a striking example of the challenges we face in balancing population growth and urban sprawl with maintaining our freshwater resources for future generations,” says Morales-Williams.
The study was published in the April issue of Proceedings of the National Academy of Sciences.
A team of scientists, led by University of Minnesota associate professor of chemical engineering and materials science Paul Dauenhauer (Ph.D. ’08), has invented a new technology to produce renewable car tires from trees and grasses. The process could shift production away from a reliance on fossil fuels toward more renewable resources.
The team created a new chemical process to make isoprene, the key molecule in car tires, using natural products like trees, grasses, or corn, Dauenhauer says. The U’s Office for Technology Commercialization has applied for a patent on the renewable rubber technology, which could be applied to other uses besides tires.
In addition to other U researchers, including professors Michael Tsapatsis and Kechun Zhang, the team consisted of scientists from the University of Massachusetts Amherst, and the Center for Sustainable Polymers, a National Science Foundation funded center at the University of Minnesota.
The study was published in the January issue of ACS Catalysis.
A research team led by University of Minnesota scientists has developed a process to successfully rewarm large-scale animal heart valves and blood vessels preserved at very low temperatures, a process that could potentially increase the availability of organs and tissues for transplantation.
John Bischof, the study’s senior author and a mechanical engineering and biomedical engineering professor, says this is the first time that anyone has been able to scale up to a larger biological system and demonstrate successful, fast, and uniform warming of preserved tissue without damaging it.
More than 60 percent of hearts and lungs donated for transplantation must be discarded each year because the tissues cannot be kept on ice for longer than four hours. Long-term preservation methods, like vitrification, that cools biological samples to an ice-free glassy state using very low temperatures (between -160 and -196 degrees Celsius) have been around for decades. But rewarming has remained an ongoing problem because tissues (particularly larger tissues) are often damaged during the rewarming process, making them unusable.
The study was published in the March issue of Science Translational Medicine.