Neuroscientist receives CAREER grant to research on auditory processing and sound localization

Twenty years ago Khaleel A. Razak was an electronics engineering student focused on creating a telephone for hearing-impaired children in Chennai, India. Today he is a neuroscientist at the University of California, Riverside whose research on how the brain processes everyday sounds may lead to therapies for age-related hearing problems and Fragile X Syndrome.

An assistant professor of psychology and neuroscience at UC Riverside, Razak has been awarded a five-year, $866,902 Faculty Early Career Development Program (CAREER) grant from the National Science Foundation to further his research.

Razak's lab at UCR focuses on how the auditory brain processes behaviorally relevant sounds and how those mechanisms are altered by developmental experience, disease and aging. The NSF grant will specifically support research on how the auditory cortex of the brain processes information about sound locations.

"Precise sound localization can be a matter of life and death," he explained. "The auditory cortex is necessary for sound localization, but our understanding of the relevant neural processing is rudimentary. Sound localization is also interesting from a computational perspective because we explore how neurons integrate inputs from the two ears."

The NSF funding will allow Razak's lab to investigate the neural computations that generate cortical maps underlying sound localization behavior in the pallid bat.

"The pallid bat is a bit unusual among bats in that it uses echolocation for general orientation and obstacle avoidance, but listens for prey on the ground, like crickets, scorpions and millipedes," he said. "Behavioral studies indicate the pallid bat can localize sounds with an accuracy of about 2 degrees."

Pallid bats and humans appear to process sound locations similarly, calculating direction via intra-cortical networks that are little understood. Razak's team will map neural selectivity for sound locations in the auditory cortex, and determine the neurotransmitters involved in shaping selectivity as well as the circuitry that shapes spatial selectivity. The project will provide fundamental insights on how intra-cortical networks shape feature detectors and maps.

In addition to basic sound localization mechanisms, Razak's research also focuses on mouse models of aging and Fragile X Syndrome, an autism spectrum disorder. Age-related hearing loss is the most preventable hearing-related problem in the world, the neuroscientist explained.

"People develop problems with processing rapid changes in sound frequency," he said. "It's a processing deficit that accumulates with age, a declining ability to distinguish, for example, the difference between 'bah' and 'dah.'" This problem gets more acute in difficult listening conditions such as a noisy room.

While hearing aids amplify sound, they don't improve speech recognition because the brain itself has changed, Razak added.

"Impaired speech recognition may lead to isolation and reduce cognitive abilities," he said. "We hope to identify the neuron types that seem to be lost or changed during aging. There may be combinations of behavioral or pharmacological therapies that could delay or prevent these changes. But we need to characterize the age-related changes first." A recent publication from the lab in the Journal of Neurophysiology provides clues on such changes in the auditory cortex with age.

Razak's research of auditory processing systems extends to Fragile X Syndrome. Research in humans and the mouse model of Fragile X Syndrome demonstrate auditory hypersensitivity and strong startle responses to sounds, he said. "An underlying problem might be hyperexcitability of individual neurons to sensory stimulus," he added. One of the major goals in the lab is to use auditory hypersensitivity in Fragile X Syndrome to develop new therapeutic approaches to alleviate symptoms. This work is funded by the FRAXA Research Foundation.

In addition to his laboratory research, Razak conducts seminars at the bat exhibit in the California Science Center in Los Angeles, for which he provides biological consulting; teaches public employees about bat survey methods and conservation; and participates in K-12 programs in the Inland Empire on neuroscience and bat biology and behavior.

Source: University of California - Riverside