Khaleel Razak, Ph.D.
Meet the Researcher
Razak received his doctorate in neuroscience at the University of Wyoming and is now an associate professor of psychology and neuroscience at the University of California, Riverside. Razak’s 2018 Emerging Research Grant is generously funded by the General Grand Chapter Royal Arch Masons International.
Brain plasticity is the major topic of interest in my research career. When it comes to presbycusis (age-related hearing loss), we know there are changes in cellular and circuit mechanisms in the auditory system. But the relative contributions of brain aging and hearing loss are not easy to disambiguate. To do this, we will compare genetically engineered, age-matched mice with one group experiencing presbycusis and a second group that ages without considerable hearing loss. We will measure spectrotemporal processing—the processing of sounds with complex changes in frequency over time, such as speech processing.
Understanding how the auditory system processes behaviorally relevant sounds and how such processing changes during development, or as a result of disorders with communication implications, are long-term goals of this project. I hope to contribute new data regarding auditory processing in the aging brain and to determine how hearing loss contributes to aging trajectories. I also hope to develop therapeutic strategies to delay or prevent central auditory processing decline due to presbycusis.
My dream as a child was to play cricket for India, and I actually made it to the university level! But I became seriously interested in science while working on my senior thesis, which was to develop a texting device (this was in the early ’90s!) for the hearing impaired. It used push-button phones to encode English letters to be transmitted through a regular landline. A decoder at the receiving end would display the text. We tested a prototype in a school for deaf children in Chennai, India, sparking my interest in hearing and
auditory processing.
Having worked in hearing science since 1996, I’d say a career highlight is receiving the National Science Foundation Career Award in 2013. It considers research as well as research/education integration, and I am passionate about both aspects. I also enjoy taking photos. Thinking about their composition makes me stop and look at a subject from multiple perspectives—I find that it’s not unlike examining research data.
Khaleel Razak, Ph.D.’s grant is generously funded by the General Grand Chapter Royal Arch Masons International. HHF thanks the Royal Arch Masons for their ongoing commitment to research in the area of central auditory processing disorders (CAPD).
The Research
University of California, Riverside
Age-related hearing loss and cortical processing
Presbycusis (age-related hearing loss) is one of the most prevalent forms of hearing impairment in humans, and contributes to speech recognition impairments and cognitive decline. Both peripheral and central auditory system changes are involved in presbycusis. The relative contributions of peripheral hearing loss and brain aging to presbycusis-related auditory processing declines remain unclear. This project will address this question by comparing genetically engineered, age-matched mice with one group experiencing presbycusis and a second group that does not. Spectrotemporal processing (such as speech processing) will be studied as an outcome measure.
Impact of age-related hearing loss on cortical processing of frequency modulated sweeps
Ageing-related plasticity of the central nervous system causes impairments in auditory processing, including speech processing difficulties. This is exacerbated by peripheral hearing loss. Speech-processing difficulties may arise due to the inability to discriminate frequency modulated (FM) sweeps. However, the mechanisms underlying deterioration ofFM sweep processing remain unknown. Understanding plasticity ofFM processing will provide fundamental insights on how spectrotemporal integration by auditory neurons is altered in the aging population. Neural selectivity for FM sweeps depends on the balance between excitatory and inhibitory inputs to auditory neurons. It is known that inhibitory neurotransmission is down-regulated during aging. The aim of the studies proposed here is to initiate research on age-related changes in inhibition in the auditory cortex of mice and the consequences of such changes to neural processing ofFM sweeps. The proposed studies will characterize the spectral bandwidth and timing of sideband inhibition in the young (1-3 months), middle aged (5-8 months), and old (>12 months) mouse cortex and test the hypothesis that weakening inhibition with age is a mechanism of altered FM processing. These studies will serve as a baseline for research into cortical processing in various genetic strains of mice with varying degrees of age-related hearing loss.
Long-term goal: To systematically examine the optimal combination of hearing aids and behavioral and pharmacological approaches to delay or prevent the declines in complex sound processing seen in presbycusis.