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Khaleel A. Razak

Associate Professor of Psychology
Khaleel Abdul Razak
Auditory Processing
Hearing plays a vital role in the way we communicate and even a small amount of hearing loss can have detrimental social and emotional impacts.  According to the World Health Organization, approximately one-third of people worldwide over age 65 are affected by disabling hearing loss.

Research by Razak, an auditory neurophysiologist, focuses on how the auditory cortex of the brain processes information about sound locations, and how those mechanisms are altered by developmental experience, disease and aging.  Razak is working to identify the neuron types that are lost or changed during aging, and to find combinations of behavioral or pharmacological therapies that could prevent brain changes affecting hearing loss.

Areas of Expertise

Areas of Expertise:
  • Minimizing age-related hearing loss
  • Reducing the effects of age-related hearing loss
  • Improving hearing as we age
  • Understanding auditory processing
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Q&A

Q: What is the goal of your research?
The fundamental goal of my research is to understand how the brain processes various sounds. We are interested in finding out how the neurons are processing these sounds differently, what circuits are involved and what the responses are that process these sounds. Based on this fundamental understanding we can identify what can go wrong with these aspects as people lose their hearing.

Q: Explain how the brain processes sound.
Neurons communicate with each other using electrical and chemical signals. When sound is present in the environment it is converted to electrical signals by your ears and then the neurons get those signals and respond differently to the different sounds. This is the way you are able to distinguish the different sounds and it’s the first step for processing and perceiving these different sounds.

Q: How do you analyze sound?
To analyze sound we use a spectrogram – a mechanism to visualize the sounds, the various frequencies that occur over a course of time within the signal and the intensity changes that happen within a sound. We are able to plot using a spectrogram and figure out the different types of phonetic changes that are present, as well as, see the different components that are present. If we understand the components of a sound, which is what the early stages of the auditory system are responding to, then we will be able to gain an understanding of how the entire auditory system is able to process the larger sound.

Q: How does our hearing change with age/disease?
There are two main changes that happen as we age that we’ve discovered – slowed down processing and increase in internal noise. As we get older the speed by which neurons communicate with each other is slower because of changes in the connection between neurons. The other thing that happens is that the processing becomes noisier.  With aging there is an increase of background noise. The signal to noise ratio is reduced. It becomes difficult from neurons to distinguish between the signals and the background noise.

Q: What have you discovered in your lab to aid age-related hearing loss?
We have identified neurons that are susceptible to aging and hearing loss. When you lose those neurons there is an increase of noise within the system. Our goal is to prevent the loss of those neurons and then see if that reduces that background noise. 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.

Q: How does your research relate to health? How does age-related hearing loss affect society?
Auditory hearing loss is the most significant auditory dysfunction in humans. We are interested in trying to understand what happens with age-related hearing loss, how the brain changes with hearing loss and how we can prevent it. In the lab we also try to understand what changes when Fragile X syndrome, which is one of the leading genetic causes of Autism Spectrum Disorder (ASD). People with Fragile X syndrome, particularly children, have abnormal responses to sounds. Close to one percent of children globally have ASD and a large percentage of them also have sensory dysfunction. We hope to understand why the brain of children with ASD reacts differently to the sounds and how the circuitry changes with the disorder.

Khaleel Abdul Razak "There is an urgent need to develop new therapeutic targets and appropriate biomarkers and outcome measures in which the underlying neural mechanism is known at multiple levels of analyses."

—Khaleel A. Razak
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