Cortical Alpha Oscillations Predict Speech Intelligibility

By Andrew Dimitrijevic, Ph.D.

Hearing Health Foundation Emerging Research Grants recipient Andrew Dimitrijevic, Ph.D., and colleagues recently published “Cortical Alpha Oscillations Predict Speech Intelligibility” in the journal Frontiers in Human Neuroscience.

The scientists measured brain activity that originates from the cortex, known as alpha rhythms. Previous research has linked these rhythms to sensory processes involving working memory and attention, two crucial tasks for listening to speech in noise. However, no previous research has studied alpha rhythms directly during a clinical speech in noise perception task. The purpose of this study was to measure alpha rhythms during attentive listening in a commonly used speech-in-noise task, known as digits-in-nose (DiN), to better understand the neural processes associated with speech hearing in noise.

Fourteen typical-hearing young adult subjects performed the DiN test while wearing electrode caps to measure alpha rhythms. All subjects completed the task in active and passive listening conditions. The active condition mimicked attentive listening and asked the subject to repeat the digits heard in varying levels of background noise. In the passive condition, the subjects were instructed to ignore the digits and watch a movie of their choice, with captions and no audio.

Two key findings emerged from this study in regards to the influence of attention, individual variability, and predictability of correct recall.

First, the authors concluded that the active condition produced alpha rhythms, while passive listening yielded no such activity. Selective auditory attention can therefore be indexed through this measurement. This result also illustrates that these alpha rhythms arise from neural processes associated with selective attention, rather than from the physical characteristics of sound. To the authors’ knowledge, these differences between passive and active conditions have not previously been reported.

Secondly, all participants showed similar brain activation that predicted when one was going to make a mistake on the DiN task. Specifically, a greater magnitude in one particular aspect of alpha rhythms was found to correlate with comprehension; a larger magnitude on correct trials was observed relative to incorrect trials. This finding was consistent throughout the study and has great potential for clinical use.

Dimitrijevic and his colleagues’ novel findings propel the field’s understanding of the neural activity related to speech-in-noise tasks. It informs the assessment of clinical populations with speech in noise deficits, such as those with auditory neuropathy spectrum disorder or central auditory processing disorder (CAPD).

Future research will attempt to use this alpha rhythms paradigm in typically developing children and those with CAPD. Ultimately, the scientists hope to develop a clinical tool to better assess listening in a more real-world situation, such as in the presence of background noise, to augment traditional audiological testing.

Andrew Dimitrijevic, Ph.D., is a 2015 Emerging Research Grantee and General Grand Chapter Royal Arch Masons International award recipient. Hearing Health Foundation would like to thank the Royal Arch Masons for their generous contributions to Emerging Research Grants scientists working in the area of central auditory processing disorders (CAPD). We appreciate their ongoing commitment to funding CAPD research.

We need your help supporting innovative hearing and balance science. Please make a contribution today.

Understanding Auditory Processing Disorder

 By Frankie Huang

April 4 is Auditory Processing Disorder Awareness Day and the Hearing Health Foundation is highlighting the effects and challenges associated with living with APD.

Auditory processing disorder (APD), also known as central auditory processing disorder (CAPD), is an auditory deficit affecting how the central nervous system interprets verbal information. Those living with APD show impairments in sound localization, specifically their ability to isolate a sound source in social environments.

Approximately 5% of school-age children have APD. Children with APD often are uncertain about what they hear and have difficulty listening in loud background noises as well as understanding rapid speech. Often distracted, they can struggle to keep up with conversations which impedes their ability to read, spell, and follow oral directions.

Researchers found a correlation between working memory capacity, which is the ability to retain and manipulate information, and speech development. They found that working memory capacity was significantly lower in children with APD and may be the cause of their inability to separate and group incoming information and, in turn, lead to poor speech perception in noisy environments.

Other researchers found that peripheral hearing loss may affect performance in certain APD tests in older adults. Older adults with mild to moderate hearing loss did significantly poorer on tests that require recalling words, identifying high and low tone patterns, and repeating short sentences.

Although APD can be difficult to diagnose, there are telltale signs: poor auditory memory, difficulty identifying sounds, and a delayed response to verbal requests and instructions. APD is sometimes misdiagnosed as ADD/ADHD or dyslexia, so if you suspect you or a loved one may have APD, it is advised that they go through an individual comprehensive assessment with an audiologist for a more accurate diagnosis.

It is important to understand that research is still needed to understand auditory processing disorders, accurate methodologies for diagnosis, and the best interventions for each child or adult. Even though there are available strategies to treat children with APD, researchers are hard at work finding alternative treatments that will improve the lives of those suffering from APD.

Learn about Hearing Health Foundation’s 2016 Emerging Research Grants recipients who are conducting research to improve the lives of those affected by APD. These grantees are General Grand Chapter Royal Arch Masons International award recipients and we are grateful to the Masons for their ongoing support.

Neural sensitivity to binaural cues with bilateral cochlear implants

By Massachusetts Eye and Ear/Harvard Medical School

Many profoundly deaf people wearing cochlear implants (CIs) still face challenges in everyday situations, such as understanding conversations in noise. Even with CIs in both ears, they have difficulty making full use of subtle differences in the sounds reaching the two ears (interaural time difference, [ITD]) to identify where the sound is coming from. This problem is especially acute at the high stimulation rates used in clinical CI processors.

 A team of researchers from Massachusetts Eye and Ear/Harvard Medical School, including past funded Emerging Research Grantee, Yoojin Chung, Ph.D., studied how the neurons in the auditory midbrain encode binaural cues delivered by bilateral CIs in an animal model. They found that the majority of neurons in the auditory midbrain were sensitive to ITDs, however, their sensitivity degraded with increasing pulse rate. This degradation paralleled pulse-rate dependence of perceptual limits in human CI users.

This study provides a better understanding of neural mechanisms underlying the limitation of current clinical bilateral CIs and suggests directions for improvement such as delivering ITD information in low-rate pulse trains.

The full paper was published in The Journal of Neuroscience and is available here. This article was republished with permission of the Massachusetts Eye and Ear/Harvard Medical School.

Dr. Yoojin Chung, Ph.D. was a 2012 and 2013 General Grand Chapter Royal Arch Masons International award recipient through our Emerging Research Grants program. Hearing Health Foundation would like to thank the Royal Arch Masons for their generous contributions to Emerging Research Grantees working in the area of central auditory processing disorders (CAPD). We appreciate their ongoing commitment to funding CAPD research.

We need your help supporting innovative hearing and balance science through our Emerging Research Grants program. Please make a contribution today.

Take It From Me: Auditory Processing Disorder in Class

By Eliza Uberuaga

My legs grow tense as a classmate’s whispers flood my ears. My breath becomes short as another taps his foot against the desk. My stomach lurches as I watch two students turn in their tests. Why can’t I block out the noise? Why can’t I answer the questions faster? Why am I the only one struggling? I must run while they walk, work while they sleep and prepare while they rest.

When I was diagnosed with a learning disability, my parents brought me to the most respected doctors in New York and enrolled me at one of the most prestigious schools in the country. However, that did not cure, fix or help me. Why? Because no doctor, teacher, parent or friend can change the world that tells me I have a problem. I am labeled with Auditory Processing Disorder (APD), characterized as slow and viewed with pity.

I am not asking for sorrowful looks, sympathy hugs or uplifting pep talks. I am asking you to understand that the student in your classroom who needs extra time wasn’t daydreaming during the test. The girl who needs directions to be repeated is listening. The boy who is last to raise his hand has the answer.

These kids likely have APD, a learning disability that slows the comprehension of information. (It is also known as central auditory processing disorder, CAPD.) It is not their hearing that is impaired, but their auditory pathways. Information that is spoken can be difficult to process if said too quickly, in a loud place or in large chunks of speech. Having APD is like listening to a voicemail on a busy street while everyone else is listening to it in a quiet space. While most people can block out that background noise, people with APD hear that noise as if it is the message itself. When given directions, most brains organize the information, as if putting it into filing cabinets. Those with APD take longer to find the filing cabinets, which slows the pace at which they comprehend.

APD affects students in a variety of ways, but students with APD (and most other students) could benefit if we looked at our classrooms the way we look at our world: valuing everyone's uniqueness—in this case, the unique ways in which they learn. Here are some techniques that helped me.

1. Stimulate the Senses
   In an art history class, we learned about the making of a blind arch. Rather than looking at a diagram, my teacher had four kids (including me) make an arch with our arms. Putting pressure on our formation and watching it collapse taught us how to make the most effective structure. I learned about arches by listening, watching and feeling, as opposed to simply listening and writing.
   

2. Teach With Variety
   In a science class, my teacher gave us an outline of the notes, wrote them on the board and lectured us on them—supporting auditory, visual and kinesthetic learners. He allowed each student to retain the information in whatever ways that worked. In this class, no kid was left behind because every kid was supported.
   

3. Create a Quiet Learning Place
   In order for all students to be able to focus, especially ones with APD, it is best to minimize all noise when students are working or trying to concentrate. Although it may seem helpful to speak in a quieter voice, for a student with APD, hearing whispers while working can actually be worse than hearing words spoken at normal levels. Although it may seem helpful to speak in a quieter voice, it is best to not talk at all.

I hope that, by writing to teachers and sharing my story, I can help the 10-year-old girl who cries when she gets home from school and tells herself she will never be smart. Although she may not feel intelligent when she goes to the library to finish a test, she must understand that she does not have a problem. She only feels like she has a problem because the world around her is unable to understand her intelligence. The day will come when she feels the way she learns is truly all right, but maybe that day will come sooner for her than it came for me.

Eliza is a high school senior in the Bronx, New York. Originally published on Teaching Tolerance, and is reprinted by permission of the author.

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To donate today to Hearing Health Foundation and support groundbreaking research, visit hhf.org/name-a-grant.

2015 Emerging Research Grants Approved!

By Laura Friedman

Hearing Health Foundation is excited to announce that the 2015 Emerging Research Grants (ERG) have been approved by our Board of Directors, after a rigorous scientific review process. The areas that we are funding for the 2015 cycle are:

• Central Auditory Processing Disorder (CAPD): Four grants were awarded for innovative research that will increase our understanding of the causes, diagnosis, and treatment of central auditory processing disorder, an umbrella term for a variety of disorders that affect the way the brain processes auditory information. All four of our CAPD grantees are General Grand Chapter Royal Arch Masons International award recipients.
  

• Hyperacusis: Two grants were awarded that is focused on innovative research (e.g., animal models, brain imaging, biomarkers, electrophysiology) that will increase our understanding of the mechanisms, causes, diagnosis, and treatments of hyperacusis and severe forms of loudness intolerance. Research that explores distinctions between hyperacusis and tinnitus is of special interest. Both of our Hyperacusis grants were funded by Hyperacuis Research.
  

• Ménière’s Disease: Two grants were awarded for innovative research that will increase our understanding of the inner ear and balance disorder Ménière’s disease. One of the grants is funded by The Estate of Howard F. Schum and the other is funded by William Randolph Hearst Foundation through their William Randolph Hearst Endowed Otologic Fellowship.
  

• Tinnitus: Two grants were awarded for innovative research that will increase our understanding of the mechanisms, causes, diagnosis, and treatment of tinnitus. One of the grants is funded by the Les Paul Foundation and the other grantee is the recipient of The Todd M. Bader Research Grant of The Barbara Epstein Foundation, Inc.

To learn more about our 2015 ERG grantees and their research proposals and goals, please visit: http://hearinghealthfoundation.org/2015_researchers

Hearing Health Foundation is also currently planning for our 2016 ERG grant cycle. If you're interested in naming a research grant in any discipline within the hearing and balance space, please contact development@hhf.org.