Tuning into a New Language on the Fly

Research Roundup updates HR readers on some of the latest research and clinical findings related to hearing health care. Where appropriate, sources and original citations are provided, and readers are encouraged to refer to the primary literature for more detailed information. Additionally, related articles can be found and keywords can be searched in the HR Online Archives.

Research conducted at Rutgers University has shown that exposure to a changed acoustic and social environment can rewire the way the brain processes sounds. Beginning in the cochlea of the inner ear, nerve cells of the auditory system parse incoming sounds into their different components. Study of the responses of individual brain cells has shown that they respond best to a particular frequency (pitch) of sound, less well to nearby frequencies, and poorly to distant sound frequencies. The range of effective frequencies can be measured as the “tuning width.” Cells with similar tuning are found together, producing an orderly map of all the possible frequencies spread out across the auditory part of the brain.

In a new study, published August 6 in the online open-access journal PLoS ONE, these tuning properties were used to study the way experience can change the brain in two species of songbirds. Songbirds provide the best-developed animal system for studying vocal learning because juvenile birds learn to sing by hearing and imitating adults, much as human infants do. The songbird brain contains an area similar to the mammalian auditory cortex (the NCM) that is specialized to discriminate and remember the songs of other birds of the same species.

In the study, adult zebra finches (which normally live in a single-species colony) were moved to a canary colony, and adult canaries were moved to a zebra finch colony. These birds experienced a novel environment because canaries and zebra finches produce learned species-typical vocalizations that differ in their acoustic components. Other birds of each species remained in their home colony and still others were placed in individual isolation.

After 9 days of altered experience, the tuning width was assessed in the brains of these animals and was found to be significantly different from that of birds that remained at home. In birds of both species that experienced life in a foreign colony, the tuning became narrower (ie, more selective). In canaries, which can learn new song elements in adulthood, these effects were also influenced by season, and may reflect the role of vocal imitation in the seasonal breeding behavior of this species. Isolation had the opposite effect: the tuning became wider (ie, less selective).

In other words, when a bird is exposed to a new acoustic and social environment, basic auditory properties in its brain change to become more finely tuned. In human terms, a possible analogy for this experiment is when a person travels to a foreign country where an unfamiliar language is spoken. The individual has to pay close attention and gradually begins to make out the words in the speech stream (and perhaps to recognize a few from the phrase book). This process of “tuning in” to the new sound and social environment may involve increased sensitivity to fine acoustic details and may produce measurable tuning changes such as those observed at the neural level in these songbirds.

In contrast, the songbirds’ tuning coarsened in the impoverished, monotonous environment provided by being housed in isolation.

The researchers suggest that these songbird results provide a useful experimental model of sensory plasticity accessibility, which is worthy of further study. Consistent with observations in other sensory systems, the tuning map in the brain is not rigid, but adjusts dynamically to current experience. Source: American Academy for the Advancement of Science.

Little Girl Gives Mom Kiss of Deaf

Original Citation

Terleph TA, Lu K, Vicario DS. Response properties of the auditory telencephalon in songbirds change with recent experience and season. Available at: www.plosone.org/article/info:doi/10.1371/journal.pone.0002854.

Hicksville, NY, homemaker Gail Schwartzman had been away for the day, and when she returned home, her daughter gave her a huge kiss on her left ear. Newsday reports it was the suction from her daughter’s kiss that managed to displace her eardrum as well as paralyze a trio of bones in her ear and left her with tinnitus.

“She grabbed me and gave me a hug and a really big kiss on the left ear. And while she was doing it, it felt like she was sucking the air out of my head. I couldn’t push her away because I had this terrible sensation in my head,” Schwartzman told Newsday. “When she was finished, I had no hearing in that ear. The hearing slowly came back but with screeching noises in my ear.”

Schwartzman’s story was widely reported in national media outlets in June 2008.

According to Levi A. Reiter, PhD, professor and audiology program head at Hofstra University, who will publish a report on Schwartzman’s situation this summer, Schwartzman’s daughter kissed the aperture of her left ear, resulting in immediate pain, screeching tinnitus, facial spasms, and total hearing loss on her left side.

“Hours later, most of her hearing returned, leaving her with a 35 dBHL sensorineural hearing loss in the lower frequencies: 250, 500, and 1,000 Hz,” Reiter says. “In addition, she was left with screeching tinnitus, hyperacusis, dysacusis (distorted hearing), and facial twitching.”

Reiter says that 6 months before the kiss, Schwartzman had her hearing tested after a cerumen cleaning and it was completely WNL bilaterally. Prior to seeing Reiter, she had seen ENTs, and had audiological evaluations—including ABR and OAE tests—but was given no diagnostic conclusion.

She was referred to Reiter, who conducted a thorough study including an ABLB to document hyperacusis, and a complete acoustic reflex battery that included contralateral and ipsilateral reflexes. That revealed a paralyzed acoustic reflex on the left side, Reiter says. After facial nerve testing, a fully functional seventh nerve was revealed, suggesting a detached stapedial ligament.

“Therefore, the way I understand it, the suction from the kiss pulled the TM laterally, which ultimately pulled the stapes forcefully away from the oval window. This damaged the stapedial muscle or tendon and paralyzed the acoustic reflex—although the ossicular chain was left completely intact (there was no conductive component),” Reiter says. “The abrupt pulling of the stapes out of the oval window caused a tsunami of sorts in the fluids of the cochlea, damaging some of the contents therein [eg, outer hair cells].”

Reiter says the absence of an acoustic reflex unilaterally results in an inability to modulate loudness, which contributed to her documented hyperacusis.

Since Schwartzman’s story was first released, Reiter has found several new cases of “Reiter’s Ear Kiss Syndrome” (REKS), as some have named this disorder. “If any audiologist or ENT comes across any suction-related cases, I would sincerely appreciate hearing from them,” Reiter says. “If verified, their data will be included in an ongoing epidemiological study.” Reiter can be contacted at [email protected]

Perfect Pitch More Common Than Previously Thought

Researchers at the University of Rochester’s Eastman School of Music and Department of Brain and Cognitive Sciences have developed a unique test for perfect pitch, and have found surprising results. Their research shows that perfect pitch—the ability to recognize and remember a tone without a reference—is apparently much more common in nonmusicians than expected. Previous tests have overlooked these people because, without extensive musical training, it’s very difficult for someone to identify a pitch by name. The new test can be used on nonmusicians, and is based on a technique to discern how infants recognize words in a language they’re learning. The findings were presented at the International Conference on Music Perception and Cognition in Sapporo, Japan, on August 25.

To the surprise of the researchers, there were a number of nonmusicians who used perfect pitch to identify groups of notes but did not know they had perfect pitch. The team is now investigating the other cognitive abilities of these listeners with perfect pitch to determine what might distinguish them from the more numerous listeners with only relative pitch perception. They are also planning to investigate a controversial hypothesis that native speakers of tonal languages, like Chinese, which utilize pitch to distinguish different words, have their perfect pitch abilities enhanced by their language’s necessary attention to pitch. Source: University of Rochester


Letters

Dear Editor,
I read with great interest your recent article (“Fitting Asymmetrical Hearing Losses,” by C. Mike Hall, AuD, and Carl Croutch, AuD) in the July issue of The Hearing Review. I was disappointed, however, that the article did not mention TransEar®, a bone conduction hearing aid developed specifically for individuals with single-sided deafness (SSD).

Each year in the US approximately 50,000 people experience SSD. Most of us in practice realize that old-school products like CROS hearing aids have a high rejection rate. Air conduction devices also have limited success. And only a minority of candidates choose to pursue surgery. The net result is that most patients with SSD choose to do nothing.

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Daniel R. Schumaier, PhD
President, Ear Technology Corporation