Neural Correlates of the Binaural Masking Level Difference in Human Frequency-Following Responses

Abstract

The binaural masking level difference (BMLD) is an auditory phenomenon where binaural tone-in-noise detection is improved when the phase of either signal or noise is inverted in one of the ears (S_πN_o or S_oN_π, respectively), relative to detection when signal and noise are in identical phase at each ear (S_oN_o). Processing related to BMLDs and interaural time differences has been confirmed in the auditory brainstem of non-human mammals; in the human auditory brainstem, phase-locked neural responses elicited by BMLD stimuli have not been systematically examined across signal-to-noise ratio. Behavioral and physiological testing was performed in three binaural stimulus conditions: S_oN_o, S_πN_o, and S_oN_π. BMLDs at 500 Hz were obtained from 14 young, normal-hearing adults (ages 21–26). Physiological BMLDs used the frequency-following response (FFR), a scalp-recorded auditory evoked potential dependent on sustained phase-locked neural activity; FFR tone-in-noise detection thresholds were used to calculate physiological BMLDs. FFR BMLDs were significantly smaller (poorer) than behavioral BMLDs, and FFR BMLDs did not reflect a physiological release from masking, on average. Raw FFR amplitude showed substantial reductions in the S_πN_o condition relative to S_oN_o and S_oN_π conditions, consistent with negative effects of phase summation from left and right ear FFRs. FFR amplitude differences between stimulus conditions (e.g., S_oN_o amplitude–S_πN_o amplitude) were significantly predictive of behavioral S_πN_o BMLDs; individuals with larger amplitude differences had larger (better) behavioral B MLDs and individuals with smaller amplitude differences had smaller (poorer) behavioral B MLDs. These data indicate a role for sustained phase-locked neural activity in BMLDs of humans and are the first to show predictive relationships between behavioral BMLDs and human brainstem responses.

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Natural Compounds as Occult Ototoxins? Ginkgo biloba Flavonoids Moderately Damage Lateral Line Hair Cells

Abstract

Several drugs, including aminoglycosides and platinum-based chemotherapy agents, are well known for their ototoxic properties. However, FDA-approved drugs are not routinely tested for ototoxicity, so their potential to affect hearing often goes unrecognized. This issue is further compounded for natural products, where there is a lack of FDA oversight and the manufacturer is solely responsible for ensuring the safety of their products. Natural products such as herbal supplements are easily accessible and commonly used in the practice of traditional eastern and alternative medicine. Using the zebrafish lateral line, we screened a natural products library to identify potential ototoxins. We found that the flavonoids quercetin and kaempferol, both from the Gingko biloba plant, demonstrated significant ototoxicity, killing up to 30 % of lateral line hair cells. We then examined a third Ginkgo flavonoid, isorhamnetin, and found similar levels of ototoxicity. After flavonoid treatment, surviving hair cells demonstrated reduced uptake of the vital dye FM 1-43FX, suggesting that the health of the remaining hair cells was compromised. We then asked if these flavonoids enter hair cells through the mechanotransduction channel, which is the site of entry for many known ototoxins. High extracellular calcium or the quinoline derivative E6 berbamine significantly protected hair cells from flavonoid damage, implicating the transduction channel as a site of flavonoid uptake. Since known ototoxins activate cellular stress responses, we asked if reactive oxygen species were necessary for flavonoid ototoxicity. Co-treatment with the antioxidant D-methionine significantly protected hair cells from each flavonoid, suggesting that antioxidant therapy could prevent hair cell loss. How these products affect mammalian hair cells is still an open question and will be the target of future experiments. However, this research demonstrates the potential for ototoxic damage caused by unregulated herbal supplements and suggests that further supplement characterization is warranted.

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Toward a Nonspeech Test of Auditory Cognition: Semantic Context Effects in Environmental Sound Identification in Adults of Varying Age and Hearing Abilities

by Valeriy Shafiro, Stanley Sheft, Molly Norris, George Spanos, Katherine Radasevich, Paige Formsma, Brian Gygi

Objective

Sounds in everyday environments tend to follow one another as events unfold over time. The tacit knowledge of contextual relationships among environmental sounds can influence their perception. We examined the effect of semantic context on the identification of sequences of environmental sounds by adults of varying age and hearing abilities, with an aim to develop a nonspeech test of auditory cognition.

Method

The familiar environmental sound test (FEST) consisted of 25 individual sounds arranged into ten five-sound sequences: five contextually coherent and five incoherent. After hearing each sequence, listeners identified each sound and arranged them in the presentation order. FEST was administered to young normal-hearing, middle-to-older normal-hearing, and middle-to-older hearing-impaired adults (Experiment 1), and to postlingual cochlear-implant users and young normal-hearing adults tested through vocoder-simulated implants (Experiment 2).

Results

FEST scores revealed a strong positive effect of semantic context in all listener groups, with young normal-hearing listeners outperforming other groups. FEST scores also correlated with other measures of cognitive ability, and for CI users, with the intelligibility of speech-in-noise.

Conclusions

Being sensitive to semantic context effects, FEST can serve as a nonspeech test of auditory cognition for diverse listener populations to assess and potentially improve everyday listening skills.

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Does unilateral single-event multilevel surgery improve gait in children with spastic hemiplegia? A retrospective analysis of a long-term follow-up

Publication date: February 2017
Source:Gait & Posture, Volume 52
Author(s): Christian Schranz, Annika Kruse, Tanja Kraus, Gerhardt Steinwender, Martin Svehlik
Single event multilevel surgery (SEMLS) has become a standard intervention for children with cerebral palsy (CP). SEMLS proved to improve the gait in bilateral spastic cerebral palsy and those improvements can be maintained in the long term. However there is no evidence on the long-term outcome of unilateral SEMLS in children with unilateral spastic cerebral palsy.The gait analyses and clinical data of 14 children (9 male/5 female, mean age 12.1) with unilateral CP (6 children Gross Motor Function Classification System Scale level I and 8 children level II) were retrospectively reviewed at four time-points: preoperatively, 1year, 3–5 years and approximately 10 years after unilateral SEMLS. The Gait Profile Score (GPS) of the affected leg was used as a main and the number of fine tuning procedures as well as complications rate (Clavien-Dindo classification) as secondary outcome measures.The gait improved postoperatively and the GPS of the affected leg significantly declined by 3.73° which is well above the minimal clinical important difference of 1.6°. No deterioration of GPS occurred throughout the follow-up period. Therefore the postoperative improvement was maintained long-term. However, additional fine-tuning procedures had to be performed during the follow-up in 5 children and three complications occurred (one level II and two level III).The results indicate that children with unilateral cerebral palsy benefit from unilateral SEMLS and maintain gait improvements long-term.



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Does unilateral single-event multilevel surgery improve gait in children with spastic hemiplegia? A retrospective analysis of a long-term follow-up

Publication date: February 2017
Source:Gait & Posture, Volume 52
Author(s): Christian Schranz, Annika Kruse, Tanja Kraus, Gerhardt Steinwender, Martin Svehlik
Single event multilevel surgery (SEMLS) has become a standard intervention for children with cerebral palsy (CP). SEMLS proved to improve the gait in bilateral spastic cerebral palsy and those improvements can be maintained in the long term. However there is no evidence on the long-term outcome of unilateral SEMLS in children with unilateral spastic cerebral palsy.The gait analyses and clinical data of 14 children (9 male/5 female, mean age 12.1) with unilateral CP (6 children Gross Motor Function Classification System Scale level I and 8 children level II) were retrospectively reviewed at four time-points: preoperatively, 1year, 3–5 years and approximately 10 years after unilateral SEMLS. The Gait Profile Score (GPS) of the affected leg was used as a main and the number of fine tuning procedures as well as complications rate (Clavien-Dindo classification) as secondary outcome measures.The gait improved postoperatively and the GPS of the affected leg significantly declined by 3.73° which is well above the minimal clinical important difference of 1.6°. No deterioration of GPS occurred throughout the follow-up period. Therefore the postoperative improvement was maintained long-term. However, additional fine-tuning procedures had to be performed during the follow-up in 5 children and three complications occurred (one level II and two level III).The results indicate that children with unilateral cerebral palsy benefit from unilateral SEMLS and maintain gait improvements long-term.



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Does unilateral single-event multilevel surgery improve gait in children with spastic hemiplegia? A retrospective analysis of a long-term follow-up

Publication date: February 2017
Source:Gait & Posture, Volume 52
Author(s): Christian Schranz, Annika Kruse, Tanja Kraus, Gerhardt Steinwender, Martin Svehlik
Single event multilevel surgery (SEMLS) has become a standard intervention for children with cerebral palsy (CP). SEMLS proved to improve the gait in bilateral spastic cerebral palsy and those improvements can be maintained in the long term. However there is no evidence on the long-term outcome of unilateral SEMLS in children with unilateral spastic cerebral palsy.The gait analyses and clinical data of 14 children (9 male/5 female, mean age 12.1) with unilateral CP (6 children Gross Motor Function Classification System Scale level I and 8 children level II) were retrospectively reviewed at four time-points: preoperatively, 1year, 3–5 years and approximately 10 years after unilateral SEMLS. The Gait Profile Score (GPS) of the affected leg was used as a main and the number of fine tuning procedures as well as complications rate (Clavien-Dindo classification) as secondary outcome measures.The gait improved postoperatively and the GPS of the affected leg significantly declined by 3.73° which is well above the minimal clinical important difference of 1.6°. No deterioration of GPS occurred throughout the follow-up period. Therefore the postoperative improvement was maintained long-term. However, additional fine-tuning procedures had to be performed during the follow-up in 5 children and three complications occurred (one level II and two level III).The results indicate that children with unilateral cerebral palsy benefit from unilateral SEMLS and maintain gait improvements long-term.



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