Cortical Processing Related to Intensity of a Modulated Noise Stimulus—a Functional Near-Infrared Study

Abstract

Sound intensity is a key feature of auditory signals. A profound understanding of cortical processing of this feature is therefore highly desirable. This study investigates whether cortical functional near-infrared spectroscopy (fNIRS) signals reflect sound intensity changes and where on the brain cortex maximal intensity-dependent activations are located. The fNIRS technique is particularly suitable for this kind of hearing study, as it runs silently. Twenty-three normal hearing subjects were included and actively participated in a counterbalanced block design task. Four intensity levels of a modulated noise stimulus with long-term spectrum and modulation characteristics similar to speech were applied, evenly spaced from 15 to 90 dB SPL. Signals from auditory processing cortical fields were derived from a montage of 16 optodes on each side of the head. Results showed that fNIRS responses originating from auditory processing areas are highly dependent on sound intensity level: higher stimulation levels led to higher concentration changes. Caudal and rostral channels showed different waveform morphologies, reflecting specific cortical signal processing of the stimulus. Channels overlying the supramarginal and caudal superior temporal gyrus evoked a phasic response, whereas channels over Broca’s area showed a broad tonic pattern. This data set can serve as a foundation for future auditory fNIRS research to develop the technique as a hearing assessment tool in the normal hearing and hearing-impaired populations.

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ABR as Screener for ASD?

A recent area of research is exploring the application of auditory brainstem response (ABR) testing in identification of autism spectrum disorder (ASD). 

Currently, ASD is typically diagnosed between the ages of 2 and 4 years. Earlier identification may allow for implementation of intervention at critical time periods of development. A review of the literature suggests that children with ASD often exhibit prolonged ABR latencies compared to controls, but there are several studies that do not support this relationship.

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Occupational Noise Exposure Linked to Cardiovascular Conditions

High blood pressure and high cholesterol are more prevalent among workers who have been exposed to loud noises, according to a new study conducted by the Centers for Disease Control and Prevention. (Am J Ind Med. 2018 Mar 14. doi: 10.1002/ajim.22833. [Epub ahead of print].) Researchers from CDC’s National Institute for Occupational Safety and Health studied National Health Survey data from 2014 and estimated the prevalence of self-reported hearing difficulty, hypertension, elevated cholesterol, and coronary heart disease or stroke by level of occupational noise exposure, industry, and occupation. They found 25 percent of current workers had a history of occupational noise exposure, and that 12 percent had hearing difficulty, 24 percent had hypertension, and 28 percent had elevated cholesterol. Of these cases, 58 percent, 14 percent, and nine percent of them can be attributed to occupational noise exposure. Industries with the highest prevalence of occupational noise exposure were mining (61%), construction (51%), and manufacturing (47%), and occupations with the highest prevalence of occupational noise exposure were production (55%); construction and extraction (54%); and installation, maintenance, and repair (54%).
 
Elizabeth Masterson, PhD, a co-author of the paper, said in a press release this study provides further evidence of an association of occupational noise exposure with high blood pressure and high cholesterol as well as the potential to prevent these conditions. “It is important that workers be screened regularly for these conditions in the workplace or through a health care provider, so interventions can occur. As these conditions are more common among noise-exposed workers, they could especially benefit from these screenings," Masterson said. 

Published: 4/6/2018 10:34:00 AM

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Occupational Noise Exposure Linked to Cardiovascular Conditions

High blood pressure and high cholesterol are more prevalent among workers who have been exposed to loud noises, according to a new study conducted by the Centers for Disease Control and Prevention. (Am J Ind Med. 2018 Mar 14. doi: 10.1002/ajim.22833. [Epub ahead of print].) Researchers from CDC’s National Institute for Occupational Safety and Health studied National Health Survey data from 2014 and estimated the prevalence of self-reported hearing difficulty, hypertension, elevated cholesterol, and coronary heart disease or stroke by level of occupational noise exposure, industry, and occupation. They found 25 percent of current workers had a history of occupational noise exposure, and that 12 percent had hearing difficulty, 24 percent had hypertension, and 28 percent had elevated cholesterol. Of these cases, 58 percent, 14 percent, and nine percent of them can be attributed to occupational noise exposure. Industries with the highest prevalence of occupational noise exposure were mining (61%), construction (51%), and manufacturing (47%), and occupations with the highest prevalence of occupational noise exposure were production (55%); construction and extraction (54%); and installation, maintenance, and repair (54%).
 
Elizabeth Masterson, PhD, a co-author of the paper, said in a press release this study provides further evidence of an association of occupational noise exposure with high blood pressure and high cholesterol as well as the potential to prevent these conditions. “It is important that workers be screened regularly for these conditions in the workplace or through a health care provider, so interventions can occur. As these conditions are more common among noise-exposed workers, they could especially benefit from these screenings," Masterson said. 

Published: 4/6/2018 10:34:00 AM

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Occupational Noise Exposure Linked to Cardiovascular Conditions

High blood pressure and high cholesterol are more prevalent among workers who have been exposed to loud noises, according to a new study conducted by the Centers for Disease Control and Prevention. (Am J Ind Med. 2018 Mar 14. doi: 10.1002/ajim.22833. [Epub ahead of print].) Researchers from CDC’s National Institute for Occupational Safety and Health studied National Health Survey data from 2014 and estimated the prevalence of self-reported hearing difficulty, hypertension, elevated cholesterol, and coronary heart disease or stroke by level of occupational noise exposure, industry, and occupation. They found 25 percent of current workers had a history of occupational noise exposure, and that 12 percent had hearing difficulty, 24 percent had hypertension, and 28 percent had elevated cholesterol. Of these cases, 58 percent, 14 percent, and nine percent of them can be attributed to occupational noise exposure. Industries with the highest prevalence of occupational noise exposure were mining (61%), construction (51%), and manufacturing (47%), and occupations with the highest prevalence of occupational noise exposure were production (55%); construction and extraction (54%); and installation, maintenance, and repair (54%).
 
Elizabeth Masterson, PhD, a co-author of the paper, said in a press release this study provides further evidence of an association of occupational noise exposure with high blood pressure and high cholesterol as well as the potential to prevent these conditions. “It is important that workers be screened regularly for these conditions in the workplace or through a health care provider, so interventions can occur. As these conditions are more common among noise-exposed workers, they could especially benefit from these screenings," Masterson said. 

Published: 4/6/2018 10:34:00 AM

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Electric-acoustic forward masking in cochlear implant users with ipsilateral residual hearing

Publication date: Available online 9 April 2018
Source:Hearing Research
Author(s): Marina Imsiecke, Benjamin Krüger, Andreas Büchner, Thomas Lenarz, Waldo Nogueira
In order to investigate the temporal mechanisms of the auditory system, psychophysical forward masking experiments were conducted in cochlear implant users who had preserved acoustic hearing in the ipsilateral ear. This unique electric-acoustic stimulation (EAS) population allowed the measurement of threshold recovery functions for acoustic or electric probes in the presence of electric or acoustic maskers, respectively. In the electric masking experiment, the forward masked threshold elevation of acoustic probes was measured as a function of the time interval after the offset of the electric masker, i.e. the masker-to-probe interval (MPI). In the acoustic masking experiment, the forward masked threshold elevation of electric probe stimuli was investigated under the influence of a preceding acoustic masker. Since electric pulse trains directly stimulate the auditory nerve, this novel experimental setup allowed the acoustic adaptation properties (attributed to the physiology of the hair cells) to be differentiated from the subsequent processing by more central mechanisms along the auditory pathway. For instance, forward electric masking patterns should result more from the auditory-nerve response to electrical stimulation, while forward acoustic masking patterns should primarily be the result of the recovery from adaptation at the hair-cell neuron interface.Electric masking showed prolonged threshold elevation of acoustic probes, which depended significantly on the masker-to-probe interval. Additionally, threshold elevation was significantly dependent on the similarity between acoustic stimulus frequency and electric place frequency, the electric-acoustic frequency difference (EAFD). Acoustic masking showed a reduced, but statistically significant effect of electric threshold elevation, which did not significantly depend on MPI. Lastly, acoustic masking showed longer decay times than electric masking and a reduced dependency on EAFD.In conclusion, the forward masking patterns observed for combined electric-acoustic stimulation provide further insights into the temporal mechanisms of the auditory system. For instance, the asymmetry in the amount of threshold elevation, the dependency on EAFD and the time constants for the recovery functions of acoustic and electric masking all indicate that there must be several processes with different latencies (e.g. neural adaptation, depression of spontaneous activity, efferent systems) that are involved in forward masking recovery functions.



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Functions of CaBP1 and CaBP2 in the peripheral auditory system

Publication date: Available online 9 April 2018
Source:Hearing Research
Author(s): Tian Yang, Ning Hu, Tina Pangrsic, Steven Green, Marlan Hansen, Amy Lee
CaBPs are a family of Ca²⁺ binding proteins related to calmodulin. Two CaBP family members, CaBP1 and CaBP2, are highly expressed in the cochlea. Here, we investigated the significance of CaBP1 and CaBP2 for hearing in mice lacking expression of these proteins (CaBP1 KO and CaBP2 KO) using auditory brain responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). In CaBP1 KO mice, ABR wave I was larger in amplitude, and shorter in latency and faster in decay, suggestive of enhanced synchrony of auditory nerve fibers. This interpretation was supported by the greater excitability of CaBP1 KO than WT neurons in whole-cell patch clamp recordings of spiral ganglion neurons in culture, and normal presynaptic function of CaBP1 KO IHCs. DPOAEs and ABR thresholds were normal in 4-week old CaBP1 KO mice, but elevated ABR thresholds became evident at 32 kHz at 9 weeks, and at 8 and 16 kHz by 6 months of age. In contrast, CaBP2 KO mice exhibited significant ABR threshold elevations at 4 weeks of age that became more severe in the mid-frequency range by 9 weeks. Though normal at 4 weeks, DPOAEs in CaBP2 KO mice were significantly reduced in the mid-frequency range by 9 weeks. Our results reveal requirements for CaBP1 and CaBP2 in the peripheral auditory system and highlight the diverse modes by which CaBPs influence sensory processing.



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Electric-acoustic forward masking in cochlear implant users with ipsilateral residual hearing

Publication date: Available online 9 April 2018
Source:Hearing Research
Author(s): Marina Imsiecke, Benjamin Krüger, Andreas Büchner, Thomas Lenarz, Waldo Nogueira
In order to investigate the temporal mechanisms of the auditory system, psychophysical forward masking experiments were conducted in cochlear implant users who had preserved acoustic hearing in the ipsilateral ear. This unique electric-acoustic stimulation (EAS) population allowed the measurement of threshold recovery functions for acoustic or electric probes in the presence of electric or acoustic maskers, respectively. In the electric masking experiment, the forward masked threshold elevation of acoustic probes was measured as a function of the time interval after the offset of the electric masker, i.e. the masker-to-probe interval (MPI). In the acoustic masking experiment, the forward masked threshold elevation of electric probe stimuli was investigated under the influence of a preceding acoustic masker. Since electric pulse trains directly stimulate the auditory nerve, this novel experimental setup allowed the acoustic adaptation properties (attributed to the physiology of the hair cells) to be differentiated from the subsequent processing by more central mechanisms along the auditory pathway. For instance, forward electric masking patterns should result more from the auditory-nerve response to electrical stimulation, while forward acoustic masking patterns should primarily be the result of the recovery from adaptation at the hair-cell neuron interface.Electric masking showed prolonged threshold elevation of acoustic probes, which depended significantly on the masker-to-probe interval. Additionally, threshold elevation was significantly dependent on the similarity between acoustic stimulus frequency and electric place frequency, the electric-acoustic frequency difference (EAFD). Acoustic masking showed a reduced, but statistically significant effect of electric threshold elevation, which did not significantly depend on MPI. Lastly, acoustic masking showed longer decay times than electric masking and a reduced dependency on EAFD.In conclusion, the forward masking patterns observed for combined electric-acoustic stimulation provide further insights into the temporal mechanisms of the auditory system. For instance, the asymmetry in the amount of threshold elevation, the dependency on EAFD and the time constants for the recovery functions of acoustic and electric masking all indicate that there must be several processes with different latencies (e.g. neural adaptation, depression of spontaneous activity, efferent systems) that are involved in forward masking recovery functions.



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Functions of CaBP1 and CaBP2 in the peripheral auditory system

Publication date: Available online 9 April 2018
Source:Hearing Research
Author(s): Tian Yang, Ning Hu, Tina Pangrsic, Steven Green, Marlan Hansen, Amy Lee
CaBPs are a family of Ca²⁺ binding proteins related to calmodulin. Two CaBP family members, CaBP1 and CaBP2, are highly expressed in the cochlea. Here, we investigated the significance of CaBP1 and CaBP2 for hearing in mice lacking expression of these proteins (CaBP1 KO and CaBP2 KO) using auditory brain responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). In CaBP1 KO mice, ABR wave I was larger in amplitude, and shorter in latency and faster in decay, suggestive of enhanced synchrony of auditory nerve fibers. This interpretation was supported by the greater excitability of CaBP1 KO than WT neurons in whole-cell patch clamp recordings of spiral ganglion neurons in culture, and normal presynaptic function of CaBP1 KO IHCs. DPOAEs and ABR thresholds were normal in 4-week old CaBP1 KO mice, but elevated ABR thresholds became evident at 32 kHz at 9 weeks, and at 8 and 16 kHz by 6 months of age. In contrast, CaBP2 KO mice exhibited significant ABR threshold elevations at 4 weeks of age that became more severe in the mid-frequency range by 9 weeks. Though normal at 4 weeks, DPOAEs in CaBP2 KO mice were significantly reduced in the mid-frequency range by 9 weeks. Our results reveal requirements for CaBP1 and CaBP2 in the peripheral auditory system and highlight the diverse modes by which CaBPs influence sensory processing.



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Electric-acoustic forward masking in cochlear implant users with ipsilateral residual hearing

Publication date: Available online 9 April 2018
Source:Hearing Research
Author(s): Marina Imsiecke, Benjamin Krüger, Andreas Büchner, Thomas Lenarz, Waldo Nogueira
In order to investigate the temporal mechanisms of the auditory system, psychophysical forward masking experiments were conducted in cochlear implant users who had preserved acoustic hearing in the ipsilateral ear. This unique electric-acoustic stimulation (EAS) population allowed the measurement of threshold recovery functions for acoustic or electric probes in the presence of electric or acoustic maskers, respectively. In the electric masking experiment, the forward masked threshold elevation of acoustic probes was measured as a function of the time interval after the offset of the electric masker, i.e. the masker-to-probe interval (MPI). In the acoustic masking experiment, the forward masked threshold elevation of electric probe stimuli was investigated under the influence of a preceding acoustic masker. Since electric pulse trains directly stimulate the auditory nerve, this novel experimental setup allowed the acoustic adaptation properties (attributed to the physiology of the hair cells) to be differentiated from the subsequent processing by more central mechanisms along the auditory pathway. For instance, forward electric masking patterns should result more from the auditory-nerve response to electrical stimulation, while forward acoustic masking patterns should primarily be the result of the recovery from adaptation at the hair-cell neuron interface.Electric masking showed prolonged threshold elevation of acoustic probes, which depended significantly on the masker-to-probe interval. Additionally, threshold elevation was significantly dependent on the similarity between acoustic stimulus frequency and electric place frequency, the electric-acoustic frequency difference (EAFD). Acoustic masking showed a reduced, but statistically significant effect of electric threshold elevation, which did not significantly depend on MPI. Lastly, acoustic masking showed longer decay times than electric masking and a reduced dependency on EAFD.In conclusion, the forward masking patterns observed for combined electric-acoustic stimulation provide further insights into the temporal mechanisms of the auditory system. For instance, the asymmetry in the amount of threshold elevation, the dependency on EAFD and the time constants for the recovery functions of acoustic and electric masking all indicate that there must be several processes with different latencies (e.g. neural adaptation, depression of spontaneous activity, efferent systems) that are involved in forward masking recovery functions.



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Functions of CaBP1 and CaBP2 in the peripheral auditory system

Publication date: Available online 9 April 2018
Source:Hearing Research
Author(s): Tian Yang, Ning Hu, Tina Pangrsic, Steven Green, Marlan Hansen, Amy Lee
CaBPs are a family of Ca²⁺ binding proteins related to calmodulin. Two CaBP family members, CaBP1 and CaBP2, are highly expressed in the cochlea. Here, we investigated the significance of CaBP1 and CaBP2 for hearing in mice lacking expression of these proteins (CaBP1 KO and CaBP2 KO) using auditory brain responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). In CaBP1 KO mice, ABR wave I was larger in amplitude, and shorter in latency and faster in decay, suggestive of enhanced synchrony of auditory nerve fibers. This interpretation was supported by the greater excitability of CaBP1 KO than WT neurons in whole-cell patch clamp recordings of spiral ganglion neurons in culture, and normal presynaptic function of CaBP1 KO IHCs. DPOAEs and ABR thresholds were normal in 4-week old CaBP1 KO mice, but elevated ABR thresholds became evident at 32 kHz at 9 weeks, and at 8 and 16 kHz by 6 months of age. In contrast, CaBP2 KO mice exhibited significant ABR threshold elevations at 4 weeks of age that became more severe in the mid-frequency range by 9 weeks. Though normal at 4 weeks, DPOAEs in CaBP2 KO mice were significantly reduced in the mid-frequency range by 9 weeks. Our results reveal requirements for CaBP1 and CaBP2 in the peripheral auditory system and highlight the diverse modes by which CaBPs influence sensory processing.



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