Using acoustic reflex threshold, auditory brainstem response and loudness judgments to investigate changes in neural gain following acute unilateral deprivation in normal hearing adults

Publication date: Available online 16 January 2017
Source:Hearing Research
Author(s): Hannah Brotherton, Christopher J. Plack, Roland Schaette, Kevin J. Munro
Unilateral auditory deprivation induces a reduction in the acoustic reflex threshold (ART) and an increase in loudness. These findings have been interpreted as a compensatory change in neural gain, governed by changes in excitatory and inhibitory neural inputs. There is also evidence to suggest that changes in neural gain can be measured using the auditory brainstem response (ABR). The present study extended Munro et al. (2014) [J. Acoust. Soc. Am. 135, 315-322] by investigating changes after 4 days of unilateral earplug use to: (i) ART, (ii) auditory brainstem response (ABR) and (iii) loudness. Because changes may occur during the post-deprivation test session (day 4), ART measurements were taken 1 hour and 2 hours post-earplug removal. There was a significant reduction in ART in the treatment ear immediately after the removal of the earplug, which is consistent with a compensatory increase in neural gain. A novel finding was the significant return of ARTs to baseline within 2 hours of earplug removal. A second novel finding was a significant decrease in the mean amplitude of ABR wave V in the treatment ear, but a significant increase in the control ear, both after 4 days of deprivation. These changes in the ABR are in the opposite direction to those predicted. We were unable to replicate the change in loudness reported in previous deprivation studies; however, the short period of earplug use may have contributed to this null finding.



from #Audiology via xlomafota13 on Inoreader http://ift.tt/2iDY3d4
via IFTTT

Metabotropic glutamate and GABA receptors modulate cellular excitability and glutamatergic transmission in chicken cochlear nucleus angularis neurons

Publication date: Available online 16 January 2017
Source:Hearing Research
Author(s): Wei Shi, Yong Lu
Neurons in the avian cochlear nucleus angularis (NA) receive glutamatergic input from the auditory nerve, and GABAergic input from the superior olivary nucleus. Physiologically heterogeneous, NA neurons perform multiple functions including encoding sound intensity information. Using in vitro whole-cell patch recordings from acute brain slices and immunohistochemistry staining, we investigated neuromodulation mediated by metabotropic glutamate and GABA receptors (mGluRs and GABABRs) in NA neurons. Based on their intrinsic firing patterns in response to somatic current injections, NA neurons were classified into one-spike (onset), damped, and tonic cells. Pharmacological activation of group II mGluRs, group III mGluRs, and GABABRs, by their respective agonists, suppressed the cellular excitability of non-onset firing NA neurons. Each of these agonists inhibited the glutamatergic transmission in NA neurons, in a cell type-independent manner. The frequency but not the amplitude of spontaneous release of glutamate was reduced by each of these agonists, suggesting that the modulation of the glutamatergic transmission was via presynaptic actions. Interestingly, activation of group I mGluRs increased cellular excitability and suppressed glutamatergic transmission in non-onset neurons. These results elaborate that auditory processing in NA neurons is subject to neuromodulation mediated by metabotropic receptors activated by native neurotransmitters.



from #Audiology via xlomafota13 on Inoreader http://ift.tt/2iyMgta
via IFTTT

Using acoustic reflex threshold, auditory brainstem response and loudness judgments to investigate changes in neural gain following acute unilateral deprivation in normal hearing adults

Publication date: Available online 16 January 2017
Source:Hearing Research
Author(s): Hannah Brotherton, Christopher J. Plack, Roland Schaette, Kevin J. Munro
Unilateral auditory deprivation induces a reduction in the acoustic reflex threshold (ART) and an increase in loudness. These findings have been interpreted as a compensatory change in neural gain, governed by changes in excitatory and inhibitory neural inputs. There is also evidence to suggest that changes in neural gain can be measured using the auditory brainstem response (ABR). The present study extended Munro et al. (2014) [J. Acoust. Soc. Am. 135, 315-322] by investigating changes after 4 days of unilateral earplug use to: (i) ART, (ii) auditory brainstem response (ABR) and (iii) loudness. Because changes may occur during the post-deprivation test session (day 4), ART measurements were taken 1 hour and 2 hours post-earplug removal. There was a significant reduction in ART in the treatment ear immediately after the removal of the earplug, which is consistent with a compensatory increase in neural gain. A novel finding was the significant return of ARTs to baseline within 2 hours of earplug removal. A second novel finding was a significant decrease in the mean amplitude of ABR wave V in the treatment ear, but a significant increase in the control ear, both after 4 days of deprivation. These changes in the ABR are in the opposite direction to those predicted. We were unable to replicate the change in loudness reported in previous deprivation studies; however, the short period of earplug use may have contributed to this null finding.



from #Audiology via ola Kala on Inoreader http://ift.tt/2iDY3d4
via IFTTT

Metabotropic glutamate and GABA receptors modulate cellular excitability and glutamatergic transmission in chicken cochlear nucleus angularis neurons

Publication date: Available online 16 January 2017
Source:Hearing Research
Author(s): Wei Shi, Yong Lu
Neurons in the avian cochlear nucleus angularis (NA) receive glutamatergic input from the auditory nerve, and GABAergic input from the superior olivary nucleus. Physiologically heterogeneous, NA neurons perform multiple functions including encoding sound intensity information. Using in vitro whole-cell patch recordings from acute brain slices and immunohistochemistry staining, we investigated neuromodulation mediated by metabotropic glutamate and GABA receptors (mGluRs and GABABRs) in NA neurons. Based on their intrinsic firing patterns in response to somatic current injections, NA neurons were classified into one-spike (onset), damped, and tonic cells. Pharmacological activation of group II mGluRs, group III mGluRs, and GABABRs, by their respective agonists, suppressed the cellular excitability of non-onset firing NA neurons. Each of these agonists inhibited the glutamatergic transmission in NA neurons, in a cell type-independent manner. The frequency but not the amplitude of spontaneous release of glutamate was reduced by each of these agonists, suggesting that the modulation of the glutamatergic transmission was via presynaptic actions. Interestingly, activation of group I mGluRs increased cellular excitability and suppressed glutamatergic transmission in non-onset neurons. These results elaborate that auditory processing in NA neurons is subject to neuromodulation mediated by metabotropic receptors activated by native neurotransmitters.



from #Audiology via ola Kala on Inoreader http://ift.tt/2iyMgta
via IFTTT

Using acoustic reflex threshold, auditory brainstem response and loudness judgments to investigate changes in neural gain following acute unilateral deprivation in normal hearing adults

Publication date: Available online 16 January 2017
Source:Hearing Research
Author(s): Hannah Brotherton, Christopher J. Plack, Roland Schaette, Kevin J. Munro
Unilateral auditory deprivation induces a reduction in the acoustic reflex threshold (ART) and an increase in loudness. These findings have been interpreted as a compensatory change in neural gain, governed by changes in excitatory and inhibitory neural inputs. There is also evidence to suggest that changes in neural gain can be measured using the auditory brainstem response (ABR). The present study extended Munro et al. (2014) [J. Acoust. Soc. Am. 135, 315-322] by investigating changes after 4 days of unilateral earplug use to: (i) ART, (ii) auditory brainstem response (ABR) and (iii) loudness. Because changes may occur during the post-deprivation test session (day 4), ART measurements were taken 1 hour and 2 hours post-earplug removal. There was a significant reduction in ART in the treatment ear immediately after the removal of the earplug, which is consistent with a compensatory increase in neural gain. A novel finding was the significant return of ARTs to baseline within 2 hours of earplug removal. A second novel finding was a significant decrease in the mean amplitude of ABR wave V in the treatment ear, but a significant increase in the control ear, both after 4 days of deprivation. These changes in the ABR are in the opposite direction to those predicted. We were unable to replicate the change in loudness reported in previous deprivation studies; however, the short period of earplug use may have contributed to this null finding.



from #Audiology via ola Kala on Inoreader http://ift.tt/2iDY3d4
via IFTTT

Metabotropic glutamate and GABA receptors modulate cellular excitability and glutamatergic transmission in chicken cochlear nucleus angularis neurons

Publication date: Available online 16 January 2017
Source:Hearing Research
Author(s): Wei Shi, Yong Lu
Neurons in the avian cochlear nucleus angularis (NA) receive glutamatergic input from the auditory nerve, and GABAergic input from the superior olivary nucleus. Physiologically heterogeneous, NA neurons perform multiple functions including encoding sound intensity information. Using in vitro whole-cell patch recordings from acute brain slices and immunohistochemistry staining, we investigated neuromodulation mediated by metabotropic glutamate and GABA receptors (mGluRs and GABABRs) in NA neurons. Based on their intrinsic firing patterns in response to somatic current injections, NA neurons were classified into one-spike (onset), damped, and tonic cells. Pharmacological activation of group II mGluRs, group III mGluRs, and GABABRs, by their respective agonists, suppressed the cellular excitability of non-onset firing NA neurons. Each of these agonists inhibited the glutamatergic transmission in NA neurons, in a cell type-independent manner. The frequency but not the amplitude of spontaneous release of glutamate was reduced by each of these agonists, suggesting that the modulation of the glutamatergic transmission was via presynaptic actions. Interestingly, activation of group I mGluRs increased cellular excitability and suppressed glutamatergic transmission in non-onset neurons. These results elaborate that auditory processing in NA neurons is subject to neuromodulation mediated by metabotropic receptors activated by native neurotransmitters.



from #Audiology via ola Kala on Inoreader http://ift.tt/2iyMgta
via IFTTT

Update on Auditory Evoked Responses: Evidence-Based ABR Protocol for Infant Hearing Assessment

Learning Outcomes Introduction Dr. Jay Hall: Today’s course will focus on an evidence-based protocol for infant hearing assessment that has evolved over the past 45 years.  This webinar is part of a 2-part series on infant hearin

from #Audiology via xlomafota13 on Inoreader http://ift.tt/2ise8Ea
via IFTTT