The Experts below are selected from a list of 1914 Experts worldwide ranked by ideXlab platform
Daniel J. Tollin - One of the best experts on this subject based on the ideXlab platform.
-
Temporal constraints on neural and psychophysical sensitivity to Interaural Level Difference cues to sound source location
The Journal of the Acoustical Society of America, 2018Co-Authors: Andrew D. Brown, Daniel J. TollinAbstract:Interaural Differences in the timing (ITD) and Level (ILD) of impinging sounds carry critical information about source location. However, in everyday listening environments, sounds are often decorrelated between the ears by reverberation and background noise, degrading the fidelity of both ITD and ILD cues. Similar distortions to ITD and ILD are also experienced by hearing-impaired humans who use hearing aids or cochlear implants, as these devices also degrade temporal and intensive features of the signal at each ear. Here, we demonstrate that behavioral ILD sensitivity (in humans) and neural ILD sensitivity (in single neurons of the chinchilla auditory midbrain) remain robust under stimulus conditions that render ITD cues undetectable. Neural and behavioral data were compared to the outputs of a model of ILD processing with a single free parameter, the duration of excitatory-inhibitory interaction. Behavioral, neural, and modeling data collectively suggest that ILD sensitivity depends on binaural integration of excitation and inhibition within a ≳3-ms temporal window, significantly longer than observed in lower brainstem neurons. This relatively slow integration potentiates a unique role for the ILD system in spatial hearing that may be of particular importance when informative ITD cues are unavailable. [Work supported by F32-DC013927 [ADB] and R01-DC011555 [DJT].]Interaural Differences in the timing (ITD) and Level (ILD) of impinging sounds carry critical information about source location. However, in everyday listening environments, sounds are often decorrelated between the ears by reverberation and background noise, degrading the fidelity of both ITD and ILD cues. Similar distortions to ITD and ILD are also experienced by hearing-impaired humans who use hearing aids or cochlear implants, as these devices also degrade temporal and intensive features of the signal at each ear. Here, we demonstrate that behavioral ILD sensitivity (in humans) and neural ILD sensitivity (in single neurons of the chinchilla auditory midbrain) remain robust under stimulus conditions that render ITD cues undetectable. Neural and behavioral data were compared to the outputs of a model of ILD processing with a single free parameter, the duration of excitatory-inhibitory interaction. Behavioral, neural, and modeling data collectively suggest that ILD sensitivity depends on binaural integra...
-
Temporary unilateral hearing loss during development impairs behavioral and neural sensitivity to Interaural Level Difference cues for sound localization
The Journal of the Acoustical Society of America, 2016Co-Authors: Kelsey L. Anbuhl, Andrew D. Brown, Nathaniel T. Greene, Victor Benichoux, Alexander T. Ferber, Daniel J. TollinAbstract:Children who experience persistent conductive hearing loss (CHL) early in life often display binaural hearing impairments that persist long after CHL is resolved, suggesting abnormal central auditory development. Abnormal sensitivity to Interaural Level Differences (ILDs) is particularly likely as a CHL (such as an ear infection) can attenuate sound in the affected ear by >30 dB, dramatically distorting ILD cues. Here, we quantified the effects of unilateral CHL on (1) behavioral spatial acuity and (2) neural information processing of ILD cues in the guinea pig auditory midbrain (inferior colliculus, IC) using the mathematical framework of Fisher information (FI). Animals raised with unilateral CHL displayed larger minimum audible angles for high-pass noise compared to age-matched controls, suggesting impaired ILD sensitivity. Based on acoustic directional transfer function measurements, ILD discrimination thresholds were elevated by ~3–6 dB. Following behavior, extracellular recordings were made in the I...
-
The Conductive Hearing Loss Due to an Experimentally Induced Middle Ear Effusion Alters the Interaural Level and Time Difference Cues to Sound Location
Journal of the Association for Research in Otolaryngology, 2012Co-Authors: Jennifer L Thornton, Kanthaiah Koka, Keely M. Chevallier, J. Eric Lupo, Daniel J. TollinAbstract:Otitis media with effusion (OME) is a pathologic condition of the middle ear that leads to a mild to moderate conductive hearing loss as a result of fluid in the middle ear. Recurring OME in children during the first few years of life has been shown to be associated with poor detection and recognition of sounds in noisy environments, hypothesized to result due to altered sound localization cues. To explore this hypothesis, we simulated a middle ear effusion by filling the middle ear space of chinchillas with different viscosities and volumes of silicone oil to simulate varying degrees of OME. While the effects of middle ear effusions on the Interaural Level Difference (ILD) cue to location are known, little is known about whether and how middle ear effusions affect Interaural time Differences (ITDs). Cochlear microphonic amplitudes and phases were measured in response to sounds delivered from several locations in azimuth before and after filling the middle ear with fluid. Significant attenuations (20–40 dB) of sound were observed when the middle ear was filled with at least 1.0 ml of fluid with a viscosity of 3.5 Poise (P) or greater. As expected, ILDs were altered by ~30 dB. Additionally, ITDs were shifted by ~600 μs for low frequency stimuli (
-
The distance-dependence of Interaural Level Difference cues to sound location and their encoding by neurons the inferior colliculus – implications for the Duplex theory
The Journal of the Acoustical Society of America, 2012Co-Authors: Heath G Jones, Kanthaiah Koka, Jennifer L Thornton, Daniel J. TollinAbstract:The Duplex theory posits that low- and high-frequency sounds are localized using two different acoustical cues, Interaural time (ITDs) and Level (ILDs) Differences, respectively. Anatomically, ITDs and ILDs are separately encoded in two parallel pathways consistent with ecological and efficiency principles which state that neural systems evolved strategies to represent the full spectrum of sensory signals as experienced by an organism in its natural habitat. ILDs are location and frequency dependent such that lower and higher frequencies exhibit smaller and larger ILDs, respectively. Neurons throughout the auditory neuraxis encode ILDs for high-frequency sounds. However, although low-frequency ILDs are negligible, humans are quite sensitive to them and physiological studies report low-frequency ILD sensitive neurons. The presence of such neurons is at odds with the Duplex theory and ecological and efficiency principles. We suggest these discrepancies arise from inadequate understanding of the ecological acoustical environment. Via measurements in the chinchilla of acoustical ILDs and their encoding by inferior colliculus neurons the hypothesis is explored that low-frequency ILDs become useful when sound source distance is varied. We demonstrate that a population of neurons is sufficient to encode the frequency-dependent range of ILDs that would be experienced as a function of location and distance. (R01-DC01155)
-
a role for low frequency sensitive neurons in the auditory brainstem in the encoding of source location distance dependent Interaural Level Difference cues
Journal of the Acoustical Society of America, 2010Co-Authors: Daniel J. Tollin, Heath G Jones, Jennifer L Thornton, Kanthaiah KokaAbstract:The duplex theory posits that low‐ and high‐frequency sounds are localized using two different acoustical cues, Interaural time delays (ITDs) and Interaural Level Differences (ILDs), respectively. Psychophysical data have generally supported the theory for pure tones. Anatomical and physiological studies have revealed two parallel brainstem pathways that appear to encode ITDs and ILDs separately. ITDs are extracted by medial superior olive neurons. ILDs are extracted by lateral superior olive (LSO) neurons. ILD‐sensitive neurons are also found in the inferior colliculus (IC). ILDs are a complex function of both source location and frequency such that lower and higher frequencies exhibit smaller and larger ILDs, respectively. LSO and IC neurons encode ILDs for high‐frequency sounds where the cues are physically available, but there are discrepancies regarding low‐frequency neurons. Although acoustically, low‐frequency ILDs are small, humans are sensitive to them and physiological studies have found low‐frequency neurons in the LSO and IC that could encode them. Here the hypothesis that low‐frequency ILDs are useful when sound source distance is varied is explored. These data demonstrate that a population of IC neurons is sufficient to encode the range of acoustic ILDs that would be experienced as a joint function of source location and distance.
Kanthaiah Koka - One of the best experts on this subject based on the ideXlab platform.
-
The Conductive Hearing Loss Due to an Experimentally Induced Middle Ear Effusion Alters the Interaural Level and Time Difference Cues to Sound Location
Journal of the Association for Research in Otolaryngology, 2012Co-Authors: Jennifer L Thornton, Kanthaiah Koka, Keely M. Chevallier, J. Eric Lupo, Daniel J. TollinAbstract:Otitis media with effusion (OME) is a pathologic condition of the middle ear that leads to a mild to moderate conductive hearing loss as a result of fluid in the middle ear. Recurring OME in children during the first few years of life has been shown to be associated with poor detection and recognition of sounds in noisy environments, hypothesized to result due to altered sound localization cues. To explore this hypothesis, we simulated a middle ear effusion by filling the middle ear space of chinchillas with different viscosities and volumes of silicone oil to simulate varying degrees of OME. While the effects of middle ear effusions on the Interaural Level Difference (ILD) cue to location are known, little is known about whether and how middle ear effusions affect Interaural time Differences (ITDs). Cochlear microphonic amplitudes and phases were measured in response to sounds delivered from several locations in azimuth before and after filling the middle ear with fluid. Significant attenuations (20–40 dB) of sound were observed when the middle ear was filled with at least 1.0 ml of fluid with a viscosity of 3.5 Poise (P) or greater. As expected, ILDs were altered by ~30 dB. Additionally, ITDs were shifted by ~600 μs for low frequency stimuli (
-
The distance-dependence of Interaural Level Difference cues to sound location and their encoding by neurons the inferior colliculus – implications for the Duplex theory
The Journal of the Acoustical Society of America, 2012Co-Authors: Heath G Jones, Kanthaiah Koka, Jennifer L Thornton, Daniel J. TollinAbstract:The Duplex theory posits that low- and high-frequency sounds are localized using two different acoustical cues, Interaural time (ITDs) and Level (ILDs) Differences, respectively. Anatomically, ITDs and ILDs are separately encoded in two parallel pathways consistent with ecological and efficiency principles which state that neural systems evolved strategies to represent the full spectrum of sensory signals as experienced by an organism in its natural habitat. ILDs are location and frequency dependent such that lower and higher frequencies exhibit smaller and larger ILDs, respectively. Neurons throughout the auditory neuraxis encode ILDs for high-frequency sounds. However, although low-frequency ILDs are negligible, humans are quite sensitive to them and physiological studies report low-frequency ILD sensitive neurons. The presence of such neurons is at odds with the Duplex theory and ecological and efficiency principles. We suggest these discrepancies arise from inadequate understanding of the ecological acoustical environment. Via measurements in the chinchilla of acoustical ILDs and their encoding by inferior colliculus neurons the hypothesis is explored that low-frequency ILDs become useful when sound source distance is varied. We demonstrate that a population of neurons is sufficient to encode the frequency-dependent range of ILDs that would be experienced as a function of location and distance. (R01-DC01155)
-
a role for low frequency sensitive neurons in the auditory brainstem in the encoding of source location distance dependent Interaural Level Difference cues
Journal of the Acoustical Society of America, 2010Co-Authors: Daniel J. Tollin, Heath G Jones, Jennifer L Thornton, Kanthaiah KokaAbstract:The duplex theory posits that low‐ and high‐frequency sounds are localized using two different acoustical cues, Interaural time delays (ITDs) and Interaural Level Differences (ILDs), respectively. Psychophysical data have generally supported the theory for pure tones. Anatomical and physiological studies have revealed two parallel brainstem pathways that appear to encode ITDs and ILDs separately. ITDs are extracted by medial superior olive neurons. ILDs are extracted by lateral superior olive (LSO) neurons. ILD‐sensitive neurons are also found in the inferior colliculus (IC). ILDs are a complex function of both source location and frequency such that lower and higher frequencies exhibit smaller and larger ILDs, respectively. LSO and IC neurons encode ILDs for high‐frequency sounds where the cues are physically available, but there are discrepancies regarding low‐frequency neurons. Although acoustically, low‐frequency ILDs are small, humans are sensitive to them and physiological studies have found low‐frequency neurons in the LSO and IC that could encode them. Here the hypothesis that low‐frequency ILDs are useful when sound source distance is varied is explored. These data demonstrate that a population of IC neurons is sufficient to encode the range of acoustic ILDs that would be experienced as a joint function of source location and distance.
-
Varying Overall Sound Intensity to the Two Ears Impacts Interaural Level Difference Discrimination Thresholds by Single Neurons in the Lateral Superior Olive
Journal of neurophysiology, 2009Co-Authors: Jeffrey J. Tsai, Kanthaiah Koka, Daniel J. TollinAbstract:The lateral superior olive (LSO) is one of the earliest sites in the auditory pathway involved in processing acoustical cues to sound location. LSO neurons encode the Interaural Level Difference (ILD) cue to azimuthal location. Here we investigated the effect of variations in the overall stimulus Levels of sounds at the two ears on the sensitivity of LSO neurons to small Differences in ILDs of pure tones. The neuronal firing rate versus ILD functions were found to depend greatly on the overall stimulus Level, typically shifting along the ILD axis toward the excitatory ear and attaining greater maximal firing rates as stimulus Level increased. Seventy-five percent of neurons showed significant shifts with changes in overall sound Level. The range of ILDs corresponding to best neural acuity for ILDs shifted accordingly. In a simulation using the empirical data, when the overall stimulus Level was randomly changed from one trial to the next, the neural discrimination thresholds for ILD, or ILD acuities, were worsened by 50–60% across the population of neurons relative to fixed stimulus Levels whether ILD acuity was measured at the azimuthal midline or the ILD pedestal producing the best acuity. The impairment in ILD discrimination was attributed to the increased neural response variance imparted by varying the stimulus Level. These results contrast to those observed in psychophysical studies where ILD discrimination thresholds under similar experimental conditions are invariant to overall changes in stimulus Level. A simple computational model that incorporated the antagonistic inputs of bilateral LSO nuclei as well as the dorsal nuclei of the lateral lemniscus to the inferior colliculus produced a more robust encoding of ILD even in the setting of roving stimulus Level. Testable predictions of this model and comparison to other computational models addressing stimulus invariance were considered.
-
Interaural Level Difference Discrimination Thresholds for Single Neurons in the Lateral Superior Olive
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2008Co-Authors: Daniel J. Tollin, Kanthaiah Koka, Jeffrey J. TsaiAbstract:The lateral superior olive (LSO) is one of the earliest sites in the auditory pathway that is involved in processing acoustical cues to sound location. Here, we tested the hypothesis that LSO neurons can signal small changes in Interaural Level Differences (ILDs), a cue to horizontal sound location, of pure tones based on discharge rate consistent with psychophysical performance in the discrimination of ILDs. Neural thresholds for ILD discrimination were determined from the discharge rates and associated response variability of single units in response to 300 ms tones in the LSO of barbiturate-anesthetized cats using detection theory. Neural response variability was well described by a power function of the mean rate, both in individual neurons and collectively; LSO neurons were less variable than expected from a Poisson process. Compared with psychophysical data, the best-threshold ILDs of single LSO neurons were comparable with or better than behavior over the full range of frequencies (0.3–35 kHz) and pedestal ILDs (±25 dB) explored in this study. With a pedestal ILD of 0 dB, ILD increments of 1 dB could be discriminated by some neurons, with a median of 4.35 dB across neurons. For pedestal ILDs away from 0 dB, the best-threshold ILDs were as low as 0.5 dB, with a median of 2.3 dB. These findings support the hypothesis that the LSO plays a role in the extraction of ILD, and that the representation of ILD by LSO neurons may set a lower bound on the behavioral sensitivity to ILDs.
Rebecca J. Curry - One of the best experts on this subject based on the ideXlab platform.
-
Intrinsic properties of avian Interaural Level Difference sound localizing neurons.
Brain research, 2021Co-Authors: Rebecca J. CurryAbstract:Intrinsic properties of neurons are one major determinant for how neurons respond to their synaptic inputs and shape their outputs in neural circuits. Here, we studied the intrinsic properties of neurons in the chicken posterior portion of the dorsal nucleus of the lateral lemniscus (LLDp), the first Interaural Level Difference (ILD) encoder of the avian auditory pathway. Using whole-cell recordings in brain slices, we revealed that the LLDp is composed of a heterogeneous neuron population based on their firing patterns. LLDp neurons were broadly classified as either phasic or tonic firing neurons, with further classification applied to tonic firing neurons, such as regular (most dominant, n = 82 out of 125 cells, 65.6%), pauser, or adaptive firing. Neurons with different firing patterns were distributed about evenly across the dorsoventral as well as mediolateral axis of LLDp. Phasic firing neurons were of faster membrane time constant, and lower excitability than tonic firing neurons. The action potentials (APs) elicited at the current thresholds displayed significant Differences in first spike latency, AP peak amplitude, half-width, and maximal rising and falling rates. Interestingly, for APs elicited at suprathreshold currents (400 pA above thresholds), some of the Differences diminished while a few others emerged. Remarkably, most parameters of the APs at thresholds were significantly different from those of APs at suprathresholds. Combined with our previous study (Curry and Lu, 2016), the results lend support to the two-cell type model for ILD coding in the avian system.
-
Synaptic Inhibition in Avian Interaural Level Difference Sound Localizing Neurons.
eneuro, 2016Co-Authors: Rebecca J. CurryAbstract:Abstract Synaptic inhibition plays a fundamental role in the neural computation of the Interaural Level Difference (ILD), an important cue for the localization of high-frequency sound. Here, we studied the inhibitory synaptic currents in the chicken posterior portion of the dorsal nucleus of the lateral lemniscus (LLDp), the first binaural Level Difference encoder of the avian auditory pathway. Using whole-cell recordings in brain slices, we provide the first evidence confirming a monosynaptic inhibition driven by direct electrical and chemical stimulation of the contralateral LLDp, establishing the reciprocal inhibitory connection between the two LLDps, a long-standing assumption in the field. This inhibition was largely mediated by GABA A receptors; however, functional glycine receptors were also identified. The reversal potential for the Cl − channels measured with gramicidin-perforated patch recordings was hyperpolarizing (−88 mV), corresponding to a low intracellular Cl − concentration (5.2 mm). Pharmacological manipulations of KCC2 (outwardly Cl − transporter) activity demonstrate that LLDp neurons can maintain a low intracellular Cl − concentration under a high Cl − load, allowing for the maintenance of hyperpolarizing inhibition. We further demonstrate that hyperpolarizing inhibition was more effective at regulating cellular excitability than depolarizing inhibition in LLDp neurons.
Michael Wehr - One of the best experts on this subject based on the ideXlab platform.
-
Synaptic mechanisms underlying Interaural Level Difference selectivity in rat auditory cortex.
Journal of neurophysiology, 2014Co-Authors: Michael Kyweriga, Whitney Stewart, Carolyn Cahill, Michael WehrAbstract:The Interaural Level Difference (ILD) is a sound localization cue that is extensively processed in the auditory brain stem and midbrain and is also represented in the auditory cortex. Here, we asked whether neurons in the auditory cortex passively inherit their ILD tuning from subcortical sources or whether their spiking preferences were actively shaped by local inhibition. If inherited, the ILD selectivity of spiking output should match that of excitatory synaptic input. If shaped by local inhibition, by contrast, excitation should be more broadly tuned than spiking output with inhibition suppressing spiking for nonpreferred stimuli. To distinguish between these two processing strategies, we compared spiking responses with excitation and inhibition in the same neurons across a range of ILDs and average binaural sound Levels. We found that cells preferring contralateral ILDs (often called EI cells) followed the inheritance strategy. In contrast, cells that were unresponsive to monaural sounds but responded predominantly to near-zero ILDs (PB cells) instead showed evidence of the local processing strategy. These PB cells received excitatory inputs that were similar to those received by the EI cells. However, contralateral monaural sounds and ILDs >0 dB elicited strong inhibition, quenching the spiking output. These results suggest that in the rat auditory cortex, EI cells do not utilize inhibition to shape ILD sensitivity, whereas PB cells do. We conclude that an auditory cortical circuit computes sensitivity for near-zero ILDs.
-
Neuronal Interaural Level Difference response shifts are Level-dependent in the rat auditory cortex
Journal of neurophysiology, 2013Co-Authors: Michael Kyweriga, Whitney Stewart, Michael WehrAbstract:How does the brain accomplish sound localization with invariance to total sound Level? Sensitivity to Interaural Level Differences (ILDs) is first computed at the lateral superior olive (LSO) and is observed at multiple Levels of the auditory pathway, including the central nucleus of inferior colliculus (ICC) and auditory cortex. In LSO, this ILD sensitivity is Level-dependent, such that ILD response functions shift toward the ipsilateral (excitatory) ear with increasing sound Level. Thus early in the processing pathway changes in firing rate could indicate changes in sound location, sound Level, or both. In ICC, while ILD responses can shift toward either ear in individual neurons, there is no net ILD response shift at the population Level. In behavioral studies of human sound localization acuity, ILD sensitivity is invariant to increasing sound Levels. Level-invariant sound localization would suggest transformation in Level sensitivity between LSO and perception of sound sources. Whether this transformation is completed at the Level of the ICC or continued at higher Levels remains unclear. It also remains unknown whether perceptual sound localization is Level-invariant in rats, as it is in humans. We asked whether ILD sensitivity is Level-invariant in rat auditory cortex. We performed single-unit and whole cell recordings in rat auditory cortex under ketamine anesthesia and measured responses to white noise bursts presented through sealed earphones at a range of ILDs. Surprisingly, we found that with increasing sound Levels ILD responses shifted toward the ipsilateral ear (which is typically inhibitory), regardless of whether cells preferred ipsilateral, contralateral, or binaural stimuli. Voltage-clamp recordings suggest that synaptic inhibition does not contribute substantially to this transformation in Level sensitivity. We conclude that the Level invariance of ILD sensitivity seen in behavioral studies is not present in rat auditory cortex.
Beverly A. Wright - One of the best experts on this subject based on the ideXlab platform.
-
An influence of amplitude modulation on Interaural Level Difference processing suggested by learning patterns of human adults.
The Journal of the Acoustical Society of America, 2009Co-Authors: Yuxuan Zhang, Beverly A. WrightAbstract:Humans rely on Interaural Level Differences (ILDs) to determine the location of sound sources, particularly for high-frequency sounds. Previously, ILD-discrimination performance with a 4-kHz pure tone was reported to improve with multi-hour training. Here the effect of the same training regimen on ILD discrimination with a 4-kHz tone sinusoidally amplitude modulated (SAM) at 0.3 kHz was examined. Ten of the 16 trained listeners improved more than untrained controls, demonstrating training-induced learning. However, compared to the learning previously obtained with the 4-kHz pure tone, learning with the SAM tone was less predictable based on starting performance, took longer to complete, and was characterized by specificity to stimulus type (SAM vs pure tones) rather than stimulus frequency. These Differences demonstrate an influence of amplitude modulation on learning of ILD discrimination. This influence suggests that the auditory system makes use of amplitude envelope information in determining ILD-discrimination performance, a form of interaction between time and Level processing in the binaural system.
-
training induced improvements on Interaural Level Difference ild and Interaural time Difference itd discrimination in human adults
Journal of the Acoustical Society of America, 2007Co-Authors: Beverly A. WrightAbstract:The two primary cues to the location of sound sources on the horizontal plane are Interaural Level Differences (ILDs) and Interaural time Differences (ITDs). The malleability of the processing of these two cues in humans was investigated by examining how multiday practice affects the discrimination of different values of ILDs and ongoing ITDs presented over headphones in adults with normal hearing. On average, the listeners improved on both ILD and ITD discrimination, but the learning patterns differed between the two cue types. Improvement was initially rapid for both cue types and appeared to generalize broadly across conditions, suggesting procedural learning. However, a subsequent slower‐improvement stage occurred solely for the ILD cue and showed some specificity to the stimulus used during training. Interestingly, for ILD discrimination, both the best and worst daily threshold estimates decreased with multiday training, indicating an improvement in fundamental processing capacity. In contrast, for ITD discrimination, the best threshold estimates remained unchanged but the worst decreased, suggesting an increased ability to access already existing capacities. One interpretation of these data is that training mediates the processing of ILDs and ITDs at a stage in the auditory pathway, where these two cues are processed separately. [Work supported by NIH/NIDCD.]
-
Training‐induced improvements on Interaural Level Difference (ILD) and Interaural time Difference (ITD) discrimination in human adults
The Journal of the Acoustical Society of America, 2007Co-Authors: Beverly A. WrightAbstract:The two primary cues to the location of sound sources on the horizontal plane are Interaural Level Differences (ILDs) and Interaural time Differences (ITDs). The malleability of the processing of these two cues in humans was investigated by examining how multiday practice affects the discrimination of different values of ILDs and ongoing ITDs presented over headphones in adults with normal hearing. On average, the listeners improved on both ILD and ITD discrimination, but the learning patterns differed between the two cue types. Improvement was initially rapid for both cue types and appeared to generalize broadly across conditions, suggesting procedural learning. However, a subsequent slower‐improvement stage occurred solely for the ILD cue and showed some specificity to the stimulus used during training. Interestingly, for ILD discrimination, both the best and worst daily threshold estimates decreased with multiday training, indicating an improvement in fundamental processing capacity. In contrast, for ITD discrimination, the best threshold estimates remained unchanged but the worst decreased, suggesting an increased ability to access already existing capacities. One interpretation of these data is that training mediates the processing of ILDs and ITDs at a stage in the auditory pathway, where these two cues are processed separately. [Work supported by NIH/NIDCD.]
-
learning of Interaural Level Difference discrimination with a 0 5 khz tone in human adults
Journal of the Acoustical Society of America, 2006Co-Authors: Yuxuan Zhang, Beverly A. WrightAbstract:Sound‐source location on the horizontal plane is primarily determined by two cues: Interaural time Differences (ITDs) for low‐frequency sounds and Interaural Level Differences (ILDs) for high‐frequency sounds. Though not available in natural listening environments, ILDs in low‐frequency sounds, when artificially delivered to listeners through headphones, also can be used to lateralize sounds. Little is known about the neural processing of such low‐frequency ILDs. Here, the modifiability of this processing was examined by training human adults on ILD discrimination with a 0.5‐kHz tone on the midline. After nine 1‐h daily training sessions, trained listeners (n=6) improved significantly more than untrained controls (n=8) on the trained condition. This learning generalized to a 4‐kHz tone and a 0.5‐kHz tone amplitude modulated at 30 Hz, but appeared not to generalize to a 1‐kHz tone, an off‐midline position, or ITD discrimination with the trained tone. This overall learning pattern differs from those previou...
-
effects of different amounts of brief training and rest on the generalization of learning from Interaural Level Difference to Interaural time Difference discrimination
Journal of the Acoustical Society of America, 2005Co-Authors: Jeanette A. Ortiz, Beverly A. WrightAbstract:Training‐induced improvements on perceptual skills can be enhanced by increasing the amount of training and by resting between training and testing. However, how these two factors affect the generalization of learning from a briefly trained condition to an untrained one is unknown. Here, listeners were trained on an Interaural‐Level‐Difference (ILD) discrimination condition (4‐kHz tones), then were tested for generalization to an Interaural‐time‐Difference (ITD) discrimination condition (0.5‐kHz tones). The amount of training and the time between training and testing differed across four groups. Listeners tested 10 hours after training had significantly lower ITD discrimination thresholds than naive listeners (n=94), regardless of whether training lasted for 20 min (n=14) or 2 hs (n=11). Thus, when there was a long time between training and testing, learning generalized from ILD to ITD discrimination regardless of the amount of training. In contrast, listeners tested immediately after training on ILD disc...