Tone Discrimination Research Articles

Effects of First Language Background and Learning Experience in Perceiving Mandarin Lexical Tones: Learners and Nonlearners From English- and Japanese-Speaking Backgrounds.

This research compared individuals from two first language (L1) backgrounds (English and Japanese) to determine how they may differ in their perception of Mandarin tones (Tones 1 vs. 2 [T1-T2], Tones 1 vs. 3 [T1-T3], Tones 1 vs. 4 [T1-T4], Tones 2 vs. 3 [T2-T3], Tones 2 vs. 4 [T2-T4], Tones 3 vs. 4 [T3-T4]) on account of their L1. The participants included two groups of learners of Mandarin (23 English speakers, 18 Japanese speakers), two groups of nonlearners of Mandarin (24 English speakers, 21 Japanese speakers), and a control group of 10 Mandarin speakers. A four-alternative forced-choice discrimination task that included 360 trials was presented in three blocks of 120 trials. The native Mandarin group was more accurate in their tonal discrimination of all six tone pairs than all the nonnative groups. While Japanese nonlearners generally outperformed English nonlearners in their overall perception of Mandarin lexical tones, L1-based differences were less extensive for the two groups of learners. Both learner groups were least accurate on T2-T3 and most accurate on T3-T4. The results suggest that with classroom experience, English speakers can overcome their initial disadvantage and learn lexical tones in a new language as successfully as speakers of Japanese with classroom experience.

When long appears short: Effects of auditory distraction on event-related potential correlates of time perception.

Attentional models of time perception assume that the perceived duration of a stimulus depends on the extent to which attentional resources are allocated to its temporal information. Here, we studied the effects of auditory distraction on time perception, using a combined attentional-distraction duration-discrimination paradigm. Participants were confronted with a random sequence of long and short tone stimuli, most of which having a uniform (standard) pitch and only a few a different (deviant) pitch. As observed in previous studies, pitch-deviant tones impaired the discrimination of tone duration and triggered a sequence of event-related potentials (ERPs) reflecting a cycle of deviance detection, involuntary attentional distraction and reorientation (MMN, P3a, RON). Contrasting ERPs of short and long tone durations revealed that long tones elicited a more pronounced fronto-central contingent negative variation (CNV) in the time interval after the expected offset of the short tone as well as a more prominent centro-parietal late positive complex (LPC). Relative to standard-pitch tones, deviant-pitch tones especially impaired the correct discrimination of long tones, which was associated with a reduction of the CNV and LPC. These results are interpreted within the theoretical framework of resource-based models of time perception, in which involuntary distraction due to a deviant event led to a withdrawal of attentional resources from the processing of time information.

Pure tone discrimination with cochlear implants and filter-band spread

For many cochlear implant (CI) users, frequency discrimination is still challenging. We studied the effect of frequency differences relative to the electrode frequency bands on pure tone discrimination. A single-center, prospective, controlled, psychoacoustic exploratory study was conducted in a tertiary university referral center. Thirty-four patients with Cochlear Ltd. and MED-EL CIs and 19 age-matched normal-hearing control subjects were included. Two sinusoidal tones were presented with varying frequency differences. The reference tone frequency was chosen according to the center frequency of basal or apical electrodes. Discrimination abilities were psychophysically measured in a three-interval, two-alternative, forced-choice procedure (3I-2AFC) for various CI electrodes. Hit rates were measured, particularly with respect to discrimination abilities at the corner frequency of the electrode frequency-bands. The mean rate of correct decision concerning pitch difference was about 60% for CI users and about 90% for the normal-hearing control group. In CI users, the difference limen was two semitones, while normal-hearing participants detected the difference of one semitone. No influence of the corner frequency of the CI electrodes was found. In CI users, pure tone discrimination seems to be independent of tone positions relative to the corner frequency of the electrode frequency-band. Differences of 2 semitones can be distinguished within one electrode.

Study of variability of cognitive performance in captive fallow deer (Dama dama) through g and c factors

Psychometric studies reveal a variability that ranges between 30 and 75 % for different cognitive processes, both in humans and non-human animals. This variability has been ascribed to a “general intelligence” factor (g). Current studies implemented in non-human animals to identify individual differences in cognitive skills are still far from those applied in humans. We tested for cognitive performance in a fallow deer herd using a test battery of eight tasks based on measures for cognitive development in untamed confined wild animals: motor control, spatial memory, colour and tone discrimination and inversion, inhibitory control and symbol discrimination tests. g factor explained 60 % of the variability in cognitive performance. Significant correlations, both positive and negative, were found between the different cognitive processes studied. Likewise, the cognitive performance of the group was affected by a “collective intelligence” factor (c), inferred through variables describing the hierarchical structure of the studied population but which, however does not affect individual intelligence quotient of the members of the group.

Perceptual assimilation of regionally accented Mandarin lexical tones by native Beijing Mandarin listeners

Pronunciations of Beijing Mandarin are those of Standard Mandarin (hereafter Mandarin), which developed from the Beijing dialect. Native speakers of other regional dialects in China learn Mandarin as an early second language, and produce its four lexical tones (level, rising, dipping, and falling) with regional accents. This study investigated how native Beijing Mandarin listeners perceptually assimilate regionally accented Mandarin lexical tones. Native Beijing Mandarin listeners (Mage = 21.31 years) were recruited to identify 16 Mandarin real words (4 consonant-vowel syllables: ba, di, du, gu × 4 tones) produced by speakers of Beijing, Shanghai, and Guangzhou dialects and to rate how similar the productions were to the Beijing accent. Stimuli were blocked by syllable, maintaining minimal contrasts between the tones. The Beijing listeners identified Mandarin words in all three accents with high accuracy (>90%), indicating that they reliably assimilated the regionally accented tones into the four Mandarin tones. However, their reaction times were longer and their rating scores were lower for the regional accents than for the Beijing stimuli. This indicates that while Mandarin listeners are sensitive to accent differences in Mandarin lexical tones, they show phonological constancy across regional accents, which is crucial for tone categorization and discrimination of tone contrasts.

A New System of Cantonese Tones? Tone Perception and Production in Hong Kong South Asian Cantonese

Studies in language contact have identified many instances of linguistic variation and grammatical innovations introduced by speakers from multi-ethnic urban neighborhoods. This study focuses on the variety of Cantonese spoken by South Asian youths in Hong Kong, specifically their production and perception of Hong Kong Cantonese tones. Our findings show that the South Asian Cantonese speakers have a smaller tonal inventory than the canonical six-tone system of standard Hong Kong Cantonese and their tonal discrimination abilities are also more impoverished relative to their ethnic Chinese peers. Further analysis shows a positive correlation between tonal discrimination accuracy and tonal realization distinctness among the South Asian speakers, but not among the ethnic Chinese. These findings suggest that South Asian Cantonese speakers might have developed a distinct tone system from their ethnic Chinese peers.

Dialect Effects on Mandarin Tone Perception Development.

This study aimed to characterize factors that influence early dialect development in a language environment with multiple dialects. Children were evaluated for these dialect effects compared with normal hearing referenced measures of speech and language development that are commonly implemented in hearing-impaired children. Dialect exposure and use were assessed longitudinally in Chinese children (2-6 years old) that were raised in a community where Putonghua (PTH) and Sichuanhua (SCH) Mandarin dialects were used. Lexical tones in these dialects are different. A total of 20 boys and 20 girls (2 years old at the beginning of the study) that attended the same nursery school were included in this study. SCH was used by the majority of subjects <4 years old. The majority of subjects >4 years old used either dialect, with a few users of both dialects at this age. PTH tone perception did not differ significantly as a function of dialect use. Tone recognition and discrimination were >90% accurate by 6 years old, in contrast to previous results for children with minimal exposure and use of PTH. Children with approximately ⩾50% PTH exposure might be accurately assessed with norm-referenced speech materials spoken in PTH, regardless of their preferred dialect. However, the current norm-referenced assessments of children with minimal PTH exposure and nonusers of the dialect might be inaccurate.

Energy optimization during walking involves implicit processing.

Gait adaptations, in response to novel environments, devices or changes to the body, can be driven by the continuous optimization of energy expenditure. However, whether energy optimization involves implicit processing (occurring automatically and with minimal cognitive attention), explicit processing (occurring consciously with an attention-demanding strategy) or both in combination remains unclear. Here, we used a dual-task paradigm to probe the contributions of implicit and explicit processes in energy optimization during walking. To create our primary energy optimization task, we used lower-limb exoskeletons to shift people's energetically optimal step frequency to frequencies lower than normally preferred. Our secondary task, designed to draw explicit attention from the optimization task, was an auditory tone discrimination task. We found that adding this secondary task did not prevent energy optimization during walking; participants in our dual-task experiment adapted their step frequency toward the optima by an amount and at a rate similar to participants in our previous single-task experiment. We also found that performance on the tone discrimination task did not worsen when participants were adapting toward energy optima; accuracy scores and reaction times remained unchanged when the exoskeleton altered the energy optimal gaits. Survey responses suggest that dual-task participants were largely unaware of the changes they made to their gait during adaptation, whereas single-task participants were more aware of their gait changes yet did not leverage this explicit awareness to improve gait adaptation. Collectively, our results suggest that energy optimization involves implicit processing, allowing attentional resources to be directed toward other cognitive and motor objectives during walking.

Native language, L2 experience, and pitch processing in music

Abstract The current study investigated how the role of pitch in one’s native language and L2 experience influenced musical melodic processing by testing Turkish and Mandarin Chinese advanced and beginning learners of English as an L2. Pitch has a lower functional load and shows a simpler pattern in Turkish than in Chinese as the former only contrasts between presence and the absence of pitch elevation, while the latter makes use of four different pitch contours lexically. Using the Musical Ear Test as the tool, we found that the Chinese listeners outperformed the Turkish listeners, and the advanced L2 learners outperformed the beginning learners. The Turkish listeners were further tested on their discrimination of bisyllabic Chinese lexical tones, and again an L2 advantage was observed. No significant difference was found for working memory between the beginning and advanced L2 learners. These results suggest that richness of tonal inventory of the native language is essential for triggering a music processing advantage, and on top of the tone language advantage, the L2 experience yields a further enhancement. Yet, unlike the tone language advantage that seems to relate to pitch expertise, learning an L2 seems to improve sound discrimination in general, and such improvement exhibits in non-native lexical tone discrimination.

The development of brain rhythms at rest and its impact on vocabulary acquisition.

A long-standing question in developmental science is how the neurodevelopment of the brain influences cognitive functions. Here, we examined the developmental change of resting EEG power and its links to vocabulary acquisition in school-age children. We further explored what mechanisms may mediate the relation between brain rhythm maturation and vocabulary knowledge. Eyes-opened resting-state EEG data were recorded from 53 typically-developing Chinese children every 2 years between the ages of 7 and 11. Our results showed first that delta, theta, and gamma power decreased over time, whereas alpha and beta power increased over time. Second, after controlling for general cognitive abilities, age, home literacy environment, and phonological skills, theta decreases explained 6.9% and 14.4% of unique variance in expressive vocabulary at ages 9 and 11, respectively. We also found that beta increase from age 7 to 9 significantly predicted receptive vocabulary at age 11. Finally, theta decrease predicted expressive vocabulary through the effects of phoneme deletion at age 9 and tone discrimination at age 11. These results substantiate the important role of brain oscillations at rest, especially theta rhythm, in language development. The developmental change of brain rhythms could serve as sensitive biomarkers for vocabulary development in school-age children, which would be of great value in identifying children at risk of language impairment.

Dissociation of tone merger and congenital amusia in Hong Kong Cantonese.

While the issue of individual variation has been widely studied in second language learning or processing, it is less well understood how perceptual and musical aptitude differences can explain individual variation in native speech processing. In the current study, we make use of tone merger in Hong Kong Cantonese, an ongoing sound change that concerns the merging of tones in perception, production or both in a portion of native speakers, to examine the possible relationship between tone merger and musical and pitch abilities. Although a previous study has reported the occurrence of tone merger independently of musical training, it has not been investigated before whether tone-merging individuals, especially those merging tones in perception, would have inferior musical perception and fine-grained pitch sensitivities, given the close relationship of speech and music. To this end, we tested three groups of tone-merging individuals with various tone perception and production profiles on musical perception and pitch threshold tasks, in comparison to a group of Cantonese speakers with congenital amusia, and another group of controls without tone merger or amusia. Additionally, the amusics were compared with tone-merging individuals on the details of their tone discrimination and production profiles. The results showed a clear dissociation of tone merger and amusia, with the tone-merging individuals exhibiting intact musical and pitch abilities; on the other hand, the amusics demonstrated widespread difficulties in tone discrimination yet intact tone production, in contrast to the highly selective confusion of a specific tone pair in production or discrimination in tone-merging individuals. These findings provide the first evidence that tone merger and amusia are distinct from each other, and further suggest that the cause of tone merger may lie elsewhere rather than being driven by musical or pitch deficits. We also discussed issues arising from the current findings regarding the neural mechanisms of tone merger and amusia.

Assessment of olfactory information in the human brain using 7-Tesla functional magnetic resonance imaging

Olfaction could prove to be an early marker of neurodegenerative diseases, including Alzheimer's and Parkinson's diseases. To use olfaction for disease diagnosis, elucidating the standard olfactory functions in healthy humans is necessary. However, the olfactory function in the human brain is less frequently assessed because of methodological difficulties associated with olfactory-related cerebral areas. Using ultra-high fields (UHF), functional magnetic resonance imaging (fMRI) with high spatial resolution and sensitivity may allow for the measurement of activation in the cerebral areas. This study aimed to apply 7-Tesla fMRI to assess olfactory function in the human brain by exposing individuals to four different odorants for 8 s. We found that olfactory stimulation mainly activated the piriform and orbitofrontal cortex in addition to the amygdala. Among these regions, univariate fMRI analysis indicated that subjective odor intensity significantly correlated with the averaged fMRI signals in the piriform cortex but not with subjective hedonic tone in any region. In contrast, multivariate fMRI analysis showed that subjective hedonic tone could be discriminated from the fMRI response patterns in the posterior orbitofrontal cortex. Thus, the piriform cortex is mainly associated with subjective odor intensity, whereas the posterior orbitofrontal cortex are involved in the discrimination of the subjective hedonic tone of the odorant. UHF-fMRI may be useful for assessing olfactory function in the human brain.

High-Variability Phonetic Training Benefits Lexical Tone Perception: An Investigation on Mandarin-Speaking Pediatric Cochlear Implant Users.

Purpose Lexical tone perception is known to be persistently difficult for individuals with cochlear implants (CIs). The purpose of this study was to evaluate the efficacy of high-variability phonetic training (HVPT) in improving Mandarin tone perception for native-speaking children with CIs. Method A total of 28 Mandarin-speaking pediatric CI recipients participated in the study. Half of the children with CIs received a five-session HVPT within a period of 3 weeks. Identification and discrimination of lexical tones produced by familiar talkers (used during training) and novel talkers (not used during training) were measured before, immediately after, and 10 weeks after training termination. The other half untrained children served as control for the identical pre- and posttests. Results Lexical tone perception significantly improved in both trained identification task and untrained discrimination task for the trainees. There was also a significant effect in transfer of learning to perceiving tones produced by novel talkers. Moreover, training-induced gains were retained for up to 10 weeks after training. By comparison, no significant pre-post changes were observed in the control group. Conclusion The results provide the first systematical assessment for the efficacy of the HVPT protocol for Mandarin-speaking pediatric CI users with congenital hearing loss, which supports the clinical utility of intensive short-term HVPT in these children's rehabilitative regimens.

Perceived colorism and lifetime psychiatric disorders among Black American adults: findings from the National Survey of American Life.

Colorism has been propagated across the globe, and skin tone discrimination may partly explain social stratification and health disparities within the Black American population. Using data from a large probability sample of Black American adults (National Survey of American Life; 2001-2003), we examined the relations between perceived colorism and psychiatric disorders. In multivariable logistic regression models, in-group colorism was associated with greater odds of having any lifetime psychiatric disorder (aOR: 1.20; 95% CI: 1.08-1.32; p = 0.00); however, out-group colorism was not significantly associated, net of sociodemographic characteristics and in-group colorism (aOR: 1.08; 95% CI: 0.99-1.18; p = 0.08). When looking at specific disorders, in-group colorism was significantly associated with greater odds of alcohol use disorder, substance use disorder, anxiety disorder, and eating disorder, but was not associated with post-traumatic stress disorder or mood disorder. Out-group colorism was not significantly associated with any psychiatric disorder except anxiety disorder. Our findings show that colorism predicts psychiatric disorders, though more research is needed to understand why the effects of in-group and out-group colorism are related to certain psychiatric disorders but not others.

Aging Effects on Categorical Perception of Mandarin Lexical Tones in Noise.

Purpose The purpose of this study was to examine the aging effects on the categorical perception (CP) of Mandarin lexical Tones 1-4 and Tones 1-2 in noise. It also investigated whether listeners' categorical tone perception in noise correlated with their general tone identification of 20 natural vowel-plus-tone signals in noise. Method Twelve younger and 12 older listeners with normal hearing were recruited in both tone identification and discrimination tasks in a CP paradigm where fundamental frequency contours of target stimuli varied systematically from the flat tone (Tone 1) to the rising/falling tones (Tones 2/4). Both tasks were conducted in quiet and noise with signal-to-noise ratios set at -5 and -10 dB, respectively, and general tone identification of natural speech signals was also tested in noise conditions. Results Compared with younger listeners, older listeners had shallower identification slopes and smaller discrimination peakedness in Tones 1-2/4 perception in all listening conditions, except for Tones 1-4 perception in quiet where no group differences were found. Meanwhile, noise affected Tones 1-2/4 perception: The signal-to-noise ratio condition at -10 dB brought shallower slope in Tones 1-2/4 identification and less peakedness in Tones 1-4 discrimination for both listener groups. Older listeners' CP in noise, the identification slopes in particular, positively correlated with their general tone identification in noise, but such correlations were partially missing for younger listeners. Conclusions Both aging and the presence of speech-shaped noise significantly reduced the CP of Mandarin Tones 1-2/4. Listeners' Mandarin tone recognition may be related to their CP of Mandarin tones.

Genetic Screening for 35delG Mutation in Egyptian Patients with Profound Sensorineural Hearing Loss Scheduled for Cochlear Implantation: A Population-Based Study

Objectives: The aim of this work was to assess the type and site of the 35delG gene mutation in patients presenting with profound SNHL and scheduled for cochlear implantation. The secondary objectives were to determine their geographical distribution throughout Egypt, screening of the parents for the mutation, and to correlate the type of mutation with clinical severity and outcomes after surgery. Methods: The study was carried out on 100 consecutive patients scheduled for cochlear implantation. Patients with syndromic hearing loss or noncongenital hearing loss (trauma, infections, and ototoxicity) were excluded. All patients were subjected to detailed history taking including geographic tagging for their origins in Egypt, imaging (CT and MRI cochlear implantation protocols), full audiological evaluation (PTA, ABR, and TEOAE), and genetic screening for GJB2 mutation using Invitrogen PCR mix and ApaI restriction enzyme (North America, CA, 10572-014). The parents of mutation-positive patients were also subjected to audiological and genetic analysis. All patients were subjected to postimplantation evaluation of hearing after 6 and 12 months. Results: There were 64 males and 36 females from 98 families. Ages ranged between 1.9 and 7 years (mean 3.72 years). They originated from all over Egypt but the majority came from the Giza and Cairo areas. The 35delG mutations were found in exon 2 in 31% of the cases and all were heterozygous. In the parents, 18 mothers and 13 fathers were positive but only 8 had mild to moderate SNHL. Hearing evaluation by pure tone and speech discrimination scores at 6 and 12 months showed that the 35delG children had a statistically better result compared to the children without this mutation. Conclusion: The prevalence of the 35delG mutation in nonsyndromic children in this sample was 31% which is different from previous studies in the Egyptian population but close to the values found in other populations in the Mediterranean basin.

Selection in working memory is resource-demanding: Concurrent task effects on the retro-cue effect

In a retro-cue paradigm, after memorizing a set of objects, people are cued to remember only a subset. Improved memory from the retro-cue suggests that selection processes can benefit items stored in working memory. Does selection in working memory require attention? If so, an attention-demanding task should disrupt retro-cue effects. Studies using a dual-task paradigm have found mixed results, with only one study (Janczyk & Berryhill, Attention, Perception, and Psychophysics, 76 (3), 715–724, 2014) showing a decreased retro-cue effect by a secondary task. Here we explore a potential issue in that study – the temporal overlap of the secondary task response with the memory test presentation. This raises questions about whether the secondary task was impairing selection processes in memory or was impacting the memory response. We replicated their paradigm by inserting a tone discrimination task at the retro-cue offset, but we also included a condition in which the tone task and the memory test were temporally separated. In Experiment 1, performing the tone task did not impair the retro-cue effect. In Experiment 2, we added an articulatory suppression task as in Janczyk and Berryhill’s study, and we found that the requirement to execute the tone task impaired retro-cue effects. This impairment was independent of whether the tone and memory tasks overlapped. These findings suggest that internal prioritization can be impaired by dual-task interference, but may only occur when such interference is robust enough, for example, due to switching between multiple tasks.

Perceived skin tone discrimination and suicidal ideation Black Americans: Findings from the National Survey of American Life

BackgroundTo examine the association between skin tone discrimination and lifetime suicidal ideation and suicide attempt among Black Americans. MethodsWe analyzed the National Survey of American Life (NSAL), which is a national probability sample of Black American adults residing in the general population of the United States. Using multivariable logistic regression, we examined the associations between skin tone discrimination (from Blacks and from whites) and suicidal ideation and suicide attempt, adjusting for sociodemographic characteristics. ResultsWhile respondents on average reported higher frequency of inter-group skin tone discrimination, only intra-group skin tone discrimination was significantly associated with greater odds of lifetime suicidal ideation [aOR: 1.21; 95% CI: 1.08-1.36] and suicide attempt [aOR: 1.22; 95% CI: 1.22; 95% CI: 1.04-1.44] adjusting for sociodemographic characteristics. Inter-group skin tone discrimination was not significantly related to suicidal ideation or suicide attempt. When stratifying by ethnicity, the effect of intra-group skin tone discrimination on suicidal ideation and attempt was stronger among Caribbean Black Americans than it was for African Americans. LimitationsAll measures in the sample were self-reported and thus vulnerable to recall bias. ConclusionsIntra-group skin tone discrimination is a risk factor for suicidal ideation among Black Americans, and especially among Caribbean Black Americans.

Episodic-like memory of rats as retrospective retrieval of incidentally encoded locations and involvement of the retrosplenial cortex

To examine episodic memory in rats, we trained rats to perform two tasks and tested them for memory of past self-behavior without making them expect to be asked about the memory later when encoding. One of the trained tasks was a delayed matching-to-position task in which the rats were required to remember the location of a presented lever. The other was a tone discrimination task in which the rats were required to discriminate between two pure tones. After learning both tasks, the rats were unexpectedly asked the location of the pressed lever after responding to the cue tone in probe trials during test sessions. The rats demonstrated a response bias that suggests that they have the ability to retrospectively recollect their self-behavior, i.e., episodic memory. We next made excitotoxic lesions in the retrosplenial cortex (RSC) and investigated the effects of the lesions on the unexpected recollection. In the rats with lesions of the RSC, the response bias disappeared. This suggests that the RSC has a role in retrospectively answering unexpected questions about self-behavior.

Endogenous Cholinergic Signaling Modulates Sound-Evoked Responses of the Medial Nucleus of the Trapezoid Body.

The medial nucleus of trapezoid body (MNTB) is a major source of inhibition in auditory brainstem circuitry. The MNTB projects well-timed inhibitory output to principal sound-localization nuclei in the superior olive (SOC) as well as other computationally important centers. Acoustic information is conveyed to MNTB neurons through a single calyx of Held excitatory synapse arising from the cochlear nucleus. The encoding efficacy of this large synapse depends on its activity rate, which is primarily determined by sound intensity and stimulus frequency. However, MNTB activity rate is additionally influenced by inhibition and possibly neuromodulatory inputs, albeit their functional role is unclear. Happe and Morley (2004) discovered prominent expression of α7 nAChRs in rat SOC, suggesting possible engagement of ACh-mediated modulation of neural activity in the MNTB. However, the existence and nature of this putative modulation have never been physiologically demonstrated. We probed nicotinic cholinergic influences on acoustic responses of MNTB neurons from adult gerbils (Meriones unguiculatus) of either sex. We recorded tone-evoked MNTB single-neuron activity in vivo using extracellular single-unit recording. Piggyback multibarrel electrodes enabled pharmacological manipulation of nAChRs by reversibly applying antagonists to two receptor types, α7 and α4β2. We observed that tone-evoked responses are dependent on ACh modulation by both nAChR subtypes. Spontaneous activity was not affected by antagonist application. Functionally, we demonstrate that ACh contributes to sustaining high discharge rates and enhances signal encoding efficacy. Additionally, we report anatomic evidence revealing novel cholinergic projections to MNTB arising from pontine and superior olivary nuclei.SIGNIFICANCE STATEMENT This study is the first to physiologically probe how acetylcholine, a pervasive neuromodulator in the brain, influences the encoding of acoustic information by the medial nucleus of trapezoid body, the most prominent source of inhibition in brainstem sound-localization circuitry. We demonstrate that this cholinergic input enhances neural discrimination of tones from noise stimuli, which may contribute to processing important acoustic signals, such as speech. Additionally, we describe novel anatomic projections providing cholinergic input to the MNTB. Together, these findings shed new light on the contribution of neuromodulation to fundamental computational processes in auditory brainstem circuitry and to a more holistic understanding of modulatory influences in sensory processing.