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Objective: To explore the differences of functional brain networks in processing auditory phonological tasks between Cantonese-Mandarin bilinguals and Mandarin monolinguals., Methods: 31 Cantonese-Mandarin bilinguals and 31 Mandarin monolinguals performed auditory rhyming tasks under a functional magnetic resonance imaging (fMRI) scanning. Bilinguals performed two language tasks (Cantonese, CC; Mandarin, CM), while monolinguals performed only one task (Mandarin, MM). Graph theory and network-based statistic (NBS) analyses were used to reveal the differences of functional brain networks among CC, CM and MM., Results: The functional brain networks of CC, CM and MM were all small-world, and there were no differences in network properties, but widespread differences in functional connectivity among distributed brain regions., Conclusions: The Cantonese-Mandarin bilingualism and Mandarin monolingualism shared similar efficient topological structure of brain network for auditory phonological processing, but varied in widespread functional connectivity. And the two languages within bilingualism employed different functional brain networks for auditory phonological processing., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Hyperacusis is a debilitating hearing condition in which normal everyday sounds are perceived as exceedingly loud, annoying, aversive or even painful. The prevalence of hyperacusis approaches 10%, making it an important, but understudied medical condition. To noninvasively identify the neural correlates of hyperacusis in an animal model, we used sound-evoked functional magnetic resonance imaging (fMRI) to locate regions of abnormal activity in the central nervous system of rats with behavioral evidence of hyperacusis induced with an ototoxic drug (sodium salicylate, 250 mg/kg, i.p.). Reaction time-intensity measures of loudness-growth revealed behavioral evidence of salicylate-induced hyperacusis at high intensities. fMRI revealed significantly enhanced sound-evoked responses in the auditory cortex (AC) to 80 dB SPL tone bursts presented at 8 and 16 kHz. Sound-evoked responses in the inferior colliculus (IC) were also enhanced, but to a lesser extent. To confirm the main results, electrophysiological recordings of spike discharges from multi-unit clusters were obtained from the central auditory pathway. Salicylate significantly enhanced tone-evoked spike-discharges from multi-unit clusters in the AC from 4 to 30 kHz at intensities ≥60 dB SPL; less enhancement occurred in the medial geniculate body (MGB), and even less in the IC. Our results demonstrate for the first time that non-invasive sound-evoked fMRI can be used to identify regions of neural hyperactivity throughout the brain in an animal model of hyperacusis., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Growing evidence shows that partial auditory deprivation leads to extensive neural functional plasticity, which occurs not only in the auditory cortex but also in other sensory regions and cognitive areas. However, studies in structural topological properties are still limited, especially those investigating the relationship between structural connectome alterations and auditory abilities. To clarify this, we investigated white matter structural connectivity changes and the relationship between connection strength and hearing abilities in individuals with long-term single-sided deafness (SSD), a common form of partial hearing deprivation, using diffusion tensor imaging and network-based analysis. The results showed globally improved connection efficiency, locally weakened visual networks, and strengthened fronto-parietal sub-networks in SSD compared to normal hearing controls. Furthermore, a strong positive correlation between hearing abilities (including speech recognition in noise and sound localization) and connection strength, mainly in the fronto-parietal areas, was found in SSD. Our study reveals alteration of the structural network connections in SSD, especially in cognitive related networks, which showed close correlation with hearing abilities. Our findings provide new insights into topological white matter reorganization of the brain after partial sensory deprivation., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Auditory target detection has been explored by a number of studies, but none have demonstrated activity in the auditory subcortical centers evoked by the top-down attentional mechanism related to target detection in humans. We applied functional magnetic resonance imaging (fMRI) with sparse sampling to explore activity in the auditory centers, particularly in the subcortex, during an active auditory target detection task. Fourteen healthy subjects with normal hearing tapped the left index finger in response to target tonal stimuli presented among other (non-target) stimuli during continuous white noise stimulation. General linear model, region-of-interest, and connectivity analyses were performed. In the cortex, bilateral auditory cortices as well as the cingulate gyrus, thalamus, and supramarginal gyrus were activated to target stimuli and functionally connected to each other. In the subcortex, the superior olivary complex (SOC) and locus coeruleus were activated to the target but not to the non-target or background noise stimuli. The SOC was the only auditory subcortical center that displayed connectivity to the auditory cortical areas as well as the cingulate and supramarginal gyri during target presentation but not during other conditions. SOC activation appears to be the first fMRI evidence of direct cortico-olivary projections in the human brain as well as SOC participation in auditory target detection. Our results may be an initial step towards developing a noninvasive methodology to evaluate the functional integrity of the auditory efferent system in humans., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Since its inception 30 years ago, diffusion-weighted magnetic resonance imaging (dMRI) has advanced to become a common component of routine clinical MRI examinations. Diffusion-weighted magnetic resonance offers a way to measure anisotropic diffusion in-vivo, which has led to the development of techniques capable of characterising the orientation of diffusion within living tissue. These modelling techniques can be used to investigate the microstructure and connectivity of white matter tracts within the human brain. Such techniques have been used to study many neural networks within the human body. There is, however, a notable paucity of research utilising dMRI techniques to investigate the white matter tracts of the auditory brainstem. In this review we provide a brief introduction to the basic principles of dMRI analysis and consider some of the difficulties associated with applying dMRI techniques to study the auditory pathways of the brainstem. We also consider aspects of current dMRI methodologies relevant to the auditory brainstem to inform future research in this area., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Functional neuroimaging has identified that the temporal, frontal and parietal cortex support core aspects of speech processing. An objective measure of speech intelligibility based on cortical activation in these brain regions would be extremely useful to speech communication and hearing device applications. In the current study, we used noise-vocoded speech to examine cortical correlates of speech intelligibility in normally-hearing listeners using functional near-infrared spectroscopy (fNIRS), a non-invasive, neuroimaging technique that is fully-compatible with hearing devices, including cochlear implants. In twenty-three normally-hearing adults we measured (1) activation in superior temporal, inferior frontal and inferior parietal cortex bilaterally and (2) behavioural speech intelligibility. Listeners heard noise-vocoded sentences targeting five equally spaced levels of intelligibility between 0 and 100% correct. Activation in superior temporal regions increased linearly with intelligibility. This relationship appears to have been driven in part by changing acoustic properties across stimulation conditions, rather than solely by intelligibility per se. Superior temporal activation was also predictive of individual differences in intelligibility in a challenging listening condition. Beyond superior temporal cortex, we identified regions in which activation varied non-linearly with intelligibility. For example, in left inferior frontal cortex, activation peaked in response to heavily degraded, yet still somewhat intelligible, speech. Activation in this region was linearly related to response time on a simultaneous behavioural task, suggesting it may contribute to decision making. Our results indicate that fNIRS has the potential to provide an objective measure of speech intelligibility in normally-hearing listeners. Should these results be found to apply similarly in the case of individuals listening through a cochlear implant, fNIRS would demonstrate potential for a clinically useful measure not only of speech intelligibility, but also of listening effort., (Crown Copyright © 2018. Published by Elsevier B.V. All rights reserved.)

The influential dual-stream model of auditory processing stipulates that information pertaining to the meaning and to the position of a given sound object is processed in parallel along two distinct pathways, the ventral and dorsal auditory streams. Functional independence of the two processing pathways is well documented by conscious experience of patients with focal hemispheric lesions. On the other hand there is growing evidence that the meaning and the position of a sound are combined early in the processing pathway, possibly already at the level of early-stage auditory areas. Here, we investigated how early auditory areas integrate sound object meaning and space (simulated by interaural time differences) using a repetition suppression fMRI paradigm at 7 T. Subjects listen passively to environmental sounds presented in blocks of repetitions of the same sound object (same category) or different sounds objects (different categories), perceived either in the left or right space (no change within block) or shifted left-to-right or right-to-left halfway in the block (change within block). Environmental sounds activated bilaterally the superior temporal gyrus, middle temporal gyrus, inferior frontal gyrus, and right precentral cortex. Repetitions suppression effects were measured within bilateral early-stage auditory areas in the lateral portion of the Heschl's gyrus and posterior superior temporal plane. Left lateral early-stages areas showed significant effects for position and change, interactions Category x Initial Position and Category x Change in Position, while right lateral areas showed main effect of category and interaction Category x Change in Position. The combined evidence from our study and from previous studies speaks in favour of a position-linked representation of sound objects, which is independent from semantic encoding within the ventral stream and from spatial encoding within the dorsal stream. We argue for a third auditory stream, which has its origin in lateral belt areas and tracks sound objects across space., (Copyright © 2018. Published by Elsevier B.V.)

From their second year, infants typically begin to show rapid acquisition of receptive and expressive language. Here, we ask why these language skills do not begin to develop earlier. One evolutionary hypothesis is that infants are born when many brains systems are immature and not yet functioning, including those critical to language, because human infants have large have a large head and their mother's pelvis size is limited, necessitating an early birth. An alternative proposal, inspired by discoveries in machine learning, is that the language systems are mature enough to function but need auditory experience to develop effective representations of speech, before the language functions that manifest in behaviour can emerge. Growing evidence, in particular from neuroimaging, is supporting this latter hypothesis. We have previously shown with magnetic resonance imaging (MRI) that the acoustic radiation, carrying rich information to auditory cortex, is largely mature by 1 month, and using functional MRI (fMRI) that auditory cortex is processing many complex features of natural sounds by 3 months. However, speech perception relies upon a network of regions beyond auditory cortex, and it is not established if this network is mature. Here we measure the maturity of the speech network using functional connectivity with fMRI in infants at 3 months (N = 6) and 9 months (N = 7), and in an adult comparison group (N = 15). We find that functional connectivity in speech networks is mature at 3 months, suggesting that the delay in the onset of language is not due to brain immaturity but rather to the time needed to develop representations through experience. Future avenues for the study of language development are proposed, and the implications for clinical care and infant education are discussed., (Copyright © 2018. Published by Elsevier B.V.)

The auditory "octave illusion" arises when dichotic tones, presented one octave apart, alternate rapidly between the ears. This study aimed to explore the link between the perception of illusory pitches and brain activity during presentation of dichotic tones. We conducted a behavioral study of how participants perceived binaural dichotic tones of octave illusions and classified them, based on the reported percepts, in an illusion (ILL) group, without an illusion (non-ILL) group, and others. We recorded brain activity using functional magnetic resonance imaging and analyzed the activation due to dichotic illusion tones. The activation in the bilateral planum polare in the auditory cortex was significantly larger in the ILL group than in the non-ILL group. In the right premotor cortex, the non-ILL group showed a significantly larger activation than did the ILL group, suggesting that the sensation of the meter to the stimulus sound was significant in the non-ILL but not in the ILL group. The results indicated that the activity in these areas was related to the occurrence of octave illusions. The nonsignificant sensation of the meter to the stimulus sound in the ILL group may be consistent with the perception of octave illusion., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The ability to understand speech in the presence of competing sound sources is an important neuroscience question in terms of how the nervous system solves this computational problem. It is also a critical clinical problem that disproportionally affects the elderly, children with language-related learning disorders, and those with hearing loss. Recent evidence that musicians have an advantage on this multifaceted skill has led to the suggestion that musical training might be used to improve or delay the decline of speech-in-noise (SIN) function. However, enhancements have not been universally reported, nor have the relative contributions of different bottom-up versus top-down processes, and their relation to preexisting factors been disentangled. This information that would be helpful to establish whether there is a real effect of experience, what exactly is its nature, and how future training-based interventions might target the most relevant components of cognitive processes. These questions are complicated by important differences in study design and uneven coverage of neuroimaging modality. In this review, we aim to systematize recent results from studies that have specifically looked at musician-related differences in SIN by their study design properties, to summarize the findings, and to identify knowledge gaps for future work., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Hearing loss is known to impact brain function. The aim of this study was to characterize cerebral metabolic Positron Emission Tomography (PET) changes in elderly patients fulfilling criteria for cochlear implant and investigate the impact of hearing loss on functional connectivity. Statistical Parametric Mapping-T-scores-maps comparisons of 18 F-FDG-PET of 27 elderly patients fulfilling criteria for cochlear implant for hearing loss (best-aided speech intelligibility lower or equal to 50%) and 27 matched healthy subjects (p < 0.005, corrected for volume extent) were performed. Metabolic connectivity was evaluated through interregional correlation analysis. Patients were found to have decreased metabolism within the right associative auditory cortex, while increased metabolism was found in prefrontal areas, pre- and post-central areas, the cingulum and the left inferior parietal gyrus. The right associative auditory cortex was integrated into a network of increased metabolic connectivity that included pre- and post-central areas, the cingulum, the right inferior parietal gyrus, as well as the striatum on both sides. Metabolic values of the right associative auditory cortex and left inferior parietal gyrus were positively correlated with performance on neuropsychological test scores. These findings provide further insight into the reorganization of the connectome through sensory loss and compensatory mechanisms in elderly patients with severe hearing loss., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Theories of brain plasticity propose that, in the absence of input from the preferred sensory modality, some specialized brain areas may be recruited when processing information from other modalities, which may result in improved performance. The Useful Field of View task has previously been used to demonstrate that early deafness positively impacts peripheral visual attention. The current study sought to determine the neural changes associated with those deafness-related enhancements in visual performance. Based on previous findings, we hypothesized that recruitment of posterior portions of Brodmann area 22, a brain region most commonly associated with auditory processing, would be correlated with peripheral selective attention as measured using the Useful Field of View task. We report data from severe to profoundly deaf adults and normal-hearing controls who performed the Useful Field of View task while cortical activity was recorded using the event-related optical signal. Behavioral performance, obtained in a separate session, showed that deaf subjects had lower thresholds (i.e., better performance) on the Useful Field of View task. The event-related optical data indicated greater activity for the deaf adults than for the normal-hearing controls during the task in the posterior portion of Brodmann area 22 in the right hemisphere. Furthermore, the behavioral thresholds correlated significantly with this neural activity. This work provides further support for the hypothesis that cross-modal plasticity in deaf individuals appears in higher-order auditory cortices, whereas no similar evidence was obtained for primary auditory areas. It is also the only neuroimaging study to date that has linked deaf-related changes in the right temporal lobe to visual task performance outside of the imaging environment. The event-related optical signal is a valuable technique for studying cross-modal plasticity in deaf humans. The non-invasive and relatively quiet characteristics of this technique have great potential utility in research with clinical populations such as deaf children and adults who have received cochlear or auditory brainstem implants., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Considerable research documents the cross-modal reorganization of auditory cortices as a consequence of congenital deafness, with remapped functions that include visual and somatosensory processing of both linguistic and nonlinguistic information. Structural changes accompany this cross-modal neuroplasticity, but precisely which specific structural changes accompany congenital and early deafness and whether there are group differences in hemispheric asymmetries remain to be established. Here, we used diffusion tensor imaging (DTI) to examine microstructural white matter changes accompanying cross-modal reorganization in 23 deaf adults who were genetically, profoundly, and congenitally deaf, having learned sign language from infancy with 26 hearing controls who participated in our previous fMRI studies of cross-modal neuroplasticity. In contrast to prior literature using a whole-brain approach, we introduce a semiautomatic method for demarcating auditory regions in which regions of interest (ROIs) are defined on the normalized white matter skeleton for all participants, projected into each participants native space, and manually constrained to anatomical boundaries. White-matter ROIs were left and right Heschl's gyrus (HG), left and right anterior superior temporal gyrus (aSTG), left and right posterior superior temporal gyrus (pSTG), as well as one tractography-defined region in the splenium of the corpus callosum connecting homologous left and right superior temporal regions (pCC). Within these regions, we measured fractional anisotropy (FA), radial diffusivity (RD), axial diffusivity (AD), and white-matter volume. Congenitally deaf adults had reduced FA and volume in white matter structures underlying bilateral HG, aSTG, pSTG, and reduced FA in pCC. In HG and pCC, this reduction in FA corresponded with increased RD, but differences in aSTG and pSTG could not be localized to alterations in RD or AD. Direct statistical tests of hemispheric asymmetries in these differences indicated the most prominent effects in pSTG, where the largest differences between groups occurred in the right hemisphere. Other regions did not show significant hemispheric asymmetries in group differences. Taken together, these results indicate that atypical white matter microstructure and reduced volume underlies regions of superior temporal primary and association auditory cortex and introduce a robust method for quantifying volumetric and white matter microstructural differences that can be applied to future studies of special populations., (Published by Elsevier B.V.)

Purpose: Our objective was to evaluate age-dependent changes in microstructure and metabolism in the auditory neural pathway, of children with profound sensorineural hearing loss (SNHL), and to differentiate between good and poor surgical outcome cochlear implantation (CI) patients by using diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS)., Materials and Methods: Ninety-two SNHL children (49 males, 43 females; mean age, 4.9 years) were studied by conventional MR imaging, DTI and MRS. Patients were divided into three groups: Group A consisted of children≤1 years old (n=20), Group B consisted of children 1-3 years old (n=31), and group C consisted of children 3-14 years old (n=41). Among the 31 patients (19 males and 12 females, 12m- 14y ) with CI, 18 patients (mean age 4.8±0.7 years) with a categories of auditory performance (CAP) score over five were classified into the good outcome group and 13 patients (mean age, 4.4±0.7 years) with a CAP score below five were classified into the poor outcome group. Two DTI parameters, fractional anisotropy (FA) and apparent diffusion coefficient (ADC), were measured in the superior temporal gyrus (STG) and auditory radiation. Regions of interest for metabolic change measurements were located inside the STG. DTI values were measured based on region-of-interest analysis and MRS values for correlation analysis with CAP scores., Results: Compared with healthy individuals, 92 SNHL patients displayed decreased FA values in the auditory radiation and STG (p<0.05). Only decreased FA values in the auditory radiation was observed in Group A. Decreased FA values in the auditory radiation and STG were both observed in B and C groups. However, in Group C, the N-acetyl aspartate/creatinine ratio in the STG was also significantly decreased (p<0.05). Correlation analyses at 12 months post-operation revealed strong correlations between the FA, in the auditory radiation, and CAP scores (r=0.793, p<0.01)., Conclusions: DTI and MRS can be used to evaluate microstructural alterations and metabolite concentration changes in the auditory neural pathway that are not detectable by conventional MR imaging. The observed changes in FA suggest that children with SNHL have a developmental delay in myelination in the auditory neural pathway, and it also display greater metabolite concentration changes in the auditory cortex in older children, suggest that early cochlear implantation might be more effective in restoring hearing in children with SNHL. This article is part of a Special Issue entitled SI: Brain and Memory., (Copyright © 2014 Elsevier B.V. All rights reserved.)

In this article, we review the PET neuroimaging literature, which indicates peculiarities of brain networks involved in speech restoration after cochlear implantation. We consider data on implanted patients during stimulation as well as during resting state, which indicates basic long-term reorganisation of brain functional architecture. On the basis of our analysis of neuroimaging literature and considering our own studies, we indicate that auditory recovery in deaf patients after cochlear implantation partly relies on visual cues. The brain develops mechanisms of audio-visual integration as a strategy to achieve high levels of speech recognition. It turns out that this neuroimaging evidence is in line with behavioural findings of better audiovisual integration in these patients. Thus, strong visually and audio-visually based rehabilitation during the first months after cochlear implantation would significantly improve and fasten the functional recovery of speech intelligibility and other auditory functions in these patients. We provide perspectives for further neuroimaging studies in cochlear implanted patients, which would help understand brain organisation to restore auditory cognitive processing in the implanted patients and would potentially suggest novel approaches for their rehabilitation. This article is part of a Special Issue entitled ., (Copyright © 2014 Elsevier B.V. All rights reserved.)

For much of the past 30 years, investigations of auditory perception and language have been enhanced or even driven by the use of functional neuroimaging techniques that specialize in localization of central responses. Beginning with investigations using positron emission tomography (PET) and gradually shifting primarily to usage of functional magnetic resonance imaging (fMRI), auditory neuroimaging has greatly advanced our understanding of the organization and response properties of brain regions critical to the perception of and communication with the acoustic world in which we live. As the complexity of the questions being addressed has increased, the techniques, experiments and analyses applied have also become more nuanced and specialized. A brief review of the history of these investigations sets the stage for an overview and analysis of how these neuroimaging modalities are becoming ever more effective tools for understanding the auditory brain. We conclude with a brief discussion of open methodological issues as well as potential clinical applications for auditory neuroimaging. This article is part of a Special Issue entitled Human Auditory Neuroimaging., (Copyright © 2013 Elsevier B.V. All rights reserved.)

It has been reported that the area of decreased glucose metabolism in the FDG-PET of prelingually deaf children correlates significantly with speech performance after cochlear implantation. In this study, we undertook to confirm changes of glucose metabolism in the cerebral cortex using an animal model with age-matching groups to completely exclude the influence of age differences between the deaf and normal-hearing groups. The cochlea was ablated bilaterally at a postnatal 10-14 days in the deaf groups; 3-4 deaf and normal rats were included at each time point at 1, 2, 4 and 8 weeks and 7 months after ablation. After injecting 2-deoxyglucose intraperitoneally, digitalized autoradiographic images were obtained, and analyzed by using two different methods; 3-dimensional voxel-wise statistical analysis and conventional 2-dimensional densitometry. The hypometabolic area analyzed using 3-dimensional analysis and the differences of optical density between normal and deaf as determined by densitometry were widest and most prominent between 4 and 8 weeks after ablation. Differences were not significant before 2 weeks or after 7 months after ablation. This result shows that the hypometabolic area becomes prominent after a critical period and it decreases as the duration of deafness increases. We believe that cross-modal plasticity may be the mechanism of changes in glucose metabolism and that this result reinforced the usefulness of evaluating hypometabolic area using FDG-PET in deaf children.

The neural mechanisms involved in listening to sentences, and then detecting and verbalizing a specific word are poorly understood, but most likely involve complex neural networks. We used positron emission tomography to identify the areas of the human brain that are activated when young, normal hearing males and females were asked to listen to a sentence and repeat the last word from the Speech in Noise (SPIN) test. Listening conditions were (1) Quiet, (2) Speech, (3) Noise, and (4) SPIN with stimuli presented monaurally to either the left ear or the right ear. The least difficult listening task, Speech, resulted in bilateral activation of superior and middle temporal gyrus and pre-central gyrus. The Noise and SPIN conditions activated many of the same regions as Speech alone plus additional sites within the cerebellum, thalamus and superior/middle frontal gyri. Comparison of the SPIN condition versus Speech revealed additional activation in the right anterior lobe of the cerebellum and right medial frontal gyrus, near the cingulate. None of the left ear-right ear stimulus comparison revealed any significant differences except for the SPIN condition that showed greater activation in the left superior temporal gyrus for stimuli presented to the right ear. No gender differences were observed. These results demonstrate that repeating the last word in a sentence activates mainly auditory and motor areas of the brain when Speech is presented, whereas more difficult tasks, such as SPIN or multi-talker Noise, activate linguistic, attentional, cognitive, working memory, and motor planning areas.