Stimulus-dependent activations and attention-related modulations in the auditory cortex: a meta-analysis of fMRI studies

Magnified interaural level differences enhance binaural unmasking in bilateral cochlear implant users

Bilateral cochlear implant (BiCI) usage makes binaural benefits a possibility for implant users. Yet for BiCI users, limited access to interaural time difference (ITD) cues and reduced saliency of interaural level difference (ILD) cues restricts perceptual benefits of spatially separating a target from masker sounds. The present study explored whether magnifying ILD cues improves intelligibility of masked speech for BiCI listeners in a "symmetrical-masker" configuration, which ensures that neither ear benefits from a long-term positive target-to-masker ratio (TMR) due to naturally occurring ILD cues. ILD magnification estimates moment-to-moment ITDs in octave-wide frequency bands, and applies corresponding ILDs to the target-masker mixtures reaching the two ears at each specific time and frequency band. ILD magnification significantly improved intelligibility in two experiments: one with normal hearing (NH) listeners using vocoded stimuli and one with BiCI users. BiCI listeners showed no benefit of spatial separation between target and maskers with natural ILDs, even for the largest target-masker separation. Because ILD magnification relies on and manipulates only the mixed signals at each ear, the strategy never alters the monaural TMR in either ear at any time. Thus, the observed improvements to masked speech intelligibility come from binaural effects, likely from increased perceptual separation of the competing sources.

Magnified interaural level differences enhance binaural unmasking in bilateral cochlear implant users

Bilateral cochlear implant (BiCI) usage makes binaural benefits a possibility for implant users. Yet for BiCI users, limited access to interaural time difference (ITD) cues and reduced saliency of interaural level difference (ILD) cues restricts perceptual benefits of spatially separating a target from masker sounds. The present study explored whether magnifying ILD cues improves intelligibility of masked speech for BiCI listeners in a "symmetrical-masker" configuration, which ensures that neither ear benefits from a long-term positive target-to-masker ratio (TMR) due to naturally occurring ILD cues. ILD magnification estimates moment-to-moment ITDs in octave-wide frequency bands, and applies corresponding ILDs to the target-masker mixtures reaching the two ears at each specific time and frequency band. ILD magnification significantly improved intelligibility in two experiments: one with NH listeners using vocoded stimuli and one with BiCI users. BiCI listeners showed no benefit of spatial separation between target and maskers with natural ILDs, even for the largest target-masker separation. Because ILD magnification relies on and manipulates only the mixed signals at each ear, the strategy never alters the monaural TMR in either ear at any time. Thus, the observed improvements to masked speech intelligibility come from binaural effects, likely from increased perceptual separation of the competing sources.

Cortical responses to looming sources are explained away by the auditory periphery

A wealth of behavioral evidence indicate that sounds with increasing intensity (i.e. appear to be looming towards the listener) are processed with increased attentional and physiological resources compared to receding sounds. However, the neurophysiological mechanism responsible for such cognitive amplification remains elusive. Here, we show that the large differences seen between cortical responses to looming and receding sounds are in fact almost entirely explained away by nonlinear encoding at the level of the auditory periphery. We collected electroencephalography (EEG) data during an oddball paradigm to elicit mismatch negativity (MMN) and others Event Related Potentials (EPRs), in response to deviant stimuli with both dynamic (looming and receding) and constant level (flat) differences to the standard in the same participants. We then combined a computational model of the auditory periphery with generative EEG methods (temporal response functions, TRFs) to model the single-participant ERPs responses to flat deviants, and used them to predict the effect of the same mechanism on looming and receding stimuli. The flat model explained 45% variance of the looming response, and 33% of the receding response. This provide striking evidence that difference wave responses to looming and receding sounds result from the same cortical mechanism that generate responses to constant-level deviants: all such differences are the sole consequence of their particular physical morphology getting amplified and integrated by peripheral auditory mechanisms. Thus, not all effects seen cortically proceed from top-down modulations by high-level decision variables, but can rather be performed early and efficiently by feed-forward peripheral mechanisms that evolved precisely to sparing subsequent networks with the necessity to implement such mechanisms.

Attention to audiovisual speech shapes neural processing through feedback-feedforward loops between different nodes of the speech network

Selective attention-related top-down modulation plays a significant role in separating relevant speech from irrelevant background speech when vocal attributes separating concurrent speakers are small and continuously evolving. Electrophysiological studies have shown that such top-down modulation enhances neural tracking of attended speech. Yet, the specific cortical regions involved remain unclear due to the limited spatial resolution of most electrophysiological techniques. To overcome such limitations, we collected both electroencephalography (EEG) (high temporal resolution) and functional magnetic resonance imaging (fMRI) (high spatial resolution), while human participants selectively attended to speakers in audiovisual scenes containing overlapping cocktail party speech. To utilise the advantages of the respective techniques, we analysed neural tracking of speech using the EEG data and performed representational dissimilarity-based EEG-fMRI fusion. We observed that attention enhanced neural tracking and modulated EEG correlates throughout the latencies studied. Further, attention-related enhancement of neural tracking fluctuated in predictable temporal profiles. We discuss how such temporal dynamics could arise from a combination of interactions between attention and prediction as well as plastic properties of the auditory cortex. EEG-fMRI fusion revealed attention-related iterative feedforward-feedback loops between hierarchically organised nodes of the ventral auditory object related processing stream. Our findings support models where attention facilitates dynamic neural changes in the auditory cortex, ultimately aiding discrimination of relevant sounds from irrelevant ones while conserving neural resources.

Categorical perception of lexical tones in Chinese people with post-stroke aphasia

This study used the categorical perception (CP) paradigm, a fine-grained perceptual method, to investigate the perceptual performance of lexical tones in Chinese people with post-stroke aphasia (PWA). Twenty patients with post-stroke aphasia (10 Broca's and 10 Wernicke's) and ten neurologically intact age-matched control participants were recruited to complete both identification and discrimination tasks of the Mandarin Tone 1-2 continuum. In addition, all participants completed tests on their auditory comprehension ability and working memory. The results showed that both Broca's and Wernicke's patients exhibited reduced sensitivity to within-category and between-category information but preserved CP of lexical tones. The degree of CP of lexical tones related to working memory in aphasic patients. Furthermore, lower-level acoustic processing underpinned higher-level phonological processing on the CP of lexical tones since both patient groups' unbalanced pitch processing ability extended to their CP of lexical tones. These findings are significant for researchers and clinicians in speech-language rehabilitation, clinical psychology, and cognitive communication.

Neural Coupling between Interhemispheric and Frontoparietal Functional Connectivity during Semantic Processing

Interhemispheric and frontoparietal functional connectivity have been reported to increase during explicit information processing. However, it is unclear how and when interhemispheric and frontoparietal functional connectivity interact during explicit semantic processing. Here, we tested the neural coupling hypothesis that explicit semantic processing promotes neural activity in the nondominant right hemispheric areas, owing to synchronization with enhanced frontoparietal functional connectivity at later processing stages. We analyzed electroencephalogram data obtained using a semantic priming paradigm, which comprised visual priming and target words successively presented under direct or indirect attention to semantic association. Scalp potential analysis demonstrated that the explicit processing of congruent targets reduced negative event-related potentials, as previously reported. Current source density analysis showed that explicit semantic processing activated the right temporal area during later temporal intervals. Subsequent dynamic functional connectivity and neural coupling analyses revealed that explicit semantic processing increased the correlation between right temporal source activities and frontoparietal functional connectivity in later temporal intervals. These findings indicate that explicit semantic processing increases neural coupling between the interhemispheric and frontoparietal functional connectivity during later processing stages.

Interoceptive Awareness of the Breath Preserves Attention and Language Networks amidst Widespread Cortical Deactivation: A Within-Participant Neuroimaging Study

Interoception, the representation of the body's internal state, serves as a foundation for emotion, motivation, and wellbeing. Yet despite its centrality in human experience, the neural mechanisms of interoceptive attention are poorly understood. The Interoceptive/Exteroceptive Attention Task (IEAT) is a novel neuroimaging paradigm that compares behavioral tracking of the respiratory cycle (Active Interoception) to tracking of a visual stimulus (Active Exteroception). Twenty-two healthy participants completed the IEAT during two separate scanning sessions (N = 44) as part of a randomized control trial of mindful awareness in body-oriented therapy (MABT). Compared with Active Exteroception, Active Interoception deactivated somatomotor and prefrontal regions. Greater self-reported interoceptive sensibility (MAIA scale) predicted sparing from deactivation within the anterior cingulate cortex (ACC) and left-lateralized language regions. The right insula, typically described as a primary interoceptive cortex, was only specifically implicated by its deactivation during an exogenously paced respiration condition (Active Matching) relative to self-paced Active Interoception. Psychophysiological interaction (PPI) analysis characterized Active Interoception as promoting greater ACC connectivity with lateral prefrontal and parietal regions commonly referred to as the dorsal attention network (DAN). In contrast to evidence relating accurate detection of liminal interoceptive signals such as the heartbeat to anterior insula activity, interoceptive attention toward salient signals such as the respiratory cycle may involve reduced cortical activity but greater ACC-DAN connectivity, with greater sensibility linked to reduced deactivation within the ACC and language-processing regions.

Brain activity during shadowing of audiovisual cocktail party speech, contributions of auditory-motor integration and selective attention

Selective listening to cocktail-party speech involves a network of auditory and inferior frontal cortical regions. However, cognitive and motor cortical regions are differentially activated depending on whether the task emphasizes semantic or phonological aspects of speech. Here we tested whether processing of cocktail-party speech differs when participants perform a shadowing (immediate speech repetition) task compared to an attentive listening task in the presence of irrelevant speech. Participants viewed audiovisual dialogues with concurrent distracting speech during functional imaging. Participants either attentively listened to the dialogue, overtly repeated (i.e., shadowed) attended speech, or performed visual or speech motor control tasks where they did not attend to speech and responses were not related to the speech input. Dialogues were presented with good or poor auditory and visual quality. As a novel result, we show that attentive processing of speech activated the same network of sensory and frontal regions during listening and shadowing. However, in the superior temporal gyrus (STG), peak activations during shadowing were posterior to those during listening, suggesting that an anterior-posterior distinction is present for motor vs. perceptual processing of speech already at the level of the auditory cortex. We also found that activations along the dorsal auditory processing stream were specifically associated with the shadowing task. These activations are likely to be due to complex interactions between perceptual, attention dependent speech processing and motor speech generation that matches the heard speech. Our results suggest that interactions between perceptual and motor processing of speech relies on a distributed network of temporal and motor regions rather than any specific anatomical landmark as suggested by some previous studies.

Brainstem speech encoding is dynamically shaped online by fluctuations in cortical α state

Experimental evidence in animals demonstrates cortical neurons innervate subcortex bilaterally to tune brainstem auditory coding. Yet, the role of the descending (corticofugal) auditory system in modulating earlier sound processing in humans during speech perception remains unclear. Here, we measured EEG activity as listeners performed speech identification tasks in different noise backgrounds designed to tax perceptual and attentional processing. We hypothesized brainstem speech coding might be tied to attention and arousal states (indexed by cortical α power) that actively modulate the interplay of brainstem-cortical signal processing. When speech-evoked brainstem frequency-following responses (FFRs) were categorized according to cortical α states, we found low α FFRs in noise were weaker, correlated positively with behavioral response times, and were more "decodable" via neural classifiers. Our data provide new evidence for online corticofugal interplay in humans and establish that brainstem sensory representations are continuously yoked to (i.e., modulated by) the ebb and flow of cortical states to dynamically update perceptual processing.

A functional magnetic resonance imaging examination of audiovisual observation of a point-light string quartet using intersubject correlation and physical feature analysis

We use functional Magnetic Resonance Imaging (fMRI) to explore synchronized neural responses between observers of audiovisual presentation of a string quartet performance during free viewing. Audio presentation was accompanied by visual presentation of the string quartet as stick figures observed from a static viewpoint. Brain data from 18 musical novices were obtained during audiovisual presentation of a 116 s performance of the allegro of String Quartet, No. 14 in D minor by Schubert played by the 'Quartetto di Cremona.' These data were analyzed using intersubject correlation (ISC). Results showed extensive ISC in auditory and visual areas as well as parietal cortex, frontal cortex and subcortical areas including the medial geniculate and basal ganglia (putamen). These results from a single fixed viewpoint of multiple musicians are greater than previous reports of ISC from unstructured group activity but are broadly consistent with related research that used ISC to explore listening to music or watching solo dance. A feature analysis examining the relationship between brain activity and physical features of the auditory and visual signals yielded findings of a large proportion of activity related to auditory and visual processing, particularly in the superior temporal gyrus (STG) as well as midbrain areas. Motor areas were also involved, potentially as a result of watching motion from the stick figure display of musicians in the string quartet. These results reveal involvement of areas such as the putamen in processing complex musical performance and highlight the potential of using brief naturalistic stimuli to localize distinct brain areas and elucidate potential mechanisms underlying multisensory integration.

Neurophysiological evidence for goal-oriented modulation of speech perception

Speech perception depends on the dynamic interplay of bottom-up and top-down information along a hierarchically organized cortical network. Here, we test, for the first time in the human brain, whether neural processing of attended speech is dynamically modulated by task demand using a context-free discrimination paradigm. Electroencephalographic signals were recorded during 3 parallel experiments that differed only in the phonological feature of discrimination (word, vowel, and lexical tone, respectively). The event-related potentials (ERPs) revealed the task modulation of speech processing at approximately 200 ms (P2) after stimulus onset, probably influencing what phonological information to retain in memory. For the phonological comparison of sequential words, task modulation occurred later at approximately 300 ms (N3 and P3), reflecting the engagement of task-specific cognitive processes. The ERP results were consistent with the changes in delta-theta neural oscillations, suggesting the involvement of cortical tracking of speech envelopes. The study thus provides neurophysiological evidence for goal-oriented modulation of attended speech and calls for speech perception models incorporating limited memory capacity and goal-oriented optimization mechanisms.

EEG and fMRI coupling and decoupling based on joint independent component analysis (jICA)

BACKGROUND

Meaningful integration of functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) requires knowing whether these measurements reflect the activity of the same neural sources, i.e., estimating the degree of coupling and decoupling between the neuroimaging modalities.

NEW METHOD

This paper proposes a method to quantify the coupling and decoupling of fMRI and EEG signals based on the mixing matrix produced by joint independent component analysis (jICA). The method is termed fMRI/EEG-jICA.

RESULTS

fMRI and EEG acquired during a syllable detection task with variable syllable presentation rates (0.25-3 Hz) were separated with jICA into two spatiotemporally distinct components, a primary component that increased nonlinearly in amplitude with syllable presentation rate, putatively reflecting an obligatory auditory response, and a secondary component that declined nonlinearly with syllable presentation rate, putatively reflecting an auditory attention orienting response. The two EEG subcomponents were of similar amplitude, but the secondary fMRI subcomponent was ten folds smaller than the primary one.

COMPARISON TO EXISTING METHOD

FMRI multiple regression analysis yielded a map more consistent with the primary than secondary fMRI subcomponent of jICA, as determined by a greater area under the curve (0.5 versus 0.38) in a sensitivity and specificity analysis of spatial overlap.

CONCLUSION

fMRI/EEG-jICA revealed spatiotemporally distinct brain networks with greater sensitivity than fMRI multiple regression analysis, demonstrating how this method can be used for leveraging EEG signals to inform the detection and functional characterization of fMRI signals. fMRI/EEG-jICA may be useful for studying neurovascular coupling at a macro-level, e.g., in neurovascular disorders.

Task-dependent cortical activations during selective attention to audiovisual speech

Selective listening to speech depends on widespread networks of the brain, but how the involvement of different neural systems in speech processing is affected by factors such as the task performed by a listener and speech intelligibility remains poorly understood. We used functional magnetic resonance imaging to systematically examine the effects that performing different tasks has on neural activations during selective attention to continuous audiovisual speech in the presence of task-irrelevant speech. Participants viewed audiovisual dialogues and attended either to the semantic or the phonological content of speech, or ignored speech altogether and performed a visual control task. The tasks were factorially combined with good and poor auditory and visual speech qualities. Selective attention to speech engaged superior temporal regions and the left inferior frontal gyrus regardless of the task. Frontoparietal regions implicated in selective auditory attention to simple sounds (e.g., tones, syllables) were not engaged by the semantic task, suggesting that this network may not be not as crucial when attending to continuous speech. The medial orbitofrontal cortex, implicated in social cognition, was most activated by the semantic task. Activity levels during the phonological task in the left prefrontal, premotor, and secondary somatosensory regions had a distinct temporal profile as well as the highest overall activity, possibly relating to the role of the dorsal speech processing stream in sub-lexical processing. Our results demonstrate that the task type influences neural activations during selective attention to speech, and emphasize the importance of ecologically valid experimental designs.

Association between aerobic fitness and the functional connectome in patients with schizophrenia

BACKGROUND

Schizophrenia is accompanied by widespread alterations in static functional connectivity associated with symptom severity and cognitive deficits. Improvements in aerobic fitness have been demonstrated to ameliorate symptomatology and cognition in people with schizophrenia, but the intermediary role of macroscale connectivity patterns remains unknown.

OBJECTIVE

Therefore, we aim to explore the relation between aerobic fitness and the functional connectome in individuals with schizophrenia. Further, we investigate clinical and cognitive relevance of the identified fitness-connectivity links.

METHODS

Patients diagnosed with schizophrenia were included in this cross-sectional resting-state fMRI analysis. Multilevel Bayesian partial correlations between aerobic fitness and functional connections across the whole brain as well as between static functional connectivity patterns and clinical and cognitive outcome were performed. Preliminary causal inferences were enabled based on mediation analyses.

RESULTS

Static functional connectivity between the subcortical nuclei and the cerebellum as well as between temporal seeds mediated the attenuating relation between aerobic fitness and total symptom severity. Functional connections between cerebellar seeds affected the positive link between aerobic fitness and global cognition, while the functional interplay between central and limbic seeds drove the beneficial association between aerobic fitness and emotion recognition.

CONCLUSION

The current study provides first insights into the interactions between aerobic fitness, the functional connectome and clinical and cognitive outcome in people with schizophrenia, but causal interpretations are preliminary. Further interventional aerobic exercise studies are needed to replicate the current findings and to enable conclusive causal inferences.

TRIAL REGISTRATION

The study which the manuscript is based on is registered in the International Clinical Trials Database (ClinicalTrials.gov identifier [NCT number]: NCT03466112) and in the German Clinical Trials Register (DRKS-ID: DRKS00009804).

The Effects of Working Memory Load on Auditory Distraction in Adults With Attention Deficit Hyperactivity Disorder

Cognitive control provides us with the ability to inter alia, regulate the locus of attention and ignore environmental distractions in accordance with our goals. Auditory distraction is a frequently cited symptom in adults with attention deficit hyperactivity disorder (aADHD)-yet few task-based fMRI studies have explored whether deficits in cognitive control (associated with the disorder) impedes on the ability to suppress/compensate for exogenously evoked cortical responses to noise in this population. In the current study, we explored the effects of auditory distraction as function of working memory (WM) load. Participants completed two tasks: an auditory target detection (ATD) task in which the goal was to actively detect salient oddball tones amidst a stream of standard tones in noise, and a visual n-back task consisting of 0-, 1-, and 2-back WM conditions whilst concurrently ignoring the same tonal signal from the ATD task. Results indicated that our sample of young aADHD (n = 17), compared to typically developed controls (n = 17), had difficulty attenuating auditory cortical responses to the task-irrelevant sound when WM demands were high (2-back). Heightened auditory activity to task-irrelevant sound was associated with both poorer WM performance and symptomatic inattentiveness. In the ATD task, we observed a significant increase in functional communications between auditory and salience networks in aADHD. Because performance outcomes were on par with controls for this task, we suggest that this increased functional connectivity in aADHD was likely an adaptive mechanism for suboptimal listening conditions. Taken together, our results indicate that aADHD are more susceptible to noise interference when they are engaged in a primary task. The ability to cope with auditory distraction appears to be related to the WM demands of the task and thus the capacity to deploy cognitive control.

Paradoxical somatic information processing for interoception and anxiety in alexithymia

The concept of alexithymia has garnered much attention in an attempt to understand the psychological mechanisms underlying the experience of feeling an emotion. In this study, we aimed to understand how the interoceptive processing in an emotional context relates to problems of alexithymia in recognizing self‐emotions. Therefore, we prepared experimental conditions to induce emotional awareness based on interoceptive information. As such, we asked participants to be aware of interoception under an anxiety‐generating situation anticipating pain, having them evaluate their subjective anxiety levels in this context. High alexithymia participants showed attenuated functional connectivity within their ‘interoception network’, particularly between the insula and the somatosensory areas when they focused on interoception. In contrast, they had enhanced functional connectivity between these regions when they focused on their anxiety about pain. Although access to somatic information is supposed to be more strongly activated while attending to interoception in the context of primary sensory processing, high alexithymia individuals were biased as this process was activated when they felt emotions, suggesting they recognize primitive and unprocessed bodily sensations as emotions. The paradoxical somatic information processing may reflect their brain function pathology for feeling emotions and their difficulty with context‐dependent emotional control.

Attentional Modulation of Hierarchical Speech Representations in a Multitalker Environment

Humans are remarkably adept in listening to a desired speaker in a crowded environment, while filtering out nontarget speakers in the background. Attention is key to solving this difficult cocktail-party task, yet a detailed characterization of attentional effects on speech representations is lacking. It remains unclear across what levels of speech features and how much attentional modulation occurs in each brain area during the cocktail-party task. To address these questions, we recorded whole-brain blood-oxygen-level-dependent (BOLD) responses while subjects either passively listened to single-speaker stories, or selectively attended to a male or a female speaker in temporally overlaid stories in separate experiments. Spectral, articulatory, and semantic models of the natural stories were constructed. Intrinsic selectivity profiles were identified via voxelwise models fit to passive listening responses. Attentional modulations were then quantified based on model predictions for attended and unattended stories in the cocktail-party task. We find that attention causes broad modulations at multiple levels of speech representations while growing stronger toward later stages of processing, and that unattended speech is represented up to the semantic level in parabelt auditory cortex. These results provide insights on attentional mechanisms that underlie the ability to selectively listen to a desired speaker in noisy multispeaker environments.

Implications for Early Diagnosis and Treatment in Schizophrenia Due to Correlation between Auditory Perceptual Deficits and Cognitive Impairment

It is indicated that auditory perception deficits are present in schizophrenia and related to formal thought disorder. The purpose of the present study was to investigate the association of auditory deficits with cognitive impairment in schizophrenia. An experimental group of 50 schizophrenia patients completed a battery of auditory processing evaluation and a neuropsychological battery of tests. Correlations between neuropsychological battery scores and auditory processing scores were examined. Cognitive impairment was correlated with auditory processing deficits in schizophrenia patients. All neuropsychological test scores were significantly correlated with at least one auditory processing test score. Our findings support the coexistence of auditory processing disorder, severe cognitive impairment, and formal thought disorder in a subgroup of schizophrenia patients. This may have important implications in schizophrenia research, as well as in early diagnosis and nonpharmacological treatment of the disorder.

Modulating Cortical Instrument Representations During Auditory Stream Segregation and Integration With Polyphonic Music

Numerous neuroimaging studies demonstrated that the auditory cortex tracks ongoing speech and that, in multi-speaker environments, tracking of the attended speaker is enhanced compared to the other irrelevant speakers. In contrast to speech, multi-instrument music can be appreciated by attending not only on its individual entities (i.e., segregation) but also on multiple instruments simultaneously (i.e., integration). We investigated the neural correlates of these two modes of music listening using electroencephalography (EEG) and sound envelope tracking. To this end, we presented uniquely composed music pieces played by two instruments, a bassoon and a cello, in combination with a previously validated music auditory scene analysis behavioral paradigm (Disbergen et al., 2018). Similar to results obtained through selective listening tasks for speech, relevant instruments could be reconstructed better than irrelevant ones during the segregation task. A delay-specific analysis showed higher reconstruction for the relevant instrument during a middle-latency window for both the bassoon and cello and during a late window for the bassoon. During the integration task, we did not observe significant attentional modulation when reconstructing the overall music envelope. Subsequent analyses indicated that this null result might be due to the heterogeneous strategies listeners employ during the integration task. Overall, our results suggest that subsequent to a common processing stage, top-down modulations consistently enhance the relevant instrument's representation during an instrument segregation task, whereas such an enhancement is not observed during an instrument integration task. These findings extend previous results from speech tracking to the tracking of multi-instrument music and, furthermore, inform current theories on polyphonic music perception.

Auditory attention following a left hemisphere stroke: comparisons of alerting, orienting, and executive control performance using an auditory Attention Network Test

INTRODUCTION

Auditory attention is a critical foundation for successful language comprehension, yet is rarely studied in individuals with acquired language disorders.

METHODS

We used an auditory version of the well-studied Attention Network Test to study alerting, orienting, and executive control in 28 persons with chronic stroke (PWS). We further sought to characterize the neurobiology of each auditory attention measure in our sample using exploratory lesion-symptom mapping analyses.

RESULTS

PWS exhibited the expected executive control effect (i.e., decreased accuracy for incongruent compared to congruent trials), but their alerting and orienting attention were disrupted. PWS did not exhibit an alerting effect and they were actually distracted by the auditory spatial orienting cue compared to the control cue. Lesion-symptom mapping indicated that poorer alerting and orienting were associated with damage to the left retrolenticular part of the internal capsule (adjacent to the thalamus) and left posterior middle frontal gyrus (overlapping with the frontal eye fields), respectively.

DISCUSSION

The behavioral findings correspond to our previous work investigating alerting and spatial orienting attention in persons with aphasia in the visual modality and suggest that auditory alerting and spatial orienting attention may be impaired in PWS due to stroke lesions damaging multi-modal attention resources.

Enhanced activations in syntax-related regions for multilinguals while acquiring a new language

The neuroscientific foundation of multilingualism, a unique cognitive capacity, necessitates further elucidation. We conducted an fMRI experiment to evaluate the acquisition of syntactic features in a new language (Kazakh) for multilinguals and bilinguals. Results showed that the multilinguals who were more proficient in their second/third languages needed fewer task trials to acquire Kazakh phonology. Regarding group differences, the reduction in response times during the initial exposure to Kazakh were significantly larger for the multilinguals than the bilinguals. For the multilinguals, activations in the bilateral frontal/temporal regions were maintained at a higher level than the initial level during subsequent new grammar conditions. For the bilinguals, activations in the basal ganglia/thalamus and cerebellum decreased to the initial level each time. Direct group comparisons showed significantly enhanced activations for the multilinguals in the left ventral inferior frontal gyrus. These results indicate that both syntax-related and domain-general brain networks were more enhanced for the multilinguals. We also unexpectedly observed significant activations in the visual areas for the multilinguals, implying the use of visual representation even when listening to speech sounds alone. Because the multilinguals were able to successfully utilize acquired knowledge in an accumulated manner, the results support the cumulative-enhancement model of language acquisition.

Attention reinforces human corticofugal system to aid speech perception in noise

Perceiving speech-in-noise (SIN) demands precise neural coding between brainstem and cortical levels of the hearing system. Attentional processes can then select and prioritize task-relevant cues over competing background noise for successful speech perception. In animal models, brainstem-cortical interplay is achieved via descending corticofugal projections from cortex that shape midbrain responses to behaviorally-relevant sounds. Attentional engagement of corticofugal feedback may assist SIN understanding but has never been confirmed and remains highly controversial in humans. To resolve these issues, we recorded source-level, anatomically constrained brainstem frequency-following responses (FFRs) and cortical event-related potentials (ERPs) to speech via high-density EEG while listeners performed rapid SIN identification tasks. We varied attention with active vs. passive listening scenarios whereas task difficulty was manipulated with additive noise interference. Active listening (but not arousal-control tasks) exaggerated both ERPs and FFRs, confirming attentional gain extends to lower subcortical levels of speech processing. We used functional connectivity to measure the directed strength of coupling between levels and characterize "bottom-up" vs. "top-down" (corticofugal) signaling within the auditory brainstem-cortical pathway. While attention strengthened connectivity bidirectionally, corticofugal transmission disengaged under passive (but not active) SIN listening. Our findings (i) show attention enhances the brain's transcription of speech even prior to cortex and (ii) establish a direct role of the human corticofugal feedback system as an aid to cocktail party speech perception.

Revealing the mechanisms behind novel auditory stimuli discrimination: An evaluation of silent functional MRI using looping star

Looping Star is a near‐silent, multi‐echo, 3D functional magnetic resonance imaging (fMRI) technique. It reduces acoustic noise by at least 25dBA, with respect to gradient‐recalled echo echo‐planar imaging (GRE‐EPI)‐based fMRI. Looping Star has successfully demonstrated sensitivity to the cerebral blood‐oxygen‐level‐dependent (BOLD) response during block design paradigms but has not been applied to event‐related auditory perception tasks. Demonstrating Looping Star's sensitivity to such tasks could (a) provide new insights into auditory processing studies, (b) minimise the need for invasive ear protection, and (c) facilitate the translation of numerous fMRI studies to investigations in sound‐averse patients. We aimed to demonstrate, for the first time, that multi‐echo Looping Star has sufficient sensitivity to the BOLD response, compared to that of GRE‐EPI, during a well‐established event‐related auditory discrimination paradigm: the “oddball” task. We also present the first quantitative evaluation of Looping Star's test–retest reliability using the intra‐class correlation coefficient. Twelve participants were scanned using single‐echo GRE‐EPI and multi‐echo Looping Star fMRI in two sessions. Random‐effects analyses were performed, evaluating the overall response to tones and differential tone recognition, and intermodality analyses were computed. We found that multi‐echo Looping Star exhibited consistent sensitivity to auditory stimulation relative to GRE‐EPI. However, Looping Star demonstrated lower test–retest reliability in comparison with GRE‐EPI. This could reflect differences in functional sensitivity between the techniques, though further study is necessary with additional cognitive paradigms as varying cognitive strategies between sessions may arise from elimination of acoustic scanner noise.

Baseline Cortical Thickness Reductions in Clinical High Risk for Psychosis: Brain Regions Associated with Conversion to Psychosis Versus Non-Conversion as Assessed at One-Year Follow-Up in the Shanghai-At-Risk-for-Psychosis (SHARP) Study

OBJECTIVE

To assess cortical thickness (CT) and surface area (SA) of frontal, temporal, and parietal brain regions in a large clinical high risk for psychosis (CHR) sample, and to identify cortical brain abnormalities in CHR who convert to psychosis and in the whole CHR sample, compared with the healthy controls (HC).

METHODS

Magnetic resonance imaging, clinical, and cognitive data were acquired at baseline in 92 HC, 130 non-converters, and 22 converters (conversion assessed at 1-year follow-up). CT and SA at baseline were calculated for frontal, temporal, and parietal subregions. Correlations between regions showing group differences and clinical scores and age were also obtained.

RESULTS

CT but not SA was significantly reduced in CHR compared with HC. Two patterns of findings emerged: (1) In converters, CT was significantly reduced relative to non-converters and controls in the banks of superior temporal sulcus, Heschl's gyrus, and pars triangularis and (2) CT in the inferior parietal and supramarginal gyrus, and at trend level in the pars opercularis, fusiform, and middle temporal gyri was significantly reduced in all high-risk individuals compared with HC. Additionally, reduced CT correlated significantly with older age in HC and in non-converters but not in converters.

CONCLUSIONS

These results show for the first time that fronto-temporo-parietal abnormalities characterized all CHR, that is, both converters and non-converters, relative to HC, while CT abnormalities in converters relative to CHR-NC and HC were found in core auditory and language processing regions.

Defining the Role of Attention in Hierarchical Auditory Processing

Communication in noise is a complex process requiring efficient neural encoding throughout the entire auditory pathway as well as contributions from higher-order cognitive processes (i.e., attention) to extract speech cues for perception. Thus, identifying effective clinical interventions for individuals with speech-in-noise deficits relies on the disentanglement of bottom-up (sensory) and top-down (cognitive) factors to appropriately determine the area of deficit; yet, how attention may interact with early encoding of sensory inputs remains unclear. For decades, attentional theorists have attempted to address this question with cleverly designed behavioral studies, but the neural processes and interactions underlying attention's role in speech perception remain unresolved. While anatomical and electrophysiological studies have investigated the neurological structures contributing to attentional processes and revealed relevant brain-behavior relationships, recent electrophysiological techniques (i.e., simultaneous recording of brainstem and cortical responses) may provide novel insight regarding the relationship between early sensory processing and top-down attentional influences. In this article, we review relevant theories that guide our present understanding of attentional processes, discuss current electrophysiological evidence of attentional involvement in auditory processing across subcortical and cortical levels, and propose areas for future study that will inform the development of more targeted and effective clinical interventions for individuals with speech-in-noise deficits.

Perceptual learning of tone patterns changes the effective connectivity between Heschl's gyrus and planum temporale

Learning of complex auditory sequences such as music can be thought of as optimizing an internal model of regularities through unpredicted events (or “prediction errors”). We used dynamic causal modeling (DCM) and parametric empirical Bayes on functional magnetic resonance imaging (fMRI) data to identify modulation of effective brain connectivity that takes place during perceptual learning of complex tone patterns. Our approach differs from previous studies in two aspects. First, we used a complex oddball paradigm based on tone patterns as opposed to simple deviant tones. Second, the use of fMRI allowed us to identify cortical regions with high spatial accuracy. These regions served as empirical regions‐of‐interest for the analysis of effective connectivity. Deviant patterns induced an increased blood oxygenation level‐dependent response, compared to standards, in early auditory (Heschl's gyrus [HG]) and association auditory areas (planum temporale [PT]) bilaterally. Within this network, we found a left‐lateralized increase in feedforward connectivity from HG to PT during deviant responses and an increase in excitation within left HG. In contrast to previous findings, we did not find frontal activity, nor did we find modulations of backward connections in response to oddball sounds. Our results suggest that complex auditory prediction errors are encoded by changes in feedforward and intrinsic connections, confined to superior temporal gyrus.

Involuntary Orienting and Conflict Resolution during Auditory Attention: The Role of Ventral and Dorsal Streams

Selective attention to sound object features such as pitch and location is associated with enhanced brain activity in ventral and dorsal streams, respectively. We examined the role of these pathways in involuntary orienting and conflict resolution using fMRI. Participants were presented with two tones that may, or may not, share the same nonspatial (frequency) or spatial (location) auditory features. In separate blocks of trials, participants were asked to attend to sound frequency or sound location and ignore the change in the task-irrelevant feature. In both attend-frequency and attend-location tasks, RTs were slower when the task-irrelevant feature changed than when it stayed the same (involuntary orienting). This behavioral cost coincided with enhanced activity in the pFC and superior temporal gyrus. Conflict resolution was examined by comparing situations where the change in stimulus features was congruent (both features changed) and incongruent (only one feature changed). Participants were slower and less accurate for incongruent than congruent sound features. This congruency effect was associated with enhanced activity in the pFC and was greater in the right superior temporal gyrus and medial frontal cortex during the attend-location task than during the attend-frequency task. Together, these findings do not support a strict division of "labor" into ventral and dorsal streams but rather suggest interactions between these pathways in situations involving changes in task-irrelevant sound feature and conflict resolution. These findings also validate the Test of Attention in Listening task by revealing distinct neural correlates for involuntary orienting and conflict resolution.

Modulation of Brain Activity by Selective Attention to Audiovisual Dialogues

In real-life noisy situations, we can selectively attend to conversations in the presence of irrelevant voices, but neurocognitive mechanisms in such natural listening situations remain largely unexplored. Previous research has shown distributed activity in the mid superior temporal gyrus (STG) and sulcus (STS) while listening to speech and human voices, in the posterior STS and fusiform gyrus when combining auditory, visual and linguistic information, as well as in left-hemisphere temporal and frontal cortical areas during comprehension. In the present functional magnetic resonance imaging (fMRI) study, we investigated how selective attention modulates neural responses to naturalistic audiovisual dialogues. Our healthy adult participants (N = 15) selectively attended to video-taped dialogues between a man and woman in the presence of irrelevant continuous speech in the background. We modulated the auditory quality of dialogues with noise vocoding and their visual quality by masking speech-related facial movements. Both increased auditory quality and increased visual quality were associated with bilateral activity enhancements in the STG/STS. In addition, decreased audiovisual stimulus quality elicited enhanced fronto-parietal activity, presumably reflecting increased attentional demands. Finally, attention to the dialogues, in relation to a control task where a fixation cross was attended and the dialogue ignored, yielded enhanced activity in the left planum polare, angular gyrus, the right temporal pole, as well as in the orbitofrontal/ventromedial prefrontal cortex and posterior cingulate gyrus. Our findings suggest that naturalistic conversations effectively engage participants and reveal brain networks related to social perception in addition to speech and semantic processing networks.

Understanding rostral-caudal auditory cortex contributions to auditory perception

There are functional and anatomical distinctions between the neural systems involved in the recognition of sounds in the environment and those involved in the sensorimotor guidance of sound production and the spatial processing of sound. Evidence for the separation of these processes has historically come from disparate literatures on the perception and production of speech, music and other sounds. More recent evidence indicates that there are computational distinctions between the rostral and caudal primate auditory cortex that may underlie functional differences in auditory processing. These functional differences may originate from differences in the response times and temporal profiles of neurons in the rostral and caudal auditory cortex, suggesting that computational accounts of primate auditory pathways should focus on the implications of these temporal response differences.

Lateralization of brain responses to auditory motion: A study using single-trial analysis

The present study investigates hemispheric asymmetry of the ERPs and low-frequency oscillatory responses evoked in both hemispheres of the brain by the sound stimuli with delayed onset of motion. EEG was recorded for three patterns of sound motion produced by changes in interaural time differences. Event-related spectral perturbation (ERSP) and inter-trial phase coherence (ITC) were computed from the time-frequency decomposition of EEG signals. The participants either read books of their choice (passive listening) or indicated the sound trajectories perceived using a graphic tablet (active listening). Our goal was to find out whether the lateralization of the motion-onset response (MOR) and oscillatory responses to sound motion were more consistent with the right-hemispheric dominance, contralateral or neglect model of interhemispheric asymmetry. Apparent dominance of the right hemisphere was found only in the ERSP responses. Stronger contralaterality of the left hemisphere corresponding to the "neglect model" of asymmetry was shown by the MOR components and by the phase coherence of the delta-alpha oscillations. Velocity and attention did not change consistently the interhemispheric asymmetry of both the MOR and the oscillatory responses. Our findings demonstrate how the lateralization pattern shown by the MOR potential was interrelated with that of the motion-related single-trial measures.

Tracking the Effects of Top-Down Attention on Word Discrimination Using Frequency-tagged Neuromagnetic Responses

Discrimination of words from nonspeech sounds is essential in communication. Still, how selective attention can influence this early step of speech processing remains elusive. To answer that question, brain activity was recorded with magnetoencephalography in 12 healthy adults while they listened to two sequences of auditory stimuli presented at 2.17 Hz, consisting of successions of one randomized word (tagging frequency = 0.54 Hz) and three acoustically matched nonverbal stimuli. Participants were instructed to focus their attention on the occurrence of a predefined word in the verbal attention condition and on a nonverbal stimulus in the nonverbal attention condition. Steady-state neuromagnetic responses were identified with spectral analysis at sensor and source levels. Significant sensor responses peaked at 0.54 and 2.17 Hz in both conditions. Sources at 0.54 Hz were reconstructed in supratemporal auditory cortex, left superior temporal gyrus (STG), left middle temporal gyrus, and left inferior frontal gyrus. Sources at 2.17 Hz were reconstructed in supratemporal auditory cortex and STG. Crucially, source strength in the left STG at 0.54 Hz was significantly higher in verbal attention than in nonverbal attention condition. This study demonstrates speech-sensitive responses at primary auditory and speech-related neocortical areas. Critically, it highlights that, during word discrimination, top-down attention modulates activity within the left STG. This area therefore appears to play a crucial role in selective verbal attentional processes for this early step of speech processing.

Change in the Neural Response to Auditory Deviance Following Cognitive Therapy for Hallucinations in Patients With Schizophrenia

Adjunctive psychotherapeutic approaches recommended for patients with schizophrenia (SZ) who are fully or partially resistant to pharmacotherapy have rarely utilized biomarkers to enhance the understanding of treatment-effective mechanisms. As SZ patients with persistent auditory verbal hallucinations (AVH) frequently evidence reduced neural responsiveness to external auditory stimulation, which may impact cognitive and functional outcomes, this study examined the effects of cognitive behavioral therapy for voices (CBTv) on clinical and AVH symptoms and the sensory processing of auditory deviants as measured with the electroencephalographically derived mismatch negativity (MMN) response. Twenty-four patients with SZ and AVH were randomly assigned to group CBTv treatment or a treatment as usual (TAU) condition. Patients in the group CBTv condition received treatment for 5 months while the matched control patients received TAU for the same period, followed by 5 months of group CBTv. Assessments were conducted at baseline and at the end of treatment. Although not showing consistent changes in the frequency of AVHs, CBTv (vs. TAU) improved patients' appraisal (p = 0.001) of and behavioral/emotional responses to AVHs, and increased both MMN generation (p = 0.001) and auditory cortex current density (p = 0.002) in response to tone pitch deviants. Improvements in AVH symptoms were correlated with change in pitch deviant MMN and current density in left primary auditory cortex. These findings of improved auditory information processing and symptom-response attributable to CBTv suggest potential clinical and functional benefits of psychotherapeutical approaches for patients with persistent AVHs.

ADHD desynchronizes brain activity during watching a distracted multi-talker conversation

Individuals with attention-deficit/hyperactivity disorder (ADHD) have difficulties navigating dynamic everyday situations that contain multiple sensory inputs that need to either be attended to or ignored. As conventional experimental tasks lack this type of everyday complexity, we administered a film-based multi-talker condition with auditory distractors in the background. ADHD-related aberrant brain responses to this naturalistic stimulus were identified using intersubject correlations (ISCs) in functional magnetic resonance imaging (fMRI) data collected from 51 adults with ADHD and 29 healthy controls. A novel permutation-based approach introducing studentized statistics and subject-wise voxel-level null-distributions revealed that several areas in cerebral attention networks and sensory cortices were desynchronized in participants with ADHD (n = 20) relative to healthy controls (n = 20). Specifically, desynchronization of the posterior parietal cortex occurred when irrelevant speech or music was presented in the background, but not when irrelevant white noise was presented, or when there were no distractors. We also show regionally distinct ISC signatures for inattention and impulsivity. Finally, post-scan recall of the film contents was associated with stronger ISCs in the default-mode network for the ADHD and in the dorsal attention network for healthy controls. The present study shows that ISCs can further our understanding of how a complex environment influences brain states in ADHD.

Loss of white matter connections after severe traumatic brain injury (TBI) and its relationship to social cognition

Adults with severe traumatic brain injury (TBI) often suffer poor social cognition. Social cognition is complex, requiring verbal, non-verbal, auditory, visual and affective input and integration. While damage to focal temporal and frontal areas has been implicated in disorders of social cognition after TBI, the role of white matter pathology has not been examined. In this study 17 adults with chronic, severe TBI and 17 control participants underwent structural MRI scans and Diffusion Tensor Imaging. The Awareness of Social Inference Test (TASIT) was used to assess their ability to understand emotional states, thoughts, intentions and conversational meaning in everyday exchanges. Track-based spatial statistics were used to perform voxelwise analysis of Fractional Anisotropy (FA) and Mean Diffusivity (MD) of white matter tracts associated with poor social cognitive performance. FA suggested a wide range of tracts were implicated in poor TASIT performance including tracts known to mediate, auditory localisation (planum temporale) communication between nonverbal and verbal processes in general (corpus callosum) and in memory in particular (fornix) as well as tracts and structures associated with semantics and verbal recall (left temporal lobe and hippocampus), multimodal processing and integration (thalamus, external capsule, cerebellum) and with social cognition (orbitofrontal cortex, frontopolar cortex, right temporal lobe). Even when controlling for non-social cognition, the corpus callosum, fornix, bilateral thalamus, right external capsule and right temporal lobe remained significant contributors to social cognitive performance. This study highlights the importance of loss of white matter connectivity in producing complex social information processing deficits after TBI.

Time and information in perceptual adaptation to speech

Perceptual adaptation to a talker enables listeners to efficiently resolve the many-to-many mapping between variable speech acoustics and abstract linguistic representations. However, models of speech perception have not delved into the variety or the quantity of information necessary for successful adaptation, nor how adaptation unfolds over time. In three experiments using speeded classification of spoken words, we explored how the quantity (duration), quality (phonetic detail), and temporal continuity of talker-specific context contribute to facilitating perceptual adaptation to speech. In single- and mixed-talker conditions, listeners identified phonetically-confusable target words in isolation or preceded by carrier phrases of varying lengths and phonetic content, spoken by the same talker as the target word. Word identification was always slower in mixed-talker conditions than single-talker ones. However, interference from talker variability decreased as the duration of preceding speech increased but was not affected by the amount of preceding talker-specific phonetic information. Furthermore, efficiency gains from adaptation depended on temporal continuity between preceding speech and the target word. These results suggest that perceptual adaptation to speech may be understood via models of auditory streaming, where perceptual continuity of an auditory object (e.g., a talker) facilitates allocation of attentional resources, resulting in more efficient perceptual processing.

Abnormal auditory tonotopy in patients with schizophrenia

Auditory hallucinations are among the most prevalent and most distressing symptoms of schizophrenia. Despite significant progress, it is still unclear whether auditory hallucinations arise from abnormalities in primary sensory processing or whether they represent failures of higher-order functions. To address this knowledge gap, we capitalized on the increased spatial resolution afforded by ultra-high field imaging at 7 Tesla to investigate the tonotopic organization of the auditory cortex in patients with schizophrenia with a history of recurrent hallucinations. Tonotopy is a fundamental feature of the functional organization of the auditory cortex that is established very early in development and predates the onset of symptoms by decades. Compared to healthy participants, patients showed abnormally increased activation and altered tonotopic organization of the auditory cortex during a purely perceptual task, which involved passive listening to tones across a range of frequencies (88–8000 Hz). These findings suggest that the predisposition to auditory hallucinations is likely to be predicated on abnormalities in the functional organization of the auditory cortex and which may serve as a biomarker for the early identification of vulnerable individuals.

Direct electrophysiological mapping of human pitch-related processing in auditory cortex

This work sought correlates of pitch perception, defined by neural activity above the lower limit of pitch (LLP), in auditory cortical neural ensembles, and examined their topographical distribution. Local field potentials (LFPs) were recorded in eight patients undergoing invasive recordings for pharmaco-resistant epilepsy. Stimuli consisted of bursts of broadband noise followed by regular interval noise (RIN). RIN was presented at rates below and above the LLP to distinguish responses related to the regularity of the stimulus and the presence of pitch itself. LFPs were recorded from human cortical homologues of auditory core, belt, and parabelt regions using multicontact depth electrodes implanted in Heschl's gyrus (HG) and Planum Temporale (PT), and subdural grid electrodes implanted over lateral superior temporal gyrus (STG). Evoked responses corresponding to the temporal regularity of the stimulus were assessed using autocorrelation of the evoked responses, and occurred for stimuli below and above the LLP. Induced responses throughout the high gamma range (60-200 Hz) were present for pitch values above the LLP, with onset latencies of approximately 70 ms. Mapping of the induced responses onto a common brain space demonstrated variability in the topographical distribution of high gamma responses across subjects. Induced responses were present throughout the length of HG and on PT, which is consistent with previous functional neuroimaging studies. Moreover, in each subject, a region within lateral STG showed robust induced responses at pitch-evoking stimulus rates. This work suggests a distributed representation of pitch processing in neural ensembles in human homologues of core and non-core auditory cortex.

Phonological Task Enhances the Frequency-Following Response to Deviant Task-Irrelevant Speech Sounds

In electroencephalography (EEG) measurements, processing of periodic sounds in the ascending auditory pathway generates the frequency-following response (FFR) phase-locked to the fundamental frequency (F0) and its harmonics of a sound. We measured FFRs to the steady-state (vowel) part of syllables /ba/ and /aw/ occurring in binaural rapid streams of speech sounds as frequently repeating standard syllables or as infrequent (p = 0.2) deviant syllables among standard /wa/ syllables. Our aim was to study whether concurrent active phonological processing affects early processing of irrelevant speech sounds reflected by FFRs to these sounds. To this end, during syllable delivery, our healthy adult participants performed tasks involving written letters delivered on a computer screen in a rapid stream. The stream consisted of vowel letters written in red, infrequently occurring consonant letters written in the same color, and infrequently occurring vowel letters written in blue. In the phonological task, the participants were instructed to press a response key to the consonant letters differing phonologically but not in color from the frequently occurring red vowels, whereas in the non-phonological task, they were instructed to respond to the vowel letters written in blue differing only in color from the frequently occurring red vowels. We observed that the phonological task enhanced responses to deviant /ba/ syllables but not responses to deviant /aw/ syllables. This suggests that active phonological task performance may enhance processing of such small changes in irrelevant speech sounds as the 30-ms difference in the initial formant-transition time between the otherwise identical syllables /ba/ and /wa/ used in the present study.

Brain activity sustaining the modulation of pain by empathetic comments

Empathetic verbal feedback from others has been shown to alleviate the intensity of experimental pain. To investigate the brain changes associated with this effect, we conducted 3T-fMRI measurements in 30 healthy subjects who received painful thermal stimuli on their left hand while overhearing empathetic, neutral or unempathetic comments, supposedly made by experimenters, via headsets. Only the empathetic comments significantly reduced pain intensity ratings. A whole-brain BOLD analysis revealed that both Empathetic and Unempathetic conditions significantly increased the activation of the right anterior insular and posterior parietal cortices to pain stimuli, while activations in the posterior cingulate cortex and precuneus (PCC/Prec) were significantly stronger during Empathetic compared to Unempathetic condition. BOLD activity increased in the DLPFC in the Empathetic condition and decreased in the PCC/Prec and vmPFC in the Unempathetic condition. In the Empathetic condition only, functional connectivity increased significantly between the vmPFC and the insular cortex. These results suggest that modulation of pain perception by empathetic feedback involves a set of high-order brain regions associated with autobiographical memories and self-awareness, and relies on interactions between such supra-modal structures and key nodes of the pain system.

Reward cues readily direct monkeys' auditory performance resulting in broad auditory cortex modulation and interaction with sites along cholinergic and dopaminergic pathways

In natural settings, the prospect of reward often influences the focus of our attention, but how cognitive and motivational systems influence sensory cortex is not well understood. Also, challenges in training nonhuman animals on cognitive tasks complicate cross-species comparisons and interpreting results on the neurobiological bases of cognition. Incentivized attention tasks could expedite training and evaluate the impact of attention on sensory cortex. Here we develop an Incentivized Attention Paradigm (IAP) and use it to show that macaque monkeys readily learn to use auditory or visual reward cues, drastically influencing their performance within a simple auditory task. Next, this paradigm was used with functional neuroimaging to measure activation modulation in the monkey auditory cortex. The results show modulation of extensive auditory cortical regions throughout primary and non-primary regions, which although a hallmark of attentional modulation in human auditory cortex, has not been studied or observed as broadly in prior data from nonhuman animals. Psycho-physiological interactions were identified between the observed auditory cortex effects and regions including basal forebrain sites along acetylcholinergic and dopaminergic pathways. The findings reveal the impact and regional interactions in the primate brain during an incentivized attention engaging auditory task.

Object-based attention in complex, naturalistic auditory streams

In vision, objects have been described as the 'units' on which non-spatial attention operates in many natural settings. Here, we test the idea of object-based attention in the auditory domain within ecologically valid auditory scenes, composed of two spatially and temporally overlapping sound streams (speech signal vs. environmental soundscapes in Experiment 1 and two speech signals in Experiment 2). Top-down attention was directed to one or the other auditory stream by a non-spatial cue. To test for high-level, object-based attention effects we introduce an auditory repetition detection task in which participants have to detect brief repetitions of auditory objects, ruling out any possible confounds with spatial or feature-based attention. The participants' responses were significantly faster and more accurate in the valid cue condition compared to the invalid cue condition, indicating a robust cue-validity effect of high-level, object-based auditory attention.

Cortical Correlates of Attention to Auditory Features

Pitch and timbre are two primary features of auditory perception that are generally considered independent. However, an increase in pitch (produced by a change in fundamental frequency) can be confused with an increase in brightness (an attribute of timbre related to spectral centroid) and vice versa. Previous work indicates that pitch and timbre are processed in overlapping regions of the auditory cortex, but are separable to some extent via multivoxel pattern analysis. Here, we tested whether attention to one or other feature increases the spatial separation of their cortical representations and if attention can enhance the cortical representation of these features in the absence of any physical change in the stimulus. Ten human subjects (four female, six male) listened to pairs of tone triplets varying in pitch, timbre, or both and judged which tone triplet had the higher pitch or brighter timbre. Variations in each feature engaged common auditory regions with no clear distinctions at a univariate level. Attending to one did not improve the separability of the neural representations of pitch and timbre at the univariate level. At the multivariate level, the classifier performed above chance in distinguishing between conditions in which pitch or timbre was discriminated. The results confirm that the computations underlying pitch and timbre perception are subserved by strongly overlapping cortical regions, but reveal that attention to one or other feature leads to distinguishable activation patterns even in the absence of physical differences in the stimuli.SIGNIFICANCE STATEMENT Although pitch and timbre are generally thought of as independent auditory features of a sound, pitch height and timbral brightness can be confused for one another. This study shows that pitch and timbre variations are represented in overlapping regions of auditory cortex, but that they produce distinguishable patterns of activation. Most importantly, the patterns of activation can be distinguished based on whether subjects attended to pitch or timbre even when the stimuli remained physically identical. The results therefore show that variations in pitch and timbre are represented by overlapping neural networks, but that attention to different features of the same sound can lead to distinguishable patterns of activation.

Interaction of the effects associated with auditory-motor integration and attention-engaging listening tasks

A number of previous studies have implicated regions in posterior auditory cortex (AC) in auditory-motor integration during speech production. Other studies, in turn, have shown that activation in AC and adjacent regions in the inferior parietal lobule (IPL) is strongly modulated during active listening and depends on task requirements. The present fMRI study investigated whether auditory-motor effects interact with those related to active listening tasks in AC and IPL. In separate task blocks, our subjects performed either auditory discrimination or 2-back memory tasks on phonemic or nonphonemic vowels. They responded to targets by either overtly repeating the last vowel of a target pair, overtly producing a given response vowel, or by pressing a response button. We hypothesized that the requirements for auditory-motor integration, and the associated activation, would be stronger during repetition than production responses and during repetition of nonphonemic than phonemic vowels. We also hypothesized that if auditory-motor effects are independent of task-dependent modulations, then the auditory-motor effects should not differ during discrimination and 2-back tasks. We found that activation in AC and IPL was significantly modulated by task (discrimination vs. 2-back), vocal-response type (repetition vs. production), and motor-response type (vocal vs. button). Motor-response and task effects interacted in IPL but not in AC. Overall, the results support the view that regions in posterior AC are important in auditory-motor integration. However, the present study shows that activation in wide AC and IPL regions is modulated by the motor requirements of active listening tasks in a more general manner. Further, the results suggest that activation modulations in AC associated with attention-engaging listening tasks and those associated with auditory-motor performance are mediated by independent mechanisms.

Singing in the brain: Neural representation of music and voice as revealed by fMRI

The ubiquity of music across cultures as a means of emotional expression, and its proposed evolutionary relation to speech, motivated researchers to attempt a characterization of its neural representation. Several neuroimaging studies have reported that specific regions in the anterior temporal lobe respond more strongly to music than to other auditory stimuli, including spoken voice. Nonetheless, because most studies have employed instrumental music, which has important acoustic distinctions from human voice, questions still exist as to the specificity of the observed "music-preferred" areas. Here, we sought to address this issue by testing 24 healthy young adults with fast, high-resolution fMRI, to record neural responses to a large and varied set of musical stimuli, which, critically, included a capella singing, as well as purely instrumental excerpts. Our results confirmed that music; vocal or instrumental, preferentially engaged regions in the superior STG, particularly in the anterior planum polare, bilaterally. In contrast, human voice, either spoken or sung, activated more strongly a large area along the superior temporal sulcus. Findings were consistent between univariate and multivariate analyses, as well as with the use of a "silent" sparse acquisition sequence that minimizes any potential influence of scanner noise on the resulting activations. Activity in music-preferred regions could not be accounted for by any basic acoustic parameter tested, suggesting these areas integrate, likely in a nonlinear fashion, a combination of acoustic attributes that, together, result in the perceived musicality of the stimuli, consistent with proposed hierarchical processing of complex auditory information within the temporal lobes.

Measuring Cortical Activity During Auditory Processing with Functional Near-Infrared Spectroscopy

Functional near-infrared spectroscopy (fNIRS) is an optical, non-invasive neuroimaging technique that investigates human brain activity by calculating concentrations of oxy- and deoxyhemoglobin. The aim of this publication is to review the current state of the art as to how fNIRS has been used to study auditory function. We address temporal and spatial characteristics of the hemodynamic response to auditory stimulation as well as experimental factors that affect fNIRS data such as acoustic and stimulus-driven effects. The rising importance that fNIRS is generating in auditory neuroscience underlines the strong potential of the technology, and it seems likely that fNIRS will become a useful clinical tool.

Graph measures in task-based fMRI: Functional integration during read-out of visual and auditory information

This study investigated how attending to auditory and visual information systematically changes graph theoretical measures of integration and functional connectivity between three network modules: auditory, visual, and a joint task core. Functional MRI BOLD activity was recorded while healthy volunteers attended to colour and/or pitch information presented within an audiovisual stimulus sequence. Network nodes and modules were based on peak voxels of BOLD contrasts, including colour and pitch sensitive brain regions as well as the dorsal attention network. Network edges represented correlations between nodes' activity and were computed separately for each condition. Connection strength was increased between the task and the visual module when participants attended to colour, and between the task and the auditory module when they attended to pitch. Moreover, several nodal graph measures showed consistent changes to attentional modulation in form of stronger integration of sensory regions in response to attention. Together, these findings corroborate dynamical adjustments of both modality-specific and modality-independent functional brain networks in response to task demands and their representation in graph theoretical measures.