What is Involved and What is Necessary for Complex Linguistic and Nonlinguistic Auditory Processing: Evidence from Functional Magnetic Resonance Imaging and Lesion Data

Situating word deafness within aphasia recovery: A case report

Word deafness is a rare neurological disorder often observed following bilateral damage to superior temporal cortex and canonically defined as an auditory modality-specific deficit in word comprehension. The extent to which word deafness is dissociable from aphasia remains unclear given its heterogeneous presentation, and some have consequently posited that word deafness instead represents a stage in recovery from aphasia, where auditory and linguistic processing are affected to varying degrees and improve at differing rates. Here, we report a case of an individual (Mr. C) with bilateral temporal lobe lesions whose presentation evolved from a severe aphasia to an atypical form of word deafness, where auditory linguistic processing was impaired at the sentence level and beyond. We first reconstructed in detail Mr. C's stroke recovery through medical record review and supplemental interviewing. Then, using behavioral testing and multimodal neuroimaging, we documented a predominant auditory linguistic deficit in sentence and narrative comprehension-with markedly reduced behavioral performance and absent brain activation in the language network in the spoken modality exclusively. In contrast, Mr. C displayed near-unimpaired behavioral performance and robust brain activations in the language network for the linguistic processing of words, irrespective of modality. We argue that these findings not only support the view of word deafness as a stage in aphasia recovery but also further instantiate the important role of left superior temporal cortex in auditory linguistic processing.

Hemispheric lateralization of language processing: insights from network-based symptom mapping and patient subgroups

The hemispheric laterality of language processing has become a hot topic in modern neuroscience. Although most previous studies have reported left-lateralized language processing, other studies found it to be bilateral. A previous neurocomputational model has proposed a unified framework to explain that the above discrepancy might be from healthy and patient individuals. This model posits an initial symmetry but imbalanced capacity in language processing for healthy individuals, with this imbalance contributing to language recovery disparities following different hemispheric injuries. The present study investigated this model by analyzing the lateralization patterns of language subnetworks across multiple attributes with a group of 99 patients (compared to nonlanguage processing) and examining the lateralization patterns of language subnetworks in subgroups with damage to different hemispheres. Subnetworks were identified using a whole-brain network-based lesion-symptom mapping method, and the lateralization index was quantitatively measured. We found that all the subnetworks in language processing were left-lateralized, while subnetworks in nonlanguage processing had different lateralization patterns. Moreover, diverse hemisphere-injury subgroups exhibited distinct language recovery effects. These findings provide robust support for the proposed neurocomputational model of language processing.

Of words and whistles: Statistical learning operates similarly for identical sounds perceived as speech and non-speech

Statistical learning is an ability that allows individuals to effortlessly extract patterns from the environment, such as sound patterns in speech. Some prior evidence suggests that statistical learning operates more robustly for speech compared to non-speech stimuli, supporting the idea that humans are predisposed to learn language. However, any apparent statistical learning advantage for speech could be driven by signal acoustics, rather than the subjective perception per se of sounds as speech. To resolve this issue, the current study assessed whether there is a statistical learning advantage for ambiguous sounds that are subjectively perceived as speech-like compared to the same sounds perceived as non-speech, thereby controlling for acoustic features. We first induced participants to perceive sine-wave speech (SWS)-a degraded form of speech not immediately perceptible as speech-as either speech or non-speech. After this induction phase, participants were exposed to a continuous stream of repeating trisyllabic nonsense words, composed of SWS syllables, and then completed an explicit familiarity rating task and an implicit target detection task to assess learning. Critically, participants showed robust and equivalent performance on both measures, regardless of their subjective speech perception. In contrast, participants who perceived the SWS syllables as more speech-like showed better detection of individual syllables embedded in speech streams. These results suggest that speech perception facilitates processing of individual sounds, but not the ability to extract patterns across sounds. Our findings suggest that statistical learning is not influenced by the perceived linguistic relevance of sounds, and that it may be conceptualized largely as an automatic, stimulus-driven mechanism.

Topology of the lateral visual system: The fundus of the superior temporal sulcus and parietal area H connect nonvisual cerebrum to the lateral occipital lobe

BACKGROUND AND PURPOSE

Mapping the topology of the visual system is critical for understanding how complex cognitive processes like reading can occur. We aim to describe the connectivity of the visual system to understand how the cerebrum accesses visual information in the lateral occipital lobe.

METHODS

Using meta-analytic software focused on task-based functional MRI studies, an activation likelihood estimation (ALE) of the visual network was created. Regions of interest corresponding to the cortical parcellation scheme previously published under the Human Connectome Project were co-registered onto the ALE to identify the hub-like regions of the visual network. Diffusion Spectrum Imaging-based fiber tractography was performed to determine the structural connectivity of these regions with extraoccipital cortices.

RESULTS

The fundus of the superior temporal sulcus (FST) and parietal area H (PH) were identified as hub-like regions for the visual network. FST and PH demonstrated several areas of coactivation beyond the occipital lobe and visual network. Furthermore, these parcellations were highly interconnected with other cortical regions throughout extraoccipital cortices related to their nonvisual functional roles. A cortical model demonstrating connections to these hub-like areas was created.

CONCLUSIONS

FST and PH are two hub-like areas that demonstrate extensive functional coactivation and structural connections to nonvisual cerebrum. Their structural interconnectedness with language cortices along with the abnormal activation of areas commonly located in the temporo-occipital region in dyslexic individuals suggests possible important roles of FST and PH in the integration of information related to language and reading. Future studies should refine our model by examining the functional roles of these hub areas and their clinical significance.

Online mouse cursor trajectories distinguish phonological activation by linguistic and nonlinguistic sounds

Four online mouse cursor tracking experiments (total N = 208) examined the activation of phonological representations by linguistic and nonlinguistic auditory stimuli. Participants hearing spoken words (e.g., "bell") produced less direct mouse cursor trajectories toward corresponding pictures or text when visual arrays also included phonologically related competitors (e.g., belt) as compared with unrelated distractors (e.g., hose), but no such phonological competition was observed during environmental sounds (e.g., the ring of a bell). While important similarities have been observed between spoken words and environmental sounds, these experiments provide novel mouse cursor evidence that environmental sounds directly activate conceptual knowledge without needing to engage linguistic knowledge, contrasting with spoken words. Implications for theories of conceptual knowledge are discussed.

Selective auditory attention within naturalistic scenes modulates reactivity to speech sounds

Rapid recognition and categorization of sounds are essential for humans and animals alike, both for understanding and reacting to our surroundings and for daily communication and social interaction. For humans, perception of speech sounds is of crucial importance. In real life, this task is complicated by the presence of a multitude of meaningful non‐speech sounds. The present behavioural, magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) study was set out to address how attention to speech versus attention to natural non‐speech sounds within complex auditory scenes influences cortical processing. The stimuli were superimpositions of spoken words and environmental sounds, with parametric variation of the speech‐to‐environmental sound intensity ratio. The participants' task was to detect a repetition in either the speech or the environmental sound. We found that specifically when participants attended to speech within the superimposed stimuli, higher speech‐to‐environmental sound ratios resulted in shorter sustained MEG responses and stronger BOLD fMRI signals especially in the left supratemporal auditory cortex and in improved behavioural performance. No such effects of speech‐to‐environmental sound ratio were observed when participants attended to the environmental sound part within the exact same stimuli. These findings suggest stronger saliency of speech compared with other meaningful sounds during processing of natural auditory scenes, likely linked to speech‐specific top‐down and bottom‐up mechanisms activated during speech perception that are needed for tracking speech in real‐life‐like auditory environments.

Chinese-English bilinguals show linguistic-perceptual links in the brain associating short spoken phrases with corresponding real-world natural action sounds by semantic category

Higher cognitive functions such as linguistic comprehension must ultimately relate to perceptual systems in the brain, though how and why this forms remains unclear. Different brain networks that mediate perception when hearing real-world natural sounds has recently been proposed to respect a taxonomic model of acoustic-semantic categories. Using functional magnetic resonance imaging (fMRI) with Chinese/English bilingual listeners, the present study explored whether reception of short spoken phrases, in both Chinese (Mandarin) and English, describing corresponding sound-producing events would engage overlapping brain regions at a semantic category level. The results revealed a double-dissociation of cortical regions that were preferential for representing knowledge of human versus environmental action events, whether conveyed through natural sounds or the corresponding spoken phrases depicted by either language. These findings of cortical hubs exhibiting linguistic-perceptual knowledge links at a semantic category level should help to advance neurocomputational models of the neurodevelopment of language systems.

Motor engagement relates to accurate perception of phonemes and audiovisual words, but not auditory words

A longstanding debate has surrounded the role of the motor system in speech perception, but progress in this area has been limited by tasks that only examine isolated syllables and conflate decision-making with perception. Using an adaptive task that temporally isolates perception from decision-making, we examined an EEG signature of motor activity (sensorimotor μ/beta suppression) during the perception of auditory phonemes, auditory words, audiovisual words, and environmental sounds while holding difficulty constant at two levels (Easy/Hard). Results revealed left-lateralized sensorimotor μ/beta suppression that was related to perception of speech but not environmental sounds. Audiovisual word and phoneme stimuli showed enhanced left sensorimotor μ/beta suppression for correct relative to incorrect trials, while auditory word stimuli showed enhanced suppression for incorrect trials. Our results demonstrate that motor involvement in perception is left-lateralized, is specific to speech stimuli, and it not simply the result of domain-general processes. These results provide evidence for an interactive network for speech perception in which dorsal stream motor areas are dynamically engaged during the perception of speech depending on the characteristics of the speech signal. Crucially, this motor engagement has different effects on the perceptual outcome depending on the lexicality and modality of the speech stimulus.

Michaelis et al. used extra-cranial EEG during a forced-choice identification task to investigate the role of the motor system in speech perception. Their findings suggest that left hemisphere dorsal stream motor areas are dynamically engaged during speech perception based on the properties of the stimulus.

Meta-Analyses Support a Taxonomic Model for Representations of Different Categories of Audio-Visual Interaction Events in the Human Brain

Our ability to perceive meaningful action events involving objects, people, and other animate agents is characterized in part by an interplay of visual and auditory sensory processing and their cross-modal interactions. However, this multisensory ability can be altered or dysfunctional in some hearing and sighted individuals, and in some clinical populations. The present meta-analysis sought to test current hypotheses regarding neurobiological architectures that may mediate audio-visual multisensory processing. Reported coordinates from 82 neuroimaging studies (137 experiments) that revealed some form of audio-visual interaction in discrete brain regions were compiled, converted to a common coordinate space, and then organized along specific categorical dimensions to generate activation likelihood estimate (ALE) brain maps and various contrasts of those derived maps. The results revealed brain regions (cortical "hubs") preferentially involved in multisensory processing along different stimulus category dimensions, including 1) living versus nonliving audio-visual events, 2) audio-visual events involving vocalizations versus actions by living sources, 3) emotionally valent events, and 4) dynamic-visual versus static-visual audio-visual stimuli. These meta-analysis results are discussed in the context of neurocomputational theories of semantic knowledge representations and perception, and the brain volumes of interest are available for download to facilitate data interpretation for future neuroimaging studies.

A parcellation-based model of the auditory network

INTRODUCTION

The auditory network plays an important role in interaction with the environment. Multiple cortical areas, such as the inferior frontal gyrus, superior temporal gyrus and adjacent insula have been implicated in this processing. However, understanding of this network's connectivity has been devoid of tractography specificity.

METHODS

Using attention task-based functional magnetic resonance imaging (MRI) studies, an activation likelihood estimation (ALE) of the auditory network was generated. Regions of interest corresponding to the cortical parcellation scheme previously published under the Human Connectome Project were co-registered onto the ALE in the Montreal Neurological Institute coordinate space, and visually assessed for inclusion in the network. Diffusion spectrum MRI-based fiber tractography was performed to determine the structural connections between cortical parcellations comprising the network.

RESULTS

Fifteen cortical regions were found to be part of the auditory network: areas 44 and 8C, auditory area 1, 4, and 5, frontal operculum area 4, the lateral belt, medial belt and parabelt, parietal area F centromedian, perisylvian language area, retroinsular cortex, supplementary and cingulate eye field and the temporoparietal junction area 1. These regions showed consistent interconnections between adjacent parcellations. The frontal aslant tract was found to connect areas within the frontal lobe, while the arcuate fasciculus was found to connect the frontal and temporal lobe, and subcortical U-fibers were found to connect parcellations within the temporal area. Further studies may refine this model with the ultimate goal of clinical application.

Activating Semantic Knowledge During Spoken Words and Environmental Sounds: Evidence From the Visual World Paradigm

Two visual world experiments investigated the activation of semantically related concepts during the processing of environmental sounds and spoken words. Participants heard environmental sounds such as barking or spoken words such as "puppy" while viewing visual arrays with objects such as a bone (semantically related competitor) and candle (unrelated distractor). In Experiment 1, a puppy (target) was also included in the visual array; in Experiment 2, it was not. During both types of auditory stimuli, competitors were fixated significantly more than distractors, supporting the coactivation of semantically related concepts in both cases; comparisons of the two types of auditory stimuli also revealed significantly larger effects with environmental sounds than spoken words. We discuss implications of these results for theories of semantic knowledge.

The Artery of Aphasia, A Uniquely Sensitive Posterior Temporal Middle Cerebral Artery Branch that Supplies Language Areas in the Brain: Anatomy and Report of Four Cases

BACKGROUND

Arterial disruption during brain surgery can cause devastating injuries to wide expanses of white and gray matter beyond the tumor resection cavity. Such damage may occur as a result of disrupting blood flow through en passage arteries. Identification of these arteries is critical to prevent unforeseen neurologic sequelae during brain tumor resection. In this study, we discuss one such artery, termed the artery of aphasia (AoA), which when disrupted can lead to receptive and expressive language deficits.

METHODS

We performed a retrospective review of all patients undergoing an awake craniotomy for resection of a glioma by the senior author from 2012 to 2018. Patients were included if they experienced language deficits secondary to postoperative infarction in the left posterior temporal lobe in the distribution of the AoA. The gross anatomy of the AoA was then compared with activation likelihood estimations of the auditory and semantic language networks using coordinate-based meta-analytic techniques.

RESULTS

We identified 4 patients with left-sided posterior temporal artery infarctions in the distribution of the AoA on diffusion-weighted magnetic resonance imaging. All 4 patients developed substantial expressive and receptive language deficits after surgery. Functional language improvement occurred in only 2/4 patients. Activation likelihood estimations localized parts of the auditory and semantic language networks in the distribution of the AoA.

CONCLUSIONS

The AoA is prone to blood flow disruption despite benign manipulation. Patients seem to have limited capacity for speech recovery after intraoperative ischemia in the distribution of this artery, which supplies parts of the auditory and semantic language networks.

Audiovisual Lexical Retrieval Deficits Following Left Hemisphere Stroke

Binding sensory features of multiple modalities of what we hear and see allows formation of a coherent percept to access semantics. Previous work on object naming has focused on visual confrontation naming with limited research in nonverbal auditory or multisensory processing. To investigate neural substrates and sensory effects of lexical retrieval, we evaluated healthy adults (n = 118) and left hemisphere stroke patients (LHD, n = 42) in naming manipulable objects across auditory (sound), visual (picture), and multisensory (audiovisual) conditions. LHD patients were divided into cortical, cortical–subcortical, or subcortical lesions (CO, CO–SC, SC), and specific lesion location investigated in a predictive model. Subjects produced lower accuracy in auditory naming relative to other conditions. Controls demonstrated greater naming accuracy and faster reaction times across all conditions compared to LHD patients. Naming across conditions was most severely impaired in CO patients. Both auditory and visual naming accuracy were impacted by temporal lobe involvement, although auditory naming was sensitive to lesions extending subcortically. Only controls demonstrated significant improvement over visual naming with the addition of auditory cues (i.e., multisensory condition). Results support overlapping neural networks for visual and auditory modalities related to semantic integration in lexical retrieval and temporal lobe involvement, while multisensory integration was impacted by both occipital and temporal lobe lesion involvement. The findings support modality specificity in naming and suggest that auditory naming is mediated by a distributed cortical–subcortical network overlapping with networks mediating spatiotemporal aspects of skilled movements producing sound.

The evolution of cognitive models: From neuropsychology to neuroimaging and back

This paper provides a historical and future perspective on how neuropsychology and neuroimaging can be used to develop cognitive models of human brain functions. Section 1 focuses on the emergence of cognitive modelling from neuropsychology, why lesion location was considered to be unimportant and the challenges faced when mapping symptoms to impaired cognitive processes. Section 2 describes how established cognitive models based on behavioural data alone cannot explain the complex patterns of distributed brain activity that are observed in functional neuroimaging studies. This has led to proposals for new cognitive processes, new cognitive strategies and new functional ontologies for cognition. Section 3 considers how the integration of data from lesion, behavioural and functional neuroimaging studies of large cohorts of brain damaged patients can be used to determine whether inter-patient variability in behaviour is due to differences in the premorbid function of each brain region, lesion site or cognitive strategy. This combination of neuroimaging and neuropsychology is providing a deeper understanding of how cognitive functions can be lost and re-learnt after brain damage - an understanding that will transform our ability to generate and validate cognitive models that are both physiologically plausible and clinically useful.

Auditory agnosia caused by bilateral putamen haemorrhage

A 55-year-old right-handed man with a history of hypertension suddenly fell and developed right hemiparesis. Neurological examination revealed that he was alert, but did not appropriately respond to verbal questions and commands. Detailed examination revealed that he could correctly respond to written commands. His speech was almost fluent, showing no paraphasia and normal articulation. His written sentences were legible. Pure tone audiometry showed that his auditory acuity was relatively preserved. His brainstem auditory evoked potential components from I to V were recorded bilaterally with normal latency. Cerebral CT demonstrated fresh bleeding in the left putamen and an old haemorrhage on the opposite side. He was treated by antihypertensive therapy and rehabilitation. Although there remained mild sensory deficit on his right extremities and he felt a slight noise during conversation, he had little difficulty with verbal communication when he was transferred to another hospital on day 38.

Auditory object perception: A neurobiological model and prospective review

Interaction with the world is a multisensory experience, but most of what is known about the neural correlates of perception comes from studying vision. Auditory inputs enter cortex with its own set of unique qualities, and leads to use in oral communication, speech, music, and the understanding of emotional and intentional states of others, all of which are central to the human experience. To better understand how the auditory system develops, recovers after injury, and how it may have transitioned in its functions over the course of hominin evolution, advances are needed in models of how the human brain is organized to process real-world natural sounds and "auditory objects". This review presents a simple fundamental neurobiological model of hearing perception at a category level that incorporates principles of bottom-up signal processing together with top-down constraints of grounded cognition theories of knowledge representation. Though mostly derived from human neuroimaging literature, this theoretical framework highlights rudimentary principles of real-world sound processing that may apply to most if not all mammalian species with hearing and acoustic communication abilities. The model encompasses three basic categories of sound-source: (1) action sounds (non-vocalizations) produced by 'living things', with human (conspecific) and non-human animal sources representing two subcategories; (2) action sounds produced by 'non-living things', including environmental sources and human-made machinery; and (3) vocalizations ('living things'), with human versus non-human animals as two subcategories therein. The model is presented in the context of cognitive architectures relating to multisensory, sensory-motor, and spoken language organizations. The models' predictive values are further discussed in the context of anthropological theories of oral communication evolution and the neurodevelopment of spoken language proto-networks in infants/toddlers. These phylogenetic and ontogenetic frameworks both entail cortical network maturations that are proposed to at least in part be organized around a number of universal acoustic-semantic signal attributes of natural sounds, which are addressed herein.

Identifying environmental sounds: a multimodal mapping study

Our environment is full of auditory events such as warnings or hazards, and their correct recognition is essential. We explored environmental sounds (ES) recognition in a series of studies. In study 1 we performed an Activation Likelihood Estimation (ALE) meta-analysis of neuroimaging experiments addressing ES processing to delineate the network of areas consistently involved in ES processing. Areas consistently activated in the ALE meta-analysis were the STG/MTG, insula/rolandic operculum, parahippocampal gyrus and inferior frontal gyrus bilaterally. Some of these areas truly reflect ES processing, whereas others are related to design choices, e.g., type of task, type of control condition, type of stimulus. In study 2 we report on 7 neurosurgical patients with lesions involving the areas which were found to be activated by the ALE meta-analysis. We tested their ES recognition abilities and found an impairment of ES recognition. These results indicate that deficits of ES recognition do not exclusively reflect lesions to the right or to the left hemisphere but both hemispheres are involved. The most frequently lesioned area is the hippocampus/insula/STG. We made sure that any impairment in ES recognition would not be related to language problems, but reflect impaired ES processing. In study 3 we carried out an fMRI study on patients (vs. healthy controls) to investigate how the areas involved in ES might be functionally deregulated because of a lesion. The fMRI evidenced that controls activated the right IFG, the STG bilaterally and the left insula. We applied a multimodal mapping approach and found that, although the meta-analysis showed that part of the left and right STG/MTG activation during ES processing might in part be related to design choices, this area was one of the most frequently lesioned areas in our patients, thus highlighting its causal role in ES processing. We found that the ROIs we drew on the two clusters of activation found in the left and in the right STG overlapped with the lesions of at least 4 out of the 7 patients' lesions, indicating that the lack of STG activation found for patients is related to brain damage and is crucial for explaining the ES deficit.

The emergence of mirror-like response properties from domain-general principles in vision and audition

Like Cook et al., we suggest that mirror neurons are a fascinating product of cross-modal learning. As predicted by an associative account, responses in motor regions are observed for novel and/or abstract visual stimuli such as point-light and android movements. Domain-specific mirror responses also emerge as a function of audiomotor expertise that is slowly acquired over years of intensive training.

Expert athletes activate somatosensory and motor planning regions of the brain when passively listening to familiar sports sounds

The present functional magnetic resonance imaging study examined the neural response to familiar and unfamiliar, sport and non-sport environmental sounds in expert and novice athletes. Results revealed differential neural responses dependent on sports expertise. Experts had greater neural activation than novices in focal sensorimotor areas such as the supplementary motor area, and pre- and postcentral gyri. Novices showed greater activation than experts in widespread areas involved in perception (i.e. supramarginal, middle occipital, and calcarine gyri; precuneus; inferior and superior parietal lobules), and motor planning and processing (i.e. inferior frontal, middle frontal, and middle temporal gyri). These between-group neural differences also appeared as an expertise effect within specific conditions. Experts showed greater activation than novices during the sport familiar condition in regions responsible for auditory and motor planning, including the inferior frontal gyrus and the parietal operculum. Novices only showed greater activation than experts in the supramarginal gyrus and pons during the non-sport unfamiliar condition, and in the middle frontal gyrus during the sport unfamiliar condition. These results are consistent with the view that expert athletes are attuned to only the most familiar, highly relevant sounds and tune out unfamiliar, irrelevant sounds. Furthermore, these findings that athletes show activation in areas known to be involved in action planning when passively listening to sounds suggests that auditory perception of action can lead to the re-instantiation of neural areas involved in producing these actions, especially if someone has expertise performing the actions.

Lesion symptom mapping of manipulable object naming in nonfluent aphasia: can a brain be both embodied and disembodied?

Embodied cognition offers an approach to word meaning firmly grounded in action and perception. A strong prediction of embodied cognition is that sensorimotor simulation is a necessary component of lexical-semantic representation. One semantic distinction where motor imagery is likely to play a key role involves the representation of manufactured artefacts. Many questions remain with respect to the scope of embodied cognition. One dominant unresolved issue is the extent to which motor enactment is necessary for representing and generating words with high motor salience. We investigated lesion correlates of manipulable relative to nonmanipulable name generation (e.g., name a school supply; name a mountain range) in patients with nonfluent aphasia (N = 14). Lesion volumes within motor (BA4, where BA = Brodmann area) and premotor (BA6) cortices were not predictive of category discrepancies. Lesion symptom mapping linked impairment for manipulable objects to polymodal convergence zones and to projections of the left, primary visual cortex specialized for motion perception (MT/V5+). Lesions to motor and premotor cortex were not predictive of manipulability impairment. This lesion correlation is incompatible with an embodied perspective premised on necessity of motor cortex for the enactment and subsequent production of motor-related words. These findings instead support a graded or "soft" approach to embodied cognition premised on an ancillary role of modality-specific cortical regions in enriching modality-neutral representations. We discuss a dynamic, hybrid approach to the neurobiology of semantic memory integrating both embodied and disembodied components.

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

We meta-analyzed 115 functional magnetic resonance imaging (fMRI) studies reporting auditory-cortex (AC) coordinates for activations related to active and passive processing of pitch and spatial location of non-speech sounds, as well as to the active and passive speech and voice processing. We aimed at revealing any systematic differences between AC surface locations of these activations by statistically analyzing the activation loci using the open-source Matlab toolbox VAMCA (Visualization and Meta-analysis on Cortical Anatomy). AC activations associated with pitch processing (e.g., active or passive listening to tones with a varying vs. fixed pitch) had median loci in the middle superior temporal gyrus (STG), lateral to Heschl's gyrus. However, median loci of activations due to the processing of infrequent pitch changes in a tone stream were centered in the STG or planum temporale (PT), significantly posterior to the median loci for other types of pitch processing. Median loci of attention-related modulations due to focused attention to pitch (e.g., attending selectively to low or high tones delivered in concurrent sequences) were, in turn, centered in the STG or superior temporal sulcus (STS), posterior to median loci for passive pitch processing. Activations due to spatial processing were centered in the posterior STG or PT, significantly posterior to pitch processing loci (processing of infrequent pitch changes excluded). In the right-hemisphere AC, the median locus of spatial attention-related modulations was in the STS, significantly inferior to the median locus for passive spatial processing. Activations associated with speech processing and those associated with voice processing had indistinguishable median loci at the border of mid-STG and mid-STS. Median loci of attention-related modulations due to attention to speech were in the same mid-STG/STS region. Thus, while attention to the pitch or location of non-speech sounds seems to recruit AC areas less involved in passive pitch or location processing, focused attention to speech predominantly enhances activations in regions that already respond to human vocalizations during passive listening. This suggests that distinct attention mechanisms might be engaged by attention to speech and attention to more elemental auditory features such as tone pitch or location. This article is part of a Special Issue entitled Human Auditory Neuroimaging.

Effects of prior information on decoding degraded speech: an fMRI study

Expectations and prior knowledge are thought to support the perceptual analysis of incoming sensory stimuli, as proposed by the predictive‐coding framework. The current fMRI study investigated the effect of prior information on brain activity during the decoding of degraded speech stimuli. When prior information enabled the comprehension of the degraded sentences, the left middle temporal gyrus and the left angular gyrus were activated, highlighting a role of these areas in meaning extraction. In contrast, the activation of the left inferior frontal gyrus (area 44/45) appeared to reflect the search for meaningful information in degraded speech material that could not be decoded because of mismatches with the prior information. Our results show that degraded sentences evoke instantaneously different percepts and activation patterns depending on the type of prior information, in line with prediction‐based accounts of perception. Hum Brain Mapp 35:61–74, 2014. © 2012 Wiley Periodicals, Inc.

A comparison of VLSM and VBM in a cohort of patients with post-stroke aphasia

Studies attempting to map post-stroke cognitive or motor symptoms to lesion location have been available in the literature for over 150 years. In the last two decades, two computational techniques have been developed to identify the lesion sites associated with behavioural impairments. Voxel Based Morphometry (VBM) has now been used extensively for this purpose in many different patient populations. More recently, Voxel-based Lesion Symptom Mapping (VLSM) was developed specifically for the purpose of identifying lesion–symptom relationships in stroke patients, and has been used extensively to study, among others functions, language, motor abilities and attention. However, no studies have compared the results of these two techniques so far. In this study we compared VLSM and VBM in a cohort of 20 patients with chronic post-stroke aphasia. Comparison of the two techniques showed overlap in regions previously found to be relevant for the tasks used, suggesting that using both techniques and looking for overlaps between them can increase the reliability of the results obtained. However, overall VBM and VLSM provided only partially concordant results and the differences between the two techniques are discussed.

Design choices in imaging speech comprehension: an Activation Likelihood Estimation (ALE) meta-analysis

The localisation of spoken language comprehension is debated extensively: is processing located anterior or posterior on the left temporal lobe, and is it left- or bilaterally organised? An Activation Likelihood Estimation (ALE) analysis was conducted on functional MRI and PET studies investigating speech comprehension to identify the neural network involved in comprehension processing. Furthermore, the analysis aimed to establish the effect of four design choices (scanning paradigm, non-speech baseline, the presence of a task, and the type of stimulus material) on this comprehension network. The analysis included 57 experiments contrasting intelligible with less intelligible or unintelligible stimuli. A large comprehension network was found across bilateral Superior Temporal Sulcus (STS), Middle Temporal Gyrus (MTG) and Superior Temporal (STS) bilaterally, in left Inferior Frontal Gyrus (IFG), left Precentral Gyrus, and Supplementary Motor Area (SMA) and pre-SMA. The core network for post-lexical processing was restricted to the temporal lobes bilaterally with the highest ALE values located anterior to Heschl's Gyrus. Activations in the ALE comprehension network outside the temporal lobes (left IFG, SMA/pre-SMA, and Precentral Gyrus) were driven by the use of sentences instead of words, the scanning paradigm, or the type of non-speech baseline.

The neural bases of difficult speech comprehension and speech production: Two Activation Likelihood Estimation (ALE) meta-analyses

The role of speech production mechanisms in difficult speech comprehension is the subject of on-going debate in speech science. Two Activation Likelihood Estimation (ALE) analyses were conducted on neuroimaging studies investigating difficult speech comprehension or speech production. Meta-analysis 1 included 10 studies contrasting comprehension of less intelligible/distorted speech with more intelligible speech. Meta-analysis 2 (21 studies) identified areas associated with speech production. The results indicate that difficult comprehension involves increased reliance of cortical regions in which comprehension and production overlapped (bilateral anterior Superior Temporal Sulcus (STS) and anterior Supplementary Motor Area (pre-SMA)) and in an area associated with intelligibility processing (left posterior MTG), and second involves increased reliance on cortical areas associated with general executive processes (bilateral anterior insulae). Comprehension of distorted speech may be supported by a hybrid neural mechanism combining increased involvement of areas associated with general executive processing and areas shared between comprehension and production.

Speech versus song: multiple pitch-sensitive areas revealed by a naturally occurring musical illusion

It is normally obvious to listeners whether a human vocalization is intended to be heard as speech or song. However, the 2 signals are remarkably similar acoustically. A naturally occurring boundary case between speech and song has been discovered where a spoken phrase sounds as if it were sung when isolated and repeated. In the present study, an extensive search of audiobooks uncovered additional similar examples, which were contrasted with samples from the same corpus that do not sound like song, despite containing clear prosodic pitch contours. Using functional magnetic resonance imaging, we show that hearing these 2 closely matched stimuli is not associated with differences in response of early auditory areas. Rather, we find that a network of 8 regions, including the anterior superior temporal gyrus (STG) just anterior to Heschl's gyrus and the right midposterior STG, respond more strongly to speech perceived as song than to mere speech. This network overlaps a number of areas previously associated with pitch extraction and song production, confirming that phrases originally intended to be heard as speech can, under certain circumstances, be heard as song. Our results suggest that song processing compared with speech processing makes increased demands on pitch processing and auditory-motor integration.

The emergence of cerebral specialization for the human voice over the first months of life

How specialized is the infant brain for processing voice within our environment? Research in adults suggests that portions of the temporal lobe play an important role in differentiating vocalizations from other environmental sounds; however, very little is known about this process in infancy. Recent research in infants has revealed discrepancies in the cortical location of voice-selective activation, as well as the age of onset of this response. The current study used functional near-infrared spectroscopy (fNIRS) to further investigate voice processing in awake 4-7-month-old infants. In listening to voice and non-voice sounds, there was robust and widespread activation in bilateral temporal cortex. Further, voice-selective regions of the bilateral anterior temporal cortex evidenced a steady increase in voice selective activation (voice > non-voice activation) over 4-7 months of age. These findings support a growing body of evidence that the emergence of cerebral specialization for human voice sounds evolves over the first 6 months of age.

Distributed processing and cortical specialization for speech and environmental sounds in human temporal cortex

Using functional MRI, we investigated whether auditory processing of both speech and meaningful non-linguistic environmental sounds in superior and middle temporal cortex relies on a complex and spatially distributed neural system. We found that evidence for spatially distributed processing of speech and environmental sounds in a substantial extent of temporal cortices. Most importantly, regions previously reported as selective for speech over environmental sounds also contained distributed information. The results indicate that temporal cortices supporting complex auditory processing, including regions previously described as speech-selective, are in fact highly heterogeneous.

Perceptual and conceptual priming of environmental sounds

It is still unknown whether sonic environments influence the processing of individual sounds in a similar way as discourse or sentence context influences the processing of individual words. One obstacle to answering this question has been the failure to dissociate perceptual (i.e., how similar are sonic environment and target sound?) and conceptual (i.e., how related are sonic environment and target?) priming effects. In this study, we dissociate these effects by creating prime-target pairs with a purely perceptual or both a perceptual and conceptual relationship. Perceptual prime-target pairs were derived from perceptual-conceptual pairs (i.e., meaningful environmental sounds) by shuffling the spectral composition of primes and targets so as to preserve their perceptual relationship while making them unrecognizable. Hearing both original and shuffled targets elicited a more positive N1/P2 complex in the ERP when targets were related to a preceding prime as compared with unrelated. Only related original targets reduced the N400 amplitude. Related shuffled targets tended to decrease the amplitude of a late temporo-parietal positivity. Taken together, these effects indicate that sonic environments influence first the perceptual and then the conceptual processing of individual sounds. Moreover, the influence on conceptual processing is comparable to the influence linguistic context has on the processing of individual words.

Cortical networks representing object categories and high-level attributes of familiar real-world action sounds

In contrast to visual object processing, relatively little is known about how the human brain processes everyday real-world sounds, transforming highly complex acoustic signals into representations of meaningful events or auditory objects. We recently reported a fourfold cortical dissociation for representing action (nonvocalization) sounds correctly categorized as having been produced by human, animal, mechanical, or environmental sources. However, it was unclear how consistent those network representations were across individuals, given potential differences between each participant's degree of familiarity with the studied sounds. Moreover, it was unclear what, if any, auditory perceptual attributes might further distinguish the four conceptual sound-source categories, potentially revealing what might drive the cortical network organization for representing acoustic knowledge. Here, we used functional magnetic resonance imaging to test participants before and after extensive listening experience with action sounds, and tested for cortices that might be sensitive to each of three different high-level perceptual attributes relating to how a listener associates or interacts with the sound source. These included the sound's perceived concreteness, effectuality (ability to be affected by the listener), and spatial scale. Despite some variation of networks for environmental sounds, our results verified the stability of a fourfold dissociation of category-specific networks for real-world action sounds both before and after familiarity training. Additionally, we identified cortical regions parametrically modulated by each of the three high-level perceptual sound attributes. We propose that these attributes contribute to the network-level encoding of category-specific acoustic knowledge representations.

Predicting language outcome and recovery after stroke: the PLORAS system

The ability to comprehend and produce speech after stroke depends on whether the areas of the brain that support language have been damaged. Here, we review two different ways to predict language outcome after stroke. The first depends on understanding the neural circuits that support language. This model-based approach is a challenging endeavor because language is a complex cognitive function that involves the interaction of many different brain areas. The second approach, by contrast, does not require an understanding of why a lesion impairs language; instead, predictions are made on the basis of the recovery of previous patients with the same lesion. This approach requires a database that records the speech and language capabilities of a large population of patients who have, collectively, incurred a comprehensive range of focal brain lesions. In addition, a system is required that converts an MRI scan from a new patient into a three-dimensional description of the lesion and compares this lesion against all others on the database. The outputs of this system are the longitudinal language outcomes of corresponding patients in the database. This approach will provide the patient with a range of probable recovery patterns over a variety of language measures.

Nonverbal auditory agnosia with lesion to Wernicke's area

We report the case of patient M, who suffered unilateral left posterior temporal and parietal damage, brain regions typically associated with language processing. Language function largely recovered since the infarct, with no measurable speech comprehension impairments. However, the patient exhibited a severe impairment in nonverbal auditory comprehension. We carried out extensive audiological and behavioral testing in order to characterize M's unusual neuropsychological profile. We also examined the patient's and controls' neural responses to verbal and nonverbal auditory stimuli using functional magnetic resonance imaging (fMRI). We verified that the patient exhibited persistent and severe auditory agnosia for nonverbal sounds in the absence of verbal comprehension deficits or peripheral hearing problems. Acoustical analyses suggested that his residual processing of a minority of environmental sounds might rely on his speech processing abilities. In the patient's brain, contralateral (right) temporal cortex as well as perilesional (left) anterior temporal cortex were strongly responsive to verbal, but not to nonverbal sounds, a pattern that stands in marked contrast to the controls' data. This substantial reorganization of auditory processing likely supported the recovery of M's speech processing.

Hearing living symbols and nonliving icons: category specificities in the cognitive processing of environmental sounds

The neurocognitive processing of environmental sounds and linguistic stimuli shares common semantic resources and can lead to the activation of motor programs for the generation of the passively heard sound or speech. We investigated the extent to which the cognition of environmental sounds, like that of language, relies on symbolic mental representations independent of the acoustic input. In a hierarchical sorting task, we found that evaluation of nonliving sounds is consistently biased toward a focus on acoustical information. However, the evaluation of living sounds focuses spontaneously on sound-independent semantic information, but can rely on acoustical information after exposure to a context consisting of nonliving sounds. We interpret these results as support for a robust iconic processing strategy for nonliving sounds and a flexible symbolic processing strategy for living sounds.

Verbal and nonverbal semantic processing in children with developmental language impairment

In an effort to clarify whether semantic integration is impaired in verbal and nonverbal auditory domains in children with developmental language impairment (a.k.a., LI and SLI), the present study obtained behavioral and neural responses to words and environmental sounds in children with language impairment and their typically developing age-matched controls (ages 7-15 years). Event-related brain potentials (ERPs) were recorded while children performed a forced-choice matching task on semantically matching and mismatching visual-auditory, picture-word and picture-environmental sound pairs. Behavioral accuracy and reaction time measures were similar for both groups of children, with environmental sounds eliciting more accurate responses than words. In picture-environmental sound trials, behavioral performance and the brain's response to semantic incongruency (i.e., the N400 effect) of the children with language impairment were comparable to those of their typically developing peers. However, in picture-word trials, children with LI tended to be less accurate than their controls and their N400 effect was significantly delayed in latency. Thus, the children with LI demonstrated a semantic integration deficit that was somewhat specific to the verbal domain. The particular finding of a delayed N400 effect is consistent with the storage deficit hypothesis of language impairment (Kail & Leonard, 1986) suggesting weakened and/or less efficient connections within the language networks of children with LI.

On-line plasticity in spoken sentence comprehension: Adapting to time-compressed speech

Listeners show remarkable flexibility in processing variation in speech signal. One striking example is the ease with which they adapt to novel speech distortions such as listening to someone with a foreign accent. Behavioural studies suggest that significant improvements in comprehension occur rapidly — often within 10–20 sentences. In the present experiment, we investigate the neural changes underlying on-line adaptation to distorted speech using time-compressed speech. Listeners performed a sentence verification task on normal-speed and time-compressed sentences while their neural responses were recorded using fMRI. The results showed that rapid learning of the time-compressed speech occurred during presentation of the first block of 16 sentences and was associated with increased activation in left and right auditory association cortices and in left ventral premotor cortex. These findings suggest that the ability to adapt to a distorted speech signal may, in part, rely on mapping novel acoustic patterns onto existing articulatory motor plans, consistent with the idea that speech perception involves integrating multi-modal information including auditory and motoric cues.

Absolute pitch--functional evidence of speech-relevant auditory acuity

Absolute pitch (AP) has been shown to be associated with morphological changes and neurophysiological adaptations in the planum temporale, a cortical area involved in higher-order auditory and speech perception processes. The direct link between speech processing and AP has hitherto not been addressed. We provide first evidence that AP compared with relative pitch (RP) ability is associated with significantly different hemodynamic responses to complex speech sounds. By systematically varying the lexical and/or prosodic information of speech stimuli, we demonstrated consistent activation differences in AP musicians compared with RP musicians and nonmusicians. These differences relate to stronger activations in the posterior part of the middle temporal gyrus and weaker activations in the anterior mid-part of the superior temporal gyrus. Furthermore, this pattern is considerably modulated by the auditory acuity of AP. Our results suggest that the neural underpinnings of pitch processing expertise exercise a strong influence on propositional speech perception (sentence meaning).

Expertise with artificial nonspeech sounds recruits speech-sensitive cortical regions

Regions of the human temporal lobe show greater activation for speech than for other sounds. These differences may reflect intrinsically specialized domain-specific adaptations for processing speech, or they may be driven by the significant expertise we have in listening to the speech signal. To test the expertise hypothesis, we used a video-game-based paradigm that tacitly trained listeners to categorize acoustically complex, artificial nonlinguistic sounds. Before and after training, we used functional MRI to measure how expertise with these sounds modulated temporal lobe activation. Participants' ability to explicitly categorize the nonspeech sounds predicted the change in pretraining to posttraining activation in speech-sensitive regions of the left posterior superior temporal sulcus, suggesting that emergent auditory expertise may help drive this functional regionalization. Thus, seemingly domain-specific patterns of neural activation in higher cortical regions may be driven in part by experience-based restructuring of high-dimensional perceptual space.

Dissociating verbal and nonverbal audiovisual object processing

This fMRI study investigates how audiovisual integration differs for verbal stimuli that can be matched at a phonological level and nonverbal stimuli that can be matched at a semantic level. Subjects were presented simultaneously with one visual and one auditory stimulus and were instructed to decide whether these stimuli referred to the same object or not. Verbal stimuli were simultaneously presented spoken and written object names, and nonverbal stimuli were photographs of objects simultaneously presented with naturally occurring object sounds. Stimulus differences were controlled by including two further conditions that paired photographs of objects with spoken words and object sounds with written words. Verbal matching, relative to all other conditions, increased activation in a region of the left superior temporal sulcus that has previously been associated with phonological processing. Nonverbal matching, relative to all other conditions, increased activation in a right fusiform region that has previously been associated with structural and conceptual object processing. Thus, we demonstrate how brain activation for audiovisual integration depends on the verbal content of the stimuli, even when stimulus and task processing differences are controlled.

Neuroanatomical distribution of five semantic components of verbs: evidence from fMRI

The Simulation Framework, also known as the Embodied Cognition Framework, maintains that conceptual knowledge is grounded in sensorimotor systems. To test several predictions that this theory makes about the neural substrates of verb meanings, we used functional magnetic resonance imaging (fMRI) to scan subjects' brains while they made semantic judgments involving five classes of verbs-specifically, Running verbs (e.g., run, jog, walk), Speaking verbs (e.g., shout, mumble, whisper), Hitting verbs (e.g., hit, poke, jab), Cutting verbs (e.g., cut, slice, hack), and Change of State verbs (e.g., shatter, smash, crack). These classes were selected because they vary with respect to the presence or absence of five distinct semantic components-specifically, ACTION, MOTION, CONTACT, CHANGE OF STATE, and TOOL USE. Based on the Simulation Framework, we hypothesized that the ACTION component depends on the primary motor and premotor cortices, that the MOTION component depends on the posterolateral temporal cortex, that the CONTACT component depends on the intraparietal sulcus and inferior parietal lobule, that the CHANGE OF STATE component depends on the ventral temporal cortex, and that the TOOL USE component depends on a distributed network of temporal, parietal, and frontal regions. Virtually all of the predictions were confirmed. Taken together, these findings support the Simulation Framework and extend our understanding of the neuroanatomical distribution of different aspects of verb meaning.