Neural Basis of Acquired Amusia and Its Recovery after Stroke

Dynamics of Pitch Perception in the Auditory Cortex

The ability to perceive pitch allows human listeners to experience music, recognize the identity and emotion conveyed by conversational partners, and make sense of their auditory environment. A pitch percept is formed by weighting different acoustic cues (e.g., signal fundamental frequency and interharmonic spacing) and contextual cues (expectation). How and when such cues are neurally encoded and integrated remains debated. In this study, 28 participants (16 female) listened to tone sequences with different acoustic cues (pure tones, complex missing fundamental tones, and tones with an ambiguous mixture), placed in predictable and less predictable sequences, while magnetoencephalography was recorded. Decoding analyses revealed that pitch was encoded in neural responses to all three tone types in the low-to-mid auditory cortex and sensorimotor cortex bilaterally, with right-hemisphere dominance. The pattern of activity generalized across cue types, offset in time: pitch was neurally encoded earlier for harmonic tones (∼85 ms) than pure tones (∼95 ms). For ambiguous tones, pitch emerged significantly earlier in predictable contexts than in unpredictable. The results suggest that a unified neural representation of pitch emerges by integrating independent pitch cues and that context alters the dynamics of pitch generation when acoustic cues are ambiguous.

Human insula neurons respond to simple sounds during passive listening

The insula is critical for integrating sensory information from the body with that arising from the environment. Although previous studies suggest that posterior insula is sensitive to sounds, auditory response properties of insula neurons have not previously been reported. Here, we provide the first report of a population of human single neuron data from the insula and provide comparative data from the primary auditory cortex, recorded intracranially from human participants during passive listening. In each condition, more than 330 single neurons were recorded in 11 participants. Almost a third of neurons in posterior insula and a smaller subset in anterior insula responded to simple tones and clicks. Responsive neurons were distributed throughout posterior and anterior insula and showed preferred frequency tuning. Onset latencies in the insula were similar to those in the primary auditory cortex but response durations were significantly shorter. Overall, these data highlight that insula neurons respond to auditory stimuli even in non-behaviorally relevant contexts and suggest an important contribution of audition to the postulated integrative functions of insular cortex.

EEG analysis of speaking and quiet states during different emotional music stimuli

Introduction

Music has a profound impact on human emotions, capable of eliciting a wide range of emotional responses, a phenomenon that has been effectively harnessed in the field of music therapy. Given the close relationship between music and language, researchers have begun to explore how music influences brain activity and cognitive processes by integrating artificial intelligence with advancements in neuroscience.

Methods

In this study, a total of 120 subjects were recruited, all of whom were students aged between 19 and 26 years. Each subject is required to listen to six 1-minute music segments expressing different emotions and speak at the 40-second mark. In terms of constructing the classification model, this study compares the classification performance of deep neural networks with other machine learning algorithms.

Results

The differences in EEG signals between different emotions during speech are more pronounced compared to those in a quiet state. In the classification of EEG signals for speaking and quiet states, using deep neural network algorithms can achieve accuracies of 95.84% and 96.55%, respectively.

Discussion

Under the stimulation of music with different emotions, there are certain differences in EEG between speaking and resting states. In the construction of EEG classification models, the classification performance of deep neural network algorithms is superior to other machine learning algorithms.

Music in the Air and in the Body: An Interoceptive System's Perspective on Musical Emotions, Awareness, and Time

Performing and perceiving music requires the integration of multimodal information, including sensations of one's own body. Research on musical engagement investigated emotional responses and the peripheral physiological activations involved, as well as bodily action tendencies, effects on time perception, and the role of awareness and focus of attention. The concept of interoception dedicates a central role to the insular cortex, as suggested by Craig and others, and offers a unifying framework for studying music as an activity that has always had a key role for individuals, groups, societies, with a strong bodily component. Chances and challenges of an interoceptive perspective on music are discussed.

Focal Brain Lesions Causing Acquired Amusia Map to a Common Brain Network

Music is a universal human attribute. The study of amusia, a neurologic music processing deficit, has increasingly elaborated our view on the neural organization of the musical brain. However, lesions causing amusia occur in multiple brain locations and often also cause aphasia, leaving the distinct neural networks for amusia unclear. Here, we utilized lesion network mapping to identify these networks. A systematic literature search was carried out to identify all published case reports of lesion-induced amusia. The reproducibility and specificity of the identified amusia network were then tested in an independent prospective cohort of 97 stroke patients (46 female and 51 male) with repeated structural brain imaging, specifically assessed for both music perception and language abilities. Lesion locations in the case reports were heterogeneous but connected to common brain regions, including bilateral temporoparietal and insular cortices, precentral gyrus, and cingulum. In the prospective cohort, lesions causing amusia mapped to a common brain network, centering on the right superior temporal cortex and clearly distinct from the network causally associated with aphasia. Lesion-induced longitudinal structural effects in the amusia circuit were confirmed as reduction of both gray and white matter volume, which correlated with the severity of amusia. We demonstrate that despite the heterogeneity of lesion locations disrupting music processing, there is a common brain network that is distinct from the language network. These results provide evidence for the distinct neural substrate of music processing, differentiating music-related functions from language, providing a testable target for noninvasive brain stimulation to treat amusia.

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.

Audiovisual integration in the McGurk effect is impervious to music training

The McGurk effect refers to an audiovisual speech illusion where the discrepant auditory and visual syllables produce a fused percept between the visual and auditory component. However, little is known about how individual differences contribute to the McGurk effect. Here, we examined whether music training experience-which involves audiovisual integration-can modulate the McGurk effect. Seventy-three participants completed the Goldsmiths Musical Sophistication Index (Gold-MSI) questionnaire to evaluate their music expertise on a continuous scale. Gold-MSI considers participants' daily-life exposure to music learning experiences (formal and informal), instead of merely classifying people into different groups according to how many years they have been trained in music. Participants were instructed to report, via a 3-alternative forced choice task, "what a person said": /Ba/, /Ga/ or /Da/. The experiment consisted of 96 audiovisual congruent trials and 96 audiovisual incongruent (McGurk) trials. We observed no significant correlations between the susceptibility of the McGurk effect and the different subscales of the Gold-MSI (active engagement, perceptual abilities, music training, singing abilities, emotion) or the general musical sophistication composite score. Together, these findings suggest that music training experience does not modulate audiovisual integration in speech as reflected by the McGurk effect.

Acquired amusia after a right middle cerebral artery infarction - a case study

A 62-year-old musician-MM-developed amusia after a right middle-cerebral-artery infarction. Initially, MM showed melodic deficits while discriminating pitch-related differences in melodies, musical memory problems, and impaired sensitivity to tonal structures, but normal pitch discrimination and spectral resolution thresholds, and normal cognitive and language abilities. His rhythmic processing was intact when pitch variations were removed. After 3 months, MM showed a large improvement in his sensitivity to tonality, but persistent melodic deficits and a decline in perceiving the metric structure of rhythmic sequences. We also found visual cues aided melodic processing, which is novel and beneficial for future rehabilitation practice.

Examining cortical tracking of the speech envelope in post-stroke aphasia

Introduction

People with aphasia have been shown to benefit from rhythmic elements for language production during aphasia rehabilitation. However, it is unknown whether rhythmic processing is associated with such benefits. Cortical tracking of the speech envelope (CTenv) may provide a measure of encoding of speech rhythmic properties and serve as a predictor of candidacy for rhythm-based aphasia interventions.

Methods

Electroencephalography was used to capture electrophysiological responses while Spanish speakers with aphasia (n = 9) listened to a continuous speech narrative (audiobook). The Temporal Response Function was used to estimate CTenv in the delta (associated with word- and phrase-level properties), theta (syllable-level properties), and alpha bands (attention-related properties). CTenv estimates were used to predict aphasia severity, performance in rhythmic perception and production tasks, and treatment response in a sentence-level rhythm-based intervention.

Results

CTenv in delta and theta, but not alpha, predicted aphasia severity. Neither CTenv in delta, alpha, or theta bands predicted performance in rhythmic perception or production tasks. Some evidence supported that CTenv in theta could predict sentence-level learning in aphasia, but alpha and delta did not.

Conclusion

CTenv of the syllable-level properties was relatively preserved in individuals with less language impairment. In contrast, higher encoding of word- and phrase-level properties was relatively impaired and was predictive of more severe language impairments. CTenv and treatment response to sentence-level rhythm-based interventions need to be further investigated.

The neuroscience of music – towards ecological validity

Studies in the neuroscience of music gained momentum in the 1990s as an integrated part of the well-controlled experimental research tradition. However, during the past two decades, these studies have moved toward more naturalistic, ecologically valid paradigms. Here, I introduce this move in three frameworks: (i) sound stimulation and empirical paradigms, (ii) study participants, and (iii) methods and contexts of data acquisition. I wish to provide a narrative historical overview of the development of the field and, in parallel, to stimulate innovative thinking to further advance the ecological validity of the studies without overlooking experimental rigor.

Music perception in acquired prosopagnosia

BACKGROUND

Acquired prosopagnosia is often associated with other deficits such as dyschromatopsia and topographagnosia, from damage to adjacent perceptual networks. A recent study showed that some subjects with developmental prosopagnosia also have congenital amusia, but problems with music perception have not been described with the acquired variant.

OBJECTIVE

Our goal was to determine if music perception was also impaired in subjects with acquired prosopagnosia, and if so, its anatomic correlate.

METHOD

We studied eight subjects with acquired prosopagnosia, all of whom had extensive neuropsychological and neuroimaging testing. They performed a battery of tests evaluating pitch and rhythm processing, including the Montréal Battery for the Evaluation of Amusia.

RESULTS

At the group level, subjects with anterior temporal lesions were impaired in pitch perception relative to the control group, but not those with occipitotemporal lesions. Three of eight subjects with acquired prosopagnosia had impaired musical pitch perception while rhythm perception was spared. Two of the three also showed reduced musical memory. These three reported alterations in their emotional experience of music: one reported music anhedonia and aversion, while the remaining two had changes consistent with musicophilia. The lesions of these three subjects affected the right or bilateral temporal poles as well as the right amygdala and insula. None of the three prosopagnosic subjects with lesions limited to the inferior occipitotemporal cortex exhibited impaired pitch perception or musical memory, or reported changes in music appreciation.

CONCLUSION

Together with the results of our previous studies of voice recognition, these findings indicate an anterior ventral syndrome that can include the amnestic variant of prosopagnosia, phonagnosia, and various alterations in music perception, including acquired amusia, reduced musical memory, and subjective reports of altered emotional experience of music.

Identifying a brain network for musical rhythm: A functional neuroimaging meta-analysis and systematic review

We conducted a systematic review and meta-analysis of 30 functional magnetic resonance imaging studies investigating processing of musical rhythms in neurotypical adults. First, we identified a general network for musical rhythm, encompassing all relevant sensory and motor processes (Beat-based, rest baseline, 12 contrasts) which revealed a large network involving auditory and motor regions. This network included the bilateral superior temporal cortices, supplementary motor area (SMA), putamen, and cerebellum. Second, we identified more precise loci for beat-based musical rhythms (Beat-based, audio-motor control, 8 contrasts) in the bilateral putamen. Third, we identified regions modulated by beat based rhythmic complexity (Complexity, 16 contrasts) which included the bilateral SMA-proper/pre-SMA, cerebellum, inferior parietal regions, and right temporal areas. This meta-analysis suggests that musical rhythm is largely represented in a bilateral cortico-subcortical network. Our findings align with existing theoretical frameworks about auditory-motor coupling to a musical beat and provide a foundation for studying how the neural bases of musical rhythm may overlap with other cognitive domains.

Subcortical Cognition: The Fruit Below the Rind

Cognitive neuroscience has highlighted the cerebral cortex while often overlooking subcortical structures. This cortical proclivity is found in basic and translational research on many aspects of cognition, especially higher cognitive domains such as language, reading, music, and math. We suggest that, for both anatomical and evolutionary reasons, multiple subcortical structures play substantial roles across higher and lower cognition. We present a comprehensive review of existing evidence, which indeed reveals extensive subcortical contributions in multiple cognitive domains. We argue that the findings are overall both real and important. Next, we advance a theoretical framework to capture the nature of (sub)cortical contributions to cognition. Finally, we propose how new subcortical cognitive roles can be identified by leveraging anatomical and evolutionary principles, and we describe specific methods that can be used to reveal subcortical cognition. Altogether, this review aims to advance cognitive neuroscience by highlighting subcortical cognition and facilitating its future investigation. Expected final online publication date for the Annual Review of Neuroscience, Volume 45 is July 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Get in Sync: Active Ingredients and Patient Profiles in Scripted-Sentence Learning in Spanish Speakers With Aphasia

PURPOSE

Script training is a well-established treatment for aphasia, but its evidence comes almost exclusively from monolingual English speakers with aphasia. Furthermore, its active ingredients and profiles of people with aphasia (PWA) that respond to this treatment remain understudied. This study aimed to adapt a scripted-sentence learning protocol to Colombian Spanish speakers with aphasia, investigate speech entrainment (i.e., unison production of sentences) as an active ingredient for scripted-sentence learning, and identify patient profiles associated with better scripted-sentence learning.

METHOD

Fourteen monolingual Spanish speakers with aphasia learned a set of 30 sentences. To examine speech entrainment as an active ingredient for scripted-sentence learning, we investigated whether sentences containing externally added rhythmic cues (involving stress-aligned vs. metronomic rhythmic cues) would result in better scripted-sentence learning compared with control sentences. Learning was measured via postsession probes and analyzed using mixed-effects logistic regression models. The relationship between scripted-sentence learning and baseline language and rhythmic processing measures was also examined.

RESULTS

Significant scripted-sentence learning over time indicated a successful adaptation of a script-training protocol to Spanish. PWA learned significantly more scripted sentences in the rhythmically enhanced conditions compared with the control condition. There were no differences between rhythmically enhanced conditions (stress-aligned vs. metronomic). In terms of patient profiles, it was found that PWA with more severe aphasia demonstrated larger learning gains, but rhythmic processing showed little association with learning estimates.

CONCLUSIONS

To our knowledge, this study provides the first adaptation of a scripted-sentence learning protocol for monolingual Spanish speakers with aphasia, demonstrating cross-linguistic benefits of script training interventions. Highlighting rhythmic features during speech entrainment facilitated scripted-sentence learning in Spanish speakers with aphasia, suggesting that speech entrainment may be an active ingredient for scripted-sentence learning. More severe aphasia was associated with better scripted-sentence learning, suggesting that more severely impaired individuals are likely to benefit most from this treatment.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.19241847.

Music processing and amusia

Music is a universal and important human trait, which is orchestrated by complex brain network centered in the temporal lobe but connecting broadly to multiple cortical and subcortical regions. In the human brain, music engages a widespread bilateral network of regions that govern auditory perception, syntactic and semantic processing, attention and memory, emotion and reward, and motor skills. The ability to perceive or produce music can be severely impaired either due to abnormal brain development or brain damage, leading to a condition called amusia. Modern neuroimaging studies of amusia have provided valuable knowledge about the structure and function of specific brain regions and white matter pathways that are crucial for music perception, highlighting the role of the right frontotemporal network in this process. In this chapter, we provide an overview on the neural basis of music processing in a healthy brain and review evidence obtained from the studies of congenital and acquired amusia.

Clinical and Neural Predictors of Treatment Response to Music Listening Intervention after Stroke

Patients with post-stroke impairments present often significant variation in response to therapeutic interventions. Recent studies have shown that daily music listening can aid post-stroke recovery of language and memory, but reliable predictors of treatment response are unknown. Utilizing data from the music intervention arms of a single-blind randomized controlled trial (RCT) on stroke patients (N = 31), we built regression models to predict the treatment response of a two-month music listening intervention on language skills and verbal memory with baseline demographic, clinical and musical data as well as fMRI data from a music listening task. Clinically, greater improvement in verbal memory and language skills after the music listening intervention were predicted by the severity of the initial deficit and educational level. Neurally, greater baseline fMRI activation during vocal music listening in the left parietal cortical and medial frontal areas predicted greater treatment-induced improvement in language skills and greater baseline engagement of the auditory network during instrumental music listening predicted improvement in both verbal memory and language skills. Our results suggest that clinical, demographic, and neuroimaging data predicts music listening treatment response. This data could be used clinically to target music-based treatments.

Right ventral stream damage underlies both poststroke aprosodia and amusia

BACKGROUND AND PURPOSE

This study was undertaken to determine and compare lesion patterns and structural dysconnectivity underlying poststroke aprosodia and amusia, using a data-driven multimodal neuroimaging approach.

METHODS

Thirty-nine patients with right or left hemisphere stroke were enrolled in a cohort study and tested for linguistic and affective prosody perception and musical pitch and rhythm perception at subacute and 3-month poststroke stages. Participants listened to words spoken with different prosodic stress that changed their meaning, and to words spoken with six different emotions, and chose which meaning or emotion was expressed. In the music tasks, participants judged pairs of short melodies as the same or different in terms of pitch or rhythm. Structural magnetic resonance imaging data were acquired at both stages, and machine learning-based lesion-symptom mapping and deterministic tractography were used to identify lesion patterns and damaged white matter pathways giving rise to aprosodia and amusia.

RESULTS

Both aprosodia and amusia were behaviorally strongly correlated and associated with similar lesion patterns in right frontoinsular and striatal areas. In multiple regression models, reduced fractional anisotropy and lower tract volume of the right inferior fronto-occipital fasciculus were the strongest predictors for both disorders, over time.

CONCLUSIONS

These results highlight a common origin of aprosodia and amusia, both arising from damage and disconnection of the right ventral auditory stream integrating rhythmic-melodic acoustic information in prosody and music. Comorbidity of these disabilities may worsen the prognosis and affect rehabilitation success.

The origins of music in (musi)language

The view of music as a byproduct of other cognitive functions has been deemed incomplete or incorrect. Revisiting the six lines of evidence that support this conclusion, it is argued that it is unclear how the hypothesis that music has its origins in (musi)language is discarded. Two additional promising research lines that can support or discard the byproduct hypothesis are presented.

Pitch and Rhythm Perception and Verbal Short-Term Memory in Acute Traumatic Brain Injury

Music perception deficits are common following acquired brain injury due to stroke, epilepsy surgeries, and aneurysmal clipping. Few studies have examined these deficits following traumatic brain injury (TBI), resulting in an under-diagnosis in this population. We aimed to (1) compare TBI patients to controls on pitch and rhythm perception during the acute phase; (2) determine whether pitch and rhythm perception disorders co-occur; (3) examine lateralization of injury in the context of pitch and rhythm perception; and (4) determine the relationship between verbal short-term memory (STM) and pitch and rhythm perception. Music perception was examined using the Scale and Rhythm tests of the Montreal Battery of Evaluation of Amusia, in association with CT scans to identify lesion laterality. Verbal short-term memory was examined using Digit Span Forward. TBI patients had greater impairment than controls, with 43% demonstrating deficits in pitch perception, and 40% in rhythm perception. Deficits were greater with right hemisphere damage than left. Pitch and rhythm deficits co-occurred 31% of the time, suggesting partly dissociable networks. There was a dissociation between performance on verbal STM and pitch and rhythm perception 39 to 42% of the time (respectively), with most individuals (92%) demonstrating intact verbal STM, with impaired pitch or rhythm perception. The clinical implications of music perception deficits following TBI are discussed.

Vocal music listening enhances post-stroke language network reorganization

Listening to vocal music has been recently shown to improve language recovery in stroke survivors. The neuroplasticity mechanisms supporting this effect are, however, still unknown. Using data from a three-arm single-blind randomized controlled trial including acute stroke patients (N=38) and a 3-month follow-up, we set out to compare the neuroplasticity effects of daily listening to self-selected vocal music, instrumental music, and audiobooks on both brain activity and structural connectivity of the language network. Using deterministic tractography we show that the 3-month intervention induced an enhancement of the microstructural properties of the left frontal aslant tract (FAT) for the vocal music group as compared to the audiobook group. Importantly, this increase in the strength of the structural connectivity of the left FAT correlated with improved language skills. Analyses of stimulus-specific activation changes showed that the vocal music group exhibited increased activations in the frontal termination points of the left FAT during vocal music listening as compared to the audiobook group from acute to 3-month post-stroke stage. The increased activity correlated with the structural neuroplasticity changes in the left FAT. These results suggest that the beneficial effects of vocal music listening on post-stroke language recovery are underpinned by structural neuroplasticity changes within the language network and extend our understanding of music-based interventions in stroke rehabilitation.Significance statementPost-stroke language deficits have a devastating effect on patients and their families. Current treatments yield highly variable outcomes and the evidence for their long-term effects is limited. Patients often receive insufficient treatment that are predominantly given outside the optimal time window for brain plasticity. Post-stroke vocal music listening improves language outcome which is underpinned by neuroplasticity changes within the language network. Vocal music listening provides a complementary rehabilitation strategy which could be safely implemented in the early stages of stroke rehabilitation and seems to specifically target language symptoms and recovering language network.

Abnormal singing can identify patients with right hemisphere cortical strokes at risk for impaired prosody

Despite lacking aphasia seen with left hemisphere (LH) infarcts involving the middle cerebral artery territory, right hemisphere (RH) strokes can result in significant difficulties in affective prosody. These impairments may be more difficult to identify but lead to significant communication problems.We determine if evaluation of singing can accurately identify stroke patients with cortical RH infarcts at risk for prosodic impairment who may benefit from rehabilitation.A prospective cohort of 36 patients evaluated with acute ischemic stroke was recruited. Participants underwent an experimental battery evaluating their singing, prosody comprehension, and prosody production. Singing samples were rated by 2 independent reviewers as subjectively "normal" or "abnormal," and analyzed for properties of the fundamental frequency. Relationships between infarct location, singing, and prosody performance were evaluated using t tests and chi-squared analysis.Eighty percent of participants with LH cortical strokes were unable to successfully complete any of the tasks due to severe aphasia. For the remainder, singing ratings corresponded to stroke location for 68% of patients. RH cortical strokes demonstrated a lower mean fundamental frequency while singing than those with subcortical infarcts (176.8 vs 130.4, P = 0.02). They also made more errors on tasks of prosody comprehension (28.6 vs 16.0, P < 0.001) and production (40.4 vs 18.4, P < 0.001).Patients with RH cortical infarcts are more likely to exhibit impaired prosody comprehension and production and demonstrate the poor variation of tone when singing compared to patients with subcortical infarcts. A simple singing screen is able to successfully identify patients with cortical lesions and potential prosodic deficits.

The Neurological Basis of Developmental Dyslexia and Related Disorders: A Reappraisal of the Temporal Hypothesis, Twenty Years on

In a now-classic article published a couple of decades ago (Brain, 2000; 123: 2373-2399), I proposed an "extended temporal processing deficit hypothesis of dyslexia", suggesting that a deficit in temporal processing could explain not only language-related peculiarities usually noticed in dyslexic children, but also a wider range of symptoms related to impaired processing of time in general. In the present review paper, I will revisit this "historical" hypothesis both in the light of a new clinical perspective, including the central yet poorly explained notion of comorbidity, and also taking a new look at the most recent experimental work, mainly focusing on brain imaging data. First, consistent with daily clinical practice, I propose to distinguish three groups of children who fail to learn to read, of fairly equal occurrence, who share the same initial presentation (difficulty in mastering the rules of grapheme-phoneme correspondence) but with differing associated signs and/or comorbid conditions (language disorders in the first group, attentional deficits in the second one, and motor coordination problems in the last one), thus suggesting, at least in part, potentially different triggering mechanisms. It is then suggested, in the light of brain imaging information available to date, that the three main clinical presentations/associations of cognitive impairments that compromise reading skills acquisition correspond to three distinct patterns of miswiring or "disconnectivity" in specific brain networks which have in common their involvement in the process of learning and their heavy reliance on temporal features of information processing. With reference to the classic temporal processing deficit of dyslexia and to recent evidence of an inability of the dyslexic brain to achieve adequate coupling of oscillatory brain activity to the temporal features of external events, a general model is proposed according to which a common mechanism of temporal uncoupling between various disconnected-and/or mis-wired-processors may account for distinct forms of specific learning disorders, with reading impairment being a more or less constant feature. Finally, the potential therapeutic implications of such a view are considered, with special emphasis on methods seeking to enhance cross-modal connectivity between separate brain systems, including those using rhythmic and musical training in dyslexic patients.

Impaired face recognition is associated with abnormal gray matter volume in the posterior cingulate cortex in congenital amusia

Congenital amusia is as a neurodevelopment disorder primarily defined by impairment in pitch discrimination and pitch memory. Interestingly, it has been reported that individuals with congenital amusia also exhibit deficits in face recognition (prosopagnosia). One explanation of such comorbidity is that the neural substrates of pitch recognition and face recognition may be similar. To test this hypothesis, face recognition ability was assessed using the Cambridge Face Memory Test (CFMT) and gray matter volume was determined through voxel-based morphometry (VBM) among participants with and without congenital amusia. As expected, participants with amusia performed worse on the CFMT test and showed reduced gray matter volume (GMV) in the middle temporal gyrus (MTG), the superior temporal gyrus (STG), and the posterior cingulate cortex (PCC) in the right hemisphere, when compared with matched controls. Furthermore, correlation analyses demonstrated that the CFMT score was positively related to MTG, STG, and PCC GMV in all participants, while separate analyses of each group found a positive correlation of CFMT score and PCC GMV in amusics. These findings suggest that face recognition is associated with a widely distributed microstructural network in the human brain and the PCC plays an important role in both pitch recognition and face recognition in amusics. In addition, neurodevelopmental disorders such as congenital amusia and prosopagnosia may share a common neural substrate.

Auditory beat perception is related to speech output fluency in post-stroke aphasia

Aphasia affects at least one third of stroke survivors, and there is increasing awareness that more fundamental deficits in auditory processing might contribute to impaired language performance in such individuals. We performed a comprehensive battery of psychoacoustic tasks assessing the perception of tone pairs and sequences across the domains of pitch, rhythm and timbre in 17 individuals with post-stroke aphasia and 17 controls. At the level of individual differences we demonstrated a correlation between metrical pattern (beat) perception and speech output fluency with strong effect (Spearman's rho = 0.72). This dissociated from more basic auditory timing perception, which did not correlate with output fluency. This was also specific in terms of the language and cognitive measures, amongst which phonological, semantic and executive function did not correlate with beat detection. We interpret the data in terms of a requirement for the analysis of the metrical structure of sound to construct fluent output, with both being a function of higher-order "temporal scaffolding". The beat perception task herein allows measurement of timing analysis without any need to account for motor output deficit, and could be a potential clinical tool to examine this. This work suggests strategies to improve fluency after stroke by training in metrical pattern perception.

Auditory agnosia with anosognosia

A 66-year-old right-handed female medical doctor suffered two consecutive cardioembolic strokes, initially affecting the right frontal lobe and the right insula, followed by a lesion in the left temporal lobe. The patient presented with distinctive phenomenology of general auditory agnosia with anosognosia for the deficit. She did not understand verbal requests and her answers to oral questions were fluent but unrelated to the topic. However, she was able to correctly answer written questions, name objects, and fluently describe their purpose, which is characteristic for verbal auditory agnosia. She was also unable to recognise environmental sounds or to recognise and repeat any melody. These inabilities represent environmental sound agnosia and amusia, respectively. Surprisingly, she was not aware of the problem, not asking any questions regarding her symptoms, and avoiding discussing her inability to understand spoken language, which is indicative of anosognosia. The deficits in our patient followed a distinct pattern of recovery. The verbal auditory agnosia was the first to resolve, followed by environmental sound agnosia. Amusia persisted the longest. The patient was clinically assessed from the first day of symptom onset and the evolution of symptoms was video documented. We give a detailed account of the patient's behaviour and provide results of audiological and neuropsychological evaluations. We discuss the anatomy of auditory agnosia and anosognosia relevant to the case. This case study may serve to better understand auditory agnosia in clinical settings. It is important to distinguish auditory agnosia from Wernicke's aphasia, because use of written language may enable normal communication.

Arcuate fasciculus architecture is associated with individual differences in pre-attentive detection of unpredicted music changes

The mismatch negativity (MMN) is an event related brain potential (ERP) elicited by unpredicted sounds presented in a sequence of repeated auditory stimuli. The neural sources of the MMN have been previously attributed to a fronto-temporo-parietal network which crucially overlaps with the so-called auditory dorsal stream, involving inferior and middle frontal, inferior parietal, and superior and middle temporal regions. These cortical areas are structurally connected by the arcuate fasciculus (AF), a three-branch pathway supporting the feedback-feedforward loop involved in auditory-motor integration, auditory working memory, storage of acoustic templates, as well as comparison and update of those templates. Here, we characterized the individual differences in the white-matter macrostructural properties of the AF and explored their link to the electrophysiological marker of passive change detection gathered in a melodic multifeature MMN-EEG paradigm in 26 healthy young adults without musical training. Our results show that left fronto-temporal white-matter connectivity plays an important role in the pre-attentive detection of rhythm modulations within a melody. Previous studies have shown that this AF segment is also critical for language processing and learning. This strong coupling between structure and function in auditory change detection might be related to life-time linguistic (and possibly musical) exposure and experiences, as well as to timing processing specialization of the left auditory cortex. To the best of our knowledge, this is the first time in which the relationship between neurophysiological (EEG) and brain white-matter connectivity indexes using DTI-tractography are studied together. Thus, the present results, although still exploratory, add to the existing evidence on the importance of studying the constraints imposed on cognitive functions by the underlying structural connectivity.

Auditory and frontal anatomic correlates of pitch discrimination in musicians, non-musicians, and children without musical training

Individual differences in pitch discrimination have been associated with the volume of both the bilateral Heschl's gyrus and the right inferior frontal gyrus (IFG). However, most of these studies used samples composed of individuals with different amounts of musical training. Here, we investigated the relationship between pitch discrimination and individual differences in the gray matter (GM) volume of these brain structures in 32 adult musicians, 28 adult non-musicians, and 32 children without musical training. The results showed that (i) the individuals without musical training (whether children or adults) who were better at pitch discrimination had greater volume of auditory regions, whereas (ii) musicians with better pitch discrimination had greater volume of the IFG. These results suggest that the relationship between pitch discrimination and the volume of auditory regions is innately established early in life, and that musical training modulates the volume of the IFG, probably improving audio-motor connectivity. This is the first study to detect a relationship between pitch discrimination ability and GM volume before beginning any musical training in children and adults.

Insula and Amygdala Atrophy Are Associated With Functional Impairment in Subjects With Presbycusis

Hearing loss is an important risk factor for dementia. However, the mechanisms that relate these disorders are still unknown. As a proxy of this relationship, we studied the structural brain changes associated with functional impairment in activities of daily living in subjects with age related hearing loss, or presbycusis. One hundred eleven independent, non-demented subjects older than 65 years recruited in the ANDES cohort were evaluated using a combined approach including (i) audiological tests: hearing thresholds and cochlear function measured by pure tone averages and the distortion product otoacoustic emissions respectively; (ii) behavioral variables: cognitive, neuropsychiatric, and functional impairment in activities of daily living measured by validated questionnaires; and (iii) structural brain imaging—assessed by magnetic resonance imaging at 3 Tesla. The mean age of the recruited subjects (69 females) was 73.95 ± 5.47 years (mean ± SD) with an average educational level of 9.44 ± 4.2 years of schooling. According to the audiometric hearing thresholds and presence of otoacoustic emissions, we studied three groups: controls with normal hearing (n = 36), presbycusis with preserved cochlear function (n = 33), and presbycusis with cochlear dysfunction (n = 38). We found a significant association (R²_D = 0.17) between the number of detected otoacoustic emissions and apathy symptoms. The presbycusis with cochlear dysfunction group had worse performance than controls in global cognition, language and executive functions, and severe apathy symptoms than the other groups. The neuropsychiatric symptoms and language deficits were the main determinants of functional impairment in both groups of subjects with presbycusis. Atrophy of insula, amygdala, and other temporal areas were related with functional impairment, apathy, and language deficits in the presbycusis with cochlear dysfunction group. We conclude that (i) the neuropsychiatric symptoms had a major effect on functional loss in subjects with presbycusis, (ii) cochlear dysfunction is relevant for the association between hearing loss and behavioral impairment, and (iii) atrophy of the insula and amygdala among other temporal areas are related with hearing loss and behavioral impairment.

Neural architectures of music - Insights from acquired amusia

The ability to perceive and produce music is a quintessential element of human life, present in all known cultures. Modern functional neuroimaging has revealed that music listening activates a large-scale bilateral network of cortical and subcortical regions in the healthy brain. Even the most accurate structural studies do not reveal which brain areas are critical and causally linked to music processing. Such questions may be answered by analysing the effects of focal brain lesions in patients´ ability to perceive music. In this sense, acquired amusia after stroke provides a unique opportunity to investigate the neural architectures crucial for normal music processing. Based on the first large-scale longitudinal studies on stroke-induced amusia using modern multi-modal magnetic resonance imaging (MRI) techniques, such as advanced lesion-symptom mapping, grey and white matter morphometry, tractography and functional connectivity, we discuss neural structures critical for music processing, consider music processing in light of the dual-stream model in the right hemisphere, and propose a neural model for acquired amusia.

Language and cognitive outcomes after childhood stroke: Theoretical implications for hemispheric specialization

The purpose of this study was to investigate language and cognitive outcomes following severe childhood stroke, and the role of age at stroke according to lesion lateralization. We retrospectively included children consecutively admitted to a physical medicine and rehabilitation department between 1992 and 2015 following childhood stroke (age at stroke 1 month to15 years). Data collection included demographic and clinical information, results of cognitive assessments on the Wechsler Intelligence scales, detailed language assessments by speech and language therapists, and long-term academic outcome. Overall, 184 children (52% boys; mean age at assessment = 8.5 years, range .7-15.4 years) were hospitalized following ischemic (n = 79) or hemorrhagic (n = 105) stroke. After a median time since stroke of 4 months (n = 135), mean Full-Scale, Verbal, and Performance Intellectual Quotient (FSIQ, VIQ and PIQ) were 85 (SD = 19), 93 (SD = 22), and 85 (SD = 20), respectively. In language tests (n = 130) assessing lexical and syntactic expression and comprehension, 26%-53% of the children exhibited impairments (scores <2SD). After a median follow-up of 40 months, only 27% of the children were following a normal curriculum without adaptations or delay, and 27% were attending special education programs. School situation was strongly associated with language and FSIQ scores. Language and verbal IQ scores were significantly lower (p < .01) among patients with lesions in the left hemisphere as opposed to the right. After a left hemisphere lesion, language skills were not associated with age at stroke, but for right hemisphere lesions, language was more impaired among children who were younger at stroke onset. PIQ tended to correlate positively with age at stroke in left hemisphere lesions (poorer PIQ in early lesions) and negatively for right hemisphere lesions (poorer PIQ in late lesions). These findings, discussed in the light of the brain vulnerability and plasticity hypotheses, are in favor of a developmental view of hemispheric specialization.

Cognitive and neural mechanisms underlying the mnemonic effect of songs after stroke

Sung melody provides a mnemonic cue that can enhance the acquisition of novel verbal material in healthy subjects. Recent evidence suggests that also stroke patients, especially those with mild aphasia, can learn and recall novel narrative stories better when they are presented in sung than spoken format. Extending this finding, the present study explored the cognitive mechanisms underlying this effect by determining whether learning and recall of novel sung vs. spoken stories show a differential pattern of serial position effects (SPEs) and chunking effects in non-aphasic and aphasic stroke patients (N = 31) studied 6 months post-stroke. The structural neural correlates of these effects were also explored using voxel-based morphometry (VBM) and deterministic tractography (DT) analyses of structural MRI data. Non-aphasic patients showed more stable recall with reduced SPEs in the sung than spoken task, which was coupled with greater volume and integrity (indicated by fractional anisotropy, FA) of the left arcuate fasciculus. In contrast, compared to non-aphasic patients, the aphasic patients showed a larger recency effect (better recall of the last vs. middle part of the story) and enhanced chunking (larger units of correctly recalled consecutive items) in the sung than spoken task. In aphasics, the enhanced chunking and better recall on the middle verse in the sung vs. spoken task correlated also with better ability to perceive emotional prosody in speech. Neurally, the sung > spoken recency effect in aphasic patients was coupled with greater grey matter volume in a bilateral network of temporal, frontal, and parietal regions and also greater volume of the right inferior fronto-occipital fasciculus (IFOF). These results provide novel cognitive and neurobiological insight on how a repetitive sung melody can function as a verbal mnemonic aid after stroke.

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Non-aphasic stroke patients show more stable recall of sung than spoken stories.

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Aphasic patients show larger recency and chunking effects to sung vs. spoken stories.

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The left dorsal pathway mediates better recall of sung stories in non-aphasics.

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The right ventral pathway mediates better recall of sung stories in aphasics.

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Large-scale bilateral cortical networks are linked to musical mnemonics in aphasia.

Separate Contribution of Striatum Volume and Pitch Discrimination to Individual Differences in Music Reward

Individual differences in the level of pleasure induced by music have been associated with the response of the striatum and differences in functional connectivity between the striatum and the auditory cortex. In this study, we tested whether individual differences in music reward are related to the structure of the striatum and the ability to discriminate pitch. We acquired a 3-D magnetization-prepared rapid-acquisition gradient-echo image for 32 musicians and 26 nonmusicians who completed a music-reward questionnaire and a test of pitch discrimination. The analysis of both groups together showed that sensitivity to music reward correlated negatively with the volume of both the caudate and nucleus accumbens and correlated positively with pitch-discrimination abilities. Moreover, musicianship, pitch discrimination, and caudate volume significantly predicted individual differences in music reward. These results are consistent with the proposal that individual differences in music reward depend on the interplay between auditory abilities and the reward network.

Musical Instrument Practice Predicts White Matter Microstructure and Cognitive Abilities in Childhood

Musical training has been associated with advantages in cognitive measures of IQ and verbal ability, as well as neural measures including white matter microstructural properties in the corpus callosum (CC) and the superior longitudinal fasciculus (SLF). We hypothesized that children who have musical training will have different microstructural properties in the SLF and CC. One hundred children aged 7.9-9.9 years (mean age 8.7) were surveyed for their musical activities, completed neuropsychological testing for general cognitive abilities, and underwent diffusion tensor imaging (DTI) as part of a larger study. Children who play a musical instrument for more than 0.5 h per week (n = 34) had higher scores on verbal ability and intellectual ability (standardized scores from the Woodcock-Johnson Tests of Cognitive Abilities), as well as higher axial diffusivity (AD) in the left SLF than those who did not play a musical instrument (n = 66). Furthermore, the intensity of musical practice, quantified as the number of hours of music practice per week, was correlated with axial diffusivity (AD) in the left SLF. Results are not explained by age, sex, socio-economic status, or physical fitness of the participants. The results suggest that the relationship between musical practice and intellectual ability is related to the maturation of white matter pathways in the auditory-motor system. The findings suggest that musical training may be a means of improving cognitive and brain health during development.

Autistic traits, resting-state connectivity, and absolute pitch in professional musicians: shared and distinct neural features

Background

Recent studies indicate increased autistic traits in musicians with absolute pitch and a higher proportion of absolute pitch in people with autism. Theoretical accounts connect both of these with shared neural principles of local hyper- and global hypoconnectivity, enhanced perceptual functioning, and a detail-focused cognitive style. This is the first study to investigate absolute pitch proficiency, autistic traits, and brain correlates in the same study.

Sample and methods

Graph theoretical analysis was conducted on resting-state (eyes closed and eyes open) EEG connectivity (wPLI, weighted phase lag index) matrices obtained from 31 absolute pitch (AP) and 33 relative pitch (RP) professional musicians. Small-worldness, global clustering coefficient, and average path length were related to autistic traits, passive (tone identification) and active (pitch adjustment) absolute pitch proficiency, and onset of musical training using Welch two-sample tests, correlations, and general linear models.

Results

Analyses revealed increased path length (delta 2–4 Hz), reduced clustering (beta 13–18 Hz), reduced small-worldness (gamma 30–60 Hz), and increased autistic traits for AP compared to RP. Only clustering values (beta 13–18 Hz) were predicted by both AP proficiency and autistic traits. Post hoc single connection permutation tests among raw wPLI matrices in the beta band (13–18 Hz) revealed widely reduced interhemispheric connectivity between bilateral auditory-related electrode positions along with higher connectivity between F7–F8 and F8–P9 for AP. Pitch-naming ability and pitch adjustment ability were predicted by path length, clustering, autistic traits, and onset of musical training (for pitch adjustment) explaining 44% and 38% of variance, respectively.

Conclusions

Results show both shared and distinct neural features between AP and autistic traits. Differences in the beta range were associated with higher autistic traits in the same population. In general, AP musicians exhibit a widely underconnected brain with reduced functional integration and reduced small-world property during resting state. This might be partly related to autism-specific brain connectivity, while differences in path length and small-worldness reflect other ability-specific influences. This is further evidenced for different pathways in the acquisition and development of absolute pitch, likely influenced by both genetic and environmental factors and their interaction.

Inefficient Involvement of Insula in Sensorineural Hearing Loss

The insular cortex plays an important role in multimodal sensory processing, audio-visual integration and emotion; however, little is known about how the insula is affected by auditory deprivation due to sensorineural hearing loss (SNHL). To address this issue, we used structural and functional magnetic resonance imaging to determine if the neural activity within the insula and its interregional functional connectivity (FC) was disrupted by SNHL and if these alterations were correlated clinical measures of emotion and cognition. Thirty-five SNHL subjects and 54 Controls enrolled in our study underwent auditory evaluation, neuropsychological assessments, functional and structure MRI, respectively. Twenty five patients and 20 Controls underwent arterial spin labeling scanning. FC of six insula subdivisions were assessed and the FC results were compared to the neuropsychological tests. Interregional connections were also compared among insula-associated networks, including salience network (SN), default mode network (DMN), and central executive network (CEN). Compared to Controls, SNHL subjects demonstrated hyperperfusion in the insula and significantly decreased FC between some insula subdivisions and other brain regions, including thalamus, putamen, precentral gyrus, postcentral gyrus, mid-cingulate cortex, dorsolateral prefrontal cortex, rolandic operculum. Anxiety, depression and cognitive impairments were correlated with FC values. Abnormal interactions among SN, DMN, and CEN were observed in SNHL group. Our result provides support for the "inefficient high-order control" theory of the insula in which the auditory deprivation caused by SNHL contributes to impaired sensory integration and central deficits in emotional and cognitive processing.

Golden oldies and silver brains: Deficits, preservation, learning, and rehabilitation effects of music in ageing-related neurological disorders

During the last decades, there have been major advances in mapping the brain regions that underlie our ability to perceive, experience, and produce music and how musical training can shape the structure and function of the brain. This progress has fueled and renewed clinical interest towards uncovering the neural basis for the impaired or preserved processing of music in different neurological disorders and how music-based interventions can be used in their rehabilitation and care. This article reviews our contribution to and the state-of-the-art of this field. We will provide a short overview outlining the key brain networks that participate in the processing of music and singing in the healthy brain and then present recent findings on the following key music-related research topics in neurological disorders: (i) the neural architecture underlying deficient processing of music (amusia), (ii) the preservation of singing in aphasia and music-evoked emotions and memories in Alzheimer's disease, (iii) the mnemonic impact of songs as a verbal learning tool, and (iv) the cognitive, emotional, and neural efficacy of music-based interventions and activities in the rehabilitation and care of major ageing-related neurological illnesses (stroke, Alzheimer's disease, and Parkinson's disease).

Musical deficits and cortical thickness in people with schizophrenia

Investigation of acquired amusia caused by brain damage suggested that cortical lesions of the right hemisphere contributed to musical deficits. We previously reported reduced musical ability in schizophrenia; these deficits were correlated with clinical manifestations such as cognitive dysfunction and negative symptoms. However, the neural substrate underlying the musical disability in schizophrenia remains unclear. We investigated the relationship between musical deficits and cortical thickness in patients with schizophrenia using structural MRI. We recruited 24 patients (13 males; age mean=45.9years old), and 22 controls (14 males, age mean=43.5years old). Musical ability was assessed with the Montreal Battery for Evaluation of Amusia (MBEA), cognitive function with the Brief Assessment of Cognition in Schizophrenia (BACS) and clinical features of illness with the Positive and Negative Syndrome Scale (PANSS). MRI Images were acquired and processed using FreeSurfer. Surface-based analysis showed that thinner cortex in left temporal and inferior frontal region was associated with lower musical ability in schizophrenia. In contrast, in controls thicker cortex in the left supramarginal region was correlated with lower musical ability. These results shed light on the clinical pathology underlying the associations of musical ability, cognitive dysfunction and negative symptoms in patients with schizophrenia.

Sung melody enhances verbal learning and recall after stroke

Coupling novel verbal material with a musical melody can potentially aid in its learning and recall in healthy subjects, but this has never been systematically studied in stroke patients with cognitive deficits. In a counterbalanced design, we presented novel verbal material (short narrative stories) in both spoken and sung formats to stroke patients at the acute poststroke stage and 6 months poststroke. The task comprised three learning trials and a delayed recall trial. Memory performance on the spoken and sung tasks did not differ at the acute stage, whereas sung stories were learned and recalled significantly better compared with spoken stories at the 6 months poststroke stage. Interestingly, this pattern of results was evident especially in patients with mild aphasia, in whom the learning of sung versus spoken stories improved more from the acute to the 6-month stages compared with nonaphasic patients. Overall, these findings suggest that singing could be used as a mnemonic aid in the learning of novel verbal material in later stages of recovery after stroke.

Reverse Engineering Tone-Deafness: Disrupting Pitch-Matching by Creating Temporary Dysfunctions in the Auditory-Motor Network

Perceiving and producing vocal sounds are important functions of the auditory-motor system and are fundamental to communication. Prior studies have identified a network of brain regions involved in pitch production, specifically pitch matching. Here we reverse engineer the function of the auditory perception-production network by targeting specific cortical regions (e.g., right and left posterior superior temporal (pSTG) and posterior inferior frontal gyri (pIFG)) with cathodal transcranial direct current stimulation (tDCS)—commonly found to decrease excitability in the underlying cortical region—allowing us to causally test the role of particular nodes in this network. Performance on a pitch-matching task was determined before and after 20 min of cathodal stimulation. Acoustic analyses of pitch productions showed impaired accuracy after cathodal stimulation to the left pIFG and the right pSTG in comparison to sham stimulation. Both regions share particular roles in the feedback and feedforward motor control of pitched vocal production with a differential hemispheric dominance.

Factors affecting pitch discrimination performance in a cohort of extensively phenotyped healthy volunteers

Despite efforts to characterize the different aspects of musical abilities in humans, many elements of this complex area remain unknown. Musical abilities are known to be associated with factors like intelligence, training, and sex, but a comprehensive evaluation of the simultaneous impact of multiple factors has not yet been performed. Here, we assessed 918 healthy volunteers for pitch discrimination abilities—their ability to tell two tones close in pitch apart. We identified the minimal threshold that the participants could detect, and we found that better performance was associated with higher intelligence, East Asian ancestry, male sex, younger age, formal music training–especially before age 6–and English as the native language. All these factors remained significant when controlling for the others, with general intelligence, musical training, and male sex having the biggest impacts. We also performed a small GWAS and gene-based collapsing analysis, identifying no significant associations. Future genetic studies of musical abilities should involve large sample sizes and an unbiased genome-wide approach, with the factors highlighted here included as important covariates.

Electrical Neuroimaging of Music Processing Reveals Mid-Latency Changes with Level of Musical Expertise

This original research focused on the effect of musical training intensity on cerebral and behavioral processing of complex music using high-density event-related potential (ERP) approaches. Recently we have been able to show progressive changes with training in gray and white matter, and higher order brain functioning using (f)MRI [(functional) Magnetic Resonance Imaging], as well as changes in musical and general cognitive functioning. The current study investigated the same population of non-musicians, amateur pianists and expert pianists using spatio-temporal ERP analysis, by means of microstate analysis, and ERP source imaging. The stimuli consisted of complex musical compositions containing three levels of transgression of musical syntax at closure that participants appraised. ERP waveforms, microstates and underlying brain sources revealed gradual differences according to musical expertise in a 300–500 ms window after the onset of the terminal chords of the pieces. Within this time-window, processing seemed to concern context-based memory updating, indicated by a P3b-like component or microstate for which underlying sources were localized in the right middle temporal gyrus, anterior cingulate and right parahippocampal areas. Given that the 3 expertise groups were carefully matched for demographic factors, these results provide evidence of the progressive impact of training on brain and behavior.

Functional neural changes associated with acquired amusia across different stages of recovery after stroke

Brain damage causing acquired amusia disrupts the functional music processing system, creating a unique opportunity to investigate the critical neural architectures of musical processing in the brain. In this longitudinal fMRI study of stroke patients (N = 41) with a 6-month follow-up, we used natural vocal music (sung with lyrics) and instrumental music stimuli to uncover brain activation and functional network connectivity changes associated with acquired amusia and its recovery. In the acute stage, amusic patients exhibited decreased activation in right superior temporal areas compared to non-amusic patients during instrumental music listening. During the follow-up, the activation deficits expanded to comprise a wide-spread bilateral frontal, temporal, and parietal network. The amusics showed less activation deficits to vocal music, suggesting preserved processing of singing in the amusic brain. Compared to non-recovered amusics, recovered amusics showed increased activation to instrumental music in bilateral frontoparietal areas at 3 months and in right middle and inferior frontal areas at 6 months. Amusia recovery was also associated with increased functional connectivity in right and left frontoparietal attention networks to instrumental music. Overall, our findings reveal the dynamic nature of deficient activation and connectivity patterns in acquired amusia and highlight the role of dorsal networks in amusia recovery.

Deficits of congenital amusia beyond pitch: Evidence from impaired categorical perception of vowels in Cantonese-speaking congenital amusics

Congenital amusia is a lifelong disorder of fine-grained pitch processing in music and speech. However, it remains unclear whether amusia is a pitch-specific deficit, or whether it affects frequency/spectral processing more broadly, such as the perception of formant frequency in vowels, apart from pitch. In this study, in order to illuminate the scope of the deficits, we compared the performance of 15 Cantonese-speaking amusics and 15 matched controls on the categorical perception of sound continua in four stimulus contexts: lexical tone, pure tone, vowel, and voice onset time (VOT). Whereas lexical tone, pure tone and vowel continua rely on frequency/spectral processing, the VOT continuum depends on duration/temporal processing. We found that the amusic participants performed similarly to controls in all stimulus contexts in the identification, in terms of the across-category boundary location and boundary width. However, the amusic participants performed systematically worse than controls in discriminating stimuli in those three contexts that depended on frequency/spectral processing (lexical tone, pure tone and vowel), whereas they performed normally when discriminating duration differences (VOT). These findings suggest that the deficit of amusia is probably not pitch specific, but affects frequency/spectral processing more broadly. Furthermore, there appeared to be differences in the impairment of frequency/spectral discrimination in speech and nonspeech contexts. The amusic participants exhibited less benefit in between-category discriminations than controls in speech contexts (lexical tone and vowel), suggesting reduced categorical perception; on the other hand, they performed inferiorly compared to controls across the board regardless of between- and within-category discriminations in nonspeech contexts (pure tone), suggesting impaired general auditory processing. These differences imply that the frequency/spectral-processing deficit might be manifested differentially in speech and nonspeech contexts in amusics—it is manifested as a deficit of higher-level phonological processing in speech sounds, and as a deficit of lower-level auditory processing in nonspeech sounds.

Revisiting the Neural Basis of Acquired Amusia: Lesion Patterns and Structural Changes Underlying Amusia Recovery

Although, acquired amusia is a common deficit following stroke, relatively little is still known about its precise neural basis, let alone to its recovery. Recently, we performed a voxel-based lesion-symptom mapping (VLSM) and morphometry (VBM) study which revealed a right lateralized lesion pattern, and longitudinal gray matter volume (GMV) and white matter volume (WMV) changes that were specifically associated with acquired amusia after stroke. In the present study, using a larger sample of stroke patients (N = 90), we aimed to replicate and extend the previous structural findings as well as to determine the lesion patterns and volumetric changes associated with amusia recovery. Structural MRIs were acquired at acute and 6-month post-stroke stages. Music perception was behaviorally assessed at acute and 3-month post-stroke stages using the Scale and Rhythm subtests of the Montreal Battery of Evaluation of Amusia (MBEA). Using these scores, the patients were classified as non-amusic, recovered amusic, and non-recovered amusic. The results of the acute stage VLSM analyses and the longitudinal VBM analyses converged to show that more severe and persistent (non-recovered) amusia was associated with an extensive pattern of lesions and GMV/WMV decrease in right temporal, frontal, parietal, striatal, and limbic areas. In contrast, less severe and transient (recovered) amusia was linked to lesions specifically in left inferior frontal gyrus as well as to a GMV decrease in right parietal areas. Separate continuous analyses of MBEA Scale and Rhythm scores showed extensively overlapping lesion pattern in right temporal, frontal, and subcortical structures as well as in the right insula. Interestingly, the recovered pitch amusia was related to smaller GMV decreases in the temporoparietal junction whereas the recovered rhythm amusia was associated to smaller GMV decreases in the inferior temporal pole. Overall, the results provide a more comprehensive picture of the lesions and longitudinal structural changes associated with different recovery trajectories of acquired amusia.

Insula-based networks in professional musicians: Evidence for increased functional connectivity during resting state fMRI

Despite considerable research on experience-dependent neuroplasticity in professional musicians, detailed understanding of an involvement of the insula is only now beginning to emerge. We investigated the effects of musical training on intrinsic insula-based connectivity in professional classical musicians relative to nonmusicians using resting-state functional MRI. Following a tripartite scheme of insula subdivisions, coactivation profiles were analyzed for the posterior, ventral anterior, and dorsal anterior insula in both hemispheres. While whole-brain connectivity across all participants confirmed previously reported patterns, between-group comparisons revealed increased insular connectivity in musicians relative to nonmusicians. Coactivated regions encompassed constituents of large-scale networks involved in salience detection (e.g., anterior and middle cingulate cortex), affective processing (e.g., orbitofrontal cortex and temporal pole), and higher order cognition (e.g., dorsolateral prefrontal cortex and the temporoparietal junction), whereas no differences were found for the reversed group contrast. Importantly, these connectivity patterns were stronger in musicians who experienced more years of musical practice, including also sensorimotor regions involved in music performance (M1 hand area, S1, A1, and SMA). We conclude that musical training triggers significant reorganization in insula-based networks, potentially facilitating high-level cognitive and affective functions associated with the fast integration of multisensory information in the context of music performance. Hum Brain Mapp 38:4834-4849, 2017. © 2017 Wiley Periodicals, Inc.