Direct Electrical Stimulation in the Human Brain Disrupts Melody Processing

IDEAL monitoring of musical skills during awake craniotomy: From step 1 to step 2

The aim of awake brain surgery is to perform a maximum resection on the one hand, and to preserve cognitive functions, quality of life and personal autonomy on the other hand. Historically, language and sensorimotor functions were most frequently monitored. Over the years other cognitive functions, including music, have entered the operation theatre. Cases about monitoring musical abilities during awake brain surgery are emerging, and a systematic method how to monitor music would be the next step. According to the IDEAL framework for surgical innovations our study aims to present future recommendation based on a systematic literature search (PRISMA) in combination with lessons learned from three case reports from our own clinical practice with professional musicians (n = 3). We plead for structured procedures including individual tailored tasks. By embracing these recommendations, we can both improve clinical care and unravel music functions in the brain.

Intraoperative cortical localization of music and language reveals signatures of structural complexity in posterior temporal cortex

Language and music involve the productive combination of basic units into structures. It remains unclear whether brain regions sensitive to linguistic and musical structure are co-localized. We report an intraoperative awake craniotomy in which a left-hemispheric language-dominant professional musician underwent cortical stimulation mapping (CSM) and electrocorticography of music and language perception and production during repetition tasks. Musical sequences were melodic or amelodic, and differed in algorithmic compressibility (Lempel-Ziv complexity). Auditory recordings of sentences differed in syntactic complexity (single vs. multiple phrasal embeddings). CSM of posterior superior temporal gyrus (pSTG) disrupted music perception and production, along with speech production. pSTG and posterior middle temporal gyrus (pMTG) activated for language and music (broadband gamma; 70-150 Hz). pMTG activity was modulated by musical complexity, while pSTG activity was modulated by syntactic complexity. This points to shared resources for music and language comprehension, but distinct neural signatures for the processing of domain-specific structural features.

Awake Craniotomy and Intraoperative Musical Performance for Brain Tumor Surgery: Case Report and Literature Review

Music experience and creation is a complex phenomenon that involves multiple brain structures. Music mapping during awake brain surgery, in addition to standard speech and motor mapping, remains a controversial topic. Music function can be impaired selectively, despite overlap with other neural networks commonly tested during direct cortical stimulation. We describe the case of a 34-year-old male patient presenting with a glioma located within eloquent cortex, who is also a professional musician and actor. We performed an awake craniotomy (AC) that mapped the standard motor and speech areas, while the patient played guitar intraoperatively and sang. Outcomes were remarkable with preservation of function and noted improvements in his musical abilities in outpatient follow-up. In addition, we performed a review of the literature in which awake craniotomies were performed for the removal of brain tumors in patients with some background in music (e.g., score reading, humming/singing). To date, only 4 patients have played a musical instrument intraoperatively during an AC for brain tumor resection. Using awake cortical mapping techniques and paradigms for preserving speech function during an intraoperative musical performance with singing is feasible and can yield a great result for patients. The use of standard brain mapping over music processing mapping did not yield a negative outcome. More experience is needed to understand and standardize this procedure as the field of brain mapping continues to grow for tumor resections.

[Mapping the musician brain during awake craniotomy]

Direct cortical stimulation during awake craniotomy with speech testing became the «gold standard» in brain mapping and preserving speech zones during neurosurgical procedures. However, there are many other cerebral functions, and their loss can be very critical for certain patients. For example, such a function is production and perception of music for musicians. This review presents the latest data on functional anatomy of musician brain, as well as aspects of neurosurgical treatment with awake craniotomy and music testing under brain mapping.

Neural processing of poems and songs is based on melodic properties

The neural processing of speech and music is still a matter of debate. A long tradition that assumes shared processing capacities for the two domains contrasts with views that assume domain-specific processing. We here contribute to this topic by investigating, in a functional magnetic imaging (fMRI) study, ecologically valid stimuli that are identical in wording and differ only in that one group is typically spoken (or silently read), whereas the other is sung: poems and their respective musical settings. We focus on the melodic properties of spoken poems and their sung musical counterparts by looking at proportions of significant autocorrelations (PSA) based on pitch values extracted from their recordings. Following earlier studies, we assumed a bias of poem-processing towards the left and a bias for song-processing on the right hemisphere. Furthermore, PSA values of poems and songs were expected to explain variance in left- vs. right-temporal brain areas, while continuous liking ratings obtained in the scanner should modulate activity in the reward network. Overall, poem processing compared to song processing relied on left temporal regions, including the superior temporal gyrus, whereas song processing compared to poem processing recruited more right temporal areas, including Heschl's gyrus and the superior temporal gyrus. PSA values co-varied with activation in bilateral temporal regions for poems, and in right-dominant fronto-temporal regions for songs. Continuous liking ratings were correlated with activity in the default mode network for both poems and songs. The pattern of results suggests that the neural processing of poems and their musical settings is based on their melodic properties, supported by bilateral temporal auditory areas and an additional right fronto-temporal network known to be implicated in the processing of melodies in songs. These findings take a middle ground in providing evidence for specific processing circuits for speech and music in the left and right hemisphere, but simultaneously for shared processing of melodic aspects of both poems and their musical settings in the right temporal cortex. Thus, we demonstrate the neurobiological plausibility of assuming the importance of melodic properties in spoken and sung aesthetic language alike, along with the involvement of the default mode network in the aesthetic appreciation of these properties.

The feasibility and added value of mapping music during awake craniotomy: A systematic review

The value of mapping musical function during awake craniotomy is unclear. Hence, this systematic review was conducted to examine the feasibility and added value of music mapping in patients undergoing awake craniotomy. An extensive search, on 26 March 2021, in four electronic databases (Medline, Embase, Web of Science and Cochrane CENTRAL register of trials), using synonyms of the words "Awake Craniotomy" and "Music Performance," was conducted. Patients performing music while undergoing awake craniotomy were independently included by two reviewers. This search resulted in 10 studies and 14 patients. Intra-operative mapping of musical function was successful in 13 out of 14 patients. Isolated music disruption, defined as disruption during music tasks with intact language/speech and/or motor functions, was identified in two patients in the right superior temporal gyrus, one patient in the right and one patient in the left middle frontal gyrus and one patient in the left medial temporal gyrus. Pre-operative functional MRI confirmed these localizations in three patients. Assessment of post-operative musical function, only conducted in seven patients by means of standardized (57%) and non-standardized (43%) tools, report no loss of musical function. With these results, we conclude that mapping music is feasible during awake craniotomy. Moreover, we identified certain brain regions relevant for music production and detected no decline during follow-up, suggesting an added value of mapping musicality during awake craniotomy. A systematic approach to map musicality should be implemented, to improve current knowledge on the added value of mapping musicality during awake craniotomy.

Brain Plasticity Reflects Specialized Cognitive Development Induced by Musical Training

Learning a musical instrument requires a long period of training and might induce structural and functional changes in the brain. Previous studies have shown brain plasticity resulting from training with a musical instrument. However, these studies did not distinguish the effects on brain plasticity of specific musical instruments as they examined the brain of musicians who had learned a single musical instrument/genre and did not control for confounding factors, such as common or interactive effects involved in music training. To address this research gap, the present work investigated musicians who had experience with both a piano and a wind instrument, for example, flute, trumpet, clarinet etc. By examining the difference between the 2 musical instruments in the same subject, we avoided the effects common to all musical instruments and the confounding factors. Therefore, we identified several high-tier brain areas displaying a brain plasticity specific to each musical instrument. Our findings show that learning a musical instrument might result in the development of high cognitive functions reflecting the skills/abilities unique to the instrument played.

Awake intraoperative mapping to identify cortical regions related to music performance: Technical note

The aim of this manuscript is to present our intraoperative technique assessing the ability to perform music. Our protocol excludes cases where performance can be disrupted by motor deficits. The positive cortical sites (the posterior part of the superior temporal gyrus and supramarginal gyrus) related purely to music performance are also reported. We present the case of a patient, an amateur piano player who underwent surgery for a symptomatic supratentorial cavernoma while awake with intraoperative brain mapping. This case report shows that amateur and possibly professional musicians may benefit from awake procedures. This report confirms that stimulation of the specific area of the brain can disturb the function of a large network responsible for high-level cognitive task, like music performance.

Altered functional connectivity during speech perception in congenital amusia

Individuals with congenital amusia have a lifelong history of unreliable pitch processing. Accordingly, they downweight pitch cues during speech perception and instead rely on other dimensions such as duration. We investigated the neural basis for this strategy. During fMRI, individuals with amusia (N = 15) and controls (N = 15) read sentences where a comma indicated a grammatical phrase boundary. They then heard two sentences spoken that differed only in pitch and/or duration cues and selected the best match for the written sentence. Prominent reductions in functional connectivity were detected in the amusia group between left prefrontal language-related regions and right hemisphere pitch-related regions, which reflected the between-group differences in cue weights in the same groups of listeners. Connectivity differences between these regions were not present during a control task. Our results indicate that the reliability of perceptual dimensions is linked with functional connectivity between frontal and perceptual regions and suggest a compensatory mechanism.

Reorganized language network connectivity after left arcuate fasciculus resection: A case study

Understanding the neural mechanisms that support spontaneous recovery of cognitive abilities can place important constraints on mechanistic theories of brain organization and function, and holds potential to inform clinical interventions. Connectivity-based MRI measures have emerged as a way to study how recovery from brain injury is modulated by changes in intra- and inter-hemispheric connectivity. Here we report a detailed and multi-modal case study of a 26 year-old male who presented with a left inferior parietal glioma infiltrating the left arcuate fasciculus. The patient underwent pre- and post-operative functional MRI and Diffusion Tensor Imaging, as well as behavioral assessments of language, motor, vision and praxis. The surgery for removal of the tumor was carried out with the patient awake, and direct electrical stimulation mapping was used to evaluate cortical language centers. The patient developed a specific difficulty with repeating sentences toward the end of the surgery, after resection of the tumor and partial transection of the arcuate fasciculus. The patient recovered from the sentence repetition impairments over several months after the operation. Coincident with the patient's cognitive recovery, we document a pattern whereby intra-hemispheric functional connectivity was reduced in the left hemisphere, while inter-hemispheric connectivity increased between classic left hemisphere language regions and their right hemisphere homologues. These findings suggest that increased synchrony between the two hemispheres, in the setting of focal transection of the left arcuate fasciculus, can facilitate functional recovery.

Awake Mapping of the Auditory Cortex during Tumor Resection in an Aspiring Musical Performer: A Case Report

INTRODUCTION

Preoperative functional MRI (fMRI) and intraoperative awake cortical mapping are established strategies to identify and preserve critical language structures during neurosurgery. There is growing appreciation for the need to similarly identify and preserve eloquent tissue critical for music production.

CASE REPORT

A 19-year-old female musician, with a 3- to 4-year history of events concerning for musicogenic seizures, was found to have a right posterior temporal tumor, concerning for a low-grade glial neoplasm. Preoperative fMRI assessing passive and active musical tasks localized areas of activation directly adjacent to the tumor margin. Cortical stimulation during various musical tasks did not identify eloquent tissue near the surgical site. A gross total tumor resection was achieved without disruption of singing ability. At 9-month follow-up, the patient continued to have preserved musical ability with full resolution of seizures and without evidence of residual lesion or recurrence.

CONCLUSION

A novel strategy for performing an awake craniotomy, incorporating preoperative fMRI data for music processing with intraoperative cortical stimulation, interpreted with the assistance of a musician expert and facilitated gross total resection of the patient's tumor without comprising her musical abilities.

A common neural signature of brain injury in concussion and subconcussion

The midbrain is biomechanically susceptible to force loading from repetitive subconcussive head impacts (RSHI), is a site of tauopathy in chronic traumatic encephalopathy (CTE), and regulates functions (e.g., eye movements) often disrupted in concussion. In a prospective longitudinal design, we demonstrate there are reductions in midbrain white matter integrity due to a single season of collegiate football, and that the amount of reduction in midbrain white matter integrity is related to the amount of rotational acceleration to which players' brains are exposed. We then replicate the observation of reduced midbrain white matter integrity in a retrospective cohort of individuals with frank concussion, and further show that variance in white matter integrity is correlated with levels of serum-based tau, a marker of blood-brain barrier disruption. These findings mean that noninvasive structural MRI of the midbrain is a succinct index of both clinically silent white matter injury as well as frank concussion.

Domain-Specific Diaschisis: Lesions to Parietal Action Areas Modulate Neural Responses to Tools in the Ventral Stream

Neural responses to small manipulable objects ("tools") in high-level visual areas in ventral temporal cortex (VTC) provide an opportunity to test how anatomically remote regions modulate ventral stream processing in a domain-specific manner. Prior patient studies indicate that grasp-relevant information can be computed about objects by dorsal stream structures independently of processing in VTC. Prior functional neuroimaging studies indicate privileged functional connectivity between regions of VTC exhibiting tool preferences and regions of parietal cortex supporting object-directed action. Here we test whether lesions to parietal cortex modulate tool preferences within ventral and lateral temporal cortex. We found that lesions to the left anterior intraparietal sulcus, a region that supports hand-shaping during object grasping and manipulation, modulate tool preferences in left VTC and in the left posterior middle temporal gyrus. Control analyses demonstrated that neural responses to "place" stimuli in left VTC were unaffected by lesions to parietal cortex, indicating domain-specific consequences for ventral stream neural responses in the setting of parietal lesions. These findings provide causal evidence that neural specificity for "tools" in ventral and lateral temporal lobe areas may arise, in part, from online inputs to VTC from parietal areas that receive inputs via the dorsal visual pathway.

Direct electrical stimulation mapping of cognitive functions in the human brain

Direct electrical stimulation (DES) is a well-established clinical tool for mapping cognitive functions while patients are undergoing awake neurosurgery or invasive long-term monitoring to identify epileptogenic tissue. Despite the proliferation of a range of invasive and noninvasive methods for mapping sensory, motor and cognitive processes in the human brain, DES remains the clinical gold standard for establishing the margins of brain tissue that can be safely removed while avoiding long-term neurological deficits. In parallel, and principally over the last two decades, DES has emerged as a powerful scientific tool for testing hypotheses of brain organization and mechanistic hypotheses of cognitive function. DES can cause transient "lesions" and thus can support causal inferences about the necessity of stimulated brain regions for specific functions, as well as the separability of sensory, motor and cognitive processes. This Special Issue of Cognitive Neuropsychology emphasizes the use of DES as a research tool to advance understanding of normal brain organization and function.

Direct electrical stimulation of the left frontal aslant tract disrupts sentence planning without affecting articulation

Sentence production involves mapping from deep structures that specify meaning and thematic roles to surface structures that specify the order and sequencing of production ready elements. We propose that the frontal aslant tract is a key pathway for sequencing complex actions with deep hierarchical structure. In the domain of language, and primarily with respect to the left FAT, we refer to this as the 'Syntagmatic Constraints On Positional Elements' (SCOPE) hypothesis. One prediction made by the SCOPE hypothesis is that disruption of the frontal aslant tract should disrupt sentence production at grammatical phrase boundaries, with no disruption of articulatory processes.  We test this prediction in a patient undergoing direct electrical stimulation mapping of the frontal aslant tract during an awake craniotomy to remove a left frontal brain tumor. We found that stimulation of the left FAT prolonged inter-word durations at the start of grammatical phrases, while inter-word durations internal to noun phrases were unaffected, and there was no effect on intra-word articulatory duration. These results provide initial support for the SCOPE hypothesis, and motivate novel directions for future research to explore the functions of this recently discovered component of the language system.

Task- and domain-specific modulation of functional connectivity in the ventral and dorsal object-processing pathways

A whole-brain network of regions collectively supports the ability to recognize and use objects-the Tool Processing Network. Little is known about how functional interactions within the Tool Processing Network are modulated in a task-dependent manner. We designed an fMRI experiment in which participants were required to either generate object pantomimes or to carry out a picture matching task over the same images of tools, while holding all aspects of stimulus presentation constant across the tasks. The Tool Processing Network was defined with an independent functional localizer, and functional connectivity within the network was measured during the pantomime and picture matching tasks. Relative to tool picture matching, tool pantomiming led to an increase in functional connectivity between ventral stream regions and left parietal and frontal-motor areas; in contrast, the matching task was associated with an increase in functional connectivity among regions in ventral temporo-occipital cortex, and between ventral temporal regions and the left inferior parietal lobule. Graph-theory analyses over the functional connectivity data indicated that the left premotor cortex and left lateral occipital complex were hub-like (exhibited high betweenness centrality) during tool pantomiming, while ventral stream regions (left medial fusiform gyrus and left posterior middle temporal gyrus) were hub-like during the picture matching task. These results demonstrate task-specific modulation of functional interactions among a common set of regions, and indicate dynamic coupling of anatomically remote regions in task-dependent manner.

Predictive regulation and human design

Organisms evolving toward greater complexity were selected across aeons to use energy and resources efficiently. Efficiency depended on prediction at every stage: first a clock to predict the planet's statistical regularities; then a brain to predict bodily needs and compute commands that dynamically adjust the flows of energy and nutrients. Predictive regulation (allostasis) frugally matches resources to needs and thus forms a core principle of our design. Humans, reaching a pinnacle of cognitive complexity, eventually produced a device (the steam engine) that converted thermal energy to work and were suddenly awash in resources. Today boundless consumption in many nations challenges all our regulatory mechanisms, causing obesity, diabetes, drug addiction and their sequelae. So far we have sought technical solutions, such as drugs, to treat complex circuits for metabolism, appetites and mood. Here I argue for a different approach which starts by asking: why does our regulatory system, which evolution tuned for small satisfactions, now constantly demand 'more'?

Direct cortical stimulation of inferior frontal cortex disrupts both speech and music production in highly trained musicians

Music and speech are human-specific behaviours that share numerous properties, including the fine motor skills required to produce them. Given these similarities, previous work has suggested that music and speech may at least partially share neural substrates. To date, much of this work has focused on perception, and has not investigated the neural basis of production, particularly in trained musicians. Here, we report two rare cases of musicians undergoing neurosurgical procedures, where it was possible to directly stimulate the left hemisphere cortex during speech and piano/guitar music production tasks. We found that stimulation to left inferior frontal cortex, including pars opercularis and ventral pre-central gyrus, caused slowing and arrest for both speech and music, and note sequence errors for music. Stimulation to posterior superior temporal cortex only caused production errors during speech. These results demonstrate partially dissociable networks underlying speech and music production, with a shared substrate in frontal regions.

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.