A rapid sound-action association effect in human insular cortex

The importance of observing the master's hand: Action Observation Training promotes the acquisition of new musical skills

Introduction

Via mirror mechanism, motor training approaches based on the alternation of action observation and execution (i.e., Action Observation Training-AOT) promote the acquisition of motor abilities. Previous studies showed that both visual and auditory stimuli may elicit a common motor representation of music-related gestures; however, the potentialities of AOT for the acquisition of musical skills are still underexplored.

Methods

Twenty-one music-naïve participants underwent two blocks of training: AOT and Key-light Observation Training (KOT). AOT consisted of the observation of a melodic sequence played on a keyboard with the right hand by an expert model, followed by participant's imitation. Observation and execution were repeated six consecutive times (T1-T6). KOT followed the same procedure, except for the visual content of the stimulus, depicting the sequential highlighting of the piano keys corresponding to the melody. The rate of correct notes (C), the trainee-model similarity of key-pressure strength (S), and the trainee-model consistency of note duration (R) were collected across T1-T6.

Results

Both AOT and KOT improved musical performance. Noteworthy, AOT showed a higher learning magnitude relative to KOT in terms of C and S.

Discussion

Action Observation Training promotes the acquisition of key elements of melodic sequences, encompassing not only the accurate sequencing of notes but also their expressive characteristics, such as key-pressure dynamics. The convergence of listening and observation of actions onto a shared motor representation not only explains several pedagogical approaches applied in all musical cultures worldwide, but also enhances the potential efficacy of current procedures for music training.

Interoception and the musical brain: Evidence from cross-sectional and longitudinal behavioral and resting-state fMRI study

Musical training has been linked to enhanced interoceptive abilities and increased resting-state (RS) functional connectivity (FC) within the interoceptive brain network. We aimed to replicate and extend these findings with a unique cross-sectional and longitudinal study design. Professional musicians and matched individuals with no prior musical experience (training group) were recruited. Participants underwent RS fMRI scans and completed heartbeat counting and discrimination tasks outside of the scanner (time point 1). The training group additionally had RS scans and interoception tests repeated after a 6-month-long keyboard course training (time point 2). We found no evidence for increased interoceptive abilities in professional musicians relative to non-musicians, nor did we observe any improvements in interoception over the course of musical training. RS FC analysis revealed increased FC within the sensorimotor network in professional musicians compared to the training group at the first time point with no change in FC over time in the Training group. These findings challenge the view that musical training may improve interoceptive abilities. Yet, the results suggest that musical training is related to increased communication within the sensorimotor RS network, which consists of some hubs important for interoceptive processing (namely pre- and postcentral gyri and supplementary motor area).

Does Cueing Need Attention? A Pilot Study in People with Parkinson's Disease

We previously showed that both open-loop (beat of a metronome) and closed-loop (phase-dependent tactile feedback) cueing may be similarly effective in reducing Freezing of Gait (FoG), assessed with a quantitative FoG Index, while turning in place in the laboratory in a group of people with Parkinson's disease (PD). Despite the similar changes on the FoG Index, it is not known whether both cueing responses require attentional control, which would explain FoG Index improvement. The mechanisms underlying cueing responses are poorly understood. Here, we tested the hypothesis that the salience network would predict responsiveness (i.e., FoG Index improvement) to open-loop and closed-loop cueing in people with and without FoG of PD, as salience network contributes to tasks requiring attention to external stimuli in healthy adults. Thirteen people with PD with high-quality imaging data were analyzed to characterize relationships between resting-state MRI functional connectivity and responses to cues. The interaction of the salience network and retrosplenial-temporal networks was the best predictor of responsiveness to open-loop cueing, presenting the largest effect size (d = 1.16). The interaction between the salience network and subcortical as well as cingulo-parietal and subcortical networks were the strongest predictors of responsiveness to closed-loop cueing, presenting the largest effect sizes (d = 1.06 and d = 0.84, respectively). Salience network activity was a common predictor of responsiveness to both cueing, which suggests that auditory and proprioceptive stimuli during turning may require some level of cognitive and insular activity, anchored within the salience network, which explain FoG Index improvements in people with PD.

Ideomotor learning: Time to generalize a longstanding principle

The ideomotor principle holds that anticipating the sensory consequences of a movement triggers an associated motor response. Even though this framework dates back to the 19th century, it continues to lie at the heart of many contemporary approaches to human action control. Here we specifically focus on the ideomotor learning mechanism that has to precede action initiation via effect anticipation. Traditional approaches to this learning mechanism focused on establishing novel action-effect (or response-effect) associations. Here we apply the theoretical concept of common coding for action and perception to argue that the same learning principle should result in response-response and stimulus-stimulus associations just as well. Generalizing ideomotor learning in such a way results in a powerful and general framework of ideomotor action control, and it allows for integrating the two seemingly separate fields of ideomotor approaches and hierarchical learning.

Neural Correlates of Listening to Varying Synchrony Between Beats in Samba Percussion and Relations to Feeling the Groove

Listening to samba percussion often elicits feelings of pleasure and the desire to move with the beat-an experience sometimes referred to as "feeling the groove"- as well as social connectedness. Here we investigated the effects of performance timing in a Brazilian samba percussion ensemble on listeners' experienced pleasantness and the desire to move/dance in a behavioral experiment, as well as on neural processing as assessed via functional magnetic resonance imaging (fMRI). Participants listened to different excerpts of samba percussion produced by multiple instruments that either were "in sync", with no additional asynchrony between instrumental parts other than what is usual in naturalistic recordings, or were presented "out of sync" by delaying the snare drums (by 28, 55, or 83 ms). Results of the behavioral experiment showed increasing pleasantness and desire to move/dance with increasing synchrony between instruments. Analysis of hemodynamic responses revealed stronger bilateral brain activity in the supplementary motor area, the left premotor area, and the left middle frontal gyrus with increasing synchrony between instruments. Listening to "in sync" percussion thus strengthens audio-motor interactions by recruiting motor-related brain areas involved in rhythm processing and beat perception to a higher degree. Such motor related activity may form the basis for "feeling the groove" and the associated desire to move to music. Furthermore, in an exploratory analysis we found that participants who reported stronger emotional responses to samba percussion in everyday life showed higher activity in the subgenual cingulate cortex, an area involved in prosocial emotions, social group identification and social bonding.

Rapid encoding of musical tones discovered in whole-brain connectivity

Information encoding has received a wide neuroscientific attention, but the underlying rapid spatiotemporal brain dynamics remain largely unknown. Here, we investigated the rapid brain mechanisms for encoding of sounds forming a complex temporal sequence. Specifically, we used magnetoencephalography (MEG) to record the brain activity of 68 participants while they listened to a highly structured musical prelude. Functional connectivity analyses performed using phase synchronisation and graph theoretical measures showed a large network of brain areas recruited during encoding of sounds, comprising primary and secondary auditory cortices, frontal operculum, insula, hippocampus and basal ganglia. Moreover, our results highlighted the rapid transition of brain activity from primary auditory cortex to higher order association areas including insula and superior temporal pole within a whole-brain network, occurring during the first 220 ms of the encoding process. Further, we discovered that individual differences along cognitive abilities and musicianship modulated the degree centrality of the brain areas implicated in the encoding process. Indeed, participants with higher musical expertise presented a stronger centrality of superior temporal gyrus and insula, while individuals with high working memory abilities showed a stronger centrality of frontal operculum. In conclusion, our study revealed the rapid unfolding of brain network dynamics responsible for the encoding of sounds and their relationship with individual differences, showing a complex picture which extends beyond the well-known involvement of auditory areas. Indeed, our results expanded our understanding of the general mechanisms underlying auditory pattern encoding in the human brain.

Manipulation of low-level features modulates grouping strength of auditory objects

A central challenge of auditory processing involves the segregation, analysis, and integration of acoustic information into auditory perceptual objects for processing by higher order cognitive operations. This study explores the influence of low-level features on auditory object perception. Participants provided perceived musicality ratings in response to randomly generated pure tone sequences. Previous work has shown that music perception relies on the integration of discrete sounds into a holistic structure. Hence, high (versus low) ratings were viewed as indicative of strong (versus weak) object formation. Additionally, participants rated sequences in which random subsets of tones were manipulated along one of three low-level dimensions (timbre, amplitude, or fade-in) at one of three strengths (low, medium, or high). Our primary findings demonstrate how low-level acoustic features modulate the perception of auditory objects, as measured by changes in musicality ratings for manipulated sequences. Secondarily, we used principal component analysis to categorize participants into subgroups based on differential sensitivities to low-level auditory dimensions, thereby highlighting the importance of individual differences in auditory perception. Finally, we report asymmetries regarding the effects of low-level dimensions; specifically, the perceptual significance of timbre. Together, these data contribute to our understanding of how low-level auditory features modulate auditory object perception.

Inter-subject Similarity of Brain Activity in Expert Musicians After Multimodal Learning: A Behavioral and Neuroimaging Study on Learning to Play a Piano Sonata

Human behavior is inherently multimodal and relies on sensorimotor integration. This is evident when pianists exhibit activity in motor and premotor cortices, as part of a dorsal pathway, while listening to a familiar piece of music, or when naïve participants learn to play simple patterns on the piano. Here we investigated the interaction between multimodal learning and dorsal-stream activity over the course of four weeks in ten skilled pianists by adopting a naturalistic data-driven analysis approach. We presented the pianists with audio-only, video-only and audiovisual recordings of a piano sonata during functional magnetic resonance imaging (fMRI) before and after they had learned to play the sonata by heart for a total of four weeks. We followed the learning process and its outcome with questionnaires administered to the pianists, one piano instructor following their training, and seven external expert judges. The similarity of the pianists' brain activity during stimulus presentations was examined before and after learning by means of inter-subject correlation (ISC) analysis. After learning, an increased ISC was found in the pianists while watching the audiovisual performance, particularly in motor and premotor regions of the dorsal stream. While these brain structures have previously been associated with learning simple audio-motor sequences, our findings are the first to suggest their involvement in learning a complex and demanding audiovisual-motor task. Moreover, the most motivated learners and the best performers of the sonata showed ISC in the dorsal stream and in the reward brain network.

Alterations in basal ganglia-cerebello-thalamo-cortical connectivity and whole brain functional network topology in Tourette's syndrome

Tourette Syndrome (TS) is a neuropsychiatric disorder characterized by the presence of motor and vocal tics. Major pathophysiological theories posit a dysfunction of the cortico-striato-thalamo-cortical circuits as being a representative hallmark of the disease. Recent evidence suggests a more widespread dysfunction of brain networks in TS including the cerebellum and going even beyond classic motor pathways. In order to characterize brain network dysfunction in TS, in this study we investigated functional and effective-like connectivity as well as topological changes of basal ganglia-thalamo-cortical and cortico-cerebellar brain networks. We collected resting-state fMRI data from 28 TS patients (age: 32 ± 11 years) and 28 age-matched, healthy controls (age: 31 ± 9 years). Region of interest based (ROI-ROI) bivariate correlation and ROI-ROI bivariate regression were employed as measures of functional and effective-like connectivity, respectively. Graph theoretical measures of centrality (degree, cost, betweenness centrality), functional segregation (clustering coefficient, local efficiency) and functional integration (average path length, global efficiency) were used to assess topological brain network changes. In this study, TS patients exhibited increased basal ganglia-cortical and thalamo-cortical connectivity, reduced cortico-cerebellar connectivity, and an increase in parallel communication through the basal ganglia, thalamus and cerebellum (increased global efficiency). Additionally, we observed a reduction in serial information transfer (reduction in average path length) within the default mode and the salience network. In summary, our findings show that TS is characterized by increased connectivity and functional integration of multiple basal ganglia-thalamo-cortical circuits, suggesting a predominance of excitatory neurotransmission and a lack of brain maturation. Moreover, topological changes of cortico-cerebellar and brain networks involved in interoception may be underestimated neural correlates of tics and the crucial premonitory urge feeling.

Correlated Resting-State Functional MRI Activity of Frontostriatal, Thalamic, Temporal, and Cerebellar Brain Regions Differentiates Stroke Survivors with High Compared to Low Depressive Symptom Scores

Background

One in three survivors of stroke experience poststroke depression (PSD). PSD has been linked with poorer recovery of function and cognition, yet our understanding of potential mechanisms is currently limited. Alterations in resting-state functional MRI have been investigated to a limited extent. Fluctuations in low frequency signal are reported, but it is unknown if interactions are present between the level of depressive symptom score and intrinsic brain activity in varying brain regions.

Objective

To investigate potential interaction effects between whole-brain resting-state activity and depressive symptoms in stroke survivors with low and high levels of depressive symptoms.

Methods

A cross-sectional analysis of 63 stroke survivors who were assessed at 3 months poststroke for depression, using the Montgomery–Åsberg Depression Rating Scale (MÅDRS-SIGMA), and for brain activity using fMRI. A MÅDRS-SIGMA score of >8 was classified as high depressive symptoms. Fractional amplitude of frequency fluctuations (fALFF) data across three frequency bands (broadband, i.e., ~0.01–0.08; subbands, i.e., slow-5: ~0.01–0.027 Hz, slow-4: 0.027–0.07) was examined.

Results

Of the 63 stroke survivors, 38 were classified as “low-depressive symptoms” and 25 as “high depressive symptoms.” Six had a past history of depression. We found interaction effects across frequency bands in several brain regions that differentiated the two groups. The broadband analysis revealed interaction effects in the left insula and the left superior temporal lobe. The subband analysis showed contrasting fALFF response between the two groups in the left thalamus, right caudate, and left cerebellum. Across the three frequency bands, we found contrasting fALFF response in areas within the fronto-limbic-thalamic network and cerebellum.

Conclusions

We provide evidence that fALFF is sensitive to changes in poststroke depressive symptom severity and implicates frontostriatal and cerebellar regions, consistent with previous studies. The use of multiband analysis could be an effective method to examine neural correlates of depression after stroke. The START-PrePARE trial is registered with the Australian New Zealand Clinical Trial Registry, number ACTRN12610000987066.

Internally Guided Lower Limb Movement Recruits Compensatory Cerebellar Activity in People With Parkinson's Disease

Background: Externally guided (EG) and internally guided (IG) movements are postulated to recruit two parallel neural circuits, in which motor cortical neurons interact with either the cerebellum or striatum via distinct thalamic nuclei. Research suggests EG movements rely more heavily on the cerebello-thalamo-cortical circuit, whereas IG movements rely more on the striato-pallido-thalamo-cortical circuit (1). Because Parkinson's (PD) involves striatal dysfunction, individuals with PD have difficulty generating IG movements (2).

Objectives: Determine whether individuals with PD would employ a compensatory mechanism favoring the cerebellum over the striatum during IG lower limb movements.

Methods: 22 older adults with mild-moderate PD, who had abstained at least 12 h from anti-PD medications, and 19 age-matched controls performed EG and IG rhythmic foot-tapping during functional magnetic resonance imaging. Participants with PD tapped with their right (more affected) foot. External guidance was paced by a researcher tapping participants' ipsilateral 3rd metacarpal in a pattern with 0.5 to 1 s intervals, while internal guidance was based on pre-scan training in the same pattern. BOLD activation was compared between tasks (EG vs. IG) and groups (PD vs. control).

Results: Both groups recruited the putamen and cerebellar regions. The PD group demonstrated less activation in the striatum and motor cortex than controls. A task (EG vs. IG) by group (PD vs. control) interaction was observed in the cerebellum with increased activation for the IG condition in the PD group.

Conclusions: These findings support the hypothesized compensatory shift in which the dysfunctional striatum is assisted by the less affected cerebellum to accomplish IG lower limb movement in individuals with mild-moderate PD. These findings are of relevance for temporal gait dysfunction and freezing of gait problems frequently noted in many people with PD and may have implications for future therapeutic application.

A cost of musical training? Sensorimotor flexibility in musical sequence learning

We report an experiment that tested the flexibility of sensorimotor learning in sequence production. Nonpianists and pianists learned simple melodies by ear under one of two auditory feedback conditions: one with normal pitch mapping (higher pitches to the right) and one with an inverted (reversed) mapping. After learning, both groups played melodies from memory while experiencing each feedback condition. Both groups exhibited sensorimotor learning and produced fewer errors at test while hearing the feedback used during training as opposed to the alternate feedback condition. However, learning was unstable for pianists who learned melodies with an inverted feedback condition, who produced more errors at test than pianists who learned melodies with normal-pitch mapping. Acquiring musical skill may therefore constrain subsequent sensorimotor flexibility.

The Action Representation Elicited by Different Types of Drug-Related Cues in Heroin-Abstinent Individuals

Drug related cue-induced reactivity plays a significant role in maintaining drug use and relapse in addicted individuals. The activation of Dorsolateral striatum-Sensorimotor system (DLS-SM) has been suggested as an important route through which drug cues may induce automatic drug using behavior. The current study used fMRI to investigate the reactivity of heroin abstinent individuals to different types of cues, to clarify the characteristics of the cues that induce the activation of the sensorimotor area. Forty heroin-dependent abstinent individuals and 29 healthy subjects were recruited to perform the heroin cue-reactivity task during fMRI. The participants’ subjective craving and physical signs were evaluated before and after scanning. Whole-brain analysis showed that compared to drug use tool and drug cues, cues related to drug use action were more likely to activate posterior central gyrus, para-hippocampus, supra marginal gyrus, superior parietal lobule (SPL) and inferior parietal lobule (IPL). These areas are involved in motor preparation and output, indicating that the sensorimotor area is also an important neural basis of craving and automatic drug using behavior, and may mediate craving and drug seeking behavior. Our findings thus suggest that cues related to drug using action may induce automatic drug seeking behavior more than cues related only to the drug itself.

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.

Interaction between Perceived Action and Music Sequences in the Left Prefrontal Area

Observing another person's piano play and listening to a melody interact with the observer's execution of piano play. This interaction is thought to occur because the execution of musical-action and the perception of both musical-action and musical-sound share a common representation in which the frontoparietal network is involved. However, it is unclear whether the perceptions of observed piano play and listened musical sound use a common neural resource. The present study used near-infrared spectroscopy to determine whether the interaction between the perception of musical-action and musical-sound sequences appear in the left prefrontal area. Measurements were obtained while participants watched videos that featured hands playing familiar melodies on a piano keyboard. Hand movements were paired with either a congruent or an incongruent melody. Two groups of participants (nine well-trained and nine less-trained) were instructed to identify the melody according to hand movements and to ignore the accompanying auditory track. Increased cortical activation was detected in the well-trained participants when hand movements were paired with incongruent melodies. Therefore, an interference effect was detected regarding the processing of action and sound sequences, indicating that musical-action sequences may be perceived with a representation that is also used for the perception of musical-sound sequences. However, in less-trained participants, such a contrast was not detected between conditions despite both groups featuring comparable key-touch reading abilities. Therefore, the current results imply that the left prefrontal area is involved in translating temporally structured sequences between domains. Additionally, expertise may be a crucial factor underlying this translation.

Divergent Human Cortical Regions for Processing Distinct Acoustic-Semantic Categories of Natural Sounds: Animal Action Sounds vs. Vocalizations

A major gap in our understanding of natural sound processing is knowledge of where or how in a cortical hierarchy differential processing leads to categorical perception at a semantic level. Here, using functional magnetic resonance imaging (fMRI) we sought to determine if and where cortical pathways in humans might diverge for processing action sounds vs. vocalizations as distinct acoustic-semantic categories of real-world sound when matched for duration and intensity. This was tested by using relatively less semantically complex natural sounds produced by non-conspecific animals rather than humans. Our results revealed a striking double-dissociation of activated networks bilaterally. This included a previously well described pathway preferential for processing vocalization signals directed laterally from functionally defined primary auditory cortices to the anterior superior temporal gyri, and a less well-described pathway preferential for processing animal action sounds directed medially to the posterior insulae. We additionally found that some of these regions and associated cortical networks showed parametric sensitivity to high-order quantifiable acoustic signal attributes and/or to perceptual features of the natural stimuli, such as the degree of perceived recognition or intentional understanding. Overall, these results supported a neurobiological theoretical framework for how the mammalian brain may be fundamentally organized to process acoustically and acoustic-semantically distinct categories of ethologically valid, real-world sounds.

Behavioral Quantification of Audiomotor Transformations in Improvising and Score-Dependent Musicians

The historically developed practice of learning to play a music instrument from notes instead of by imitation or improvisation makes it possible to contrast two types of skilled musicians characterized not only by dissimilar performance practices, but also disparate methods of audiomotor learning. In a recent fMRI study comparing these two groups of musicians while they either imagined playing along with a recording or covertly assessed the quality of the performance, we observed activation of a right-hemisphere network of posterior superior parietal and dorsal premotor cortices in improvising musicians, indicating more efficient audiomotor transformation. In the present study, we investigated the detailed performance characteristics underlying the ability of both groups of musicians to replicate music on the basis of aural perception alone. Twenty-two classically-trained improvising and score-dependent musicians listened to short, unfamiliar two-part excerpts presented with headphones. They played along or replicated the excerpts by ear on a digital piano, either with or without aural feedback. In addition, they were asked to harmonize or transpose some of the excerpts either to a different key or to the relative minor. MIDI recordings of their performances were compared with recordings of the aural model. Concordance was expressed in an audiomotor alignment score computed with the help of music information retrieval algorithms. Significantly higher alignment scores were found when contrasting groups, voices, and tasks. The present study demonstrates the superior ability of improvising musicians to replicate both the pitch and rhythm of aurally perceived music at the keyboard, not only in the original key, but also in other tonalities. Taken together with the enhanced activation of the right dorsal frontoparietal network found in our previous fMRI study, these results underscore the conclusion that the practice of improvising music can be associated with enhanced audiomotor transformation in response to aurally perceived music.

Broca Pars Triangularis Constitutes a "Hub" of the Language-Control Network during Simultaneous Language Translation

Until now, several branches of research have fundamentally contributed to a better understanding of the ramifications of bilingualism, multilingualism, and language expertise on psycholinguistic-, cognitive-, and neural implications. In this context, it is noteworthy to mention that from a cognitive perspective, there is a strong convergence of data pointing to an influence of multilingual speech competence on a variety of cognitive functions, including attention, short-term- and working memory, set shifting, switching, and inhibition. In addition, complementary neuroimaging findings have highlighted a specific set of cortical and subcortical brain regions which fundamentally contribute to administrate cognitive control in the multilingual brain, namely Broca's area, the middle-anterior cingulate cortex, the inferior parietal lobe, and the basal ganglia. However, a disadvantage of focusing on group analyses is that this procedure only enables an approximation of the neural networks shared within a population while at the same time smoothing inter-individual differences. In order to address both commonalities (i.e., within group analyses) and inter-individual variability (i.e., single-subject analyses) in language control mechanisms, here I measured five professional simultaneous interpreters while the participants overtly translated or repeated sentences with a simple subject-verb-object structure. Results demonstrated that pars triangularis was commonly activated across participants during backward translation (i.e., from L2 to L1), whereas the other brain regions of the "control network" showed a strong inter-individual variability during both backward and forward (i.e., from L1 to L2) translation. Thus, I propose that pars triangularis plays a crucial role within the language-control network and behaves as a fundamental processing entity supporting simultaneous language translation.

The activity in the anterior insulae is modulated by perceptual decision-making difficulty

Previous neuroimaging studies provide evidence for the involvement of the anterior insulae (INSs) in perceptual decision-making processes. However, how the insular cortex is involved in integration of degraded sensory information to create a conscious percept of environment and to drive our behaviors still remains a mystery. In this study, using functional magnetic resonance imaging (fMRI) and four different perceptual categorization tasks in visual and audio-visual domains, we measured blood oxygen level dependent (BOLD) signals and examined the roles of INSs in easy and difficult perceptual decision-making. We created a varying degree of degraded stimuli by manipulating the task-specific stimuli in these four experiments to examine the effects of task difficulty on insular cortex response. We hypothesized that significantly higher BOLD response would be associated with the ambiguity of the sensory information and decision-making difficulty. In all of our experimental tasks, we found the INS activity consistently increased with task difficulty and participants' behavioral performance changed with the ambiguity of the presented sensory information. These findings support the hypothesis that the anterior insulae are involved in sensory-guided, goal-directed behaviors and their activities can predict perceptual load and task difficulty.

Contributions of Subsurface Cortical Modulations to Discrimination of Executed and Imagined Grasp Forces through Stereoelectroencephalography

Stereoelectroencephalographic (SEEG) depth electrodes have the potential to record neural activity from deep brain structures not easily reached with other intracranial recording technologies. SEEG electrodes were placed through deep cortical structures including central sulcus and insular cortex. In order to observe changes in frequency band modulation, participants performed force matching trials at three distinct force levels using two different grasp configurations: a power grasp and a lateral pinch. Signals from these deeper structures were found to contain information useful for distinguishing force from rest trials as well as different force levels in some participants. High frequency components along with alpha and beta bands recorded from electrodes located near the primary motor cortex wall of central sulcus and electrodes passing through sensory cortex were found to be the most useful for classification of force versus rest although one participant did have significant modulation in the insular cortex. This study electrophysiologically corroborates with previous imaging studies that show force-related modulation occurs inside of central sulcus and insular cortex. The results of this work suggest that depth electrodes could be useful tools for investigating the functions of deeper brain structures as well as showing that central sulcus and insular cortex may contain neural signals that could be used for control of a grasp force BMI.

Freezing of gait in Parkinson's disease is associated with altered functional brain connectivity

BACKGROUND

Patients with Parkinson's disease (PD) may develop several gait disturbances during the course of illness and Freezing of gait (FOG) is one of them. Several neuroimaging studies have been conducted to identify the neural correlates of FOG but results have not been uniform. Resting state functional MRI (rs-fMRI) is relatively less explored in PD patients with FOG. This study aims to compare the whole brain resting state connectivity of PD patients with and without FOG using rs-fMRI.

METHODS

rs-fMRI was obtained for 28 PD patients (15 with and 13 patients without FOG) who were matched for various demographic and clinical characteristics. Seed to voxel analysis was performed at whole brain level and compared between the two groups.

RESULTS

When compared to patients without FOG, the patients with FOG had reduced functional connectivity across multiple seeds. Major finding was reduced inter-hemispheric connectivity of left parietal opercular cortex with multiple regions of the brain primarily involving the primary somatosensory and auditory areas, which also negatively correlated with the FOGQ scores.

CONCLUSION

Our findings suggest that alterations in the resting state functional connectivity of the opercular parietal cortex may be one of the substrates of FOG. Reduced interhemispheric connectivity probably is the reason for impairment of control and coordination in bilateral leg movements while walking.

Evidence for Enhanced Interoceptive Accuracy in Professional Musicians

Interoception is defined as the perceptual activity involved in the processing of internal bodily signals. While the ability of internal perception is considered a relatively stable trait, recent data suggest that learning to integrate multisensory information can modulate it. Making music is a uniquely rich multisensory experience that has shown to alter motor, sensory, and multimodal representations in the brain of musicians. We hypothesize that musical training also heightens interoceptive accuracy comparable to other perceptual modalities. Thirteen professional singers, twelve string players, and thirteen matched non-musicians were examined using a well-established heartbeat discrimination paradigm complemented by self-reported dispositional traits. Results revealed that both groups of musicians displayed higher interoceptive accuracy than non-musicians, whereas no differences were found between singers and string-players. Regression analyses showed that accumulated musical practice explained about 49% variation in heartbeat perception accuracy in singers but not in string-players. Psychometric data yielded a number of psychologically plausible inter-correlations in musicians related to performance anxiety. However, dispositional traits were not a confounding factor on heartbeat discrimination accuracy. Together, these data provide first evidence indicating that professional musicians show enhanced interoceptive accuracy compared to non-musicians. We argue that musical training largely accounted for this effect.

Attenuation of brain grey matter volume in brachial plexus injury patients

Brachial plexus injury (BPI) causes functional changes in the brain, but the structural changes resulting from BPI remain unknown. In this study, we compared grey matter volume between nine BPI patients and ten healthy controls by means of voxel-based morphometry. This was the first study of cortical morphology in BPI. We found that brain regions including the cerebellum, anterior cingulate cortex, bilateral inferior, medial, superior frontal lobe, and bilateral insula had less grey matter in BPI patients. Most of the affected brain regions of BPI patients are closely related to motor function. We speculate that the loss of grey matter in multiple regions might be the neural basis of the difficulties in the motor rehabilitation of BPI patients. The mapping result might provide new target regions for interventions of motor rehabilitation.

Thalamocortical Sensorimotor Circuit Damage Associated with Disorders of Consciousness for Diffuse Axonal Injury Patients

The relationship of structural and functional brain damage and disorders of consciousness (DOC) for diffuse axonal injury (DAI) is still not fully explored. We employed diffusion tensor imaging (DTI) and resting-state fMRI (RS-fMRI) to examine the changes of resting activations and white matter (WM) integrity for DAI with DOC. WM damages were observed in the body and genu of the corpus callosum, right external capsule (EC) and superior corona radiate (SCR), left superior cerebellar peduncle (SCP) and posterior thalamic radiation (PTR). The RS-fMRI revealed augmented amplitude of low-frequency fluctuation (ALFF) in the anterior cingulate cortex, hippocampus, insula, amygdala and putamen, and reduced ALFF in the precuneus, thalamus, pre-central and post-central gyri. Correlation analysis identified positive associations between the Glasgow Coma Scale (GCS) and activation of the precuneus and between GCS and DTI measurements in the left PTR and SCP, but a negative correlation was found between GCS and activation of the thalamus. Cross modality association analyses indicated that activations of the amygdala and postcentral gyrus were correlated with DTI measurements of the right EC and left PTR respectively. These results implicate that the WM damages in thalamocortical sensorimotor circuit and aberrant brain activity responding to self-awareness and sensation are critical factors to DOC, which expand the current understanding of the neural mechanisms underlying DAI.

A proof-of-principle study of multi-site real-time functional imaging at 3T and 7T: Implementation and validation

Real-time functional Magnetic Resonance Imaging (rtfMRI) is used mainly for neurofeedback or for brain-computer interfaces (BCI). But multi-site rtfMRI could in fact help in the application of new interactive paradigms such as the monitoring of mutual information flow or the controlling of objects in shared virtual environments. For that reason, a previously developed framework that provided an integrated control and data analysis of rtfMRI experiments was extended to enable multi-site rtfMRI. Important new components included a data exchange platform for analyzing the data of both MR scanners independently and/or jointly. Information related to brain activation can be displayed separately or in a shared view. However, a signal calibration procedure had to be developed and integrated in order to permit the connecting of sites that had different hardware and to account for different inter-individual brain activation levels. The framework was successfully validated in a proof-of-principle study with twelve volunteers. Thus the overall concept, the calibration of grossly differing signals, and BCI functionality on each site proved to work as required. To model interactions between brains in real-time, more complex rules utilizing mutual activation patterns could easily be implemented to allow for new kinds of social fMRI experiments.

Hyperactive external awareness against hypoactive internal awareness in disorders of consciousness using resting-state functional MRI: highlighting the involvement of visuo-motor modulation

Resting-state functional MRI (fMRI) has emerged as a valuable tool to characterize the complex states encompassing disorders of consciousness (DOC). Awareness appears to comprise two coexistent, anticorrelated components named the external and internal awareness networks. The present study hypothesizes that DOC interrupts the balance between the internal and external awareness networks. To gain more understanding of this phenomenon, the present study analyzed resting-state fMRI data from 12 patients with DOC versus 12 healthy age-matched controls. The data were explored using independent component analysis and amplitude of low-frequency fluctuation (ALFF) analysis. The results indicated that DOC deactivated midline areas associated with internal awareness. In addition, external awareness was strengthened in DOC because of increased activation in the insula, lingual gyrus, paracentral and supplementary motor area. The activity patterns suggested strengthened external awareness against weakened internal awareness in DOC. In particular, increased activity found in the insula, lingual gyrus, paracentral and supplementary motor area of patients with DOC implied possible involvement of augmented visuo-motor modulation in these patients. DOC is probably related to hyperactive external awareness opposing hypoactive internal awareness. This unique pattern of brain activity may potentially be a prognostic marker for DOC.

Neural correlates of musical creativity: differences between high and low creative subjects

Previous studies of musical creativity suggest that this process involves multi-regional intra and interhemispheric interactions, particularly in the prefrontal cortex. However, the activity of the prefrontal cortex and that of the parieto-temporal regions, seems to depend on the domains of creativity that are evaluated and the task that is performed. In the field of music, only few studies have investigated the brain process of a creative task and none of them have investigated the effect of the level of creativity on the recruit networks. In this work we used magnetic resonance imaging to explore these issues by comparing the brain activities of subjects with higher creative abilities to those with lesser abilities, while the subjects improvised on different rhythmic fragments. We evaluated the products the subjects created during the fMRI scan using two musical parameters: fluidity and flexibility, and classified the subjects according to their punctuation. We examined the relation between brain activity and creativity level. Subjects with higher abilities generated their own creations based on modifications of the original rhythm with little adhesion to it. They showed activation in prefrontal regions of both hemispheres and the right insula. Subjects with lower abilities made only partial changes to the original musical patterns. In these subjects, activation was only observed in left unimodal areas. We demonstrated that the activations of prefrontal and paralimbic areas, such as the insula, are related to creativity level, which is related to a widespread integration of networks that are mainly associated with cognitive, motivational and emotional processes.

Structural basis of empathy and the domain general region in the anterior insular cortex

Empathy is key for healthy social functioning and individual differences in empathy have strong implications for manifold domains of social behavior. Empathy comprises of emotional and cognitive components and may also be closely linked to sensorimotor processes, which go along with the motivation and behavior to respond compassionately to another person's feelings. There is growing evidence for local plastic change in the structure of the healthy adult human brain in response to environmental demands or intrinsic factors. Here we have investigated changes in brain structure resulting from or predisposing to empathy. Structural MRI data of 101 healthy adult females was analyzed. Empathy in fictitious as well as real-life situations was assessed using a validated self-evaluation measure. Furthermore, empathy-related structural effects were also put into the context of a functional map of the anterior insular cortex (AIC) determined by activation likelihood estimate (ALE) meta-analysis of previous functional imaging studies. We found that gray matter (GM) density in the left dorsal AIC correlates with empathy and that this area overlaps with the domain general region (DGR) of the anterior insula that is situated in-between functional systems involved in emotion-cognition, pain, and motor tasks as determined by our meta-analysis. Thus, we propose that this insular region where we find structural differences depending on individual empathy may play a crucial role in modulating the efficiency of neural integration underlying emotional, cognitive, and sensorimotor information which is essential for global empathy.

Therapeutic subthalamic nucleus deep brain stimulation reverses cortico-thalamic coupling during voluntary movements in Parkinson's disease

Deep brain stimulation of the subthalamic nucleus (STN DBS) has become an accepted treatment for patients experiencing the motor complications of Parkinson's disease (PD). While its successes are becoming increasingly apparent, the mechanisms underlying its action remain unclear. Multiple studies using radiotracer-based imaging have investigated DBS-induced regional changes in neural activity. However, little is known about the effect of DBS on connectivity within neural networks; in other words, whether DBS impacts upon functional integration of specialized regions of cortex. In this work, we report the first findings of fMRI in 10 subjects with PD and fully implanted DBS hardware receiving efficacious stimulation. Despite the technical demands associated with the safe acquisition of fMRI data from patients with implanted hardware, robust activation changes were identified in the insula cortex and thalamus in response to therapeutic STN DBS. We then quantified the neuromodulatory effects of DBS and compared sixteen dynamic causal models of effective connectivity between the two identified nodes. Using Bayesian model comparison, we found unequivocal evidence for the modulation of extrinsic (between region), i.e. cortico-thalamic and thalamo-cortical connections. Using Bayesian model parameter averaging we found that during voluntary movements, DBS reversed the effective connectivity between regions of the cortex and thalamus. This casts the therapeutic effects of DBS in a fundamentally new light, emphasising a role in changing distributed cortico-subcortical interactions. We conclude that STN DBS does impact upon the effective connectivity between the cortex and thalamus by changing their sensitivities to extrinsic afferents. Furthermore, we confirm that fMRI is both feasible and is tolerated well by these patients provided strict safety measures are adhered to.

The neural substrate of the ideomotor principle revisited: evidence for asymmetries in action-effect learning

Ideomotor theory holds that the perception or anticipatory imagination of action effects activates motor tendencies toward the action that is known to produce these effects, herein referred to as ideomotor response activation (IRA). IRA presupposes that the agent has previously learned which action produces which effects, and that this learning process has created bidirectional associations between the sensory effect codes and the motor codes producing the sensory effects. Here, we refer to this process as ideomotor learning. In the presented fMRI study, we adopted a standard two-phase ideomotor learning paradigm; a mixed between/within-subjects design allowed us to assess the neural substrate of both, IRA and ideomotor learning. We replicated earlier findings of a hand asymmetry in ideomotor processing with significantly stronger IRA by left-hand than right-hand action effects. Crucially, we traced this effect back to more pronounced associative learning for action-contingent effects of the left hand compared with effects of the right hand. In this context, our findings point to the caudate nucleus and the angular gyrus as central structures of the neural network underlying ideomotor learning.

A rostro-caudal gradient of structured sequence processing in the left inferior frontal gyrus

In this paper, we present two novel perspectives on the function of the left inferior frontal gyrus (LIFG). First, a structured sequence processing perspective facilitates the search for functional segregation within the LIFG and provides a way to express common aspects across cognitive domains including language, music and action. Converging evidence from functional magnetic resonance imaging and transcranial magnetic stimulation studies suggests that the LIFG is engaged in sequential processing in artificial grammar learning, independently of particular stimulus features of the elements (whether letters, syllables or shapes are used to build up sequences). The LIFG has been repeatedly linked to processing of artificial grammars across all different grammars tested, whether they include non-adjacent dependencies or mere adjacent dependencies. Second, we apply the sequence processing perspective to understand how the functional segregation of semantics, syntax and phonology in the LIFG can be integrated in the general organization of the lateral prefrontal cortex (PFC). Recently, it was proposed that the functional organization of the lateral PFC follows a rostro-caudal gradient, such that more abstract processing in cognitive control is subserved by more rostral regions of the lateral PFC. We explore the literature from the viewpoint that functional segregation within the LIFG can be embedded in a general rostro-caudal abstraction gradient in the lateral PFC. If the lateral PFC follows a rostro-caudal abstraction gradient, then this predicts that the LIFG follows the same principles, but this prediction has not yet been tested or explored in the LIFG literature. Integration might provide further insights into the functional architecture of the LIFG and the lateral PFC.

Altered spontaneous activity in anisometropic amblyopia subjects: revealed by resting-state FMRI

Amblyopia, also known as lazy eye, usually occurs during early childhood and results in poor or blurred vision. Recent neuroimaging studies have found cortical structural/functional abnormalities in amblyopia. However, until now, it was still not known whether the spontaneous activity of the brain changes in amblyopia subjects. In the present study, regional homogeneity (ReHo), a measure of the homogeneity of functional magnetic resonance imaging signals, was used for the first time to investigate changes in resting-state local spontaneous brain activity in individuals with anisometropic amblyopia. Compared with age- and gender-matched subjects with normal vision, the anisometropic amblyopia subjects showed decreased ReHo of spontaneous brain activity in the right precuneus, the left medial prefrontal cortex, the left inferior frontal gyrus, and the left cerebellum, and increased ReHo of spontaneous brain activity was found in the bilateral conjunction area of the postcentral and precentral gyri, the left paracentral lobule, the left superior temporal gyrus, the left fusiform gyrus, the conjunction area of the right insula, putamen and the right middle occipital gyrus. The observed decreases in ReHo may reflect decreased visuo-motor processing ability, and the increases in ReHo in the somatosensory cortices, the motor areas and the auditory area may indicate compensatory plasticity in amblyopia.

The Investigation of Simultaneous Interpreters as an Alternative Approach to Address the Signature of Multilingual Speech Processing

In the field of cognitive neuroscience, understanding the functional, temporal, and anatomical characteristics of multilingual speech processing has previously been a topic of intense investigations. In this article, I will attempt to describe how the investigation of simultaneous interpreters can be used as a fruitful and alternative approach for better comprehending the neuronal signature of multilingual speech processing, foreign language acquisition, as well as the functional and structural adaptivity of the human brain in general. Thereby, I will primarily focus on the commonalities underlying different degrees of speech competence rather than on the differences. In this context, particular emphasis will be placed on the contribution of extra-linguistic brain functions which are necessary for accommodating cognitive and motor control mechanisms in the multilingual brain. Certainly, the framework outlined in this article will not replace the meanwhile established psycholinguistic or neuroscientific models of speech processing, but only attempts to provide a novel and alternative perspective.

Pain and emotion in the insular cortex: evidence for functional reorganization in major depression

Major Depressive Disorder (MDD) is among the top causes of disability worldwide and many patients with depression experience pain symptoms. Little is known regarding what makes depressed persons feel like they are in pain. An increasing number of neuroimaging studies show that both physical pain and depression involve the insular cortex. The present study aimed to investigate whether emotional processing in MDD patients is topologically shifted towards the insular area(s) involved in pain processing in healthy individuals. To achieve this aim, we investigated the functional organization of the insula by conducting meta-analyses of previously published neuroimaging studies on: (1) emotion in patients with MDD, (2) emotion in healthy subjects, and (3) physical pain in healthy subjects. Our results show that the dorsal part of the insula is reproducibly activated during experimental pain in healthy individuals, with multiple separate pain-related areas aligned along its dorsal border. Regions with maximal pain-related activation likelihood estimate (ALE) were located in the posterior (left) and dorsal mid-anterior insula (left and right). Furthermore, emotion-related peaks in healthy subjects were found both in its ventral (as shown in a previous meta-analysis) and dorsal anterior part. Importantly, emotion-related peaks in depressed patients were shifted to the dorsal anterior insula, where regions related to physical pain in healthy subjects are located. This shift was reflected in the observation that median z-coordinates of emotion-related responses in the left hemisphere were significantly larger in depressed patients than in healthy controls. This shift of emotion-related responses to the dorsal insula, i.e., where pain-processing takes place in healthy subjects, may play a role in "emotional allodynia" - a notion that individuals with MDD experience pain in response to stimuli that are normally not painful.

Rhythm evokes action: early processing of metric deviances in expressive music by experts and laymen revealed by ERP source imaging

To examine how musical expertise tunes the brain to subtle metric anomalies in an ecological musical context, we presented piano compositions ending on standard and deviant cadences (endings) to expert pianists and musical laymen, while high-density EEG was recorded. Temporal expectancies were manipulated by substituting standard "masculine" cadences at metrically strong positions with deviant, metrically unaccented, "feminine" cadences. Experts detected metrically deviant cadences better than laymen. Analyses of event-related potentials demonstrated that an early P3a-like component (~150-300 ms), elicited by musical closure, was significantly enhanced at frontal and parietal electrodes in response to deviant endings in experts, whereas a reduced response to deviance occurred in laymen. Putative neuronal sources contributing to the modulation of this component were localized in a network of brain regions including bilateral supplementary motor areas, middle and posterior cingulate cortex, precuneus, associative visual areas, as well as in the right amygdala and insula. In all these regions, experts showed enhanced responses to metric deviance. Later effects demonstrated enhanced activations within the same brain network, as well as higher processing speed for experts. These results suggest that early brain responses to metric deviance in experts may rely on motor representations mediated by the supplementary motor area and motor cingulate regions, in addition to areas involved in self-referential imagery and relevance detection. Such motor representations could play a role in temporal sensory prediction evolved from musical training and suggests that rhythm evokes action more strongly in highly trained instrumentalists.

Neuroarchitecture of verbal and tonal working memory in nonmusicians and musicians

Working memory (WM) for auditory information has been thought of as a unitary system, but whether WM for verbal and tonal information relies on the same or different functional neuroarchitectures has remained unknown. This fMRI study examines verbal and tonal WM in both nonmusicians (who are trained in speech, but not in music) and highly trained musicians (who are trained in both domains). The data show that core structures of WM are involved in both tonal and verbal WM (Broca's area, premotor cortex, pre-SMA/SMA, left insular cortex, inferior parietal lobe), although with significantly different structural weightings, in both nonmusicians and musicians. Additionally, musicians activated specific subcomponents only during verbal (right insular cortex) or only during tonal WM (right globus pallidus, right caudate nucleus, and left cerebellum). These results reveal the existence of two WM systems in musicians: A phonological loop supporting rehearsal of phonological information, and a tonal loop supporting rehearsal of tonal information. Differences between groups for tonal WM, and between verbal and tonal WM within musicians, were mainly related to structures involved in controlling, programming and planning of actions, thus presumably reflecting differences in action-related sensorimotor coding of verbal and tonal information.