Parametric analysis of rate-dependent hemodynamic response functions of cortical and subcortical brain structures during auditorily cued finger tapping: a fMRI study

A review of psychological and neuroscientific research on musical groove

When listening to music, we naturally move our bodies rhythmically to the beat, which can be pleasurable and difficult to resist. This pleasurable sensation of wanting to move the body to music has been called "groove." Following pioneering humanities research, psychological and neuroscientific studies have provided insights on associated musical features, behavioral responses, phenomenological aspects, and brain structural and functional correlates of the groove experience. Groove research has advanced the field of music science and more generally informed our understanding of bidirectional links between perception and action, and the role of the motor system in prediction. Activity in motor and reward-related brain networks during music listening is associated with the groove experience, and this neural activity is linked to temporal prediction and learning. This article reviews research on groove as a psychological phenomenon with neurophysiological correlates that link musical rhythm perception, sensorimotor prediction, and reward processing. Promising future research directions range from elucidating specific neural mechanisms to exploring clinical applications and socio-cultural implications of groove.

Improving fMRI in Parkinson's disease by accounting for brain region-specific activity patterns

In functional magnetic imaging (fMRI) in Parkinson's disease (PD), a paradigm consisting of blocks of finger tapping and rest along with a corresponding general linear model (GLM) is often used to assess motor activity. However, this method has three limitations: (i) Due to the strong magnetic field and the confined environment of the cylindrical bore, it is troublesome to accurately monitor motor output and, therefore, variability in the performed movement is typically ignored. (ii) Given the loss of dopaminergic neurons and ongoing compensatory brain mechanisms, motor control is abnormal in PD. Therefore, modeling of patients' tapping with a constant amplitude (using a boxcar function) and the expected Parkinsonian motor output are prone to mismatch. (iii) The motor loop involves structures with distinct hemodynamic responses, for which only one type of modeling (e.g., modeling the whole block of finger tapping) may not suffice to capture these structure's temporal activation. The first two limitations call for considering results from online recordings of the real motor output that may lead to significant sensitivity improvements. This was shown in previous work using a non-magnetic glove to capture details of the patients' finger movements in a so-called kinematic approach. For the third limitation, modeling motion initiation instead of the whole tapping block has been suggested to account for different temporal activation signatures of the motor loop's structures. In the present study we propose improvements to the GLM as a tool to study motor disorders. For this, we test the robustness of the kinematic approach in an expanded cohort (n = 31), apply more conservative statistics than in previous work, and evaluate the benefits of an event-related model function. Our findings suggest that the integration of the kinematic approach offers a general improvement in detecting activations in subcortical structures, such as the basal ganglia. Additionally, modeling motion initiation using an event-related design yielded superior performance in capturing medication-related effects in the putamen. Our results may guide adaptations in analysis strategies for functional motor studies related to PD and also in more general applications.

Gating at cortical level contributes to auditory-motor synchronization during repetitive finger tapping

Sensory integration contributes to temporal coordination of the movement with external rhythms. How the information flowing of sensory inputs is regulated with increasing tapping rates and its function remains unknown. Here, somatosensory evoked potentials to ulnar nerve stimulation were recorded during auditory-cued repetitive right-index finger tapping at 0.5, 1, 2, 3, and 4 Hz in 13 healthy subjects. We found that sensory inputs were suppressed at subcortical level (represented by P14) and primary somatosensory cortex (S1, represented by N20/P25) during repetitive tapping. This suppression was decreased in S1 but not in subcortical level during fast repetitive tapping (2, 3, and 4 Hz) compared with slow repetitive tapping (0.5 and 1 Hz). Furthermore, we assessed the ability to analyze temporal information in S1 by measuring the somatosensory temporal discrimination threshold (STDT). STDT increased during fast repetitive tapping compared with slow repetitive tapping, which was negatively correlated with the task performance of phase shift and positively correlated with the peak-to-peak amplitude (% of resting) in S1 but not in subcortical level. These novel findings indicate that the increased sensory input (lower sensory gating) in S1 may lead to greater temporal uncertainty for sensorimotor integration dereasing the performance of repetitive movement during increasing tapping rates.

Dissecting Motor and Cognitive Component Processes of a Finger-Tapping Task With Hybrid Dopamine Positron Emission Tomography and Functional Magnetic Resonance Imaging

Striatal dopamine is involved in facilitation of motor action as well as various cognitive and emotional functions. Positron emission tomography (PET) is the primary imaging method used to investigate dopamine function in humans. Previous PET studies have shown striatal dopamine release during simple finger tapping in both the putamen and the caudate. It is likely that dopamine release in the putamen is related to motor processes while dopamine release in the caudate could signal sustained cognitive component processes of the task, but the poor temporal resolution of PET has hindered firm conclusions. In this study we simultaneously collected [11C]Raclopride PET and functional Magnetic Resonance Imaging (fMRI) data while participants performed finger tapping, with fMRI being able to isolate activations related to individual tapping events. The results revealed fMRI-PET overlap in the bilateral putamen, which is consistent with a motor component process. Selective PET responses in the caudate, ventral striatum, and right posterior putamen, were also observed but did not overlap with fMRI responses to tapping events, suggesting that these reflect non-motor component processes of finger tapping. Our findings suggest an interplay between motor and non-motor-related dopamine release during simple finger tapping and illustrate the potential of hybrid PET-fMRI in revealing distinct component processes of cognitive functions.

Local and distributed cortical markers of effort expenditure during sustained goal pursuit

The adaptive adjustment of behavior in pursuit of desired goals is critical for survival. To accomplish this complex feat, individuals must weigh the potential benefits of a given action against time, energy, and resource costs. Here, we examine brain responses associated with willingness to exert physical effort during the sustained pursuit of desired goals. Our analyses reveal a distributed pattern of brain activity in aspects of ventral medial prefrontal cortex that tracks with trial-level variability in effort expenditure. Indicating the brain represents echoes of effort at the point of feedback, whole-brain searchlights identified signals reflecting past effort expenditure in medial and lateral prefrontal cortices, encompassing broad swaths of frontoparietal and dorsal attention networks. These data have important implications for our understanding of how the brain's valuation mechanisms contend with the complexity of real-world dynamic environments with relevance for the study of behavior across health and disease.

Oral diadochokinetic rates across languages: Multilingual speakers comparison

BACKGROUND

It is unclear whether oral diadochokinetic rate (oral-DDK) performance is affected by different languages within a multilingual country.

AIMS

This study investigated the effects of age, sex, and stimulus type (real word in L1, L2 vs. non-word) on oral-DDK rates among healthy Malaysian-Malay speakers in order to establish language- and age-sensitive norms. The second aim was to compared the nonword 'pataka' oral-DDK rates produced by Malaysian-Malay speakers on currently available normative data for Hebrew speakers and Malaysian-Mandarin speakers.

METHODS & PROCEDURES

Oral-DDK performance of 90 participants (aged 20-77 years) using nonword ('pataka'), Malay real word ('patahkan'), and English real word ('buttercake') was audio recorded. The number of syllables produced in 8 seconds was calculated. Mixed analysis of variance (ANOVA) was conducted to examine the effects of stimulus type (nonword, Malay, and English real word), sex (male, female), age (younger, 20-40 years; middle, 41-60 years; older, ≥61 years), and their interactions on the oral-DDK rate. Data obtained were also compared with the raw data of Malaysian-Mandarin and Hebrew speakers from the previous studies.

OUTCOMES & RESULTS

A normative oral-DDK rate has been established for healthy Malaysian-Malay speakers. The oral-DDK rate was significantly affected by stimuli (p < 0.001). Malay real word showed the slowest rate, whereas there was no significant difference between English real word and nonword. The oral-DDK rate for Malay speakers was significantly higher than Mandarin and Hebrew speakers across stimuli (all p < 0.01). Interestingly, oral-DDK rates were not affected by age group for Malay speakers.

CONCLUSIONS & IMPLICATIONS

Stimuli type and language affect the oral-DDK rate, indicating that speech-language therapists should consider using language-specific norms when assessing multilingual speakers.

WHAT THIS PAPER ADDS

What is already known on the subject Age, sex, and language are factors that need to be considered when developing oral-DDK normative protocol. It is unclear whether oral-DDK performance is affected by different languages within a multilingual country. What this paper adds to existing knowledge No ageing effect across real word versus nonword on oral-DDK performance was observed among Malaysian-Malay speakers, contrasting with current available literature that speech movements slow down as we age. Additionally, Malaysian-Malay speakers have faster oral-DDK rates than Malaysian-Mandarin and Hebrew speakers across all stimuli. What are the potential or actual clinical implications of this work? Establishing normative data of different languages will enable speech-language therapists to select the appropriate reference dataset based on the language mastery of these multilingual speakers.

Pre-surgical fMRI Localization of the Hand Motor Cortex in Brain Tumors: Comparison Between Finger Tapping Task and a New Visual-Triggered Finger Movement Task

Introduction: Pre-surgical mapping is clinically essential in the surgical management of brain tumors to preserve functions. A common technique to localize eloquent areas is functional magnetic resonance imaging (fMRI). In tumors involving the peri-rolandic regions, the finger tapping task (FTT) is typically administered to delineate the functional activation of hand-knob area. However, its selectivity may be limited. Thus, here, a novel cue-induced fMRI task was tested, the visual-triggered finger movement task (VFMT), aimed at eliciting a more accurate functional cortical mapping of the hand region as compared with FTT.

Method: Twenty patients with glioma in the peri-rolandic regions underwent pre-operative mapping performing both FTT and VFMT. The fMRI data were analyzed for surgical procedures. When the craniotomy allowed to expose the motor cortex, the correspondence with intraoperative direct electrical stimulation (DES) was evaluated through sensitivity and specificity (mean sites = 11) calculated as percentage of true-positive and true-negative rates, respectively.

Results: Both at group level and at single-subject level, differences among the tasks emerged in the functional representation of the hand-knob. Compared with FTT, VFMT showed a well-localized activation within the hand motor area and a less widespread activation in associative regions. Intraoperative DES confirmed the greater specificity (97%) and sensitivity (100%) of the VFMT in determining motor eloquent areas.

Conclusion: The study provides a novel, external-triggered fMRI task for pre-surgical motor mapping. Compared with the traditional FTT, the new VFMT may have potential implications in clinical fMRI and surgical management due to its focal identification of the hand-knob region and good correspondence to intraoperative DES.

Directionality of corticomuscular coupling in essential tremor and cortical myoclonic tremor

OBJECTIVE

A role of the motor cortex in tremor generation in essential tremor (ET) is assumed, yet the directionality of corticomuscular coupling is unknown. Our aim is to clarify the role of the motor cortex. To this end we also study 'familial cortical myoclonic tremor with epilepsy' (FCMTE) and slow repetitive voluntary movements with a known cortical drive.

METHODS

Directionality of corticomuscular coupling (EEG-EMG) was studied with renormalized partial directed coherence (rPDC) during tremor in 25 ET patients, 25 healthy controls (mimicked) and in seven FCMTE patients; and during a self-paced 2 Hz task in eight ET patients and seven healthy controls.

RESULTS

Efferent coupling around tremor frequency was seen in 33% of ET patients, 45.5% of healthy controls, all FCMTE patients, and, around 2 Hz, in all ET patients and all healthy controls. Ascending coupling, seen in the majority of all participants, was weaker in ET than in healthy controls around 5-6 Hz.

CONCLUSIONS

Possible explanations are that tremor in ET results from faulty subcortical output bypassing the motor cortex; rate-dependent transmission similar to generation of rhythmic movements; and/or faulty feedforward mechanism resulting from decreased afferent (sensory) coupling.

SIGNIFICANCE

A linear cortical drive is lacking in the majority of ET patients.

Behavioural performance improvement in visuomotor learning correlates with functional and microstructural brain changes

A better understanding of practice-induced functional and structural changes in our brains can help us design more effective learning environments that provide better outcomes. Although there is growing evidence from human neuroimaging that experience-dependent brain plasticity is expressed in measurable brain changes that are correlated with behavioural performance, the relationship between behavioural performance and structural or functional brain changes, and particularly the time course of these changes, is not well characterised. To understand the link between neuroplastic changes and behavioural performance, 15 healthy participants in this study followed a systematic eye movement training programme for 30 min daily at home, 5 days a week and for 6 consecutive weeks. Behavioural performance statistics and eye tracking data were captured throughout the training period to evaluate learning outcomes. Imaging data (DTI and fMRI) were collected at baseline, after two and six weeks of continuous training, and four weeks after training ended. Participants showed significant improvements in behavioural performance (faster task completion time, lower fixation number and fixation duration). Spatially overlapping reductions in microstructural diffusivity measures (MD, AD and RD) and functional activation increases (BOLD signal) were observed in two main areas: extrastriate visual cortex (V3d) and the frontal part of the cerebellum/Fastigial Oculomotor Region (FOR), which are both involved in visual processing. An increase of functional activity was also recorded in the right frontal eye field. Behavioural, structural and functional changes were correlated. Microstructural change is a better predictor for long-term behavioural change than functional activation is, whereas the latter is superior in predicting instantaneous performance. Structural and functional measures at week 2 of the training programme also predict performance at week 6 and 10, which suggests that imaging data at an early stage of training may be useful in optimising practice environments or rehabilitative training programmes.

Comparing hand movement rate dependence of cerebral blood volume and BOLD responses at 7T

Functional magnetic resonance imaging (fMRI) based on the Blood Oxygenation Level Dependent (BOLD) contrast takes advantage of the coupling between neuronal activity and the hemodynamics to allow a non-invasive localisation of the neuronal activity. In general, fMRI experiments assume a linear relationship between neuronal activation and the observed hemodynamics. However, the relationship between BOLD responses, neuronal activity, and behaviour are often nonlinear. In addition, the nonlinearity between BOLD responses and behaviour may be related to neuronal process rather than a neurovascular uncoupling. Further, part of the nonlinearity may be driven by vascular nonlinearity effects in particular from large vessel contributions. fMRI based on cerebral blood volume (CBV), promises a higher microvascular specificity, potentially without vascular nonlinearity effects and reduced contamination of the large draining vessels compared to BOLD. In this study, we aimed to investigate differences in BOLD and VASO-CBV signal changes during a hand movement task over a broad range of movement rates. We used a double readout 3D-EPI sequence at 7T to simultaneously measure VASO-CBV and BOLD responses in the sensorimotor cortex. The measured BOLD and VASO-CBV responses increased very similarly in a nonlinear fashion, plateauing for movement rates larger than 1 Hz. Our findings show a tight relationship between BOLD and VASO-CBV responses, indicating that the overall interplay of CBV and BOLD responses are similar for the assessed range of movement rates. These results suggest that the observed nonlinearity of neuronal origin is already present in VASO-CBV measurements, and consequently shows relatively unchanged BOLD responses.

MR Imaging of SCA3/MJD

Spinocerebellar ataxia type 3/Machado-Joseph disease (SCA3/MJD) is a progressive autosomal dominantly inherited cerebellar ataxia characterized by the aggregation of polyglutamine-expanded protein within neuronal nuclei in the brain, which can lead to brain damage that precedes the onset of clinical manifestations. Magnetic resonance imaging (MRI) techniques such as morphometric MRI, diffusion tensor imaging (DTI), functional magnetic resonance imaging (fMRI), and magnetic resonance spectroscopy (MRS) have gained increasing attention as non-invasive and quantitative methods for the assessment of structural and functional alterations in clinical SCA3/MJD patients as well as preclinical carriers. Morphometric MRI has demonstrated typical patterns of atrophy or volume loss in the cerebellum and brainstem with extensive lesions in some supratentorial areas. DTI has detected widespread microstructural alterations in brain white matter, which indicate disrupted brain anatomical connectivity. Task-related fMRI has presented unusual brain activation patterns within the cerebellum and some extracerebellar tissue, reflecting the decreased functional connectivity of these brain regions in SCA3/MJD subjects. MRS has revealed abnormal neurochemical profiles, such as the levels or ratios of N-acetyl aspartate, choline, and creatine, in both clinical cases and preclinical cases before the alterations in brain anatomical structure. Moreover, a number of studies have reported correlations of MR imaging alterations with clinical and genetic features. The utility of these MR imaging techniques can help to identify preclinical SCA3/MJD carriers, monitor disease progression, evaluate response to therapeutic interventions, and illustrate the pathophysiological mechanisms underlying the occurrence, development, and prognosis of SCA3/MJD.

Functional connectivity of supplementary motor area during finger-tapping in major depression

Psychomotor disturbance has been consistently regarded as an essential feature of depressive disorders. Studying objectively measurable motor behaviors like finger-tapping may help advance the diagnostic methods. Twenty-five patients with major depressive disorder (MDD) and 15 healthy participants underwent functional magnetic resonance imaging (fMRI) measurements while tapping their index fingers. The finger-tapping (FT) task was performed by the right hand (the tapping frequency varied between 1, 2 and 4 Hz) or both hands either in synchrony or alternation (the tapping frequency varied between 1 and 2 Hz). A mixed-model ANOVA was used for between- and within-group comparisons of the task accuracy and fMRI percent signal change in the supplementary motor area (SMA) during 26-second sequences of finger-tapping. Furthermore, using seed-based correlation analyses we compared the connectivity of the SMA between the two samples. At the behavioral level, no significant group differences in FT performance between the patient and control groups was observed. The mean fMRI percent signal change of the SMA was significantly elevated at higher levels of speed in both groups. In the MDD group, an increased connectivity of the left SMA with the bilateral cortical and cerebellar motor- and vision-related regions was found. Most importantly, a decreased connectivity between the SMA and the basal ganglia was found at frequencies of 4 Hz. Our findings support the contention that, in depression, brain connectivity measures during motor performance may reveal deviant neural processes that are potentially relevant to measurable (bio)markers for individual diagnosis and treatment.

Influence of Alternate Hot and Cold Thermal Stimulation in Cortical Excitability in Healthy Adults: An fMRI Study

Stroke rehabilitation using alternate hot and cold thermal stimulation (altTS) has been reported to improve motor function in hemiplegia; however, the influence of brain excitability induced by altTS remains unclear. This study examined cortical activation induced by altTS in healthy adults, focusing on motor-related areas. This involved a repeated crossover experimental design with two temperature settings (innocuous altTS with alternate heat-pain and cold-pain thermal and noxious altTS with alternate heat and cold thermal) testing both arms (left side and right side). Thirty-one healthy, right-handed participants received four episodes of altTS on four separate days. Functional magnetic resonance imaging scans were performed both before and after each intervention to determine whether altTS intervention affects cortical excitability, while participants performed a finger-tapping task during scanning. The findings revealed greater response intensity of cortical excitability in participants who received noxious altTS in the primary motor cortex, supplementary motor cortex, and somatosensory cortex than in those who received innocuous altTS. Moreover, there was more motor-related excitability in the contra-lateral brain when heat was applied to the dominant arm, and more sensory-associated excitability in the contra-lateral brain when heat was applied to the nondominant arm. The findings highlight the effect of heat on cortical excitability and provide insights into the application of altTS in stroke rehabilitation.

The Neural Correlates of Time: A Meta-analysis of Neuroimaging Studies

During the last two decades, our inner sense of time has been repeatedly studied with the help of neuroimaging techniques. These investigations have suggested the specific involvement of different brain areas in temporal processing. At least two distinct neural systems are likely to play a role in measuring time: One is mainly constituted of subcortical structures and is supposed to be more related to the estimation of time intervals below the 1-sec range (subsecond timing tasks), and the other is mainly constituted of cortical areas and is supposed to be more related to the estimation of time intervals above the 1-sec range (suprasecond timing tasks). Tasks can then be performed in motor or nonmotor (perceptual) conditions, thus providing four different categories of time processing. Our meta-analytical investigation partly confirms the findings of previous meta-analytical works. Both sub- and suprasecond tasks recruit cortical and subcortical areas, but subcortical areas are more intensely activated in subsecond tasks than in suprasecond tasks, which instead receive more contributions from cortical activations. All the conditions, however, show strong activations in the SMA, whose rostral and caudal parts have an important role not only in the discrimination of different time intervals but also in relation to the nature of the task conditions. This area, along with the striatum (especially the putamen) and the claustrum, is supposed to be an essential node in the different networks engaged when the brain creates our sense of time.

Encoding of kinetic and kinematic movement parameters in the sensorimotor cortex: A Brain-Computer Interface perspective

For severely paralyzed people, Brain-Computer Interfaces (BCIs) can potentially replace lost motor output and provide a brain-based control signal for augmentative and alternative communication devices or neuroprosthetics. Many BCIs focus on neuronal signals acquired from the hand area of the sensorimotor cortex, employing changes in the patterns of neuronal firing or spectral power associated with one or more types of hand movement. Hand and finger movement can be described by two groups of movement features, namely kinematics (spatial and motion aspects) and kinetics (muscles and forces). Despite extensive primate and human research, it is not fully understood how these features are represented in the SMC and how they lead to the appropriate movement. Yet, the available information may provide insight into which features are most suitable for BCI control. To that purpose, the current paper provides an in-depth review on the movement features encoded in the SMC. Even though there is no consensus on how exactly the SMC generates movement, we conclude that some parameters are well represented in the SMC and can be accurately used for BCI control with discrete as well as continuous feedback. However, the vast evidence also suggests that movement should be interpreted as a combination of multiple parameters rather than isolated ones, pleading for further exploration of sensorimotor control models for accurate BCI control.

Neural substrates of internally-based and externally-cued timing: An activation likelihood estimation (ALE) meta-analysis of fMRI studies

A dynamic interplay exists between Internally-Based (IBT) and Externally-Cued (ECT) time processing. While IBT processes support the self-generation of context-independent temporal representations, ECT mechanisms allow constructing temporal representations primarily derived from the structure of the sensory environment. We performed an activation likelihood estimation (ALE) meta-analysis on 177 fMRI experiments, from 79 articles, to identify brain areas involved in timing; two individual ALEs tested the hypothesis of a neural segregation between IBT and ECT. The general ALE highlighted a network involving supplementary motor area (SMA), intraparietal sulcus, inferior frontal gyrus (IFG), insula (INS) and basal ganglia. We found evidence of a partial dissociation between IBT and ECT. IBT relies on a subset of areas also involved in ECT, however ECT tasks activate SMA, right IFG, left precentral gyrus and INS in a significantly stronger way. Present results suggest that ECT involves the detection of environmental temporal regularities and their integration with the output of the IBT processing, to generate a representation of time which reflects the temporal metric of the environment.

Temporal Processing in Audition: Insights from Music

Music is a curious example of a temporally patterned acoustic stimulus, and a compelling pan-cultural phenomenon. This review strives to bring some insights from decades of music psychology and sensorimotor synchronization (SMS) literature into the mainstream auditory domain, arguing that musical rhythm perception is shaped in important ways by temporal processing mechanisms in the brain. The feature that unites these disparate disciplines is an appreciation of the central importance of timing, sequencing, and anticipation. Perception of musical rhythms relies on an ability to form temporal predictions, a general feature of temporal processing that is equally relevant to auditory scene analysis, pattern detection, and speech perception. By bringing together findings from the music and auditory literature, we hope to inspire researchers to look beyond the conventions of their respective fields and consider the cross-disciplinary implications of studying auditory temporal sequence processing. We begin by highlighting music as an interesting sound stimulus that may provide clues to how temporal patterning in sound drives perception. Next, we review the SMS literature and discuss possible neural substrates for the perception of, and synchronization to, musical beat. We then move away from music to explore the perceptual effects of rhythmic timing in pattern detection, auditory scene analysis, and speech perception. Finally, we review the neurophysiology of general timing processes that may underlie aspects of the perception of rhythmic patterns. We conclude with a brief summary and outlook for future research.

Cortical and subcortical areas involved in the regulation of reach movement speed in the human brain: An fMRI study

Reach movements are characterized by multiple kinematic variables that can change with age or due to medical conditions such as movement disorders. While the neural control of reach direction is well investigated, the elements of the neural network regulating speed (the nondirectional component of velocity) remain uncertain. Here, we used a custom made magnetic resonance (MR)-compatible arm movement tracking system to capture the real kinematics of the arm movements while measuring brain activation with functional magnetic resonance imaging to reveal areas in the human brain in which BOLD-activation covaries with the speed of arm movements. We found significant activation in multiple cortical and subcortical brain regions positively correlated with endpoint (wrist) speed (speed-related activation), including contralateral premotor cortex (PMC), supplementary motor area (SMA), thalamus (putative VL/VA nuclei), and bilateral putamen. The hand and arm regions of primary sensorimotor cortex (SMC) and a posterior region of thalamus were significantly activated by reach movements but showed a more binary response characteristics (movement present or absent) than with continuously varying speed. Moreover, a subregion of contralateral SMA also showed binary movement activation but no speed-related BOLD-activation. Effect size analysis revealed bilateral putamen as the most speed-specific region among the speed-related clusters whereas primary SMC showed the strongest specificity for movement versus non-movement discrimination, independent of speed variations. The results reveal a network of multiple cortical and subcortical brain regions that are involved in speed regulation among which putamen, anterior thalamus, and PMC show highest specificity to speed, suggesting a basal-ganglia-thalamo-cortical loop for speed regulation.

Fast noninvasive functional diffuse optical tomography for brain imaging

Advances in epilepsy studies have shown that specific changes in hemodynamics precede and accompany seizure onset and propagation. However, it has been challenging to noninvasively detect these changes in real time and in humans, due to the lack of fast functional neuroimaging tools. In this study, we present a functional diffuse optical tomography (DOT) method with the guidance of an anatomical human head atlas for 3-dimensionally mapping the brain in real time. Central to our DOT system is a human head interface coupled with a technique that can incorporate topological information of the brain surface into the DOT image reconstruction. The performance of the DOT system was tested by imaging motor tasks-involved brain activities on N = 6 subjects (3 epilepsy patients and 3 healthy controls). We observed diffuse areas of activations from the reconstructed [HbT] images of patients, relative to more focal activations for healthy subjects. Moreover, significant pretask hemodynamic activations were also seen in the motor cortex of patients, which indicated abnormal activities persistent in the brain of an epilepsy patient. This work demonstrates that fast functional DOT is a valuable tool for noninvasive 3-dimensional mapping of brain hemodynamics.

Localization of cortical primary motor area of the hand using navigated transcranial magnetic stimulation, BOLD and arterial spin labeling fMRI

BACKGROUND

Although the relationship between neuronavigated transcranial magnetic stimulation (nTMS) and functional magnetic resonance imaging (fMRI) has been widely studied in motor mapping, it is unknown how the motor response type or the choice of motor task affect this relationship.

NEW METHOD

Centers of gravity (CoGs) and response maxima were measured with blood-oxygen-level dependent (BOLD) and arterial spin labeling (ASL) fMRI during motor tasks against nTMS CoGs and response maxima, which were mapped with motor evoked potentials (MEPs) and silent periods (SPs).

RESULTS

No differences in motor representations (CoGs and response maxima) were observed in lateral-medial direction (p=0.265). fMRI methods localized the motor representation more posterior than nTMS (p<0.001). This was not affected by the BOLD fMRI motor task (p>0.999) nor nTMS response type (p>0.999). ASL fMRI maxima did not differ from the nTMS nor BOLD fMRI CoGs (p≥0.070), but the ASL CoG was deeper in comparison to other methods (p≤0.042). The BOLD fMRI motor task did not influence the depth of the motor representation (p≥0.745). The median Euclidean distances between the nTMS and fMRI motor representations varied between 7.7mm and 14.5mm and did not differ between the methods (F≤1.23, p≥0.318).

COMPARISON WITH EXISTING METHODS

The relationship between fMRI and nTMS mapped excitatory (MEP) and inhibitory (SP) responses, and whether the choice of motor task affects this relationship, have not been studied before.

CONCLUSIONS

The congruence between fMRI and nTMS is good. The choice of nTMS motor response type nor BOLD fMRI motor task had no effect on this relationship.

Sensory Entrainment Mechanisms in Auditory Perception: Neural Synchronization Cortico-Striatal Activation

The auditory system displays modulations in sensitivity that can align with the temporal structure of the acoustic environment. This sensory entrainment can facilitate sensory perception and is particularly relevant for audition. Systems neuroscience is slowly uncovering the neural mechanisms underlying the behaviorally observed sensory entrainment effects in the human sensory system. The present article summarizes the prominent behavioral effects of sensory entrainment and reviews our current understanding of the neural basis of sensory entrainment, such as synchronized neural oscillations, and potentially, neural activation in the cortico-striatal system.

The Neural Substrates Underlying the Implementation of Phonological Rule in Lexical Tone Production: An fMRI Study of the Tone 3 Sandhi Phenomenon in Mandarin Chinese

This study examined the neural substrates underlying the implementation of phonological rule in lexical tone by the Tone 3 sandhi phenomenon in Mandarin Chinese. Tone 3 sandhi is traditionally described as the substitution of Tone 3 with Tone 2 when followed by another Tone 3 (33 →23) during speech production. Tone 3 sandhi enables the examination of tone processing in the phonological level with the least involvement of segments. Using the fMRI technique, we measured brain activations corresponding to the monosyllable and disyllable sequences of the four Chinese lexical tones, while manipulating the requirement on overt oral response. The application of Tone 3 sandhi to disyllable sequence of Tone 3 was confirmed by our behavioral results. Larger brain responses to overtly produced disyllable Tone 3 (33 > 11, 22, and 44) were found in right posterior IFG by both whole-brain and ROI analyses. We suggest that the right IFG was responsible for the processing of Tone 3 sandhi. Intense temporo-frontal interaction is needed in speech production for self-monitoring. The involvement of the right IFG in tone production might result from its interaction with the right auditory cortex, which is known to specialize in pitch. Future studies using tools with better temporal resolutions are needed to illuminate the dynamic interaction between the right inferior frontal regions and the left-lateralized language network in tone languages.

The role of the supplementary motor area for speech and language processing

Apart from its function in speech motor control, the supplementary motor area (SMA) has largely been neglected in models of speech and language processing in the brain. The aim of this review paper is to summarize more recent work, suggesting that the SMA has various superordinate control functions during speech communication and language reception, which is particularly relevant in case of increased task demands. The SMA is subdivided into a posterior region serving predominantly motor-related functions (SMA proper) whereas the anterior part (pre-SMA) is involved in higher-order cognitive control mechanisms. In analogy to motor triggering functions of the SMA proper, the pre-SMA seems to manage procedural aspects of cognitive processing. These latter functions, among others, comprise attentional switching, ambiguity resolution, context integration, and coordination between procedural and declarative memory structures. Regarding language processing, this refers, for example, to the use of inner speech mechanisms during language encoding, but also to lexical disambiguation, syntax and prosody integration, and context-tracking.

Parametric fMRI of paced motor responses uncovers novel whole-brain imaging biomarkers in spinocerebellar ataxia type 3

Machado-Joseph Disease, inherited type 3 spinocerebellar ataxia (SCA3), is the most common form worldwide. Neuroimaging and neuropathology have consistently demonstrated cerebellar alterations. Here we aimed to discover whole-brain functional biomarkers, based on parametric performance-level-dependent signals. We assessed 13 patients with early SCA3 and 14 healthy participants. We used a combined parametric behavioral/functional neuroimaging design to investigate disease fingerprints, as a function of performance levels, coupled with structural MRI and voxel-based morphometry. Functional magnetic resonance imaging (fMRI) was designed to parametrically analyze behavior and neural responses to audio-paced bilateral thumb movements at temporal frequencies of 1, 3, and 5 Hz. Our performance-level-based design probing neuronal correlates of motor coordination enabled the discovery that neural activation and behavior show critical loss of parametric modulation specifically in SCA3, associated with frequency-dependent cortico/subcortical activation/deactivation patterns. Cerebellar/cortical rate-dependent dissociation patterns could clearly differentiate between groups irrespective of grey matter loss. Our findings suggest functional reorganization of the motor network and indicate a possible role of fMRI as a tool to monitor disease progression in SCA3. Accordingly, fMRI patterns proved to be potential biomarkers in early SCA3, as tested by receiver operating characteristic analysis of both behavior and neural activation at different frequencies. Discrimination analysis based on BOLD signal in response to the applied parametric finger-tapping task significantly often reached >80% sensitivity and specificity in single regions-of-interest.Functional fingerprints based on cerebellar and cortical BOLD performance dependent signal modulation can thus be combined as diagnostic and/or therapeutic targets in hereditary ataxia. Hum Brain Mapp 37:3656-3668, 2016. © 2016 Wiley Periodicals, Inc.

Effects of a 60 Hz Magnetic Field Exposure Up to 3000 μT on Human Brain Activation as Measured by Functional Magnetic Resonance Imaging

Several aspects of the human nervous system and associated motor and cognitive processes have been reported to be modulated by extremely low-frequency (ELF, < 300 Hz) time-varying Magnetic Fields (MF). Due do their worldwide prevalence; power-line frequencies (60 Hz in North America) are of particular interest. Despite intense research efforts over the last few decades, the potential effects of 60 Hz MF still need to be elucidated, and the underlying mechanisms to be understood. In this study, we have used functional Magnetic Resonance Imaging (fMRI) to characterize potential changes in functional brain activation following human exposure to a 60 Hz MF through motor and cognitive tasks. First, pilot results acquired in a first set of subjects (N=9) were used to demonstrate the technical feasibility of using fMRI to detect subtle changes in functional brain activation with 60 Hz MF exposure at 1800 μT. Second, a full study involving a larger cohort of subjects tested brain activation during 1) a finger tapping task (N=20), and 2) a mental rotation task (N=21); before and after a one-hour, 60 Hz, 3000 μT MF exposure. The results indicate significant changes in task-induced functional brain activation as a consequence of MF exposure. However, no impact on task performance was found. These results illustrate the potential of using fMRI to identify MF-induced changes in functional brain activation, suggesting that a one-hour 60 Hz, 3000 μT MF exposure can modulate activity in specific brain regions after the end of the exposure period (i.e., residual effects). We discuss the possibility that MF exposure at 60 Hz, 3000 μT may be capable of modulating cortical excitability via a modulation of synaptic plasticity processes.

Finding the beat: a neural perspective across humans and non-human primates

Humans possess an ability to perceive and synchronize movements to the beat in music ('beat perception and synchronization'), and recent neuroscientific data have offered new insights into this beat-finding capacity at multiple neural levels. Here, we review and compare behavioural and neural data on temporal and sequential processing during beat perception and entrainment tasks in macaques (including direct neural recording and local field potential (LFP)) and humans (including fMRI, EEG and MEG). These abilities rest upon a distributed set of circuits that include the motor cortico-basal-ganglia-thalamo-cortical (mCBGT) circuit, where the supplementary motor cortex (SMA) and the putamen are critical cortical and subcortical nodes, respectively. In addition, a cortical loop between motor and auditory areas, connected through delta and beta oscillatory activity, is deeply involved in these behaviours, with motor regions providing the predictive timing needed for the perception of, and entrainment to, musical rhythms. The neural discharge rate and the LFP oscillatory activity in the gamma- and beta-bands in the putamen and SMA of monkeys are tuned to the duration of intervals produced during a beat synchronization-continuation task (SCT). Hence, the tempo during beat synchronization is represented by different interval-tuned cells that are activated depending on the produced interval. In addition, cells in these areas are tuned to the serial-order elements of the SCT. Thus, the underpinnings of beat synchronization are intrinsically linked to the dynamics of cell populations tuned for duration and serial order throughout the mCBGT. We suggest that a cross-species comparison of behaviours and the neural circuits supporting them sets the stage for a new generation of neurally grounded computational models for beat perception and synchronization.

The 3-second rule in hereditary pure cerebellar ataxia: a synchronized tapping study

The '3-second rule' has been proposed based on miscellaneous observations that a time period of around 3 seconds constitutes the fundamental unit of time related to the neuro-cognitive machinery in normal humans. The aim of paper was to investigate the temporal processing in patients with spinocerebellar ataxia type 6 (SCA6) and SCA31, pure cerebellar types of spinocerebellar degeneration, using a synchronized tapping task. Seventeen SCA patients (11 SCA6, 6 SCA31) and 17 normal age-matched volunteers participated. The task required subjects to tap a keyboard in synchrony with sequences of auditory stimuli presented at fixed interstimulus intervals (ISIs) between 200 and 4800 ms. In this task, the subjects required non-motor components to estimate the time of forthcoming tone in addition to motor components to tap. Normal subjects synchronized their taps to the presented tones at shorter ISIs, whereas as the ISI became longer, the normal subjects displayed greater latency between the tone and the tapping (transition zone). After the transition zone, normal subjects pressed the button delayed relative to the tone. On the other hand, SCA patients could not synchronize their tapping with the tone even at shorter ISIs, although they pressed the button delayed relative to the tone earlier than normal subjects did. The earliest time of delayed tapping appearance after the transition zone was 4800 ms in normal subjects but 1800 ms in SCA patients. The span of temporal integration in SCA patients is shortened compared to that in normal subjects. This could represent non-motor cerebellar dysfunction in SCA patients.

Dopamine agonist modifies cortical activity in Parkinson disease: a functional neuroimaging study

OBJECTIVES

To investigate, using functional magnetic resonance imaging, the influence of a long-term dopaminergic therapy on brain activation during a simple motor task in early, previously untreated patients with Parkinson disease.

METHODS

Thirteen patients with Parkinson disease in Hoehn-Yahr stage 1 or 2, with a right predominance of the disease, underwent functional magnetic resonance imaging during self-paced continuous right-hand tapping before and after 6 months of therapy with ropinirole 15 mg/d. The task was monitored online with a dedicated device, which measures the strength and frequency of the tapping.

RESULTS

All patients with Parkinson disease on ropinirole treatment showed a clinically significant improvement, and their functional magnetic resonance imaging pattern after treatment showed a reduced activation in the right postcentral (primary sensory-motor area), supramarginal and inferior parietal gyri compared with the activation pattern before treatment. No area of increased activation was observed after therapy.

CONCLUSIONS

In line with the classical functional deafferentation hypothesis, dopaminergic stimulation should increase motor cortex activity as a result of restoration of the striatocortical loops. On the contrary, our results challenge this hypothesis as we found decreased cerebral activity after a short-term chronic dopaminergic treatment. We suggest that the recruitment of cortical motor circuits aimed to overcome the functional deficit of the striatocortical loops lessens after dopaminergic treatment.

Validation of the hypercapnic calibrated fMRI method using DOT-fMRI fusion imaging

Calibrated functional magnetic resonance imaging (fMRI) is a widely used method to investigate brain function in terms of physiological quantities such as the cerebral metabolic rate of oxygen (CMRO2). The first and one of the most common methods of fMRI calibration is hypercapnic calibration. This is achieved via simultaneous measures of the blood-oxygenation-level dependent (BOLD) and the arterial spin labeling (ASL) signals during a functional task that evokes regional changes in CMRO2. A subsequent acquisition is then required during which the subject inhales carbon dioxide for short periods of time. A calibration constant, typically labeled M, is then estimated from the hypercapnic data and is subsequently used together with the BOLD-ASL recordings to compute evoked changes in CMRO2 during the functional task. The computation of M assumes a constant CMRO2 during the CO2 inhalation, an assumption that has been questioned since the origin of calibrated fMRI. In this study we used diffuse optical tomography (DOT) together with BOLD and ASL--an alternative calibration method that does not require any gas manipulation and therefore no constant CMRO2 assumption--to cross-validate the estimation of M obtained from a traditional hypercapnic calibration. We found a high correlation between the M values (R=0.87, p<0.01) estimated using these two approaches. The findings serve to validate the hypercapnic fMRI calibration technique and suggest that the inter-subject variability routinely obtained for M is reproducible with an alternative method and might therefore reflect inter-subject physiological variability.

Impact of regional striatal dopaminergic function on kinematic parameters of Parkinson's disease

Among the cardinal parkinsonian motor deficits, the severity of bradykinesia correlates with striatal dopamine loss. However, the impact of regional striatal dopamine loss on specific components of bradykinesia remains unknown. Using gyroscopes, we measured the amplitude, speed, and frequency of finger tapping in 24 untreated patients with Parkinson's disease (PD) and 28 healthy controls. Using positron emission tomography (PET) studies and [(18)F]-N-3-fluoropropyl-2-beta-carboxymethoxy-3-beta-(4-iodophenyl) nortropane (FP-CIT) in PD patients, we investigated the relationship between the mean values, variability and decrements of various kinematic parameters of finger tapping on one side (e.g. the mean, variability and decrement) and contralateral striatal FP-CIT binding. Compared with controls, PD patients had reduced amplitudes and speeds of tapping and showed greater decrement in those parameters. PD patients also exhibited greater irregularity in amplitude, speed, and frequency. Putaminal FP-CIT uptake levels correlated with the mean speed and amplitude, and caudate uptake levels correlated with mean amplitude. The variability of amplitude and speed correlated only with the caudate uptake levels. Neither caudate nor putaminal uptake correlated with frequency-related parameters or decrement in amplitude or speed. Reduced amplitude and speed of repetitive movement may be related to striatal dopaminergic deficit. Dopaminergic action in the caudate nucleus is required to maintain consistency of amplitude and speed. Although decrement of amplitude and speed is known to be specific for PD, we found that it did not mirror the degree of striatal dopamine depletion.

Neural correlates of rate-dependent finger-tapping in Parkinson's disease

Functional imaging demonstrated hemodynamic activation within specific brain areas that contribute to frequency-dependent movement control. Previous investigations demonstrated a linear relationship between movement and hemodynamic response rates within cortical regions, whereas the basal ganglia displayed an inverse neural activation pattern. We now investigated neural correlates of frequency-related finger movements in patients with Parkinson's disease (PD) to further elucidate the neurofunctional alterations in cortico-subcortical networks in that disorder. We studied ten PD patients (under dopaminergic medication) and ten healthy subjects using a finger-tapping task at three different frequencies (1-4 Hz), implemented in an event-related, sparse sampling fMRI design. FMRI data were analyzed by means of a parametric approach to relate movement rates and regional BOLD signal alteration. Compared to healthy controls, PD patients showed higher tapping response rates only during the lower 1 Hz condition. FMRI analysis revealed a rate-dependent neural activity within the supplemental motor area, primary sensorimotor cortex, thalamus and the cerebellum with higher neural activity at higher frequency conditions in both groups. Within the putamen/pallidum, an inverse neural activity and frequency response correlation could be observed in healthy subjects with higher BOLD signal responses in slow frequencies, whereas this relationship was not evident in PD patients. We could demonstrate similar behavioral responses and neural activation patterns at the level both of frontal and cerebellar areas in PD compared to healthy controls, whereas regions like the putamen/pallidum appear to be still dysfunctional under medication regarding frequency-related neural activation. These findings may, potentially, serve as a neural signature of basal ganglia dysfunctions in frequency-related task requirements.

Remember the future II: meta-analyses and functional overlap of working memory and delay discounting

Previously we showed that working memory training decreased the discounting of future rewards in stimulant addicts without affecting a go/no-go task. While a relationship between delay discounting and working memory is consistent with other studies, the unique brain regions of plausible causality between these two abilities have yet to be determined. Activation likelihood estimation meta-analyses were performed on foci from studies of delay discounting (DD = 449), working memory (WM = 452), finger tapping (finger tapping = 450), and response inhibition (RI = 450). Activity maps from relatively less (finger tapping) and more (RI) demanding executive tasks were contrasted with maps of DD and WM. Overlap analysis identified unique functional coincidence between DD and WM. The anterior cingulate cortex was engaged by all tasks. Finger tapping largely engaged motor-related brain areas. In addition to motor-related areas, RI engaged frontal brain regions. The right lateral prefrontal cortex was engaged by RI, DD, and WM and was contrasted out of overlap maps. A functional cluster in the posterior portion of the left lateral prefrontal cortex emerged as the largest location of unique overlap between DD and WM. A portion of the left lateral prefrontal cortex is a unique location where delay discounting and working memory processes overlap in the brain. This area, therefore, represents a therapeutic target for improving behaviors that rely on the integration of the recent past with the foreseeable future.

Windowed correlation: a suitable tool for providing dynamic fMRI-based functional connectivity neurofeedback on task difficulty

The goal of neurofeedback training is to provide participants with relevant information on their ongoing brain processes in order to enable them to change these processes in a meaningful way. Under the assumption of an intrinsic brain-behavior link, neurofeedback can be a tool to guide a participant towards a desired behavioral state, such as a healthier state in the case of patients. Current research in clinical neuroscience regarding the most robust indicators of pathological brain processes in psychiatric and neurological disorders indicates that fMRI-based functional connectivity measures may be among the most important biomarkers of disease. The present study therefore investigated the general potential of providing fMRI neurofeedback based on functional correlations, computed from short-window time course data at the level of single task periods. The ability to detect subtle changes in task performance with block-wise functional connectivity measures was evaluated based on imaging data from healthy participants performing a simple motor task, which was systematically varied along two task dimensions representing two different aspects of task difficulty. The results demonstrate that fMRI-based functional connectivity measures may provide a better indicator for an increase in overall (motor) task difficulty than activation level-based measures. Windowed functional correlations thus seem to provide relevant and unique information regarding ongoing brain processes, which is not captured equally well by standard activation level-based neurofeedback measures. Functional connectivity markers, therefore, may indeed provide a valuable tool to enhance and monitor learning within an fMRI neurofeedback setup.

Neural mechanisms of rhythm perception: present findings and future directions

The capacity to synchronize movements to the beat in music is a complex, and apparently uniquely human characteristic. Synchronizing movements to the beat requires beat perception, which entails prediction of future beats in rhythmic sequences of temporal intervals. Absolute timing mechanisms, where patterns of temporal intervals are encoded as a series of absolute durations, cannot fully explain beat perception. Beat perception seems better accounted for by relative timing mechanisms, where temporal intervals of a pattern are coded relative to a periodic beat interval. Evidence from behavioral, neuroimaging, brain stimulation and neuronal cell recording studies suggests a functional dissociation between the neural substrates of absolute and relative timing. This chapter reviews current findings on relative timing in the context of rhythm and beat perception.

Nicotine increases cerebellar activity during finger tapping

Nicotine improves performance on several cognitive and sensorimotor tasks. The neuronal mechanisms associated with these changes in performance are, however, largely unknown. Functional magnetic resonance imaging (fMRI) was used to examine the effect of nicotine on neuronal response in nineteen healthy subjects while they performed an auditory-paced finger tapping task. Subjects performed the task, after receiving either a nicotine patch or placebo treatment, in a single blind, crossover design. Compared to placebo, nicotine treatment increased response in the cerebellar vermis. Increased vermal activity, in the absence of changes in other task-related regions suggests specificity in nicotine's effects.

BOLD consistently matches electrophysiology in human sensorimotor cortex at increasing movement rates: a combined 7T fMRI and ECoG study on neurovascular coupling

Blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is widely used to measure human brain function and relies on the assumption that hemodynamic changes mirror the underlying neuronal activity. However, an often reported saturation of the BOLD response at high movement rates has led to the notion of a mismatch in neurovascular coupling. We combined BOLD fMRI at 7T and intracranial electrocorticography (ECoG) to assess the relationship between BOLD and neuronal population activity in human sensorimotor cortex using a motor task with increasing movement rates. Though linear models failed to predict BOLD responses from the task, the measured BOLD and ECoG responses from the same tissue were in good agreement. Electrocorticography explained almost 80% of the mismatch between measured- and model-predicted BOLD responses, indicating that in human sensorimotor cortex, a large portion of the BOLD nonlinearity with respect to behavior (movement rate) is well predicted by electrophysiology. The results further suggest that other reported examples of BOLD mismatch may be related to neuronal processes, rather than to neurovascular uncoupling.

Differences and commonalities in the judgment of causality in physical and social contexts: an fMRI study

Understanding cause and effect is a fundamental aspect of human cognition. When shown videos of simple two-dimensional shapes colliding, humans experience one object causing the other to move, e.g., one billiard-like ball seeming to hit and move the other. The impression of causality can also occur when people attribute social interactions to moving objects. Whether the judgment of social and physical causality engages distinct or shared neural networks is not known. In a functional magnetic imaging (fMRI) study, participants were presented with two types of dynamic videos: a blue ball colliding with a red ball (P; physical condition) and a blue ball ("Mr. Blue") passing a red ball ("Mrs. Red") without making contact (S; social condition). Participants judged causal relationships (C) or movement direction (D; control task) in both video types, resulting in four conditions (PC; SC; PD; SD). We found common neural activations for physical and social causality judgments (SC > SD)∩(PC > PD) in the right middle/inferior frontal gyrus, right inferior parietal lobule, the right supplementary motor area, and bilateral insulae. For social causal judgments (SC > PC), we found distinct neural activity in the right temporo-parietal junction (rTPJ). These results provide evidence for a common neural network underlying judgments of causality that apply to both physical and social situations. The results also indicate that social causality judgments recruit additional neural resources in an area critical for determining animacy and intentionality.

Finding and feeling the musical beat: striatal dissociations between detection and prediction of regularity

Perception of temporal patterns is critical for speech, movement, and music. In the auditory domain, perception of a regular pulse, or beat, within a sequence of temporal intervals is associated with basal ganglia activity. Two alternative accounts of this striatal activity are possible: "searching" for temporal regularity in early stimulus processing stages or "prediction' of the timing of future tones after the beat is found (relying on continuation of an internally generated beat). To resolve between these accounts, we used functional magnetic resonance imaging (fMRI) to investigate different stages of beat perception. Participants heard a series of beat and nonbeat (irregular) monotone sequences. For each sequence, the preceding sequence provided a temporal beat context for the following sequence. Beat sequences were preceded by nonbeat sequences, requiring the beat to be found anew ("beat finding" condition), or by beat sequences with the same beat rate ("beat continuation"), or a different rate ("beat adjustment"). Detection of regularity is highest during beat finding, whereas generation and prediction are highest during beat continuation. We found the greatest striatal activity for beat continuation, less for beat adjustment, and the least for beat finding. Thus, the basal ganglia's response profile suggests a role in beat prediction, not in beat finding.

The subthalamic microlesion story in Parkinson's disease: electrode insertion-related motor improvement with relative cortico-subcortical hypoactivation in fMRI

Electrode implantation into the subthalamic nucleus for deep brain stimulation in Parkinson's disease (PD) is associated with a temporary motor improvement occurring prior to neurostimulation. We studied this phenomenon by functional magnetic resonance imaging (fMRI) when considering the Unified Parkinson's Disease Rating Scale (UPDRS-III) and collateral oedema. Twelve patients with PD (age 55.9± (SD)6.8 years, PD duration 9-15 years) underwent bilateral electrode implantation into the subthalamic nucleus. The fMRI was carried out after an overnight withdrawal of levodopa (OFF condition): (i) before and (ii) within three days after surgery in absence of neurostimulation. The motor task involved visually triggered finger tapping. The OFF/UPDRS-III score dropped from 33.8±8.7 before to 23.3±4.8 after the surgery (p<0.001), correlating with the postoperative oedema score (p<0.05). During the motor task, bilateral activation of the thalamus and basal ganglia, motor cortex and insula were preoperatively higher than after surgery (p<0.001). The results became more enhanced after compensation for the oedema and UPDRS-III scores. In addition, the rigidity and axial symptoms score correlated inversely with activation of the putamen and globus pallidus (p<0.0001). One month later, the OFF/UPDRS-III score had returned to the preoperative level (35.8±7.0, p = 0.4).In conclusion, motor improvement induced by insertion of an inactive electrode into the subthalamic nucleus caused an acute microlesion which was at least partially related to the collateral oedema and associated with extensive impact on the motor network. This was postoperatively manifested as lowered movement-related activation at the cortical and subcortical levels and differed from the known effects of neurostimulation or levodopa. The motor system finally adapted to the microlesion within one month as suggested by loss of motor improvement and good efficacy of deep brain stimulation.

Dissociation between neuronal activity in sensorimotor cortex and hand movement revealed as a function of movement rate

It is often assumed that similar behavior is generated by the same brain activity. However, this does not take into account the brain state or recent behavioral history and movement initiation or continuation may not be similarly generated in the brain. To study whether similar movements are generated by the same brain activity, we measured neuronal population activity during repeated movements. Three human subjects performed a motor repetition task in which they moved their hand at four different rates (0.3, 0.5, 1, and 2 Hz). From high-resolution electrocorticography arrays implanted on motor and sensory cortex, high-frequency power (65-95 Hz) was extracted as a measure of neuronal population activity. During the two faster movement rates, high-frequency power was significantly suppressed, whereas movement parameters remained highly similar. This suppression was nonlinear: after the initial movement, neuronal population activity was reduced most strongly, and the data fit a model in which a fast decline rapidly converged to saturation. The amplitude of the beta-band suppression did not change with different rates. However, at the faster rates, beta power did not return to baseline between movements but remained suppressed. We take these findings to indicate that the extended beta suppression at the faster rates, which may suggest a release of inhibition in motor cortex, facilitates movement initiation. These results show that the relationship between behavior and neuronal activity is not consistent: recent movement influences the state of motor cortex and facilitates next movements by reducing the required level of neuronal activity.

A functional MRI study of motor dysfunction in Friedreich's ataxia

Friedreich's ataxia (FRDA) is the most common form of hereditary ataxia. In addition to proximal spinal cord and brain stem atrophy, mild to moderate atrophy of the cerebellum has been reported in advanced FRDA. The aim of this study was to examine dysfunction in motor-related areas involved in the execution of finger tapping tasks in individuals with FRDA, and to investigate functional re-organization of cortico-cerebellar, cortico-striatal and parieto-frontal loops as a result of the cerebellar pathology. Thirteen right-handed individuals with FRDA and fourteen right-handed controls participated. Functional MRI images were acquired during four different finger tapping tasks consisting of visually cued regular and irregular single finger tapping tasks, a self-paced regular finger tapping task, and a visually cued multi-finger tapping task. Both groups showed significant activation of the motor-related network including the pre-central cortex and supplementary motor area bilaterally; the left primary motor cortex, somatosensory cortex and putamen; and the right cerebellum. During the visually cued regular finger tapping task, the right hemisphere of the cerebellar cortex, bilateral supplementary motor areas and right inferior parietal cortex showed higher activation in the healthy control group, while in individuals with FRDA the left premotor cortex, left somatosensory cortex and left inferior parietal cortex were more active. In addition, during the visually cued irregular finger tapping task, the right middle temporal gyrus in the control group and the right superior parietal lobule and left superior and middle temporal gyri in the individuals with FRDA showed higher activation. During visually cued multi-finger tapping task, the control group showed higher activation in the bilateral middle frontal gyri, bilateral somatosensory cortices, bilateral inferior parietal lobules, left premotor cortex, left supplementary area, right superior frontal gyrus and right cerebellum, while individuals with FRDA showed increased activity in the left inferior parietal lobule, left primary motor cortex, left middle occipital gyrus, right somatosensory cortex and the left cerebellum. Only the right crus I/II of the cerebellum showed higher activation in individuals with FRDA during the self-paced regular finger tapping task, whereas wide-spread regions including the left superior frontal gyrus, left central opercular cortex, left somatosensory cortex, left putamen, right cerebellum, bilateral primary motor cortices, bilateral inferior parietal lobules and the left insula were more active in the control group. Although the pattern of the BOLD signal from the putamen was different during the self-paced regular finger tapping task to the other tasks in controls, in individuals with FRDA there was no distinction of the signal between the tasks suggesting that primary cerebellar pathology may cause secondary basal ganglia dysregulation. While individuals with FRDA tapped at a slightly lower rate (0.59Hz) compared with controls (0.74Hz) they showed significantly decreased activity of the SMA and the inferior parietal lobule, which may suggest disruption to the fronto-parietal connections. These findings suggest that the motor impairments in individuals with FRDA result from dysfunction extending beyond the spinal cord and cerebellum to include sub-cortical and cortical brain regions.

A corticostriatal neural system enhances auditory perception through temporal context processing

The temporal context of an acoustic signal can greatly influence its perception. The present study investigated the neural correlates underlying perceptual facilitation by regular temporal contexts in humans. Participants listened to temporally regular (periodic) or temporally irregular (nonperiodic) sequences of tones while performing an intensity discrimination task. Participants performed significantly better on intensity discrimination during periodic than nonperiodic tone sequences. There was greater activation in the putamen for periodic than nonperiodic sequences. Conversely, there was greater activation in bilateral primary and secondary auditory cortices (planum polare and planum temporale) for nonperiodic than periodic sequences. Across individuals, greater putamen activation correlated with lesser auditory cortical activation in both right and left hemispheres. These findings suggest that temporal regularity is detected in the putamen, and that such detection facilitates temporal-lobe cortical processing associated with superior auditory perception. Thus, this study reveals a corticostriatal system associated with contextual facilitation for auditory perception through temporal regularity processing.

Internalized timing of isochronous sounds is represented in neuromagnetic β oscillations

Moving in synchrony with an auditory rhythm requires predictive action based on neurodynamic representation of temporal information. Although it is known that a regular auditory rhythm can facilitate rhythmic movement, the neural mechanisms underlying this phenomenon remain poorly understood. In this experiment using human magnetoencephalography, 12 young healthy adults listened passively to an isochronous auditory rhythm without producing rhythmic movement. We hypothesized that the dynamics of neuromagnetic beta-band oscillations (~20 Hz)-which are known to reflect changes in an active status of sensorimotor functions-would show modulations in both power and phase-coherence related to the rate of the auditory rhythm across both auditory and motor systems. Despite the absence of an intention to move, modulation of beta amplitude as well as changes in cortico-cortical coherence followed the tempo of sound stimulation in auditory cortices and motor-related areas including the sensorimotor cortex, inferior-frontal gyrus, supplementary motor area, and the cerebellum. The time course of beta decrease after stimulus onset was consistent regardless of the rate or regularity of the stimulus, but the time course of the following beta rebound depended on the stimulus rate only in the regular stimulus conditions such that the beta amplitude reached its maximum just before the occurrence of the next sound. Our results suggest that the time course of beta modulation provides a mechanism for maintaining predictive timing, that beta oscillations reflect functional coordination between auditory and motor systems, and that coherence in beta oscillations dynamically configure the sensorimotor networks for auditory-motor coupling.

Functional magnetic resonance imaging study comparing rhythmic finger tapping in children and adults

This study compared brain activation during unpaced rhythmic finger tapping in 12-year-old children with that of adults. Subjects pressed a button at a pace initially indicated by a metronome (12 consecutive tones), and then continued for 16 seconds of unpaced tapping to provide an assessment of their ability to maintain a steady rhythm. These analyses focused on the superior vermis of the cerebellum, which is known to play a key role in timing. Twelve adults and 12 children performed this rhythmic finger tapping task in a 3 T scanner. Whole-brain analyses were performed in Brain Voyager, with a random-effects analysis of variance using a general linear model. A dedicated cerebellar atlas was used to localize cerebellar activations. As in adults, unpaced rhythmic finger tapping in children demonstrated activations in the primary motor cortex, premotor cortex, and cerebellum. However, overall activation was different, in that adults demonstrated much more deactivation in response to the task, particularly in the occipital and frontal cortices. The other main differences involved the additional recruitment of motor and premotor areas in children compared with adults, and increased activity in the vermal region of the cerebellum. These findings suggest that the timing component of the unpaced rhythmic finger tapping task is less efficient and automatic in children, who need to recruit the superior vermis more intensively to maintain the rhythm, although they performed somewhat more poorly than adults.

Nonlinear denoising and analysis of neuroimages with kernel principal component analysis and pre-image estimation

We investigate the use of kernel principal component analysis (PCA) and the inverse problem known as pre-image estimation in neuroimaging: i) We explore kernel PCA and pre-image estimation as a means for image denoising as part of the image preprocessing pipeline. Evaluation of the denoising procedure is performed within a data-driven split-half evaluation framework. ii) We introduce manifold navigation for exploration of a nonlinear data manifold, and illustrate how pre-image estimation can be used to generate brain maps in the continuum between experimentally defined brain states/classes. We base these illustrations on two fMRI BOLD data sets - one from a simple finger tapping experiment and the other from an experiment on object recognition in the ventral temporal lobe.