Model-free characterization of brain functional networks for motor sequence learning using fMRI

A longitudinal study of the effect of visuomotor learning on functional brain connectivity

Neural adaptation in the frontoparietal and motor cortex-sensorimotor circuits is crucial for acquiring visuomotor skills. However, the specific nature of highly dynamic neural connectivity in these circuits during the acquisition of visuomotor skills remains unclear. To achieve a more comprehensive understanding of the relationship between acquisition of visuomotor skills and neural connectivity, we used electroencephalographic coherence to capture highly dynamic nature of neural connectivity. We recruited 60 male novices who were randomly assigned to either the experimental group (EG) or the control group (CG). Participants in EG were asked to engage in repeated putting practice, but CG did not engage in golf practice. In addition, we analyzed the connectivity by using 8-13 Hz imaginary inter-site phase coherence in the frontoparietal networks (Fz-P3 and Fz-P4) and the motor cortex-sensorimotor networks (Cz-C3 and Cz-C4) during a golf putting task. To gain a deeper understanding of the dynamic nature of learning trajectories, we compared data at three time points: baseline (T1), 50% improvement from baseline (T2), and 100% improvement from baseline (T3). The results primarily focused on EG, an inverted U-shaped coherence curve was observed in the connectivity of the left motor cortex-sensorimotor circuit, whereas an increase in the connectivity of the right frontoparietal circuit from T2 to T3 was revealed. These results imply that the dynamics of cortico-cortical communication, particularly involving the left motor cortex-sensorimotor and frontal-left parietal circuits. In addition, our findings partially support Hikosaka et al.'s model and provide additional insight into the specific role of these circuits in visuomotor learning.

Decreased long-range temporal correlations in the resting-state functional magnetic resonance imaging blood-oxygen-level-dependent signal reflect motor sequence learning up to 2 weeks following training

Decreased long-range temporal correlations (LRTC) in brain signals can be used to measure cognitive effort during task execution. Here, we examined how learning a motor sequence affects long-range temporal memory within resting-state functional magnetic resonance imaging signal. Using the Hurst exponent (HE), we estimated voxel-wise LRTC and assessed changes over 5 consecutive days of training, followed by a retention scan 12 days later. The experimental group learned a complex visuomotor sequence while a complementary control group performed tightly matched movements. An interaction analysis revealed that HE decreases were specific to the complex sequence and occurred in well-known motor sequence learning associated regions including left supplementary motor area, left premotor cortex, left M1, left pars opercularis, bilateral thalamus, and right striatum. Five regions exhibited moderate to strong negative correlations with overall behavioral performance improvements. Following learning, HE values returned to pretraining levels in some regions, whereas in others, they remained decreased even 2 weeks after training. Our study presents new evidence of HE's possible relevance for functional plasticity during the resting-state and suggests that a cortical subset of sequence-specific regions may continue to represent a functional signature of learning reflected in decreased long-range temporal dependence after a period of inactivity.

Cortico-spinal modularity in the parieto-frontal system: A new perspective on action control

Classical neurophysiology suggests that the motor cortex (MI) has a unique role in action control. In contrast, this review presents evidence for multiple parieto-frontal spinal command modules that can bypass MI. Five observations support this modular perspective: (i) the statistics of cortical connectivity demonstrate functionally-related clusters of cortical areas, defining functional modules in the premotor, cingulate, and parietal cortices; (ii) different corticospinal pathways originate from the above areas, each with a distinct range of conduction velocities; (iii) the activation time of each module varies depending on task, and different modules can be activated simultaneously; (iv) a modular architecture with direct motor output is faster and less metabolically expensive than an architecture that relies on MI, given the slow connections between MI and other cortical areas; (v) lesions of the areas composing parieto-frontal modules have different effects from lesions of MI. Here we provide examples of six cortico-spinal modules and functions they subserve: module 1) arm reaching, tool use and object construction; module 2) spatial navigation and locomotion; module 3) grasping and observation of hand and mouth actions; module 4) action initiation, motor sequences, time encoding; module 5) conditional motor association and learning, action plan switching and action inhibition; module 6) planning defensive actions. These modules can serve as a library of tools to be recombined when faced with novel tasks, and MI might serve as a recombinatory hub. In conclusion, the availability of locally-stored information and multiple outflow paths supports the physiological plausibility of the proposed modular perspective.

Reduced duration of stuttering-like disfluencies and consistent anticipatory slowing during an adaptation task

PURPOSE

The adaptation effect in stuttering, traditionally described as the reduction of stuttering moments over repeated readings, provides a context to investigate fluency facilitation as well as a relatively controlled means of comparing fluent speech in the immediate vicinity of words that were stuttered versus fluently produced. Acoustic studies have documented decreased duration of fluent speech during adaptation but rarely address changes in disfluencies or the speech preceding or following the disfluencies. This study addresses this gap in the research by documenting frequency and duration changes in both fluent and stuttered syllables.

METHOD

Fifteen people who stutter read passages aloud five times in succession. Frequency and duration of fluent syllables, pauses, stuttering-like disfluencies (SLDs) and other disfluencies (ODs) were compared across the five readings. In addition, durations for syllables before and after pauses and SLDs were compared to determine if there were anticipation or carryover effects of SLDs on surrounding syllables.

RESULTS

Durations measured for more than 22 000 fluent syllables, 1531 pauses, 128 ODs and 1752 SLDs. For most of the 15 participants, significant decreases in both frequency and duration of SLDs over the five readings were observed. In addition, lengthening of fluent syllables immediately preceding the disfluent syllables was observed: this pre-SLD lengthening did not change over the five readings.

CONCLUSIONS

Decreased duration of SLDs across readings supports the motor practice hypothesis, which assumes that successive reading of the same text increases the efficiency of the speech motor plans resulting in less stuttering and decreased durations of the stuttering that persists. Pre-SLD lengthening merits further study, because it informs our knowledge of the time course of stuttered events and may be associated with conscious or unconscious anticipation of upcoming SLDs that does not decrease with motor practice.

WHAT THIS PAPER ADDS

What is already known on this subject The frequency of stuttering-like disfluencies (SLDs) can be reduced using a variety of fluency-enhancing strategies. For example, the adaptation effect, in which a reduction of stuttered events occurs over repeated readings of the same material, has been widely studied. Previous studies have shown that durations of fluent syllables decrease during adaptation, supporting the hypothesis that repeated practice of the motor plan leads to increased fluency. However, temporal changes in disfluent syllables and syllables preceding and following SLDs have rarely been studied, so our understanding of the effect of motor practice on stuttering reduction is incomplete. What this study adds This study has two significant findings. First, stuttered disfluencies that persisted after the initial reading of the adaptation task tended to become shorter in duration. Fluently produced syllables and those that were stuttered, both of which are speech events related to motor control of articulators, were affected in a similar manner by the motor practice associated with adaptation. Second, lengthening of fluent syllables immediately preceding stuttered syllables was observed. This pre-stuttering lengthening, however, did not decrease in duration over the five readings: the mechanism that drives this anticipatory behaviour is not affected by repeated practice. What are the clinical implications of this work? People who stutter have neural differences that lead to speech motor planning and/or execution that is less efficient than that of typical speakers. The finding that stuttering is reduced and that persisting SLDs become shorter in duration over repeated readings provides evidence that motor practice can influence the manifestation of stuttering by temporarily making those specific motor plans more efficient. This may inform treatments for stuttering. The observation that fluent syllables immediately before SLDs were lengthened, and that this lengthening was not influenced by repeated practice, extends our understanding of the time course of stuttering events and may be useful in understanding anticipation and listener reactions to stuttering.

Differential effects of conventional and high-definition transcranial direct-current stimulation of the motor cortex on implicit motor sequence learning

Conventional transcranial direct-current stimulation (tDCS) delivered to the primary motor cortex (M1) has been shown to enhance implicit motor sequence learning (IMSL). Conventional tDCS targets M1 but also the motor association cortices (MAC), making the precise contribution of these areas to IMSL presently unclear. We aimed to address this issue by comparing conventional tDCS of M1 and MAC to 4 * 1 high-definition (HD) tDCS, which more focally targets M1. In this mixed-factorial, sham-controlled, crossover study in 89 healthy young adults, we used mixed-effects models to analyse sequence-specific and general learning effects in the acquisition and short- and long-term consolidation phases of IMSL, as measured by the serial reaction time task. Conventional tDCS did not influence general learning, improved sequence-specific learning during acquisition (anodal: M = 42.64 ms, sham: M = 32.87 ms, p = .041), and seemingly deteriorated it at long-term consolidation (anodal: M = 75.37 ms, sham: M = 86.63 ms, p = .019). HD tDCS did not influence general learning, slowed performance specifically in sequential blocks across all learning phases (all p's < .050), and consequently deteriorated sequence-specific learning during acquisition (anodal: M = 24.13 ms, sham: M = 35.67 ms, p = .014) and long-term consolidation (anodal: M = 60.03 ms, sham: M = 75.01 ms, p = .002). Our findings indicate that the observed superior conventional tDCS effects on IMSL are possibly attributable to a generalized stimulation of M1 and/or adjacent MAC, rather than M1 alone. Alternatively, the differential effects can be attributed to cathodal inhibition of other cortical areas involved in IMSL by the 4 * 1 HD tDCS return electrodes, and/or more variable electric field strengths induced by HD tDCS, compared with conventional tDCS.

Modulation of cortical resting state functional connectivity during a visuospatial attention task in Parkinson's disease

Visual dysfunction is a recognized early symptom of Parkinson's disease (PD) that partly scales motor symptoms, yet its background is heterogeneous. With additional deficits in visuospatial attention, the two systems are hard to disentangle and it is not known whether impaired functional connectivity in the visual cortex is translative in nature or disrupted attentional modulation also contributes. In this study, we investigate functional connectivity modulation during a visuospatial attention task in patients with PD. In total, 15 PD and 16 age-matched healthy controls performed a visuospatial attention task while undergoing fMRI, in addition to a resting-state fMRI scan. Tensorial independent component analysis was used to investigate task-related network activity patterns. Independently, an atlas-based connectivity modulation analysis was performed using the task potency method. Spearman's rank correlation was calculated between task-related network expression, connectivity modulation, and clinical characteristics. Task-related networks including mostly visual, parietal, and prefrontal cortices were expressed to a significantly lesser degree in patients with PD (p < 0.027). Resting-state functional connectivity did not differ between the healthy and diseased cohorts. Connectivity between the precuneus and ventromedial prefrontal cortex was modulated to a higher degree in patients with PD (p < 0.004), while connections between the posterior parietal cortex and primary visual cortex, and also the superior frontal gyrus and opercular cortex were modulated to a lesser degree (p < 0.001 and p < 0.011). Task-related network expression and superior frontal gyrus–opercular cortex connectivity modulation were significantly associated with UPDRSIII motor scores and the Hoehn–Yahr stages (R = −0.72, p < 0.006 and R = −0.90, p < 0.001; R = −0.68, p < 0.01 and R = −0.71, p < 0.007). Task-related networks function differently in patients with PD in association with motor symptoms, whereas impaired modulation of visual and default-mode network connectivity was not correlated with motor function.

Nonlinear refinement of functional brain connectivity in golf players of different skill levels

Different functional connectivities in the brain, specifically in the frontoparietal and motor cortex-sensorimotor circuits, have been associated with superior performance in athletes. However, previous electroencephalogram (EEG) studies have only focused on the frontoparietal circuit and have not provided a comprehensive understanding of the cognitive-motor processes underlying superior performance. We used EEG coherence analysis to examine the motor cortex-sensorimotor circuit in golfers of different skill levels. Twenty experts, 18 amateurs, and 21 novices performed 60 putts at individual putting distances (40-60% success rate). The imaginary inter-site phase coherence (imISPC) was used to compute 8-13 Hz coherence that can be used to distinguish expert-novice and expert-amateur differences during motor preparation. We assessed the 8-13 Hz imISPC between the Cz and F3, F4, C3, C4, T3, T4, P3, P4, O1, and O2 regions. (1) Amateurs had lower 8-13 Hz imISPC in the central regions (Cz-C3 and C4) than novices and experts, but experts had lower 8-13 Hz imISPC than novices. (2) Skilled golfers (experts and amateurs) had lower 8-13 Hz imISPC in the central-parietal regions (Cz-P3 and P4) than novices. (3) Experts had lower 8-13 Hz imISPC in the central-left temporal regions (Cz-T7) than amateurs and novices. Our study revealed that refinement of the motor cortex-sensorimotor circuit follows a U-shaped coherence pattern based on the stage of learning. The early learning stage (i.e., novice to amateur) is characterized by lower connectivity between the regions associated with motor control and visuospatial processes, whereas the late learning stage (i.e., amateur to expert) is characterized by lower connectivity in the regions associated with verbal-analytic and motor control processes.

Brain Activity and Functional Connectivity Patterns Associated With Fast and Slow Motor Sequence Learning in Late Middle Adulthood

The human brain undergoes structural and functional changes across the lifespan. The study of motor sequence learning in elderly subjects is of particularly interest since previous findings in young adults might not replicate during later stages of adulthood. The present functional magnetic resonance imaging (fMRI) study assessed the performance, brain activity and functional connectivity patterns associated with motor sequence learning in late middle adulthood. For this purpose, a total of 25 subjects were evaluated during early stages of learning [i.e., fast learning (FL)]. A subset of these subjects (n = 11) was evaluated after extensive practice of a motor sequence [i.e., slow learning (SL) phase]. As expected, late middle adults improved motor performance from FL to SL. Learning-related brain activity patterns replicated most of the findings reported previously in young subjects except for the lack of hippocampal activity during FL and the involvement of cerebellum during SL. Regarding functional connectivity, precuneus and sensorimotor lobule VI of the cerebellum showed a central role during improvement of novel motor performance. In the sample of subjects evaluated, connectivity between the posterior putamen and parietal and frontal regions was significantly decreased with aging during SL. This age-related connectivity pattern may reflect losses in network efficiency when approaching late adulthood. Altogether, these results may have important applications, for instance, in motor rehabilitation programs.

Network properties and regional brain morphology of the insular cortex correlate with individual pain thresholds

Pain thresholds vary considerably across individuals and are influenced by a number of behavioral, genetic and neurobiological factors. However, the neurobiological underpinnings that account for individual differences remain to be fully elucidated. In this study, we used voxel‐based morphometry (VBM) and graph theory, specifically the local clustering coefficient (CC) based on resting‐state connectivity, to identify brain regions, where regional gray matter volume and network properties predicted individual pain thresholds. As a main finding, we identified a cluster in the left posterior insular cortex (IC) reaching into the left parietal operculum, including the secondary somatosensory cortex, where both regional gray matter volume and the local CC correlated with individual pain thresholds. We also performed a resting‐state functional connectivity analysis using the left posterior IC as seed region, demonstrating that connectivity to the pre‐ as well as postcentral gyrus bilaterally; that is, to the motor and primary sensory cortices were correlated with individual pain thresholds. To our knowledge, this is the first study that applied VBM in combination with voxel‐based graph theory in the context of pain thresholds. The co‐location of the VBM and the local CC cluster provide first evidence that both structure and function map to the same brain region while being correlated with the same behavioral measure; that is, pain thresholds. The study highlights the importance of the posterior IC, not only for pain perception in general, but also for the determination of individual pain thresholds.

Cathodal Transcranial Direct Current Stimulation (tDCS) Applied to the Left Premotor Cortex Interferes with Explicit Reproduction of a Motor Sequence

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that allows the modulation of cortical excitability. TDCS effects can outlast the stimulation period presumably due to changes of GABA concentration which play a critical role in use-dependent plasticity. Consequently, tDCS and learning-related synaptic plasticity are assumed to share common mechanisms. Motor sequence learning has been related to activation changes within a cortico-subcortical network and findings from a meta-analysis point towards a core network comprising the cerebellum as well as the primary motor (M1) and the dorsolateral premotor cortex (dPMC). The latter has been particularly related to explicit motor learning by means of brain imaging techniques. We here test whether tDCS applied to the left dPMC affects the acquisition and reproduction of an explicitly learned motor sequence. To this end, 18 healthy volunteers received anodal, cathodal and sham tDCS to the left dPMC and were then trained on a serial reaction time task (SRTT) with their right hand. Immediately after the training and after overnight sleep, reproduction of the learned sequence was tested by means of reaction times as well as explicit recall. Regression analyses suggest that following cathodal tDCS reaction times at the end of the SRTT training-block explained a significant proportion of the number of correctly reported sequence items after overnight sleep. The present data suggest the left premotor cortex as one possible target for the application of non-invasive brain stimulation techniques in explicit motor sequence learning with the right hand.

Altered brain network function during attention-modulated visual processing in multiple sclerosis

BACKGROUND

Multiple sclerosis may damage cognitive performance in several domains, including attention. Although attention network deficits were described during rest, studies that investigate their function during task performance are scarce.

OBJECTIVE

To investigate connectivity within and between task-related networks in multiple sclerosis during a visual attention task as a function of cognitive performance.

METHODS

A total of 23 relapsing-remitting multiple sclerosis (RRMS) patients and 29 healthy controls underwent task-functional magnetic resonance imaging (fMRI) scans using a visual attention paradigm on a 3T scanner. Scans were analysed using tensor-independent component analysis (TICA). Functional connectivity was calculated within and between components. We assessed cognitive function with the Brief International Cognitive Assessment for MS (BICAMS) battery.

RESULTS

TICA extracted components related to visual processing, attention, executive function and the default-mode network. Subject scores of visual/attention-related and executive components were greater in healthy controls (p < 0.032, p < 0.023). Connectivity between visual/attention-related and default-mode components was higher in patients (p < 0.043), correlating with Brief Visuospatial Memory Test-Revised (BVMT-R) scores (R = -0.48, p < 0.036). Patients showed reduced connectivity between the right intraparietal sulcus (rIPS) and frontal eye field (rFEF), and bilateral frontal eye fields (p < 0.012, p < 0.003). Reduced rIPS-rFEF connectivity came with lower Symbol Digit Modalities Test (SDMT)/BVMT-R scores in patients (R = 0.53, p < 0.02, R = 0.46, p < 0.049).

CONCLUSION

Attention-related networks show altered connectivity during task performance in RRMS patients, scaling with cognitive disability.

The posterior parietal cortex mediates early offline-rather than online-motor sequence learning

Learning of new motor skills occurs particularly during training on a task (i.e. online) but has been observed between training-blocks lasting up to days after the end of the training (i.e. offline). Offline-learning occurs as further improvement in task performance indicated by increased accuracy and/or faster responses as well as less interference with respect to a distracting condition. Successful motor learning requires the functional interplay between cortical as well as subcortical brain areas. While the involvement of the primary motor cortex in online-as well as early offline-learning is well established, the functional significance of the posterior parietal cortex (PPC) is less clear. Since the PPC may act as sensory-motor interface, a causal involvement in motor learning is conceivable. In order to characterize the functional significance of the left PPC for motor sequence learning, transcranial direct current stimulation (tDCS) was applied either immediately prior to, during or immediately after training on a serial reaction time task (SRTT) in a total of 54 healthy volunteers. While the analysis did not provide evidence for a significant modulation of reaction times during SRTT training (i.e. online-learning), cathodal tDCS decelerated reaction times of the learned sequences as compared to anodal and sham stimulation 30 min after the end of training. The findings suggest that cathodal tDCS over the left parietal cortex interferes with the reproduction of learned sequences.

A critical re-evaluation of fMRI signatures of motor sequence learning

Despite numerous studies, there is little agreement about what brain changes accompany motor sequence learning, partly because of a general publication bias that favors novel results. We therefore decided to systematically reinvestigate proposed functional magnetic resonance imaging correlates of motor learning in a preregistered longitudinal study with four scanning sessions over 5 weeks of training. Activation decreased more for trained than untrained sequences in premotor and parietal areas, without any evidence of learning-related activation increases. Premotor and parietal regions also exhibited changes in the fine-grained, sequence-specific activation patterns early in learning, which stabilized later. No changes were observed in the primary motor cortex (M1). Overall, our study provides evidence that human motor sequence learning occurs outside of M1. Furthermore, it shows that we cannot expect to find activity increases as an indicator for learning, making subtle changes in activity patterns across weeks the most promising fMRI correlate of training-induced plasticity.

Pain-free resting-state functional brain connectivity predicts individual pain sensitivity

Individual differences in pain perception are of interest in basic and clinical research as altered pain sensitivity is both a characteristic and a risk factor for many pain conditions. It is, however, unclear how individual sensitivity to pain is reflected in the pain-free resting-state brain activity and functional connectivity. Here, we identify and validate a network pattern in the pain-free resting-state functional brain connectome that is predictive of interindividual differences in pain sensitivity. Our predictive network signature allows assessing the individual sensitivity to pain without applying any painful stimulation, as might be valuable in patients where reliable behavioural pain reports cannot be obtained. Additionally, as a direct, non-invasive readout of the supraspinal neural contribution to pain sensitivity, it may have implications for translational research and the development and assessment of analgesic treatment strategies.

G-Causality Brain Connectivity Differences of Finger Movements between Motor Execution and Motor Imagery

Motor imagery is one of the classical paradigms which have been used in brain-computer interface and motor function recovery. Finger movement-based motor execution is a complex biomechanical architecture and a crucial task for establishing most complicated and natural activities in daily life. Some patients may suffer from alternating hemiplegia after brain stroke and lose their ability of motor execution. Fortunately, the ability of motor imagery might be preserved independently and worked as a backdoor for motor function recovery. The efficacy of motor imagery for achieving significant recovery for the motor cortex after brain stroke is still an open question. In this study, we designed a new paradigm to investigate the neural mechanism of thirty finger movements in two scenarios: motor execution and motor imagery. Eleven healthy participants performed or imagined thirty hand gestures twice based on left and right finger movements. The electroencephalogram (EEG) signal for each subject during sixty trials left and right finger motor execution and imagery were recorded during our proposed experimental paradigm. The Granger causality (G-causality) analysis method was employed to analyze the brain connectivity and its strength between contralateral premotor, motor, and sensorimotor areas. Highest numbers for G-causality trials of 37 ± 7.3, 35.5 ± 8.8, 36.3 ± 10.3, and 39.2 ± 9.0 and lowest Granger causality coefficients of 9.1 ± 3.2, 10.9 ± 3.7, 13.2 ± 0.6, and 13.4 ± 0.6 were achieved from the premotor to motor area during execution/imagination tasks of right and left finger movements, respectively. These results provided a new insight into motor execution and motor imagery based on hand gestures, which might be useful to build a new biomarker of finger motor recovery for partially or even completely plegic patients. Furthermore, a significant difference of the G-causality trial number was observed during left finger execution/imagery and right finger imagery, but it was not observed during the right finger execution phase. Significant difference of the G-causality coefficient was observed during left finger execution and imagery, but it was not observed during right finger execution and imagery phases. These results suggested that different MI-based brain motor function recovery strategies should be taken for right-hand and left-hand patients after brain stroke.

Model-Based and Model-Free Techniques for Amyotrophic Lateral Sclerosis Diagnostic Prediction and Patient Clustering

Amyotrophic lateral sclerosis (ALS) is a complex progressive neurodegenerative disorder with an estimated prevalence of about 5 per 100,000 people in the United States. In this study, the ALS disease progression is measured by the change of Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS) score over time. The study aims to provide clinical decision support for timely forecasting of the ALS trajectory as well as accurate and reproducible computable phenotypic clustering of participants. Patient data are extracted from DREAM-Phil Bowen ALS Prediction Prize4Life Challenge data, most of which are from the Pooled Resource Open-Access ALS Clinical Trials Database (PRO-ACT) archive. We employed model-based and model-free machine-learning methods to predict the change of the ALSFRS score over time. Using training and testing data we quantified and compared the performance of different techniques. We also used unsupervised machine learning methods to cluster the patients into separate computable phenotypes and interpret the derived subcohorts. Direct prediction of univariate clinical outcomes based on model-based (linear models) or model-free (machine learning based techniques - random forest and Bayesian adaptive regression trees) was only moderately successful. The correlation coefficients between clinically observed changes in ALSFRS scores relative to the model-based/model-free predicted counterparts were 0.427 (random forest) and 0.545(BART). The reliability of these results were assessed using internal statistical cross validation and well as external data validation. Unsupervised clustering generated very reliable and consistent partitions of the patient cohort into four computable phenotypic subgroups. These clusters were explicated by identifying specific salient clinical features included in the PRO-ACT archive that discriminate between the derived subcohorts. There are differences between alternative analytical methods in forecasting specific clinical phenotypes. Although predicting univariate clinical outcomes may be challenging, our results suggest that modern data science strategies are useful in clustering patients and generating evidence-based ALS hypotheses about complex interactions of multivariate factors. Predicting univariate clinical outcomes using the PRO-ACT data yields only marginal accuracy (about 70%). However, unsupervised clustering of participants into sub-groups generates stable, reliable and consistent (exceeding 95%) computable phenotypes whose explication requires interpretation of multivariate sets of features. HIGHLIGHTS: • Used a large ALS data archive of 8,000 patients consisting of 3 million records, including 200 clinical features tracked over 12 months. • Employed model-based and model-free methods to predict ALSFRS changes over time, cluster patients into cohorts, and derive computable phenotypes. • Research findings include stable, reliable, and consistent (95%) patient stratification into computable phenotypes. However, clinical explication of the results requires interpretation of multivariate information. Graphical Abstract ᅟ.

Practice modulates motor-related beta oscillations differently in adolescents and adults

KEY POINTS

Magnetoencephalography data were acquired during a leg force task in pre-/post-practice sessions in adolescents and adults. Strong peri-movement alpha and beta oscillations were mapped to the cortex. Following practice, performance improved and beta oscillations were altered. Beta oscillations decreased in the sensorimotor cortex in adolescents after practice, but increased in adults. No pre-/post-practice differences were detected for alpha oscillations.

ABSTRACT

There is considerable evidence that there are motor performance and practice differences between adolescents and adults. Behavioural studies have suggested that these motor performance differences are simply due to experience. However, the neurophysiological nexus for these motor performance differences remains unknown. The present study investigates the short-term changes (e.g. fast motor learning) in the alpha and beta event-related desynchronizations (ERDs) associated with practising an ankle plantarflexion motor action. To this end, we utilized magnetoencephalography to identify changes in the alpha and beta ERDs in healthy adolescents (n = 21; age = 14 ± 2.1 years) and middle-aged adults (n = 22; age = 36.6 ± 5 years) after practising an isometric ankle plantarflexion target-matching task. After practice, all of the participants matched more targets and matched the targets faster, and had improved accuracy, faster reaction times and faster force production. However, the motor performance of the adults exceeded what was seen in the adolescents regardless of practice. In conjunction with the behavioural results, the strength of the beta ERDs across the motor planning and execution stages was reduced after practice in the sensorimotor cortices of the adolescents, but was stronger in the adults. No pre-/post-practice changes were found in the alpha ERDs. These outcomes suggest that there are age-dependent changes in the sensorimotor cortical oscillations after practising a motor task. We suspect that these noted differences might be related to familiarity with the motor task, GABA levels and/or maturational differences in the integrity of the white matter fibre tracts that comprise the respective cortical areas.

Neurophysiological changes in the visuomotor network after practicing a motor task

Although it is well appreciated that practicing a motor task updates the associated internal model, it is still unknown how the cortical oscillations linked with the motor action change with practice. The present study investigates the short-term changes (e.g., fast motor learning) in the α- and β-event-related desynchronizations (ERD) associated with the production of a motor action. To this end, we used magnetoencephalography to identify changes in the α- and β-ERD in healthy adults after participants practiced a novel isometric ankle plantarflexion target-matching task. After practicing, the participants matched the targets faster and had improved accuracy, faster force production, and a reduced amount of variability in the force output when trying to match the target. Parallel with the behavioral results, the strength of the β-ERD across the motor-planning and execution stages was reduced after practice in the sensorimotor and occipital cortexes. No pre/postpractice changes were found in the α-ERD during motor planning or execution. Together, these outcomes suggest that fast motor learning is associated with a decrease in β-ERD power. The decreased strength likely reflects a more refined motor plan, a reduction in neural resources needed to perform the task, and/or an enhancement of the processes that are involved in the visuomotor transformations that occur before the onset of the motor action. These results may augment the development of neurologically based practice strategies and/or lead to new practice strategies that increase motor learning. NEW & NOTEWORTHY We aimed to determine the effects of practice on the movement-related cortical oscillatory activity. Following practice, we found that the performance of the ankle plantarflexion target-matching task improved and the power of the β-oscillations decreased in the sensorimotor and occipital cortexes. These novel findings capture the β-oscillatory activity changes in the sensorimotor and occipital cortexes that are coupled with behavioral changes to demonstrate the effects of motor learning.

Resting-state Functional Connectivity is an Age-dependent Predictor of Motor Learning Abilities

This magnetoencephalography study investigates how ageing modulates the relationship between pre-learning resting-state functional connectivity (rsFC) and subsequent learning. Neuromagnetic resting-state activity was recorded 5 min before motor sequence learning in 14 young (19-30 years) and 14 old (66-70 years) participants. We used a seed-based beta-band power envelope correlation approach to estimate rsFC maps, with the seed located in the right primary sensorimotor cortex. In each age group, the relation between individual rsFC and learning performance was investigated using Pearson's correlation analyses. Our results show that rsFC is predictive of subsequent motor sequence learning but involves different cross-network interactions in the two age groups. In young adults, decreased coupling between the sensorimotor network and the cortico-striato-cerebellar network is associated with better motor learning, whereas a similar relation is found in old adults between the sensorimotor, the dorsal-attentional and the DMNs. Additionally, age-related correlational differences were found in the dorsolateral prefrontal cortex, known to subtend attentional and controlled processes. These findings suggest that motor skill learning depends-in an age-dependent manner-on subtle interactions between resting-state networks subtending motor activity on the one hand, and controlled and attentional processes on the other hand.

Anger-sensitive networks: characterizing neural systems recruited during aggressive social interactions using data-driven analysis

Social neuroscience uses increasingly complex paradigms to improve ecological validity, as investigating aggressive interactions with functional magnetic resonance imaging (fMRI). Standard analyses for fMRI data typically use general linear models (GLM), which require a priori models of task effects on neural processes. These may inadequately model non-stimulus-locked or temporally overlapping cognitive processes, as mentalizing about other agents. We used the data-driven approach of independent component analysis (ICA) to investigate neural processes involved in a competitive interaction. Participants were confronted with an angry-looking opponent while having to anticipate the trial outcome and the opponent’s behaviour. We show that several spatially distinctive neural networks with associated temporal dynamics were modulated by the opponent’s facial expression. These results dovetail and extend the main effects observed in the GLM analysis of the same data. Additionally, the ICA approach identified effects of the experimental condition on neural systems during inter-trial intervals. We demonstrate that cognitive processes during aggressive interactions are poorly modelled by simple stimulus onset/duration variables and instead have more complex temporal dynamics. This highlights the utility of using data-driven analyses to elucidate the distinct cognitive processes recruited during complex social paradigms.

Behavioral and neural effects of congruency of visual feedback during short-term motor learning

Visual feedback can facilitate or interfere with movement execution. Here, we describe behavioral and neural mechanisms by which the congruency of visual feedback during physical practice of a motor skill modulates subsequent performance gains. 18 healthy subjects learned to execute rapid sequences of right hand finger movements during fMRI scans either with or without visual feedback. Feedback consisted of a real-time, movement-based display of virtual hands that was either congruent (right virtual hand movement), or incongruent (left virtual hand movement yoked to the executing right hand). At the group level, right hand performance gains following training with congruent visual feedback were significantly higher relative to training without visual feedback. Conversely, performance gains following training with incongruent visual feedback were significantly lower. Interestingly, across individual subjects these opposite effects correlated. Activation in the Supplementary Motor Area (SMA) during training corresponded to individual differences in subsequent performance gains. Furthermore, functional coupling of SMA with visual cortices predicted individual differences in behavior. Our results demonstrate that some individuals are more sensitive than others to congruency of visual feedback during short-term motor learning and that neural activation in SMA correlates with such inter-individual differences.

The Neuropsychology of Movement and Movement Disorders: Neuroanatomical and Cognitive Considerations

This paper highlights major developments over the past two to three decades in the neuropsychology of movement and its disorders. We focus on studies in healthy individuals and patients, which have identified cognitive contributions to movement control and animal work that has delineated the neural circuitry that makes these interactions possible. We cover advances in three major areas: (1) the neuroanatomical aspects of the "motor" system with an emphasis on multiple parallel circuits that include cortical, corticostriate, and corticocerebellar connections; (2) behavioral paradigms that have enabled an appreciation of the cognitive influences on the preparation and execution of movement; and (3) hemispheric differences (exemplified by limb praxis, motor sequencing, and motor learning). Finally, we discuss the clinical implications of this work, and make suggestions for future research in this area. (JINS, 2017, 23, 768-777).

Modulation of the sensorimotor system by sustained manual pressure stimulation

In Vojta physiotherapy, also known as reflex locomotion therapy, prolonged peripheral pressure stimulation induces complex generalized involuntary motor responses and modifies subsequent behavior, but its neurobiological basis remains unknown. We hypothesized that the stimulation would induce sensorimotor activation changes in functional magnetic resonance imaging (fMRI) during sequential finger opposition. Thirty healthy volunteers (mean age 24.2) underwent two randomized fMRI sessions involving manual pressure stimulation applied either at the right lateral heel according to Vojta, or at the right lateral ankle (control site). Participants were scanned before and after the stimulation when performing auditory-paced sequential finger opposition with their right hand. Despite an extensive activation decrease following both stimulation paradigms, the stimulation of the heel specifically led to an increase in task-related activation in the predominantly contralateral pontomedullary reticular formation and bilateral posterior cerebellar hemisphere and vermis. Our findings suggest that sustained pressure stimulation of the foot is associated with differential short-term changes in hand motor task-related activation depending on the stimulation. This is the first evidence for brainstem modulation after peripheral pressure stimulation, suggesting that the after-effects of reflex locomotion physiotherapy involve a modulation of the pontomedullary reticular formation.

Age-related differences in practice-dependent resting-state functional connectivity related to motor sequence learning

Decreased neural plasticity is observed with healthy ageing in the primary sensorimotor (SM1) cortex thought to participate in motor learning and memory consolidation processes. In the present magnetoencephalography study, the post-training reorganization of resting-state functional connectivity (rsFC) and its relation with motor learning and early consolidation in 14 young (19-30 years) and 14 old (66-70 years) healthy participants were investigated. At the behavioral level, participants were trained on a motor sequence learning task then retested 20-30 min later for transient offline gains in performance. Using a sensorimotor seed-based approach, rsFC relying on beta band power envelope correlation was estimated immediately before and 10 min after the learning episode. Post-training changes in rsFC (from before to after learning) were correlated with motor learning performance and with the offline improvement in performance within the hour after learning. Young and old participants exhibited differential patterns of sensorimotor-related rsFC, bearing specific relationships with motor learning and consolidation. Our findings suggest that rsFC changes following learning reflect the offline processing of the new motor skill and contribute to the early memory consolidation within the hour after learning. Furthermore, differences in post-training changes in rsFC between young and old participants support the hypothesis that ageing modulates the neural circuits underlying the learning of a new motor skill and the early subsequent consolidation stages. Hum Brain Mapp 38:923-937, 2017. © 2016 Wiley Periodicals, Inc.

The cerebellum, internal models and prediction in 'non-motor' aspects of language: A critical review

The emergence of studies on cerebellar contributions in 'non-motor' aspects of predictive language processing has long been awaited by researchers investigating the neural foundations of language and cognition. Despite (i) progress in research implicating the cerebellum in language processing, (ii) the widely-accepted nature of the uniform, multi-modal computation that the cerebellum implements in the form of internal models, as well as (iii) the long tradition of psycholinguistic studies addressing prediction mechanisms, research directly addressing cerebellar contributions to 'non-motor' predictive language processing has only surfaced in the last five years. This paper provides the first review of this novel field, along with a critical assessment of the studies conducted so far. While encouraging, the evidence for cerebellar involvement in 'non-motor' aspects of predictive language processing remains inconclusive under further scrutiny. Future directions are finally discussed with respect to outstanding questions in this novel field of research.

Compensatory motor network connectivity is associated with motor sequence learning after subcortical stroke

Following stroke, functional networks reorganize and the brain demonstrates widespread alterations in cortical activity. Implicit motor learning is preserved after stroke. However the manner in which brain reorganization occurs, and how it supports behavior within the damaged brain remains unclear. In this functional magnetic resonance imaging (fMRI) study, we evaluated whole brain patterns of functional connectivity during the performance of an implicit tracking task at baseline and retention, following 5 days of practice. Following motor practice, a significant difference in connectivity within a motor network, consisting of bihemispheric activation of the sensory and motor cortices, parietal lobules, cerebellar and occipital lobules, was observed at retention. Healthy subjects demonstrated greater activity within this motor network during sequence learning compared to random practice. The stroke group did not show the same level of functional network integration, presumably due to the heterogeneity of functional reorganization following stroke. In a secondary analysis, a binary mask of the functional network activated from the aforementioned whole brain analyses was created to assess within-network connectivity, decreasing the spatial distribution and large variability of activation that exists within the lesioned brain. The stroke group demonstrated reduced clusters of connectivity within the masked brain regions as compared to the whole brain approach. Connectivity within this smaller motor network correlated with repeated sequence performance on the retention test. Increased functional integration within the motor network may be an important neurophysiological predictor of motor learning-related change in individuals with stroke.

Uncovering the interaction between empathetic pain and cognition

Recent studies have demonstrated that empathizing with pain involves both cognitive and affective components of pain. How does empathetic pain impact cognition? To investigate this question, in the present study, participants performed a classic color-word Stroop task that followed a pain portraying or a corresponding control image. We found that observing pain experience in another had a basic slowing down effect on Reaction times (RTs) during neutral Stroop trials. Further, it affected cognition in a way that it decreased interference and increased facilitation. Moreover, our findings revealed that RTs during the incongruent and congruent trials were essentially unchanged by pain observing (empathy vs. control). The data are best accounted by a two-opposing effect model that empathetic pain impacts cognition through two different ways: it slows down performance in general, and facilitates performance during incongruent and congruent trials in particular. In this way, the present study also lends support to an idea that all components of empathy should be understood from an integrative approach.

Impairment of functional integration of the default mode network correlates with cognitive outcome at three months after stroke

Resting‐state studies conducted with stroke patients are scarce. The study of brain activity and connectivity at rest provides a unique opportunity for the investigation of brain rewiring after stroke and plasticity changes. This study sought to identify dynamic changes in the functional organization of the default mode network (DMN) of stroke patients at three months after stroke. Eleven patients (eight male and three female; age range: 48–72) with right cortical and subcortical ischemic infarctions and 17 controls (eleven males and six females; age range: 57–69) were assessed by neurological and neuropsychological examinations and scanned with resting‐state functional magnetic ressonance imaging. First, we explored group differences in functional activity within the DMN by means of probabilistic independent component analysis followed by a dual regression approach. Second, we estimated functional connectivity between 11 DMN nodes both locally by means of seed‐based connectivity analysis, as well as globally by means of graph‐computation analysis. We found that patients had greater DMN activity in the left precuneus and the left anterior cingulate gyrus when compared with healthy controls (P < 0.05 family‐wise error corrected). Seed‐based connectivity analysis showed that stroke patients had significant impairment (P = 0.014; threshold = 2.00) in the connectivity between the following five DMN nodes: left superior frontal gyrus (lSFG) and posterior cingulate cortex (t = 2.01); left parahippocampal gyrus and right superior frontal gyrus (t = 2.11); left parahippocampal gyrus and lSFG (t = 2.39); right parietal and lSFG (t = 2.29). Finally, mean path length obtained from graph‐computation analysis showed positive correlations with semantic fluency test (r_s = 0.454; P = 0.023), phonetic fluency test (r_s = 0.523; P = 0.007) and the mini mental state examination (r_s = 0.528; P = 0.007). In conclusion, the ability to regulate activity of the DMN appears to be a central part of normal brain function in stroke patients. Our study expands the understanding of the changes occurring in the brain after stroke providing a new avenue for investigating lesion‐induced network plasticity. Hum Brain Mapp 36:577–590, 2015. © 2014 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

The feasibility of using haptic devices to engage people with chronic traumatic brain injury in virtual 3D functional tasks

BACKGROUND

The primary aim of this study was to assess the level of engagement in computer-based simulations of functional tasks, using a haptic device for people with chronic traumatic brain injury. The objectives were to design functional tasks using force feedback device and determine if it could measure motor performance improvement.

METHODS

A prospective crosssectional study was performed in a biomedical research facility. The testing environment consisted of a single, interactive, stylus-driven computer session navigating virtual scenes in 3D space. Subjects had a haptic training session (TRAIN) and then had three chances to perform each virtual task: (i) remove tools from a workbench (TOOL), (ii) compose 3 letter words (SPELL), (iii) manipulate utensils to prepare a sandwich (SAND), and (iv) tool use (TUSE). Main Outcome Measures included self-report of engagement in the activities, improved performance on simulated tasks and observer estimate as measured by time to completion or number of words completed from baseline, correlations among performance measures and self-reports of boredom, neuropsychological symptom inventory (NSI), and The Purdue Peg Motor Test (PPT).

RESULTS

Participants were 19 adults from the community with a 1 year history of non-penetrating traumatic brain injury (TBI) and were able to use computers. Seven had mild, 3 moderate and 9 severe TBIs. Mean score on the Boredom Proneness Scale (BPS): 107 (normal range 81-117); mean NSI:32; mean PPT 54 (normal range for assembly line workers >67). Responses to intervention: 3 (15%)subjects did not repeat all three trials of the tasks; 100% reported they were highly engaged in the interactions; 6 (30%) reported they had a high level of frustration with the tasks, but completed them with short breaks. Performance measures: Comparison of baseline to post training: TOOL time decreased by (mean) 60 sec; SPELL increased by 2.7 words; TUSE time decreased by (mean) 68 sec; and SAND time decreased by (mean) 72 sec. PPT correlated with TOOL (r=-0.65, p=0.016) and TUSE time (r=-0.6, p=0.014). SPELL correlated with Boredom score (r=0.41, p=0.08) and NSI (r=-.49, p=0.05).

CONCLUSION

People with chronic TBI of various ages and severity report being engaged in using haptic devices that interact with 3D virtual environments. Haptic devices are able to capture objective data that provide useful information about fine motor and cognitive performance.

Done that: short-term repetition related modulations of motor cortex activity as a stable signature for overnight motor memory consolidation

An almost universally accepted tacit expectation is that learning and memory consolidation processes must be reflected in the average brain activity in brain areas relevant to task performance. Motor cortex (M1) plasticity has been implicated in motor skill acquisition and its consolidation. Nevertheless, no consistent pattern of changes in the average signal, related to motor learning or motor memory consolidation following a single session of training, has emerged from imaging studies. Here we show that the pattern and magnitude of short-term brain activity modulations in response to task repetition, in M1, may provide a robust signature for effective motor memory consolidation processes. We studied participants during the paced performance of a finger-to-thumb opposition sequence (FOS), intensively trained a day earlier, and a similarly constructed untrained FOS. In addition to within-session "on-line" gains, most participants expressed delayed, consolidation-phase gains in the performance of the trained FOS. The execution of the trained FOS induced repetition enhancements in the contralateral M1 and bilaterally in the medial-temporal lobes, offsetting novelty-related repetition suppression effects. Moreover, the M1 modulations were positively correlated with the magnitude of each participant's overnight delayed gains but not with absolute performance levels. Our results suggest that short-term enhancements of brain signals upon task repetition reflect the effectiveness of overnight motor memory consolidation. We propose that procedural memory consolidation processes may affect the excitation-inhibition balance within cortical representations of the trained movements; this new balance is better reflected in repetition effects than in the average level of evoked neural activity.

Off-line consolidation of motor sequence learning results in greater integration within a cortico-striatal functional network

The consolidation of motor sequence learning is known to depend on sleep. Work in our laboratory and others have shown that the striatum is associated with this off-line consolidation process. In this study, we aimed to quantify the sleep-dependent dynamic changes occurring at the network level using a measure of functional integration. We directly compared changes in connectivity before and after sleep or the simple passage of daytime. As predicted, the results revealed greater integration within the cortico-striatal network after sleep, but not an equivalent daytime period. Importantly, a similar pattern of results was also observed using a data-driven approach; the increase in integration being specific to a cortico-striatal network, but not to other known functional networks. These findings reveal, for the first time, a new signature of motor sequence consolidation: a greater between-regions interaction within the cortico-striatal system.

Delineating the cortico-striatal-cerebellar network in implicit motor sequence learning

Theoretical models and experimental evidence suggest that cortico-striatal-cerebellar networks play a crucial role in mediating motor sequence learning. However, how these different regions interact in order to mediate learning is less clear. In the present fMRI study, we used dynamic causal modeling to investigate effective connectivity within the cortico-striatal-cerebellar network while subjects performed a serial reaction time task. Using Bayesian model selection and family wise inference, we show that the cortico-cerebellar loop had higher model evidence than the cortico-striatal loop during motor learning. We observed significant negative modulatory effects on the connections from M1 to cerebellum bilaterally during learning. The results suggest that M1 causes the observed decrease in activity in the cerebellum as learning progresses. The current study stresses the significant role that the cerebellum plays in motor learning as previously suggested by fMRI studies in healthy subjects as well as behavioral studies in patients with cerebellar dysfunction. These results provide important insight into the neural mechanisms underlying motor learning.

Temporal structure of motor variability is dynamically regulated and predicts motor learning ability

Individual differences in motor learning ability are widely acknowledged, yet little is known about the factors that underlie them. Here we explore whether movement-to-movement variability in motor output, a ubiquitous if often unwanted characteristic of motor performance, predicts motor learning ability. Surprisingly, we found that higher levels of task-relevant motor variability predicted faster learning both across individuals and across tasks in two different paradigms, one relying on reward-based learning to shape specific arm movement trajectories and the other relying on error-based learning to adapt movements in novel physical environments. We proceeded to show that training can reshape the temporal structure of motor variability, aligning it with the trained task to improve learning. These results provide experimental support for the importance of action exploration, a key idea from reinforcement learning theory, showing that motor variability facilitates motor learning in humans and that our nervous systems actively regulate it to improve learning.

Motor execution and motor imagery: a comparison of functional connectivity patterns based on graph theory

Motor execution and imagery (ME and MI), as the basic abilities of human beings, have been considered to be effective strategies in motor skill learning and motor abilities rehabilitation. Neuroimaging studies have revealed several critical regions from functional activation for ME as well as MI. Recently, investigations have probed into functional connectivity of ME; however, few explorations compared the functional connectivity between the two tasks. With betweenness centrality (BC) of graph theory, we explored and compared the functional connectivity between two finger tapping tasks of ME and MI. Our results showed that using BC, the key node for the ME task mainly focused on the supplementary motor area, while the key node for the MI task mainly located in the right premotor area. These results characterized the connectivity patterns of ME and MI and may provide new insights into the neural mechanism underlying motor execution and imagination of movements.

Baseline activity predicts working memory load of preceding task condition

The conceptual notion of the so-called resting state of the brain has been recently challenged by studies indicating a continuing effect of cognitive processes on subsequent rest. In particular, activity in posterior parietal and medial prefrontal areas has been found to be modulated by preceding experimental conditions. In this study, we investigated which brain areas show working memory dependent patterns in subsequent baseline periods and how specific they are for the preceding experimental condition. During functional magnetic resonance imaging, 94 subjects performed a letter-version of the n-back task with the conditions 0-back and 2-back followed by a low-level baseline in which subjects had to passively observe the letters appearing. In a univariate analysis, 2-back served as control condition while 0-back, baseline after 0-back and baseline after 2-back were modeled as regressors to test for activity changes between both baseline conditions. Additionally, we tested, using Gaussian process classifiers, the recognition of task condition from functional images acquired during baseline. Besides the expected activity changes in the precuneus and medial prefrontal cortex, we found differential activity in the thalamus, putamen, and postcentral gyrus that were affected by the preceding task. The multivariate analysis revealed that images of the subsequent baseline block contain task related patterns that yield a recognition rate of 70%. The results suggest that the influence of a cognitive task on subsequent baseline is strong and specific for some areas but not restricted to areas of the so-called default mode network.

Striatal denervation pattern predicts levodopa effects on sequence learning in Parkinson's disease

Mild to moderate Parkinson's disease shows more denervation in the posterodorsal striatum and sparing of the anteroventral striatum. Dopaminergic medications can interfere with anteroventral striatum function by overdosing this relatively intact structure. The authors determined how regional striatal denervation affects medication-associated sequence learning impairment in Parkinson's disease. Eighteen Parkinson's patients performed motor sequence learning on and off levodopa. Patients underwent (11)C-dihydrotetrabenazine positron emission tomography scans to measure nigrostriatal denervation. Patients with more preserved putamen were more likely to exhibit levodopa-associated sequence learning impairments. Furthermore, the ratio of denervation in the anterior to posterior dorsal putamen predicted the level of learning differences on and off levodopa. These results demonstrate that the spatial pattern of nigrostriatal dopaminergic denervation predicts medication responsiveness for motor sequence learning.

A comprehensive neuropsychological mapping battery for functional magnetic resonance imaging

Existing batteries for FMRI do not precisely meet the criteria for comprehensive mapping of cognitive functions within minimum data acquisition times using standard scanners and head coils. The goal was to develop a battery of neuropsychological paradigms for FMRI that can also be used in other brain imaging techniques and behavioural research. Participants were 61 healthy, young adult volunteers (48 females and 13 males, mean age: 22.25 ± 3.39 years) from the university community. The battery included 8 paradigms for basic (visual, auditory, sensory-motor, emotional arousal) and complex (language, working memory, inhibition/interference control, learning) cognitive functions. Imaging was performed using standard functional imaging capabilities (1.5-T MR scanner, standard head coil). Structural and functional data series were analysed using Brain Voyager QX2.9 and Statistical Parametric Mapping-8. For basic processes, activation centres for individuals were within a distance of 3-11 mm of the group centres of the target regions and for complex cognitive processes, between 7 mm and 15 mm. Based on fixed-effect and random-effects analyses, the distance between the activation centres was 0-4 mm. There was spatial variability between individual cases; however, as shown by the distances between the centres found with fixed-effect and random-effects analyses, the coordinates for individual cases can be used to represent those of the group. The findings show that the neuropsychological brain mapping battery described here can be used in basic science studies that investigate the relationship of the brain to the mind and also as functional localiser in clinical studies for diagnosis, follow-up and pre-surgical mapping.

High-frequency TRNS reduces BOLD activity during visuomotor learning

Transcranial direct current stimulation (tDCS) and transcranial random noise stimulation (tRNS) consist in the application of electrical current of small intensity through the scalp, able to modulate perceptual and motor learning, probably by changing brain excitability. We investigated the effects of these transcranial electrical stimulation techniques in the early and later stages of visuomotor learning, as well as associated brain activity changes using functional magnetic resonance imaging (fMRI). We applied anodal and cathodal tDCS, low-frequency and high-frequency tRNS (lf-tRNS, 0.1–100 Hz; hf-tRNS 101–640 Hz, respectively) and sham stimulation over the primary motor cortex (M1) during the first 10 minutes of a visuomotor learning paradigm and measured performance changes for 20 minutes after stimulation ceased. Functional imaging scans were acquired throughout the whole experiment. Cathodal tDCS and hf-tRNS showed a tendency to improve and lf-tRNS to hinder early learning during stimulation, an effect that remained for 20 minutes after cessation of stimulation in the late learning phase. Motor learning-related activity decreased in several regions as reported previously, however, there was no significant modulation of brain activity by tDCS. In opposition to this, hf-tRNS was associated with reduced motor task-related-activity bilaterally in the frontal cortex and precuneous, probably due to interaction with ongoing neuronal oscillations. This result highlights the potential of lf-tRNS and hf-tRNS to differentially modulate visuomotor learning and advances our knowledge on neuroplasticity induction approaches combined with functional imaging methods.

Task-dependent interactions between dopamine D2 receptor polymorphisms and L-DOPA in patients with Parkinson's disease

Variants in genes regulating dopamine transmission affect performance on tasks including working memory and executive function as well as temporal processing and sequence learning. In the current study, we determined whether a dopamine D2 receptor DNA sequence polymorphism interacts with L-DOPA during motor tasks in patients with Parkinson's disease (PD). Forty-five PD patients were genotyped for the DRD2 polymorphism (rs 1076560, G>T). Patients performed an explicit motor sequence learning task and the grooved pegboard test in both ON and OFF L-DOPA states. For motor sequence learning, DRD2 genotype mediated L-DOPA effects such that L-DOPA associated improvements were only observed in the minor T allele carriers (associated with lower D2 receptor availability, t10=-2.71, p=0.022), whereas G homozygotes showed no performance change with L-DOPA. For the grooved pegboard test, performance improved with L-DOPA independent of patients' DRD2 genotype. Collectively these results demonstrate that common DRD2 allelic differences found in the human population may explain how dopamine differentially contributes to performance across tasks and individuals.

Cognitive functions in ataxia with oculomotor apraxia type 2

Background: Ataxia with oculomotor apraxia type 2 (AOA2) is characterized by cerebellar atrophy, peripheral neuropathy, oculomotor apraxia, and elevated serum alpha-fetoprotein (AFP) levels. The disease is caused by a recessive mutation in the senataxin gene. Since it is a very rare cerebellar disorder, no detailed examination of cognitive functions in AOA2 has been published to date. The aim of the present study was to investigate the neuropsychological profile of a 54-year-old patient with AOA2. Methods: A broad range of neuropsychological examination protocol was administered including the following domains: short-term, working- and episodic-memories, executive functions, implicit sequence learning, and the temporal parameters of speech. Results: The performance on the Listening Span, Letter Fluency, Serial Reaction Time Task, and pause ratio in speech was 2 or more standard deviations (SD) lower compared to controls, and 1 SD lower on Backward Digit Span, Semantic Fluency, articulation rate, and speech tempo. Conclusion: These findings indicate that the pathogenesis of the cerebrocerebellar circuit in AOA2 is responsible for the weaker coordination of complex cognitive functions such as working memory, executive functions, speech, and sequence learning.

Age related differences in the neural substrates of motor sequence learning after interleaved and repetitive practice

Practice of tasks in an interleaved order generally induces superior retention compared to practicing in a repetitive order. Younger and older adults practiced serial reaction time tasks that were arranged in a repeated or an interleaved order on 2 successive days. Retention was tested on Day 5. For both groups, reaction times in the interleaved condition were slower than the repetitive condition during practice, but the reverse was true during retention on Day 5. After interleaved practice, changes in M1 excitability measured by paired-pulse TMS were greater than after repetitive practice, and this effect was more pronounced in older adults. Moreover, the increased M1 excitability correlated with the benefit of interleaved practice. BOLD signal was also increased for interleaved compared to repetitive practice in both groups. However, the pattern of correlations between increased BOLD during practice and subsequent benefit of the interleaved condition differed by group. In younger adults, dorsolateral-prefrontal activity during practice was related to this benefit, while in older adults, activation in sensorimotor regions and rostral prefrontal cortex during practice correlated with the benefit of interleaving on retention. Older adults may engage compensatory mechanisms during interleaved practice such as increasing sensorimotor recruitment which in turn benefits learning.