Functional interactions between the cerebellum and the premotor cortex for error correction during the slow rate force production task: an fMRI study

Toward Predicting Human Performance Outcomes From Wearable Technologies: A Computational Modeling Approach

Wearable technologies for measuring digital and chemical physiology are pervading the consumer market and hold potential to reliably classify states of relevance to human performance including stress, sleep deprivation, and physical exertion. The ability to efficiently and accurately classify physiological states based on wearable devices is improving. However, the inherent variability of human behavior within and across individuals makes it challenging to predict how identified states influence human performance outcomes of relevance to military operations and other high-stakes domains. We describe a computational modeling approach to address this challenge, seeking to translate user states obtained from a variety of sources including wearable devices into relevant and actionable insights across the cognitive and physical domains. Three status predictors were considered: stress level, sleep status, and extent of physical exertion; these independent variables were used to predict three human performance outcomes: reaction time, executive function, and perceptuo-motor control. The approach provides a complete, conditional probabilistic model of the performance variables given the status predictors. Construction of the model leverages diverse raw data sources to estimate marginal probability density functions for each of six independent and dependent variables of interest using parametric modeling and maximum likelihood estimation. The joint distributions among variables were optimized using an adaptive LASSO approach based on the strength and directionality of conditional relationships (effect sizes) derived from meta-analyses of extant research. The model optimization process converged on solutions that maintain the integrity of the original marginal distributions and the directionality and robustness of conditional relationships. The modeling framework described provides a flexible and extensible solution for human performance prediction, affording efficient expansion with additional independent and dependent variables of interest, ingestion of new raw data, and extension to two- and three-way interactions among independent variables. Continuing work includes model expansion to multiple independent and dependent variables, real-time model stimulation by wearable devices, individualized and small-group prediction, and laboratory and field validation.

Dynamics of Top-Down Control and Motor Networks in Parkinson's Disease

BACKGROUND

Motor symptoms in Parkinson's disease (PD) patients might be related to high-level task-control deficits. We aimed at investigating the dynamics between sensorimotor network and top-down control networks (frontal-parietal, cingulo-opercular, and cerebellar) in PD and at determining the effects of levodopa on the dynamics of these networks.

METHODS

We investigated dynamic functional connectivity (dFC), during resting state functional magnetic resonance imaging, between sensorimotor network and top-down control networks in 36 PD patients (OFF medication, PD-OFF) and 36 healthy volunteers. We further assessed the effect of medication on dFC in18 PD patients who were also scanned ON medication.

RESULTS

The dFC analyses identified three discrete states: State I (35.68%) characterized by connections between the cerebellum and sensorimotor network, State II (34.17%) with connections between the sensorimotor and frontal-parietal network, and State III (30.15%) with connection between the sensorimotor and cingulo-opercular network. PD patients have significantly fewer occurrences and overall spent less time (shorter dwell time) in State II compared to healthy controls. After levodopa intake, dwell time improved toward normal. The change in dwell time before and after taking levodopa was negatively related to the respective changes in Unified Parkinson's Disease Rating Scale, Part III. PD-OFF showed significantly decreased connectivity between sensorimotor and control networks and increased connectivity within control networks. These changes were partially improved after levodopa intake.

CONCLUSIONS

Dopamine depletion in PD is associated with abnormalities in temporal and spatial properties between cognitive control and sensorimotor network, possibly contributing to clinical deficits. Levodopa partially restores the network function toward the values observed in healthy volunteers. © 2021 International Parkinson and Movement Disorder Society.

An Increase in Postural Load Facilitates an Anterior Shift of Processing Resources to Frontal Executive Function in a Postural-Suprapostural Task

Increase in postural-demand resources does not necessarily degrade a concurrent motor task, according to the adaptive resource-sharing hypothesis of postural-suprapostural dual-tasking. This study investigated how brain networks are organized to optimize a suprapostural motor task when the postural load increases and shifts postural control into a less automatic process. Fourteen volunteers executed a designated force-matching task from a level surface (a relative automatic process in posture) and from a stabilometer board while maintaining balance at a target angle (a relatively controlled process in posture). Task performance of the postural and suprapostural tasks, synchronization likelihood (SL) of scalp EEG, and graph-theoretical metrics were assessed. Behavioral results showed that the accuracy and reaction time of force-matching from a stabilometer board were not affected, despite a significant increase in postural sway. However, force-matching in the stabilometer condition showed greater local and global efficiencies of the brain networks than force-matching in the level-surface condition. Force-matching from a stabilometer board was also associated with greater frontal cluster coefficients, greater mean SL of the frontal and sensorimotor areas, and smaller mean SL of the parietal-occipital cortex than force-matching from a level surface. The contrast of supra-threshold links in the upper alpha and beta bands between the two stance conditions validated load-induced facilitation of inter-regional connections between the frontal and sensorimotor areas, but that contrast also indicated connection suppression between the right frontal-temporal and the parietal-occipital areas for the stabilometer stance condition. In conclusion, an increase in stance difficulty alters the neurocognitive processes in executing a postural-suprapostural task. Suprapostural performance is not degraded by increase in postural load, due to (1) increased effectiveness of information transfer, (2) an anterior shift of processing resources toward frontal executive function, and (3) cortical dissociation of control hubs in the parietal-occipital cortex for neural economy.

Lateralization of brain activity pattern during unilateral movement in Parkinson's disease

We investigated the lateralization of brain activity pattern during performance of unilateral movement in drug-naïve Parkinson's disease (PD) patients with only right hemiparkinsonian symptoms. Functional MRI was obtained when the subjects performed strictly unilateral right hand movement. A laterality index was calculated to examine the lateralization. Patients had decreased activity in the left putamen and left supplementary motor area, but had increased activity in the right primary motor cortex, right premotor cortex, left postcentral gyrus, and bilateral cerebellum. The laterality index was significantly decreased in PD patients compared with controls (0.41 ± 0.14 vs. 0.84 ± 0.09). The connectivity from the left putamen to cortical motor regions and cerebellum was decreased, while the interactions between the cortical motor regions, cerebellum, and right putamen were increased. Our study demonstrates that in early PD, the lateralization of brain activity during unilateral movement is significantly reduced. The dysfunction of the striatum-cortical circuit, decreased transcallosal inhibition, and compensatory efforts from cortical motor regions, cerebellum, and the less affected striatum are likely reasons contributing to the reduced motor lateralization. The disruption of the lateralized brain activity pattern might be a reason underlying some motor deficits in PD, like mirror movements or impaired bilateral motor coordination.

Performance monitoring and behavioral adaptation during task switching: an fMRI study

Despite significant advances, the neural correlates and neurochemical mechanisms involved in performance monitoring and behavioral adaptation are still a matter for debate. Here, we used a modified Eriksen-Flanker task in a magnetic resonance imaging (MRI) study that required the participants to derive the correct stimulus-response association based on a feedback given after each flanker stimulus. Participants had to continuously monitor and adapt their performance as the stimulus-response association switched after a jittered time interval without notice. After every switch an increase of reaction times was observed. At the neural level, the feedback indicating the need to switch was associated with activation of the precuneus, the cingulate cortex, the insula and a brainstem region tentatively identified as the locus coeruleus. This brainstem system appears to interact with this cortical network and seems to be essential for performance monitoring and behavioral adaptation. In contrast, the cerebellum crus and prefrontal areas are activated during error feedback processing. Furthermore we found activations of the hippocampus and parahippocampal gyrus bilaterally after a correct feedback in learnable stimulus-response associations. These results highlight the contribution of brainstem nuclei to performance adaptation.

Consensus paper: roles of the cerebellum in motor control--the diversity of ideas on cerebellar involvement in movement

Considerable progress has been made in developing models of cerebellar function in sensorimotor control, as well as in identifying key problems that are the focus of current investigation. In this consensus paper, we discuss the literature on the role of the cerebellar circuitry in motor control, bringing together a range of different viewpoints. The following topics are covered: oculomotor control, classical conditioning (evidence in animals and in humans), cerebellar control of motor speech, control of grip forces, control of voluntary limb movements, timing, sensorimotor synchronization, control of corticomotor excitability, control of movement-related sensory data acquisition, cerebro-cerebellar interaction in visuokinesthetic perception of hand movement, functional neuroimaging studies, and magnetoencephalographic mapping of cortico-cerebellar dynamics. While the field has yet to reach a consensus on the precise role played by the cerebellum in movement control, the literature has witnessed the emergence of broad proposals that address cerebellar function at multiple levels of analysis. This paper highlights the diversity of current opinion, providing a framework for debate and discussion on the role of this quintessential vertebrate structure.

Bidirectional gray matter changes after complex motor skill learning

Long-term motor skill learning has been consistently shown to result in functional as well as structural changes in the adult human brain. However, the effect of short learning periods on brain structure is not well understood. In the present study, subjects performed a sequential pinch force task (SPFT) for 20 min on 5 consecutive days. Changes in brain structure were evaluated with anatomical magnetic resonance imaging (MRI) scans acquired on the first and last day of motor skill learning. Behaviorally, the SPFT resulted in sequence-specific learning with the trained (right) hand. Structural gray matter (GM) alterations in left M1, right ventral premotor cortex (PMC) and right dorsolateral prefrontal cortex (DLPFC) correlated with performance improvements in the SPFT. More specifically we found that subjects with strong sequence-specific performance improvements in the SPFT also had larger increases in GM volume in the respective brain areas. On the other hand, subjects with small behavioral gains either showed no change or even a decrease in GM volume during the time course of learning. Furthermore, cerebellar GM volume before motor skill learning predicted (A) individual learning-related changes in the SPFT and (B) the amount of structural changes in left M1, right ventral PMC and DLPFC. In summary, we provide novel evidence that short-term motor skill learning is associated with learning-related structural brain alterations. Additionally, we showed that practicing a motor skill is not exclusively accompanied by increased GM volume. Instead, bidirectional structural alterations explained the variability of the individual learning success.

Dissociation of brain areas associated with force production and stabilization during manipulation of unstable objects

Multifinger dexterous manipulation of unstable or deformable objects requires control of both direction and magnitude of fingertip force vectors. Our aim was to study the neuroanatomical correlates of these two distinct control functions. Brain activity was measured using functional magnetic resonance imaging while 16 male subjects (age: 26-42, M = 32, SD ± 4 years) compressed four springs representing a 2 × 2 factorial design with two levels of force and instability requirements. Significant activations associated with higher instability were located bilaterally in the precentral gyri, the postcentral gyrus, and the cerebellum. In the main effect for high force, activity was found in areas located in the primary motor regions contralateral to the active hand and bilaterally in the cerebellum. An overlap in activation between the two main effects was found bilaterally in the cerebellum (lobule VI). This study not only confirms a recently described bilateral fronto-parieto-cerebellar network for manipulation of increasingly unstable objects, but critically extends our understanding by describing its differentiated modulation with both force magnitude and instability requirements. Our results, therefore, expose a previously unrecognized and context-sensitive system of brain regions that enable dexterous manipulation for different force magnitude and instability requirements of the task.

Mirror movements in healthy humans across the lifespan: effects of development and ageing

AIM

mirror movements are a transient phenomenon during childhood, which decrease in intensity with motor development. An increasing inhibitory competence resulting in the ability of movement lateralization is thought to be the underlying mechanism. We aimed to quantify unintended mirror movements systematically across the lifespan and to investigate the influences of age, sex, handedness, and task frequency.

METHOD

a total of 236 participants (127 females, 109 males; 216 right-handed, 20 left-handed; age range 3-96y, median 25y 8mo) first performed four clinical routine tests while mirror movements were rated by the observer. They were then asked to hold a force transducer in each hand between the thumb and index finger and to perform oscillatory grip force changes in one hand, while the other hand had to prevent the force transducer from dropping.

RESULTS

age showed a strong nonlinear effect on the mirror-movement ratio (the amplitude ratio of the mirror and active hand, adjusted by the respective maximum grip force). Initially, there was a steep decline in the mirror-movement ratio during childhood and adolescence, followed by a gradual rise during adulthood. Males had lower mirror-movement ratios than females. The high-frequency condition triggered lower mirror-movement ratios. No significant differences of mirror movements between dominant and non-dominant hand, or left- and right-handed participants, were found.

INTERPRETATION

this study provides, for the first time to our knowledge, normative values of mirror movements across the lifespan that can aid differentiation between physiological and pathological mirror movements.

Multivariate information-theoretic measures reveal directed information structure and task relevant changes in fMRI connectivity

The human brain undertakes highly sophisticated information processing facilitated by the interaction between its sub-regions. We present a novel method for interregional connectivity analysis, using multivariate extensions to the mutual information and transfer entropy. The method allows us to identify the underlying directed information structure between brain regions, and how that structure changes according to behavioral conditions. This method is distinguished in using asymmetric, multivariate, information-theoretical analysis, which captures not only directional and non-linear relationships, but also collective interactions. Importantly, the method is able to estimate multivariate information measures with only relatively little data. We demonstrate the method to analyze functional magnetic resonance imaging time series to establish the directed information structure between brain regions involved in a visuo-motor tracking task. Importantly, this results in a tiered structure, with known movement planning regions driving visual and motor control regions. Also, we examine the changes in this structure as the difficulty of the tracking task is increased. We find that task difficulty modulates the coupling strength between regions of a cortical network involved in movement planning and between motor cortex and the cerebellum which is involved in the fine-tuning of motor control. It is likely these methods will find utility in identifying interregional structure (and experimentally induced changes in this structure) in other cognitive tasks and data modalities.

A cerebellar thalamic cortical circuit for error-related cognitive control

Error detection and behavioral adjustment are core components of cognitive control. Numerous studies have focused on the anterior cingulate cortex (ACC) as a critical locus of this executive function. Our previous work showed greater activation in the dorsal ACC and subcortical structures during error detection, and activation in the ventrolateral prefrontal cortex (VLPFC) during post-error slowing (PES) in a stop signal task (SST). However, the extent of error-related cortical or subcortical activation across subjects was not correlated with VLPFC activity during PES. So then, what causes VLPFC activation during PES? To address this question, we employed Granger causality mapping (GCM) and identified regions that Granger caused VLPFC activation in 54 adults performing the SST during fMRI. These brain regions, including the supplementary motor area (SMA), cerebellum, a pontine region, and medial thalamus, represent potential targets responding to errors in a way that could influence VLPFC activation. In confirmation of this hypothesis, the error-related activity of these regions correlated with VLPFC activation during PES, with the cerebellum showing the strongest association. The finding that cerebellar activation Granger causes prefrontal activity during behavioral adjustment supports a cerebellar function in cognitive control. Furthermore, multivariate GCA described the "flow of information" across these brain regions. Through connectivity with the thalamus and SMA, the cerebellum mediates error and post-error processing in accord with known anatomical projections. Taken together, these new findings highlight the role of the cerebello-thalamo-cortical pathway in an executive function that has heretofore largely been ascribed to the anterior cingulate-prefrontal cortical circuit.

The neural basis of agency: an fMRI study

Agency, a feeling that the self is the cause of action, has a strong relationship to the processing of discrepancies between the predicted multi-sensory feedback from one's intended action and its actual outcome (hereafter, agency error). Although previous studies have explored the neural basis of agency by assessing the brain's response to agency error, the effects found are confounded by two types of error irrelevant to agency: a mismatch between different sensory inputs in general (sensory mismatch, SM error) and a basic response to any type of prediction error (oddball error). In this functional magnetic resonance imaging study, we identified the neural response specific to agency error by dissociating it from responses to SM and oddball errors. Subjects played a game in which they controlled an on-screen character. Neural responses to rare events of violated control and congruency between types of audio-visual feedback were compared to dissociate agency from SM error. In a separate session, subjects viewed repetitive motions of the character, and neural responses to rare events of unpredictable change in movement were identified as related to oddball error. Agency-error-specific activation was observed in the supplementary motor area (SMA), left cerebellum, right posterior parietal cortex (PPC), and right extrastriate body area (EBA). Oddball errors also activated areas near the PPC and EBA peaks. SM errors activated the pre-SMA and the right posterior superior temporal sulcus. Our results suggest that the SMA, cerebellum, and some parts of the PPC and EBA serve as the neural bases of agency.

Separating coordinative and executive dysfunction in cerebellar patients during motor skill acquisition

OBJECTIVE

Patients with cerebellar stroke are impaired in motor skill acquisition and cognitive/executive performance. The aim was to test whether skill acquisition in cerebellar patients is influenced by executive demands such as the intermittent exercise of a conflicting motor task.

METHODS

Patients with cerebellar stroke and healthy controls were tested in two serial reaction time experiments. In Experiment 1, participants performed practice runs (always same sequence) and interference runs (new sequence for each run) in a strictly alternating fashion. In Experiment 2, participants rested between successive practice runs; the duration of rests was adapted to the duration of interference runs in the other experiment. Participants of Experiment 1 were also tested for cognitive-executive functions (Wisconsin Card Sort, Word Fluency, Trail Making, Digit Span backwards).

RESULTS

(1) Patients in Experiment 1, although always slower than controls, acquired motor skills in the first run before interference but in contrast to controls failed to improve their performance in subsequent runs. (2) Patients in Experiment 2 improved their performance consistently over several runs. (3) Patients of Experiment 1 were worse than controls in several cognitive-executive functions; however, these deficits did not correlate with the degree of interference in motor skill acquisition.

INTERPRETATION

Simple movement coordination and higher order context-related movement organisation are separate cerebellar functions. In cerebellar patients, impaired movement coordination is associated with generally slower reaction times whereas organisational deficits are associated with a specific impairment to change between motor sets. Motor-executive functions responsible for the latter impairment might be independent from cognitive-executive functions.