Diffusion magnetic resonance imaging connectome features are predictive of functional lateralization of semantic processing in the anterior temporal lobes.

Assessment of regional language lateralization is crucial in many scenarios, but not all populations are suited for its evaluation via task-functional magnetic resonance imaging (fMRI). In this study, the utility of structural connectome features for the classification of language lateralization in the anterior temporal lobes (ATLs) was investigated. Laterality indices for semantic processing in the ATL were computed from task-fMRI in 1038 subjects from the Human Connectome Project who were labeled as stronger rightward lateralized (RL) or stronger leftward to bilaterally lateralized (LL) in a data-driven approach. Data of unrelated subjects (n = 432) were used for further analyses. Structural connectomes were generated from diffusion-MRI tractography, and graph theoretical metrics (node degree, betweenness centrality) were computed. A neural network (NN) and a random forest (RF) classifier were trained on these metrics to classify subjects as RL or LL. After classification, comparisons of network measures were conducted via permutation testing. Degree-based classifiers produced significant above-chance predictions both during cross-validation (NN: AUC-ROC[CI] = 0.68[0.64-0.73], accuracy[CI] = 68.34%[63-73.2%]; RF: AUC-ROC[CI] = 0.7[0.66-0.73], accuracy[CI] = 64.81%[60.9-68.5]) and testing (NN: AUC-ROC[CI] = 0.69[0.53-0.84], accuracy[CI] = 68.09[53.2-80.9]; RF: AUC-ROC[CI] = 0.68[0.53-0.84], accuracy[CI] = 68.09[55.3-80.9]). Comparison of network metrics revealed small effects of increased node degree within the right posterior middle temporal gyrus (pMTG) in subjects with RL, while degree was decreased in the right posterior cingulate cortex (PCC). Above-chance predictions of functional language lateralization in the ATL are possible based on diffusion-MRI connectomes alone. Increased degree within the right pMTG as a right-sided homologue of a known semantic hub, and decreased hubness of the right PCC may form a structural basis for rightward-lateralized semantic processing.

Prediction of Movement Ratings and Deep Brain Stimulation Parameters in Idiopathic Parkinson's Disease.

BACKGROUND: Deep brain stimulation (DBS) parameter fine-tuning after lead implantation is laborious work because of the almost uncountable possible combinations. Patients and practitioners often gain the perception that assistive devices could be beneficial for adjusting settings effectively. OBJECTIVE: We aimed at a proof-of-principle study to assess the benefits of noninvasive movement recordings as a means to predict best DBS settings. MATERIALS AND METHODS: For this study, 32 patients with idiopathic Parkinson's disease, under chronic subthalamic nucleus stimulation with directional leads, were recorded. During monopolar review, each available contact was activated with currents between 0.5 and 5 mA, and diadochokinesia, rigidity, and tapping ability were rated clinically. Moreover, participants' movements were measured during four simple hand movement tasks while wearing a commercially available armband carrying an inertial measurement unit (IMU). We trained random forest models to learn the relations between clinical ratings, electrode settings, and movement features obtained from the IMU. RESULTS: Firstly, we could show that clinical mobility ratings can be predicted from IMU features with correlations of up to r = 0.68 between true and predicted values. Secondly, these features also enabled a prediction of DBS parameters, which showed correlations of up to approximately r = 0.8 with clinically optimal DBS settings and were associated with congruent volumes of tissue activated. CONCLUSION: Movement recordings from customer-grade mobile IMU carrying devices are promising candidates, not only for remote symptom assessment but also for closed-loop DBS parameter adjustment, and could thus extend the list of available aids for effective programming beyond imaging techniques.

Center or side: biases in selecting grasp points on small bars.

Choosing appropriate grasp points is necessary for successfully interacting with objects in our environment. We brought two possible determinants of grasp point selection into conflict: the attempt to grasp an object near its center of mass to minimize torque and ensure stability and the attempt to minimize movement distance. We let our participants grasp two elongated objects of different mass and surface friction that were approached from different distances to both sides of the object. Maximizing stability predicts grasp points close to the object's center, while minimizing movement costs predicts a bias of the grasp axis toward the side at which the movement started. We found smaller deviations from the center of mass for the smooth and heavy object, presumably because the larger torques and more slippery surface for the heavy object increase the chance of unwanted object rotation. However, our right-handed participants tended to grasp the objects to the right of the center of mass, irrespective of where the movement started. The rightward bias persisted when vision was removed once the hand was half way to the object. It was reduced when the required precision was increased. Starting the movement above the object eliminated the bias. Grasping with the left hand, participants tended to grasp the object to the left of its center. Thus, the selected grasp points seem to reflect a compromise between maximizing stability by grasping near the center of mass and grasping on the side of the acting hand, perhaps to increase visibility of the object.

Structural connectivity of low-frequency subthalamic stimulation for improving stride length in Parkinson's disease.

BACKGROUND: A reduction in stride length is considered a key characteristic of gait kinematics in Parkinson's disease (PD) and has been identified as a predictor of falls. Although low-frequency stimulation (LFS) has been suggested as a method to improve gait characteristics, the underlying structural network is not well understood. OBJECTIVE: This study aims to investigate the structural correlates of changes in stride length during LFS (85 Hz). METHODS: Objective gait performance was retrospectively evaluated in 19 PD patients who underwent deep brain stimulation (DBS) at 85 Hz and 130 Hz. Individual DBS contacts and volumes of activated tissue (VAT) were computed using preoperative magnetic resonance imaging (MRI) and postoperative computed tomography (CT) scans. Structural connectivity profiles to predetermined cortical and mesencephalic areas were estimated using a normative connectome. RESULTS: LFS led to a significant improvement in stride length compared to 130 Hz stimulation. The intersection between VAT and the associative subregion of the subthalamic nucleus (STN) was associated with an improvement in stride length and had structural connections to the supplementary motor area, prefrontal cortex, and pedunculopontine nucleus. Conversely, we found that a lack of improvement was linked to stimulation volumes connected to cortico-diencephalic fibers bypassing the STN dorsolaterally. The robustness of the connectivity model was verified through leave-one-patient-out, 5-, and 10-fold cross cross-validation paradigms. CONCLUSION: These findings offer new insights into the structural connectivity that underlies gait changes following LFS. Targeting the non-motor subregion of the STN with LFS on an individual level may present a potential therapeutic approach for PD patients with gait disorders.

Study protocol of the HessenKohorte2042: a prospective, longitudinal cohort study characterising quality of life in people with Parkinson's disease and their caregivers using a bio-psycho-social approach.

INTRODUCTION: Quality of life (QoL) is of paramount importance as an outcome to monitor and guide therapies for people with Parkinson's disease (PwPD). In particular, due to the heterogeneous symptoms that PwPD may experience during their disease course, QoL can deteriorate not only in patients but also in their caregivers, with a variety of psychosocial consequences. However, there is a lack of longitudinal studies that explore how QoL evolves over time and what factors are significant. Furthermore, holistic approaches that consider bio-psycho-social determinants are rare. In the worst cases, these gaps can lead to suboptimal care and therefore unmet needs for patients and their caregivers, resulting in unnecessary symptom burden and increased healthcare costs for society. METHODS AND ANALYSIS: This prospective, longitudinal study will follow 1000 PwPD along with their caregivers for 20 years, with up to 40 semi-annual assessments. Patient data and sample collection will include clinical assessments, self-reported outcome measures focusing on QoL, biospecimen collection and MRI. Caregiver burden will be systematically assessed through self-administered questionnaires. The use of digitised surveys will allow efficient data collection and convenient assessment at home. Our primary objective is to attain a holistic understanding of QoL in PwPD and establish a tool to measure it. The secondary objective is to explore the psycho-social and biological variables associated with QoL of patients and caregivers over the progression of the disease. This will provide key information for diagnostic and prognostic prediction, therapeutic patient stratification and adaptation of therapy in the future. ETHICS AND DISSEMINATION: The study was approved by the local ethics committee of the University Hospital of Marburg (study number: 209/19). The results will be disseminated by means of publication in peer-reviewed journals, international conference contributions, annual patient meetings and a dedicated website. TRIAL REGISTRATION NUMBER: German Clinical Trials Register (DRKS00023598).

Human grasp point selection.

When we grasp an object, our visuomotor system has to solve an intricate problem: how to find the best out of an infinity of possible contact points of the fingers with the object? The contact point selection model (CoPS) we present here solves this problem and predicts human grasp point selection in precision grip grasping by combining a few basic rules that have been identified in human and robotic grasping. Usually, not all of the rules can be perfectly satisfied. Therefore, we assessed their relative importance by creating simple stimuli that put them into conflict with each other in pairs. Based on these conflict experiments we made model-based grasp point predictions for another experiment with a novel set of complexly shaped objects. The results show that our model predicts the human choice of grasp points very well, and that observers' preferences for their natural grasp angles is as important as physical stability constraints. Incorporating a human grasp point selection model like the one presented here could markedly improve current approaches to cortically guided arm and hand prostheses by making movements more natural while also allowing for a more efficient use of the available information.

Prediction of motor Unified Parkinson's Disease Rating Scale scores in patients with Parkinson's disease using surface electromyography.

OBJECTIVE: Parkinson's disease (PD) is a chronic neurodegenerative disorder with increasing prevalence in the elderly. Especially patients with advanced PD often require complex medication regimens due to fluctuations, that is abrupt transitions from ON to OFF or vice versa. Current gold standard to quantify PD-patients' motor symptoms is the assessment of the Unified Parkinson's Disease Rating Scale (UPDRS), which, however, is cumbersome and may depend upon investigators. This work aimed at developing a mobile, objective and unobtrusive measurement of motor symptoms in PD. METHODS: Data from 45 PD-patients was recorded using surface electromyography (sEMG) electrodes attached to a wristband. The motor paradigm consisted of a tapping task performed with and without dopaminergic medication. Our aim was to predict UPDRS scores from the sEMG characteristics with distinct regression models and machine learning techniques. RESULTS: A random forest regression model outnumbered other regression models resulting in a correlation of 0.739 between true and predicted UPDRS values. CONCLUSIONS: PD-patients' motor affection can be extrapolated from sEMG data during a simple tapping task. In the future, such records could help determine the need for medication changes in telemedicine applications. SIGNIFICANCE: Our findings support the utility of wearables to detect Parkinson's symptoms and could help in developing tailored therapies in the future.

Grasping isoluminant stimuli.

We used a virtual reality setup to let participants grasp discs, which differed in luminance, chromaticity and size. Current theories on perception and action propose a division of labor in the brain into a color proficient perception pathway and a less color-capable action pathway. In this study, we addressed the question whether isoluminant stimuli, which provide only a chromatic but no luminance contrast for action planning, are harder to grasp than stimuli providing luminance contrast or both kinds of contrast. Although we found that grasps of isoluminant stimuli had a slightly steeper slope relating the maximum grip aperture to disc size, all other measures of grip quality were unaffected. Overall, our results do not support the view that isoluminance of stimulus and background impedes the planning of a grasping movement.

Does bimanual grasping of the Müller-Lyer illusion provide evidence for a functional segregation of dorsal and ventral streams?

Studies claiming a differential processing of visual illusions for perception and action have been subjected to many challenges. One criticism is that attentional demands were mismatched between the perception and action tasks. Dewar and Carey (2006) reexamined this argument by comparing bimanual grasping to bimanual size estimation and concluded that manual size estimation (ManEst) was affected by the illusion to a greater extent than grasping, supporting the case for two functionally distinct streams of visual processing. We tested whether this result may be due to their use of closed loop visual conditions by replicating their study under both closed and open loop conditions. We found that the difference in illusion effects between grasping and ManEst disappeared under open loop conditions, indicating that Dewar and Carey's findings can be explained by the availability of visual feedback and not a perception/action dissociation. We also discuss potential shortcomings of bimanual designs.

Grasping trapezoidal objects.

When grasping rectangular or circular objects with a precision grip the digits close in on the object in opposite directions. In doing so the digits move perpendicular to the local surface orientation as they approach opposite sides of the object. This perpendicular approach is advantageous for accurately placing the digits. Trapezoidal objects have non-parallel surfaces so that moving the digits in opposite directions would make the digits approach the contact surfaces at an angle that is not 90 degrees . In this study we examined whether this happens, or whether subjects tend to approach trapezoidal objects' surfaces perpendicularly. We used objects of different sizes and with different surface slants. Subjects tended to approach the object's surfaces orthogonally, suggesting that they aim for an optimal precision of digit placement rather than simply closing their hand as it reaches the object.