1,721,207 research outputs found
On the importance of using both T1-weighted and T2-weighted structural magnetic resonance imaging scans to model electric fields induced by non-invasive brain stimulation in SimNIBS
No full textThis work was supported by the Special Research Fund (BOF) of Hasselt University (BOF20KP18) and an NIH NINDS F31 NRSA grant (Principal Investigator: Kevin A. Caulfield; 1F31NS126019-01). Data were provided by the Human Connectome Project, WU-Minn Consortium (Principal Investigators: David Van Essen and Kamil Ugurbil; 1U54MH091657) funded by the 16 NIH Institutes and Centers that support the NIH Blueprint for Neuroscience Research; and by the McDonnell Center for Systems Neuroscience at Washington University. SVH and KAC equally contributed to this work
Directional constraints during bimanual coordination: The interplay between intrinsic and extrinsic directions as revealed by head motions
No full textThe role of directional compatibility was investigated during the production of in-phase and anti-phase coordination patterns involving both arms as well as the head. Our first aim was to compare the quality of coordination between both arms when symmetrical arm posture manipulations were used to disentangle muscle homology from the mutual direction of limb motions in extrinsic space. Findings revealed that in-phase coordination, characterized by the simultaneous activation of homologous muscle groups, was resistant to posture manipulations. Conversely, during anti-phase coordination, the influence of extrinsic direction became more prevalent whereby isodirectionality in extrinsic space contributed to stabilization of anti-phase coordination patterns. The second aim was to study the effect of periodic head movements upon the assembling of a coordinative synergy among the body segments. The findings demonstrated that the in-phase patterns were hardly affected by directionality of head motion. Conversely, the anti-phase patterns were more vulnerable to the directional influence of head movements, showing less accurate and stable coordination during non-isodirectional than isodirectional head motions. These observations underscore the robust nature of coordination patterns based on muscle homology, even in the absence of symmetric arm positions. Moreover, isodirectional head movements became easily integrated with the overall coordination pattern, whereas head-limb coupling was poor when the head moved anti-directional with the limbs. (C) 2007 Elsevier B.V. All rights reserved.Support for the present study was provided through a grant from the Research Council of K.U. Leuven, Belgium (Contract No. OT/03/61) and the Research Programme of the Research Foundation – Flanders (FWO-Vlaanderen G.0460.04 & G.0577.06)
The effect of anodal transcranial direct current stimulation on multi-limb coordination performance
No full textMotor coordination is the combination of body movements performed in a well-planned and controlled manner based upon motor commands from the brain. Several interventions have been in practice to improve motor control. Transcranial direct current stimulation (tDCS) is getting a lot of attention these days for its effect in improving motor functions. Studies focusing on the ability of tDCS to improve motor control, inhibition and coordination are sparse. Therefore, the influence of tDCS stimulation at the right dorsolateral prefrontal cortex (DLPFC) on motor control and coordination was investigated, in a sham-controlled double-blinded pseudo-randomized design, with a multi-limb coordination task in healthy young subjects. Number of errors and reaction time were used as outcome parameters. Our findings showed that, anodal tDCS reduced the number of errors only in the heterolateral coordination condition, however there was no change in reaction time. No changes were found for the homolateral and three-limb coordination conditions.sponsorship: This work is supported by the Flanders Fund for Scientific Research (G075810) and the Special Research Fund UHasselt. The authors like to thank I-BioStat (Interuniversity Institute for Biostatistics and statistical Bioinformatics, Hasselt University) for their contribution in the statistical analysis. (Flanders Fund for Scientific Research|G075810, Special Research Fund UHasselt)status: Publishe
Are exercise prescriptions for patients with cardiovascular disease, made by physiotherapists, in agreement with European recommendations?
No full textAims Physiotherapists often treat patients with (elevated risk for) cardiovascular disease (CVD), and should thus be able to provide evidence-based exercise advice to these patients. This study, therefore, aims to examine whether exercise prescriptions by physiotherapists to patients with CVD are in accordance with European recommendations. Methods and results This prospective observational survey included forty-seven Belgian physiotherapists. The participants agreed to prescribe exercise intensity, frequency, session duration, program duration, and exercise type (endurance or strength training) for the same three patient cases. Exercise prescriptions were compared between physiotherapists and relations with their characteristics were studied. The agreement between physiotherapists' exercise prescriptions and those from European recommendations ('agreement score': based on a maximal score of 60/per case) was assessed. A wide inter-clinician variability was noticed for all exercise modalities, leading to a large variance for total peak-effort training minutes (from 461 up to 9000 over the three cases). The exercise frequency was prescribed fully out of range of the recommendations and the prescription of additional exercise modes was generally flawed. Exercise intensity and program duration were prescribed partially correct. The addition of strength exercises and session duration was prescribed correctly. This led to physiotherapist agreement scores of 25.3 & PLUSMN; 9.6, 23.2 & PLUSMN; 9.9, and 27.1 & PLUSMN; 10.6 (all out of 60), for cases one, two, and three, respectively. A greater agreement score was found in younger colleagues and those holding a Ph.D. Conclusion Exercise prescriptions for CVD patients vary widely among physiotherapists and often disagree with European recommendations. Registration ClinicalTrials.gov NCT05449652We would like to thank Wim Ramakers for his contribution to this study
Cerebellum and Neurorehabilitation in Emotion with a Focus on Neuromodulation
No full textMore and more research has focused on the role of the cerebellum in emotions and social cognition. Structural cerebellar and cerebello-cerebral connectivity abnormalities have been identified in several prevalent neuropsychiatric conditions, which have in some cases even been linked to the severity of the emotional disorder. Non-invasive brain stimulation (NIBS) techniques are currently used to modulate neuronal excitability and tune the connectivity within and between neuronal networks. Targeting the cerebellum with NIBS in order to improve emotions and social behavior in neuropsychiatric conditions seems to be a very interesting and innovative approach. Several studies have already explored the effect of cerebellar vermis stimulation in patients with schizophrenia with promising results. Other neuropsychiatric disorders such as bipolar disorder (BD), obsessive-compulsive disorder (OCD), major depressive disorder, or generalized anxiety disorder (GAD) have received less attention with respect to cerebellar stimulation, although the cerebellum has been implicated in these disorders. We will address NIBS and neuropsychiatric disorders in this chapter. Future research should focus on combining cerebellar NIBS with neuroimaging to unravel the specific role of the cerebellum in emotional disorders. Such studies will be very valuable in establishing causal relationships between the structural and functional abnormalities that can be observed in these disorders, and in the search for neurophysiological biomarkers for emotions. However, it is still unclear which stimulation parameters are optimal. Moreover, an important factor to consider when applying cerebellar NIBS in order to improve emotional or other functioning is cerebellar reserve. Although the cerebellum has a wide variety of plasticity mechanisms and its structural organization intrinsically incorporates a lot of redundancy, this redundancy can be depleted. A certain amount of cerebellar reserve should be preserved to successfully apply NIBS. Systematic studies are therefore needed to clarify the optimal stimulation parameters, and methods should be developed to quantify cerebellar reserve in order to estimate the possible added value of NIBS in the rehabilitation of emotions
Accurate tissue segmentation from including both T1-weighted and T2-weighted MRI scans significantly affect electric field simulations of prefrontal but not motor TMS
No full textAccurate tissue segmentation from including both T1-weighted and T2-weighted MRI scans significantly affect electric field simulations of prefrontal but not motor TMS Keywords: Electric field (E-field) modeling Transcranial magnetic stimulation (TMS) Finite element method (FEM) T1w structural MRI scan T2w structural MRI scan Computational modeling Computational electric field (E-field) modeling is a valuable tool to simulate the cortical effects of noninvasive brain stimulation based on a person's head anatomy. E-field modeling involves seg-mentation of a structural magnetic resonance imaging (MRI) scan into different tissue layers, and creation of an anatomically accurate head model. On this head model, the effects of noninvasive brain stimulation are then simulated. Given the interest in E-field modeling for understanding dose-response relationships and even prospective E-field dosing [1], it is important to maximize accuracy by critically evaluating E-field modeling methodology. Recently, we showed that head meshes created from T1w þ T2w MRI scans more accurately represent E-fields induced by high-definition transcranial electric current (tES) over the motor cortex than meshes created from T1w scans [2]. Further analyses indicated that the higher E-field variability of T1w only models was mostly attributable to poorer tissue layer segmentation, particularly of the cerebrospinal fluid (CSF) and skull. However, the use of E-field simulations is not exclusive to tES, but also relates to transcranial magnetic stimulation (TMS). Although tES and TMS both induce cortical E-fields to noninvasively alter neural activity, their differing mechanisms of actions (i.e., electric versus electromagnetic E-field generation) imply that the results of our previous work cannot be directly extrapolated to TMS. There is reason to believe that the more accurate tissue segmentation obtained from including an additional T2w scan might be less impactful for TMS modeling as TMS simulations were found to be less susceptible to head model and tissue accuracy decreases than tES simulations [3,4]. Here, we set out to extend our prior tES results to TMS. Furthermore , we aimed to test whether there is brain region specificity to simulation accuracy by simulating TMS over the motor and pre-frontal cortices. We examined the influence of tissue thicknesses between the coil and cortex at both regions of interest (ROIs), as variations in scalp-to-cortex distance (SCD) could be a potential source of differences, given that distance is a determinant of magnetic field strength [5]. We computed E-field models in 100 healthy younger adults (57 females, 22e35 years old), randomly selected from the Human Connectome Project dataset [6]. T1w and T2w structural MRI-scans were acquired with the Siemens MAGNETOM 3T scanner (for detailed scanning parameters, see Ref. [6]). Two finite element method (FEM) tetrahedral head meshes were constructed per participant with headreco (Fig. 1A). The first mesh was based on a T1w MRI scan; the second mesh was based on a T1w þ T2w MRI scan. With SimNIBS (v3.2.3) [7], we simulated two TMS targets in each participant (one motor target, one prefrontal target), for a total of 400 E-field simulations (100 participants * 2 meshes * 2 TMS targets). All simulations were performed with a MagVenture 70mm figure-of-eight coil at 50% stimulator output on a MagPro R30 machine (dI/dt ¼ 75e6 A/s). For motor stimulation, the coil center was placed over C3 according to the electroencephalography 10e20 system, with a 45 angle to the sagittal plane. For prefrontal stimulation , the coil center was placed over F3 with a 45 angle. Standard conductivity values were used for the modeled tissues (white matter: 0.126 S/m, grey matter: 0.275 S/m, CSF: 1.654 S/m, bone: 0.01 S/m, skin: 0.465 S/m, and eyes: 0.5 S/m). For both meshes, the average E-field induced in the primary motor cortex (C3 TMS) and dorsolateral prefrontal cortex (F3 TMS) was extracted using a ROI analysis [2,7]. We centered the ROI at the subject space transformed peak MNI coordinate of the primary motor cortex (x ¼ À37, y ¼ À21, z ¼ 58) or dorsolateral prefrontal cortex (x ¼ À30, y ¼ À43, z ¼ 23) and extracted the average E-field in a 10 mm radius grey matter sphere in each model [8,9]. Linear mixed models were constructed with E-FIELD STRENGTH as the dependent variable, and MESHING APPROACH and ROI and their interaction as fixed effects. PARTICIPANT was included as random intercept. Results of the mixed model were investigated via Bonferroni-corrected post-hoc tests. The significance level was set to a ¼ 0.05. Previously, we used dice calculations to demonstrate that T1w þ T2w MRI scans produce more accurate head meshes primarily by improving skull and CSF tissue segmentation accuracy [2]. However, dice measures only provide information on whole head Abbreviations: tES, transcranial electric stimulation; TMS, transcra-nial magnetic stimulation; E-field, electric field; MRI, magnetic resonance imaging; ROI, region of interest; SCD, scalp-to-cortex distance; FEM, finite element method.This work was supported by the Special Research Fund (BOF) of Hasselt University (BOF20KP18), Research Foundation Flanders (G039821 N principal investigator Raf L.J. Meesen) and an NIH NINDS F31 NRSA grant (Principal Investigator: Kevin A. Caulfield; 1F31NS126019-01). Data were provided by the Human Connectome Project, WU-Minn Consortium (Principal Investigators: David Van Essen and Kamil Ugurbil; 1U54MH091657) funded by the 16 NIH Institutes and Centers that support the NIH Blueprint for Neuroscience Research; and by the McDonnell Center for Systems Neuroscience at Washington University
Age-dependent non-linear neuroplastic effects of cathodal tDCS in the elderly population: a titration study
No full textBACKGROUND: Neuromodulatory effects of transcranial direct current stimulation (tDCS) in older humans have shown heterogeneous results, possibly due to sub-optimal stimulation protocols associated with limited knowledge about optimized stimulation parameters in this age group. We systematically explored the association between the stimulation dosage of cathodal tDCS and induced after-effects on motor cortex excitability in the elderly. METHOD: Thirty-nine healthy volunteers in two age groups, namely Pre-Elderly (50–65 years) and Elderly (66–80 years), participated in the study. Ten sessions of cathodal tDCS, with a combination of four intensities (1, 2, 3 mA and sham) and three durations (15, 20, 30 min) were conducted over the M1 in each participant. Cortical excitability changes were monitored with TMS-induced motor evoked potentials (MEPs) for up to 2 h after stimulation. RESULTS: Motor cortex excitability was reduced by cathodal stimulation intensities of 1 and 3 mA in both age groups, in accordance with results observed in the younger age groups of previous studies. For the 2 mA stimulation condition, an age-dependent conversion of plasticity into a stimulation duration-dependent excitability enhancement was observed in the Pre-Elderly group, whereas in the Elderly group, LTD-like plasticity was preserved, or abolished, depending on stimulation duration. CONCLUSION: The LTD-like plasticity effects induced by cathodal tDCS originally described in young adults are also observable in older humans, but non-linearities of the resulting plasticity were partially preserved only in the Pre-Elderly, but not the Elderly group. These results aid in understanding age-dependent plasticity dynamics in humans, and to define more efficient tDCS protocols in the aging brain
Addressing transcranial electrical stimulation variability through prospective individualized dosing of electric field strength in 300 participants across two samples:the 2-SPED approach
No full textObjective. Transcranial electrical stimulation (tES) is a promising method for modulating brain activity and excitability with variable results to date. To minimize electric (E-)field strength variability, we introduce the 2-sample prospective E-field dosing (2-SPED) approach, which uses E-field strengths induced by tES in a first population to individualize stimulation intensity in a second population. Approach. We performed E-field modeling of three common tES montages in 300 healthy younger adults. First, permutation analyses identified the sample size required to obtain a stable group average E-field in the primary motor cortex (M1), with stability being defined as the number of participants where all group-average E-field strengths ± standard deviation did not leave the population’s 5-95 percentile range. Second, this stable group average was used to individualize tES intensity in a second independent population (n = 100). The impact of individualized versus fixed intensity tES on E-field strength variability was analyzed. Main results. In the first population, stable group average E-field strengths (V/m) in M1 were achieved at 74-85 participants, depending on the tES montage. Individualizing the stimulation intensity (mA) in the second population resulted in uniform M1 E-field strength (all p < 0.001) and significantly diminished peak cortical E-field strength variability (all p < 0.01), across all montages. Significance. 2-SPED is a feasible way to prospectively induce more uniform E-field strengths in a region of interest. Future studies might apply 2-SPED to investigate whether decreased E-field strength variability also results in decreased physiological and behavioral variability in response to tES.</p
Validation of frailty assessment batteries in relation to prognosis in older patients with cardiovascular disease
No full textBackground
Frailty is accompanied by, or can be caused by, a combination of several physical, psychosocial and cognitive problems, and is highly prevalent in older patients with cardiovascular disease (CVD). However, different frailty assessment batteries (e.g. Fried and Vigorito) remain to be compared in terms of prognosis, as well as the subcomponents within those batteries.
Purpose
To examine which frailty measurements contribute to the prediction of frailty in CVD patients, and prognosis, and thus should be executed in clinical settings.
Methods
In 133 CVD patients (mean age 78.1±6.7 years) the presence of frailty was examined by the Fried criteria and compared with the outcome from the multi-component frailty assessment tool of Vigorito including the Mini Nutritional Assessment (MNA), Katz-scale, 4.6 m gait speed, Timed Up and Go Test (TUG), handgrip strength, Mini Mental State Examination (MMSE), Geriatric Depression Scale (GDS-15) and number of medications. Additional tests were executed to further enhance the prediction of frailty. Patients were followed to register hospitalisations (general and urgent) and mortality up to 6 months after the frailty assessment. First, it was then analysed whether the Fried or Vigorito test battery would equally predict complications during follow-up, and secondly a new frailty test battery was developed with evaluation towards complication risk predictions.
Results
According to the tool of Vigorito, significantly more CVD patients suffered from minor vs. moderate frailty (34% vs. 10%, p<0.001) while the Phenotype of Fried did not succeed in detecting any significant difference in the number of pre-frail vs. frail patients (26% vs. 38%, p=0.11). Moreover, the largest part of the pre-frail patients of Fried seems to be not frail according to Vigorito and the frail patients of Fried seems to be mainly minor frail according to Vigorito.
Significant associations were found between hospitalisations and frailty according to Fried while mortality was significantly associated with frailty according to Vigorito and the newly developed formula (p=0.013). Finally, based on the multivariate regression model (R2=0.95), sex, MNA, Katz scale, TUG, handgrip strength (dominant hand), MMSE, GDS-15, total number of medications and the interaction effect between the Katz-scale and TUG should be assessed to detect frailty. Based on these parameters, a new formula to detect frailty was developed (r=0.95 with Vigorito score, p<0.001).
Conclusions
In comparison with the frailty assessment tool of Vigorito, the Fried criteria may overestimate frailty and its severity. Moreover, frailty seems to be significantly associated with 6-months hospitalisations as well as with mortality. The newly developed frailty assessment battery has the potential to detect frailty in a multidimensional way, and, moreover, to predict mortality
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