Imaging fibres in the brain

Contains fulltext : 127118.pdf (publisher's version ) (Open Access)Radboud Universiteit Nijmegen, 19 mei 2014Promotores : Ruiter, D.J., Norris, D.G. Co-promotores : Cappellen van Walsum, A.M. van, Barth, M

Golf performance enhancement by means of ‘real-life neurofeedback’ training based on personalized event-locked EEG profiles

Contains fulltext : 73297.pdf (publisher's version ) (Closed access)Background. This study reports on a new method for golf performance enhancement employing personalized real-life neurofeedback during golf putting. Method. Participants (n = 6) received an assessment and three real-life neurofeedback training sessions. In the assessment, a personal event-locked electroencephalographic (EEG) profile at FPz was determined for successful versus unsuccessful putts. Target frequency bands and amplitudes marking optimal prefrontal brain state were derived from the profile by two raters. The training sessions consisted of four series of 80 putts in an ABAB design. The feedback in the second and fourth series was administered in the form of a continuous NoGo tone, whereas in the first and third series no feedback was provided. This tone was terminated only when the participants EEG met the assessment-defined criteria. In the feedback series, participants were instructed to perform the putt only after the NoGo tone had ceased. Results. From the personalized event-locked EEG profiles, individual training protocols were established. The interrater reliability was 91%. The overall percentage of successful putts was significantly larger in the second and fourth series (feedback) of training compared to the first and third series (no feedback). Furthermore, most participants improved their performance with feedback on their personalized EEG profile, with 25% on average. Conclusions. This study demonstrates that the “zone” or the optimal mental state for golf putting shows clear recognizable personalized patterns. The learning effects suggest that this real-life approach to neurofeedback improves learning speed, probably by tapping into learning associated with contextual conditioning rather than operant conditioning, indicating perspectives for clinical applications.8 p

Discrete-trial SCP and GSR Training and the Interrelationship between Central and Peripheral Arousal

Contains fulltext : 90160.pdf (publisher's version ) (Closed access)Introduction. Slow Cortical Potential (SCP) neurofeedback and Galvanic Skin Response (GSR) biofeedback training were used to investigate self-regulatory control over central and peripheral arousal processes in two groups of healthy participants. Method. One group completed the SCP neurofeedback training procedure; the other group performed the GSR biofeedback procedure. Both groups underwent treatment while the other variable was passively recorded. The participants were instructed to either increase (Up trials) or decrease (Down trials) arousal. Twenty sessions were completed by each of the 18 participants over an 8-week period. Results. Participants in each group performed better on the variable they were trained on. In the GSR group, a significant increase in performance over blocks was obtained for both trial types (Up and Down). In the SCP group a better performance on the Down trials was obtained. When comparing performance of both trial types, the SCP-trained participants showed a marginal increase and the GSR-trained participants a significant increase over time preliminary-training. Conclusion. Overall, the results showed that GSR regulation is easier to learn than SCP training with neurofeedback, that both variables can be trained in a bidirectional design, and that the SCP training subjects were predominantly able to learn performance at the Down trials. Preliminary results from the cross-correlations are inconsistent over trial types, trained parameters, and participants. However, the general trend shows a more positive correlation at the end of training compared to the start of training. Cross-correlation analysis suggests that this training encourages positive correlation between the SCP and GSR. Future research directions should be aimed at improving motivational conditions, implementing contingent reward principles, and controlling confounding variables

Comparison of discrete-trial based SMR and SCP training and the interrelationship between SCP and SMR networks: Implications for Brain-Computer Interfaces and Neurofeedback

Contains fulltext : 72797.pdf (publisher's version ) (Closed access)Background. Operant conditioning of one's slow cortical potential (SCP) or sensorimotor rhythm (SMR) can be used to control epilepsy or to manipulate external devices, as applied in BCI (Brain-Computer Interface). A commonly accepted view that both SCP and SMR are reflections of central arousal suggests a functional relationship between SCP and SMR networks. Method. The operant conditioning of SCP or SMR was tested with a single electroencephalographic (EEG) channel wireless biofeedback system. A series of trainings taught 19 participants to control SCP or SMR over vertex during 20 neurofeedback sessions. Each session consisted of 96 trials to decrease cortical arousal (SCP positivity/SMR enhancement) and 64 trials to increase cortical arousal (SCP negativity/SMR suppression). In each trial, participants were required to exceed an individual threshold level of the feedback parameter relative to a 500-msec prefeedback baseline and to hold this level for 2 sec (SCP) or 0.5 sec (SMR) to obtain reinforcement. Results. Ten of the 19 participants achieved control over their EEG. In the SCP-trained group, 4 of 9 participants increased the differentiation between their SCP responses on positivity-required versus negativity-required trials. SMR suppression and enhancement was achieved by 3 and 4 of the 10 SMR-trained participants. The SMR-trained responders did not show differentiation in their SMR responses, but did show a differentiation in their SCP response—while trained on SMR. Conclusions. The results showed the proposed method was successful to teach control of SCP or SMR. Bidirectional control was very difficult to achieve with the present SMR training procedure. SCP positivity and SMR enhancement were easier to learn. The results suggest that SMR training modulates excitability thresholds in the striatal-thalamocortical motor loop, whereas changes in the loop's excitability thresholds by SCP training do not affect the thalamic bursting that underlies the SMR.18 p

Diffusion tensor characteristics of gyrencephaly using high resolution diffusion MRI in vivo at 7T

Contains fulltext : 155025.pdf (Publisher’s version ) (Closed access)Gyrification of the human cerebral cortex allows for the surface expansion that accommodates many more cortical neurons in comparison to other mammals. For neuroimaging, however, it forms a feature that complicates analysis. For example, it has long been established that cortical layers do not occupy the same depth in gyri and sulci. Recently, in vivo diffusion imaging has provided insights into the fibre architecture of the cortex, usually showing radial tensor orientations. This makes it relevant to investigate whether cortical diffusion tensor metrics depend on the gyral pattern. High-resolution (1mm isotropic) diffusion weighted MRI of the medial wall of the hemispheres was performed at 7 T. Diffusion data were resampled to surfaces in the cortex and underlying white matter, where the cortical surfaces obeyed the equivolume principle for cortical laminae over the cortical curvature. Diffusion tensor metrics were averaged over bins of curvature to obtain maps of characteristic patterns in the gyrus. Diffusivity, anisotropy and radiality varied with curvature. Radiality was maximal in intermediate layers of the cortex next to the crown of the gyrus, not in white matter or on the crown. In the fundus, the deep cortical layers had tangential tensor orientations. In the white matter, tensor orientation changed from radial on the crown to tangential under the banks and fundus. White matter anisotropy gradually increased from the crown to the fundus. The characteristic pattern in the gyrus demonstrated here is in accordance with ex vivo diffusion MR microscopy and histological studies. The results indicate the necessity of taking into account the gyral pattern when cortical diffusion data is analysed. Additionally, the data suggest a confound for tractography approaches when reaching the gyrus, resulting in a possible bias towards the gyral crown. The implications for mechanisms that could drive cortical folding are discussed.10 p

Gray and white matter degeneration revealed by diffusion in an Alzheimer mouse model

Item does not contain fulltextIn patients with Alzheimer's disease (AD) the severity of white matter degeneration correlates with the clinical symptoms of the disease. In this study, we performed diffusion-tensor magnetic resonance imaging at ultra-high field in a mouse model for AD (APP(swe)/PS1(dE9)) in combination with a voxel-based approach and tractography to detect changes in water diffusivity in white and gray matter, because these reflect structural alterations in neural tissue. We found substantial changes in water diffusion parallel and perpendicular to axonal tracts in several white matter regions like corpus callosum and fimbria of the hippocampus, that match with previous findings of axonal disconnection and myelin degradation in AD patients. Moreover, we found a significant increase in diffusivity in specific hippocampal subregions, which is supported by neuronal loss as visualized with Kluver-Barrera staining. This work demonstrates the potential of ultra-high field diffusion-tensor magnetic resonance imaging as a noninvasive modality to describe white and gray matter structural changes in mouse models for neurodegenerative disorders, and provides valuable knowledge to assess future AD prevention strategies in translational research

Predictive Performance of Cardiovascular Disease Risk Prediction Algorithms in People Living With HIV

Immunogenetics and cellular immunology of bacterial infectious disease