The role of diffusion MRI in neuroscience Assaf, Yaniv; Johansen‐Berg, Heidi; Thiebaut de Schotten, Michel
NMR in biomedicine,
April 2019, Letnik:
32, Številka:
4
Journal Article
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Diffusion‐weighted imaging has pushed the boundaries of neuroscience by allowing us to examine the white matter microstructure of the living human brain. By doing so, it has provided answers to ...fundamental neuroscientific questions, launching a new field of research that had been largely inaccessible. We briefly summarize key questions that have historically been raised in neuroscience concerning the brain's white matter. We then expand on the benefits of diffusion‐weighted imaging and its contribution to the fields of brain anatomy, functional models and plasticity. In doing so, this review highlights the invaluable contribution of diffusion‐weighted imaging in neuroscience, presents its limitations and proposes new challenges for future generations who may wish to exploit this powerful technology to gain novel insights.
Diffusion weighted imaging informs about brain regions' structural connectivity and structural connectivity defines brain regions' functional specificity. The application of diffusion weighted imaging in living specimen is also an unique opportunity to study the functional plasticity of the brain.
Highlights • Twenty-six studies were identified as eligible for this systematic review. • Mobility was positively associated with cognitive measures in healthy older adults. • The cognition-mobility ...relationship spans across cognitive domains. • Meta-analyses on extracted data revealed significant, albeit small, effect sizes.
Diffusion MRI (or dMRI) came into existence in the mid-1980s. During the last 25years, diffusion MRI has been extraordinarily successful (with more than 300,000 entries on Google Scholar for ...diffusion MRI). Its main clinical domain of application has been neurological disorders, especially for the management of patients with acute stroke. It is also rapidly becoming a standard for white matter disorders, as diffusion tensor imaging (DTI) can reveal abnormalities in white matter fiber structure and provide outstanding maps of brain connectivity. The ability to visualize anatomical connections between different parts of the brain, non-invasively and on an individual basis, has emerged as a major breakthrough for neurosciences. The driving force of dMRI is to monitor microscopic, natural displacements of water molecules that occur in brain tissues as part of the physical diffusion process. Water molecules are thus used as a probe that can reveal microscopic details about tissue architecture, either normal or in a diseased state.
Summary Diffusion-based tractography enables the graphical reconstruction of the white matter pathways in the brain and spinal cord of living humans. This technique has many potential clinical ...applications, including the investigation of stroke, multiple sclerosis, epilepsy, neurodegenerative diseases, and spinal cord disorders, and it enables hypotheses to be tested that could not previously be considered in living humans. This Review will outline the limitations of tractography, describe its current clinical applications in the most common neurological diseases, and highlight future opportunities.
Human brain imaging has identified structural changes in gray and white matter that occur with learning. However, ascribing imaging measures to underlying cellular and molecular events is ...challenging. Here we review human neuroimaging findings of structural plasticity and then discuss cellular and molecular level changes that could underlie observed imaging effects. Greater dialog between researchers in these different fields would help to facilitate cross-talk between cellular and systems level explanations of how learning sculpts brain structure.
Neural basis of induced phantom limb pain relief Kikkert, Sanne; Mezue, Melvin; O'Shea, Jacinta ...
Annals of neurology,
January 2019, 2019-01-00, 20190101, Letnik:
85, Številka:
1
Journal Article
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Objective
Phantom limb pain (PLP) is notoriously difficult to treat, partly due to an incomplete understanding of PLP‐related disease mechanisms. Noninvasive brain stimulation (NIBS) is used to ...modulate plasticity in various neuropathological diseases, including chronic pain. Although NIBS can alleviate neuropathic pain (including PLP), both disease and treatment mechanisms remain tenuous. Insight into the mechanisms underlying both PLP and NIBS‐induced PLP relief is needed for future implementation of such treatment and generalization to related conditions.
Methods
We used a within‐participants, double‐blind, and sham‐controlled design to alleviate PLP via task‐concurrent NIBS over the primary sensorimotor missing hand cortex (S1/M1). To specifically influence missing hand signal processing, amputees performed phantom hand movements during anodal transcranial direct current stimulation. Brain activity was monitored using neuroimaging during and after NIBS. PLP ratings were obtained throughout the week after stimulation.
Results
A single session of intervention NIBS significantly relieved PLP, with effects lasting at least 1 week. PLP relief associated with reduced activity in the S1/M1 missing hand cortex after stimulation. Critically, PLP relief and reduced S1/M1 activity correlated with preceding activity changes during stimulation in the mid‐ and posterior insula and secondary somatosensory cortex (S2).
Interpretation
The observed correlation between PLP relief and decreased S1/M1 activity confirms our previous findings linking PLP with increased S1/M1 activity. Our results further highlight the driving role of the mid‐ and posterior insula, as well as S2, in modulating PLP. Lastly, our novel PLP intervention using task‐concurrent NIBS opens new avenues for developing treatment for PLP and related pain conditions. ANN NEUROL 2019;85:59–73.
Oligodendrocytes continue to differentiate from their precursor cells even in adulthood, a process that can be modulated by neuronal activity and experience. Previous work has indicated that ...conditional ablation of oligodendrogenesis in adult mice leads to learning and memory deficits in a range of behavioral tasks. The current study replicated and re‐evaluated evidence for a role of oligodendrogenesis in motor learning, using a complex running wheel task. Further, we found that ablating oligodendrogenesis alters brain microstructure (ex vivo MRI) and brain activity (in vivo EEG) independent of experience with the task. This suggests a role for adult oligodendrocyte formation in the maintenance of brain function and indicates that task‐independent changes due to oligodendrogenesis ablation need to be considered when interpreting learning and memory deficits in this model.
Main Points
Disrupting oligodendrocytes formation in young adults causes a behavioral deficit in the complex wheel task within hours of testing.
Reduced oligodendrogenesis also leads to task‐independent alterations in brain microstructure and brain activity
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