Mark Hallett

Bio: Mark Hallett is an academic researcher from National Institutes of Health. The author has contributed to research in topics: Transcranial magnetic stimulation & Motor cortex. The author has an hindex of 186, co-authored 1170 publications receiving 123741 citations. Previous affiliations of Mark Hallett include Government of the United States of America & Armed Forces Institute of Pathology.

Transducer‐based evaluation of tremor

Abstract: The International Parkinson and Movement Disorder Society established a task force on tremor that reviewed the use of transducer-based measures in the quantification and characterization of tremor. Studies of accelerometry, electromyography, activity monitoring, gyroscopy, digitizing tablet-based measures, vocal acoustic analysis, and several other transducer-based methods were identified by searching PubMed.gov. The availability, use, acceptability, reliability, validity, and responsiveness were reviewed for each measure using the following criteria: (1) used in the assessment of tremor; (2) used in published studies by people other than the developers; and (3) adequate clinimetric testing. Accelerometry, gyroscopy, electromyography, and digitizing tablet-based measures fulfilled all three criteria. Compared to rating scales, transducers are far more sensitive to changes in tremor amplitude and frequency, but they do not appear to be more capable of detecting a change that exceeds random variability in tremor amplitude (minimum detectable change). The use of transducer-based measures requires careful attention to their limitations and validity in a particular clinical or research setting. © 2016 International Parkinson and Movement Disorder Society.

Recent Advances in Stroke Rehabilitation

Abstract: Following hemiparetic stroke, recovery of motor function is often not adequate. There are now multiple approaches that seem promising for promoting recovery of the weakened limb, and they are often guided by new understandings of biological principles, many relating to brain plasticity, including: (a) Use of a body part enhances its function. Intensive, focused physical therapy does help, as has been demonstrated, for example, by constraint-induced movement therapy. Other techniques use the same principle. (b) The ipsilateral hemisphere can contribute to motor control, and bilateral, symmetrical arm movement training may help on this basis. (c) Sensory stimulation enhances plasticity. (d) Reduction of inhibition enhances plasticity. This has been demonstrated to be useful for rehabilitation utilizing transient deafferentation. (e) Pharmacological agents such as amphetamines can enhance plasticity. (f) Transcranial magnetic stimulation can enhance plasticity. (g) Spasticity can be reduced with oral, intrathecal, or intramuscular agents. (h) Cortical activity can be interpreted for the intended movement and a signal derived to control a prosthesis. (i) Lost tissue might be replaced with either regrowth of tissue or implantation. Following hemiparetic stroke, although there is typically some recovery of motor function in the weakened limb, it is often not adequate. Until recently, it has not been clear whether this improvement could be facilitated by any intervention. Clearly, physical and occupational therapy directed to activities of daily living are commonly successful, but this may be due to substitutions by the unaffected body parts. There are now multiple approaches that seem promising for promoting recovery of the weakened limb, and they are often guided by new understandings of biological principles, many relating to brain plasticity. Brain plasticity is the concept that the brain is able to change (Hallett 1999, 2000, 2001a, 2001b). Neurons and neural networks can change their function by several mechanisms. Alterations in the balance of excitation and inhibition may occur, including reduction in inhibition called “unmasking.” Synaptic strength can increase or decrease by mechanisms such as long-term potentiation or depression. The excitability of neuronal membrane can change, and new synapses can form. Not only can these processes occur, they are constantly occurring. To harness these for recovery is now a major task for rehabilitation.

The Brain's Default Network Anatomy, Function, and Relevance to Disease

Abstract: Thirty years of brain imaging research has converged to define the brain’s default network—a novel and only recently appreciated brain system that participates in internal modes of cognition Here we synthesize past observations to provide strong evidence that the default network is a specific, anatomically defined brain system preferentially active when individuals are not focused on the external environment Analysis of connectional anatomy in the monkey supports the presence of an interconnected brain system Providing insight into function, the default network is active when individuals are engaged in internally focused tasks including autobiographical memory retrieval, envisioning the future, and conceiving the perspectives of others Probing the functional anatomy of the network in detail reveals that it is best understood as multiple interacting subsystems The medial temporal lobe subsystem provides information from prior experiences in the form of memories and associations that are the building blocks of mental simulation The medial prefrontal subsystem facilitates the flexible use of this information during the construction of self-relevant mental simulations These two subsystems converge on important nodes of integration including the posterior cingulate cortex The implications of these functional and anatomical observations are discussed in relation to possible adaptive roles of the default network for using past experiences to plan for the future, navigate social interactions, and maximize the utility of moments when we are not otherwise engaged by the external world We conclude by discussing the relevance of the default network for understanding mental disorders including autism, schizophrenia, and Alzheimer’s disease

Parallel Organization of Functionally Segregated Circuits Linking Basal Ganglia and Cortex

Abstract: Information about the basal ganglia has accumulated at a prodigious pace over the past decade, necessitating major revisions in our concepts of the structural and functional organization of these nuclei. From earlier data it had appeared that the basal ganglia served primarily to integrate diverse inputs from the entire cerebral cortex and to "funnel" these influences, via the ventrolateral thalamus, to the motor cortex (Allen & Tsukahara 1974, Evarts & Thach 1969, Kemp & Powell 1971). In particular, the basal

FieldTrip: open source software for advanced analysis of MEG, EEG, and invasive electrophysiological data

Abstract: This paper describes FieldTrip, an open source software package that we developed for the analysis of MEG, EEG, and other electrophysiological data. The software is implemented as a MATLAB toolbox and includes a complete set of consistent and user-friendly high-level functions that allow experimental neuroscientists to analyze experimental data. It includes algorithms for simple and advanced analysis, such as time-frequency analysis using multitapers, source reconstruction using dipoles, distributed sources and beamformers, connectivity analysis, and nonparametric statistical permutation tests at the channel and source level. The implementation as toolbox allows the user to perform elaborate and structured analyses of large data sets using the MATLAB command line and batch scripting. Furthermore, users and developers can easily extend the functionality and implement new algorithms. The modular design facilitates the reuse in other software packages.

Principles of Neural Science

Abstract: I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or