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.

Treatable Dystonia Presenting as Spastic Cerebral Palsy

Abstract: To the Editor.— Cerebral palsy is a disorder with nonprogressive motor impairment that begins in early infancy and is characterized by spasticity or involuntary movements.1 It is classified according to the primary motor disturbance present (spastic, extrapyramidal, hypotonic, and mixed). Approximately 65% of patients with cerebral palsy have the spastic type.2 The term does not imply a specific cause. Prematurity, anoxia, infection, trauma, and metabolic or other pathologic processes may be responsible in individual patients.

Association of Essential Tremor With Novel Risk Loci

Abstract: Key Points Question Can common genetic variants associated with essential tremor (ET) be identified? Findings In this genome-wide association study and meta-analysis including genetic data on 483 054 individuals, 5 genome-wide significant loci were associated with risk of ET and common variants were associated with approximately 18% of ET heritability. Meaning Findings of this study may help identify new genes and inform ET biology.

Impairment of eyeblink classical conditioning in progressive supranuclear palsy.

Abstract: In a previous study we showed that learning in eyeblink classical conditioning (EBCC) is normal in Parkinson's disease (PD) and that the serial reaction time task (SRTT) is only marginally impaired. Since pathological lesions are more widespread in the atypical parkinsonian disorder of progressive supranuclear palsy (PSP) than in PD, we hypothesized that PSP patients may show more profound deficits in the EBCC and SRTT learning tasks. We therefore investigated EBCC with a delay and two trace paradigms, an SRTT and the California Verbal Learning Test (CVLT) in eight patients with PSP and an age-matched control group. In all EBCC paradigms, we found a significant difference between groups with no significant learning in PSP patients. In the SRTT, implicit learning may have been impaired, but verbal and manual sequence recall were only marginally impaired. Verbal memory was significantly worse in PSP patients than in the control group. Our study shows a dissociated pattern of learning abilities in PSP, where the EBCC as a measure of implicit learning is impaired, the explicit sequence detection in the SRTT is relatively preserved, and the verbal memory impaired. We hypothesize that the PSP patients' deficits in EBCC learning may be due to lesions of deep cerebellar nuclei. There may be a clinical role for EBCC in distinguishing PD and PSP patients.

Hiding in Plain Sight: Functional Neurological Disorders in the News.

Abstract: Objective:Functional movement and seizure disorders are still widely misunderstood and receive little public and academic attention. This is in stark contrast to their high prevalence and levels of...

The first agonist and antagonist burst in patients with an upper motor neuron syndrome.

Abstract: Rapid elbow flexion movements were studied in patients with an upper motor neuron syndrome following a stroke The velocity of movements was slower than normal The initial bursts of electromyographic (EMG) activity in both the agonist and antagonist muscles were prolonged As in normal subjects, the first agonist burst increased in duration with larger movements, but it generally remained about 40 ms longer than normal The size of the first agonist burst also increased with larger movements A fixed linkage between burst duration and level of motor unit recruitment, together with a deficient corticospinal command, could explain the prolonged burst duration with preserved ability to modulate the burst

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