Author
Mark Hallett
Other affiliations: Government of the United States of America, Armed Forces Institute of Pathology, University Hospital of Lausanne ...read more
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.
Papers published on a yearly basis
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TL;DR: Freezing of gait appears to result from a number of fundamental problems in patients with Parkinson disease, including deficiency of internal forces to initiate movement, and some difficulty inregulation of internal versus external factors and in regulation of different external factors.
Abstract: Freezing of gait appears to result from a number of fundamental problems in patients with Parkinson disease. Automaticity is impaired, putting more stress on voluntary mechanisms. Internal drivers of movement are impaired, likely because of deficient basal ganglia function. Deficiency of internal forces to initiate movement is a major factor in freezing. This deficiency gives a greater influence to external or sensory factors. The sensory factors can both help or hinder freezing. Analogous to the problem with set-shifting, there is also some difficulty in regulation of internal versus external factors and in regulation of different external factors.
105 citations
TL;DR: It is found that during automaticity, the rostral supplementary motor area, cerebellum, and cingulate motor area had increased effective connectivity with brain networks in PD patients, and in controls, in addition to these regions, the putamen also had automaticity-related strengthened interactions withbrain networks.
105 citations
TL;DR: Compared the activation patterns related to bimanual movements using functional magnetic resonance imaging in 12 healthy right-handed subjects, paying special attention to the anatomical variability of the frontal medial wall.
104 citations
TL;DR: The effects of transcranial magnetic stimulation on the performance of a warned, forced-choice response time task by normal adults were studied in this article, where subjects were asked to choose the right or left finger only after the go-signal was delivered.
Abstract: The effects of transcranial magnetic stimulation were studied on the performance of a warned, forced-choice response time task by normal adults. The task consisted of extension of the index finger in response to the click produced by the discharge of the magnetic coil (go-signal). The subjects were asked to choose the right or left finger only after the go-signal was delivered. Single magnetic stimuli were delivered to the prefrontal or motor area, and in the control situation, away from the head. Magnetic stimulation affected hand preference only when it was delivered to the motor area. With stimulation of this area, subjects more often chose the hand contralateral to the site stimulated with response times that were mainly less than 200 ms. With longer response times (between 200 and 1100 ms), magnetic stimulation had no effect on hand preference regardless of the site stimulated. Stimulation of prefrontal areas yielded results similar to the control situation. These results suggest that response bias in this paradigm is caused by an effect of magnetic stimulation on neural structures within, or closely related to, the motor areas of the brain. Although the response bias was clear and predictable, the subjects were unaware of its existence. It is possible to influence endogenous processes of movement preparation externally without disrupting the conscious perception of volition.
103 citations
TL;DR: It appears that within the human PcG, there are two parallel systems potentially capable of controlling ipsilateral hand movements: ventral premotor cortex and M1, which may be differentially influenced by developmental or pathologic changes.
Abstract: Several human neuroimaging studies have reported activity in the precentral gyrus (PcG) ipsilateral to the side of hand movements. This activity has been interpreted as the part of the primary moto...
102 citations
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9,362 citations
TL;DR: Past observations are synthesized 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, and for understanding mental disorders including autism, schizophrenia, and Alzheimer's 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
8,448 citations
TL;DR: The basal ganglia serve primarily to integrate diverse inputs from the entire cerebral cortex and to "funnel" these influences, via the ventrolateral thalamus, to the motor 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
8,111 citations
TL;DR: FieldTrip is an open source software package that 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.
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.
7,963 citations
TL;DR: 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 her own research.
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
7,563 citations