Mark Hallett

National Institutes of Health, 베서스다, Maryland, United States

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Publications (563)3017.04 Total impact

  • Simon Mitchell · Jennifer Gao · Mark Hallett · Valerie Voon
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    ABSTRACT: sec> Aims Novelty preference or sensation seeking is an important trait related to initiating and maintaining risky behaviours, including substance abuse. Here we introduce a novel or familiar prime (image) preceding a risk choice and focus on behavioural and imaging correlates to the prime that might predict risk seeking in healthy volunteers. We aim to investigate whether novel or familiar primes affect judgments of risk. We hypothesize that subjects would be more risk seeking following a novel relative to familiar stimulus and that subjects who are more novelty seeking will have increased striatal and hippocampal activity to the novel stimulus. Methods We adapted a risk-taking task involving acceptance or rejection of a 50:50 choice of gain or loss which was preceded by a familiar (pre-test familiarization) or novel face prime. Neutral expression faces of males and females from The Karolinska Directed Emotional Faces database were used as primes. Subjects were tested behaviourally and scanned using functional MRI as they were performing a different version of the same task. Results Twenty-four healthy volunteers were recruited for the behavioral study and eighteen for the fMRI study. We show enhanced risk taking following novel relative to familiar images and particularly for the low gain condition. Subjects had faster reaction times to the prime when accepting rather than rejecting the risky choice. We further show that right putamen activity to novel versus familiar primes were positively correlated with risk taking choices. Conclusions Novelty appears to have a contextually enhancing effect on augmenting risky choices possibly mediated via putaminal activity. These findings highlight the role of context in risk taking and have important implications for a wide range of behaviours including substance abuse. </sec
    Journal of Neurology Neurosurgery & Psychiatry 09/2015; 86(9). DOI:10.1136/jnnp-2015-311750.54 · 5.58 Impact Factor
  • Jung E Park · Katharine Alter · Mark Hallett
    08/2015; DOI:10.1001/jamaneurol.2015.1456
  • Mark Hallett
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    ABSTRACT: While the steps in the action of botulinum neurotoxin (BoNT) are well known, the factors underlying the timing of these steps are not fully understood. After toxin is injected into a muscle, it resides in the extracellular space and must be taken up into the nerve terminals. More toxin will be taken up if near the endplate. Toxin is distributed mainly by convection and there is likely little diffusion. Toxin that is not taken up will go into the general circulation where it may have a slight systemic effect. The uptake is activity and temperature dependent. Encouraging the unwanted muscle contractions after injection should be helpful. Cooling will decrease the uptake. The times for washout from the extracellular space and uptake of the toxin are not well established, but are likely measured in minutes. Toxin in the general circulation has a long half time. The time from injection to weakness is determined by how long it takes to get sufficient damage of the SNARE proteins to interfere with synaptic release. Toxins are zinc dependent proteases, and supplemental zinc may produce a greater effect. There will be weakness as long as there is residual toxin in the nerve ending. Copyright © 2015. Published by Elsevier Ltd.
    Toxicon 07/2015; 93. DOI:10.1016/j.toxicon.2015.07.013 · 2.58 Impact Factor
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    ABSTRACT: Functional imaging studies have shown that control of planned movement involves a distributed network that involves the premotor (PMv) and posterior parietal cortices (PPC). Similarly, anatomical studies show that these regions are densely interconnected via white matter tracts. We therefore hypothesized that the PPC influence over the motor cortex is partly via a connection with the PMv. Using a novel three-pulse ipsilateral transcranial magnetic stimulation technique, we preconditioned the PPC (80% RMT) at ISIs from 4-15ms prior to stimulating the PMv and M1 at ISIs of 4 and 6ms. As previously shown, PMv-M1 paired-pulse stimulation resulted in inhibition of the MEP (90% RMT, 4-6ms) and PPC-M1 paired-pulse stimulation resulted in facilitation of the MEP (90% RMT, 4-8ms). PPC-M1 paired-pulse stimulation at 80% RMT preconditioning had no effect on M1. PPC-PMv-M1 stimulation resulted in reversal of inhibition observed with PMv-M1 stimulation at ISIs ranging from 6 to 15ms. The reversal of inhibition observed with PPC-PMv-M1 stimulation suggests that the parietal connection to the PMv plays a role in the modulation of M1. This is the first study to stimulate three intrahemispheric regions in order to test a disynaptic connection with M1. The described network may be important in a variety of movement disorders. Published by Elsevier Ireland Ltd.
    Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 07/2015; DOI:10.1016/j.clinph.2015.06.031 · 2.98 Impact Factor
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    ABSTRACT: Functional reaching is impaired in dystonia. Here, we analyze upper extremity kinematics to quantify timing and coordination abnormalities during unimanual reach-to-grasp movements in individuals with childhood-onset unilateral wrist dystonia. Kinematics were measured during movements of both upper limbs in a patient group (n = 11, age = 17.5 ± 5 years), and a typically developing control group (n = 9, age = 16.6 ± 5 years). Hand aperture was computed to study the coordination of reach and grasp. Time-varying joint synergies within one upper limb were calculated using a novel technique based on principal component analysis to study intra-limb coordination. In the non-dominant arm, results indicate reduced coordination between reach and grasp in patients who could not lift the grasped object compared to those who could lift it. Lifters exhibit incoordination in distal upper extremity joints later in the movement and non-lifters lacked coordination throughout the movement and in the whole upper limb. The amount of atypical coordination correlates with dystonia severity in patients. Reduced coordination during movement may reflect deficits in the execution of simultaneous movements, motor planning, or muscle activation. Rehabilitation efforts can focus on particular time points when kinematic patterns deviate abnormally to improve functional reaching in individuals with childhood-onset dystonia.
    IEEE transactions on neural systems and rehabilitation engineering: a publication of the IEEE Engineering in Medicine and Biology Society 07/2015; DOI:10.1109/TNSRE.2015.2458293 · 2.82 Impact Factor
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    ABSTRACT: The cerebellum is involved in sensorimotor operations, cognitive tasks and affective processes. Here, we revisit the concept of the cerebellar syndrome in the light of recent advances in our understanding of cerebellar operations. The key symptoms and signs of cerebellar dysfunction, often grouped under the generic term of ataxia, are discussed. Vertigo, dizziness, and imbalance are associated with lesions of the vestibulo-cerebellar, vestibulo-spinal, or cerebellar ocular motor systems. The cerebellum plays a major role in the online to long-term control of eye movements (control of calibration, reduction of eye instability, maintenance of ocular alignment). Ocular instability, nystagmus, saccadic intrusions, impaired smooth pursuit, impaired vestibulo-ocular reflex (VOR), and ocular misalignment are at the core of oculomotor cerebellar deficits. As a motor speech disorder, ataxic dysarthria is highly suggestive of cerebellar pathology. Regarding motor control of limbs, hypotonia, a- or dysdiadochokinesia, dysmetria, grasping deficits and various tremor phenomenologies are observed in cerebellar disorders to varying degrees. There is clear evidence that the cerebellum participates in force perception and proprioceptive sense during active movements. Gait is staggering with a wide base, and tandem gait is very often impaired in cerebellar disorders. In terms of cognitive and affective operations, impairments are found in executive functions, visual-spatial processing, linguistic function, and affective regulation (Schmahmann's syndrome). Nonmotor linguistic deficits including disruption of articulatory and graphomotor planning, language dynamics, verbal fluency, phonological, and semantic word retrieval, expressive and receptive syntax, and various aspects of reading and writing may be impaired after cerebellar damage. The cerebellum is organized into (a) a primary sensorimotor region in the anterior lobe and adjacent part of lobule VI, (b) a second sensorimotor region in lobule VIII, and (c) cognitive and limbic regions located in the posterior lobe (lobule VI, lobule VIIA which includes crus I and crus II, and lobule VIIB). The limbic cerebellum is mainly represented in the posterior vermis. The cortico-ponto-cerebellar and cerebello-thalamo-cortical loops establish close functional connections between the cerebellum and the supratentorial motor, paralimbic and association cortices, and cerebellar symptoms are associated with a disruption of these loops.
    The Cerebellum 06/2015; DOI:10.1007/s12311-015-0687-3 · 2.86 Impact Factor
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    ABSTRACT: While the presence of co-existing psychological stressors has historically been used as a supportive factor in the diagnosis of functional neurological disorders, many patients with functional neurological disorders deny the presence of these stressors. The stress response circuitry in these patients remains largely unexplored. We performed an observational study examining biological stress levels in patients with functional movement disorders as compared with matched healthy controls. Specifically, we compared levels of circulating cortisol, the end-product of the hypothalamic-pituitary-adrenal axis. Salivary cortisol samples were collected from patients with "clinically definite" functional movement disorders (n = 33) and their age- and sex-matched controls (n = 33). Collections were performed at five standardized time points, reflecting participants' diurnal cortisol cycles. To rule out confounders, participants also underwent extensive psychological assessment including Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Hamilton Anxiety Rating Scale, and Hamilton Rating Scale for Depression. Patients with functional movement disorders did not differ from matched controls with respect to levels of circulating cortisol. We demonstrate that current stress levels are not altered in patients with functional movement disorders. Our results warrant careful review of current management of patients with functional neurological symptoms, and suggest that the insistence on heightened stress levels in these patients is unjustified. Published by Elsevier Ltd.
    Parkinsonism & Related Disorders 06/2015; DOI:10.1016/j.parkreldis.2015.06.017 · 4.13 Impact Factor
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    Tao Wu · Mark Hallett · Piu Chan
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    ABSTRACT: Bradykinesia is the most important feature contributing to motor difficulties in Parkinson's disease (PD). However, the pathophysiology underlying bradykinesia is not fully understood. One important aspect is that PD patients have difficulty in performing learned motor skills automatically, but this problem has been generally overlooked. Here we review motor automaticity associated motor deficits in PD, such as reduced arm swing, decreased stride length, freezing of gait, micrographia and reduced facial expression. Recent neuroimaging studies have revealed some neural mechanisms underlying impaired motor automaticity in PD, including less efficient neural coding of movement, failure to shift automated motor skills to the sensorimotor striatum, instability of the automatic mode within the striatum, and use of attentional control and/or compensatory efforts to execute movements usually performed automatically in healthy people. PD patients lose previously acquired automatic skills due to their impaired sensorimotor striatum, and have difficulty in acquiring new automatic skills or restoring lost motor skills. More investigations on the pathophysiology of motor automaticity, the effect of L-dopa or surgical treatments on automaticity, and the potential role of using measures of automaticity in early diagnosis of PD would be valuable. Copyright © 2015. Published by Elsevier Inc.
    Neurobiology of Disease 06/2015; 82. DOI:10.1016/j.nbd.2015.06.014 · 5.20 Impact Factor
  • Nineteenth International Congress of Parkinson's Disease and Movement Disorders; 06/2015
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    ABSTRACT: Surround inhibition (SI) is a feature of motor control in which activation of task-related muscles is associated with inhibition of neighboring, non-protagonist muscles, allowing selective motor control. The physiological basis for SI still remains unknown. In all previous studies, SI in the motor system was measured during movement initiation using transcranial magnetic stimulation (TMS) to deliver a postero-anterior current at single supra-threshold intensity. To expand our understanding of SI, we explored this phenomenon at a wide range of intensities and by stimulating motor cortex with currents along antero-posterior and latero-medial directions. Fifteen healthy volunteers performed a brief isometric index finger flexion on hearing a tone. Electromyography was recorded from the synergist and surround finger muscles. Single-pulse TMS was applied to stimulate the surround muscle at different intensities at rest or movement initiation. The motor evoked potential (MEP) amplitudes were then plotted against stimulation intensities to obtain the MEP recruitment curves for the rest and movement initiation conditions, and for the three current directions for every subject. From the recruitment curves, we found that surround inhibition could be elicited only by the postero-anterior current. Hence we postulate that surround inhibition is mediated by intracortical circuits in the motor cortex. Also, for the first time we observed surround facilitation when the motor cortex was stimulated with antero-posterior current. Further studies are needed to investigate the mechanisms underlying both these phenomena individually in healthy subjects and patients with dystonia and other movement disorders. Copyright © 2014, Journal of Neurophysiology.
    Journal of Neurophysiology 06/2015; DOI:10.1152/jn.00791.2014 · 3.04 Impact Factor
  • Sanjay Pandey · Debra L. Byler · Mark Hallett
    JAMA Neurology 05/2015; 72(5):606-607. · 7.01 Impact Factor
  • Sanjay Pandey · Debra L Byler · Mark Hallett
    05/2015; 72(5):606-607. DOI:10.1001/jamaneurol.2015.0147
  • Jung E. Park · Carine W. Maurer · Mark Hallett
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    ABSTRACT: Making the diagnosis of functional movement disorders can be challenging. Identifying positive physical signs and diagnostic maneuvers is critical to this process. Distractibility, entrainability, and variability are examples of classic physical findings in these patients. In this case series, we identify and characterize another phenomenon observed in some of these patients. In this phenomenon, movement suppression of one body part is followed by immediate reemergence of movement in another. We propose that this phenomenon be referred to as the “whack-a-mole” sign. This name is derived from the arcade game whack-a-mole, in which a mole, when hit into its original hole, re-emerges elsewhere. We present a case series of 4 patients with functional movement disorders who exhibit this sign.
    05/2015; DOI:10.1002/mdc3.12177
  • Prachaya Srivanitchapoom · Mark Hallett
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    ABSTRACT: Camptocormia is an axial postural deformity characterised by abnormal thoracolumbar spinal flexion. The symptom usually presents while standing, walking or exercising and is alleviated while sitting, lying in a recumbent position, standing against a wall or using walking support. There is no consensus on the degree of thoracolumbar flexion to define camptocormia. However, most authors usually use an arbitrary number of at least 45° flexion of the thoracolumbar spine when the individual is standing or walking. Aetiologies of camptocormia are heterogeneous, and Parkinson's disease (PD) is one of its many causes. The prevalence of camptocormia in PD ranges from 3% to 18%. Central and peripheral mechanisms might both contribute to its pathogenesis. Although there is no established consensus for treatment of camptocormia in PD, there are non-pharmacological, pharmacological and surgical approaches that can be used. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.
    Journal of neurology, neurosurgery, and psychiatry 04/2015; DOI:10.1136/jnnp-2014-310049 · 5.58 Impact Factor
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    ABSTRACT: The mid-posterior part of the insula is involved in processing bodily sensations and urges and is activated during tic generation in Tourette syndrome. The dorsal anterior part of the insula, however, integrates sensory and emotional information with cognitive valuation and is implicated in interoception. The right dorsal anterior insula also participates in urge suppression in healthy subjects. This study examined the role of the right dorsal anterior insula in the urge to tic in Tourette syndrome. Resting-state functional magnetic resonance imaging was performed in 13 adult Tourette patients and 13 matched controls. The role of the right dorsal anterior insula within the urge-tic network was investigated using graph theory-based neural network analysis. The functional connectivity of the right dorsal anterior insula was also correlated with urge and tic severity. Even though the patients did not exhibit any overt tics, the right dorsal anterior insula demonstrated higher connectivity, especially with the frontostriatal nodes of the urge-tic network in patients compared with controls. The functional connectivity between the right dorsal anterior insula and bilateral supplementary motor area also correlated positively with urge severity in patients. These results suggest that the right dorsal anterior insula is part of the urge-tic network and could influence the urge- and tic-related cortico-striato-thalamic regions even during rest in Tourette syndrome. It might be responsible for heightened awareness of bodily sensations generating premonitory urges in Tourette syndrome. © 2015 International Parkinson and Movement Disorder Society. © 2015 International Parkinson and Movement Disorder Society.
    Movement Disorders 04/2015; DOI:10.1002/mds.26230 · 5.68 Impact Factor
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    ABSTRACT: Psychogenic dystonia is a challenging entity to diagnose and treat because little is known about its pathophysiology. We describe two cases of psychogenic dystonia who underwent deep brain stimulation when thought to have organic dystonia. The intraoperative microelectrode recordings in globus pallidus internus were retrospectively compared with those of five patients with known DYT1 dystonia using spontaneous discharge parameters of rate and bursting, as well as movement-related discharges. Our data suggest that simple intraoperative neurophysiology measures in single subjects do not differentiate psychogenic dystonia from DYT1 dystonia.
    04/2015; 2(6). DOI:10.1002/acn3.206
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    ABSTRACT: Existing scales for rating the severity of blepharospasm (BSP) are limited by a number of potential drawbacks. We therefore developed and validated a novel scale for rating the severity of BSP. The development of the scale started with careful examination of the clinical spectrum of the condition by a panel of experts who selected phenomenological aspects thought to be relevant to disease severity. Thereafter, selected items were first checked for reliability, then reliable items were combined to generate the scale, and clinimetric properties of the scale were evaluated. Finally, the confidence with which the scale could be used by people without high levels of movement disorders skill was assessed. The new scale, based on objective criteria, yielded moderate to almost perfect reliability, acceptable internal consistency, satisfactory scaling assumptions, lack of floor and ceiling effects, partial correlations with a prior severity scale and with a quality of life scale, and good sensitivity to change. Despite a few limitations, the foregoing features make the novel scale more suitable than existing scales to assess the severity of BSP in natural history and pathophysiologic studies as well as in clinical trials. © 2015 International Parkinson and Movement Disorder Society. © 2015 International Parkinson and Movement Disorder Society.
    Movement Disorders 04/2015; 30(4). DOI:10.1002/mds.26156 · 5.68 Impact Factor
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    ABSTRACT: Accumulating evidence suggests that storing speech sounds requires transposing rapidly fluctuating sound waves into more easily encoded oromotor sequences. If so, then the classical speech areas in the caudalmost portion of the temporal gyrus (pSTG) and in the inferior frontal gyrus (IFG) may be critical for performing this acoustic-oromotor transposition. We tested this proposal by applying repetitive transcranial magnetic stimulation (rTMS) to each of these left-hemisphere loci, as well as to a nonspeech locus, while participants listened to pseudowords. After 5 minutes these stimuli were re-presented together with new ones in a recognition test. Compared to control-site stimulation, pSTG stimulation produced a highly significant increase in recognition error rate, without affecting reaction time. By contrast, IFG stimulation led only to a weak, non-significant, trend toward recognition memory impairment. Importantly, the impairment after pSTG stimulation was not due to interference with perception, since the same stimulation failed to affect pseudoword discrimination examined with short interstimulus intervals. Our findings suggest that pSTG is essential for transforming speech sounds into stored motor plans for reproducing the sound. Whether or not the IFG also plays a role in speech-sound recognition could not be determined from the present results.
    PLoS ONE 03/2015; 10(3):e0119472. DOI:10.1371/journal.pone.0119472 · 3.23 Impact Factor
  • Brain Stimulation 03/2015; 8(2):367. DOI:10.1016/j.brs.2015.01.180 · 5.43 Impact Factor
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Publication Stats

31k Citations
3,017.04 Total Impact Points

Institutions

  • 1986–2015
    • National Institutes of Health
      • • Division of Intramural Research (Dental Research)
      • • Division of Functional and Molecular Imaging
      • • Branch of Neurogenetics
      • • Branch of Cognitive Neuroscience
      베서스다, Maryland, United States
  • 2014
    • Govind Ballabh Pant Hospital
      New Dilli, NCT, India
  • 2013
    • Xuanwu hospital
      Peping, Beijing, China
  • 2012–2013
    • George Washington University
      • • Department of Neurology
      • • School of Medicine and Health Sciences
      Washington, Washington, D.C., United States
  • 2011–2013
    • National Eye Institute
      베서스다, Maryland, United States
  • 2007–2013
    • Sapienza University of Rome
      • Department of Neurology and Psychiatry
      Roma, Latium, Italy
    • Kagawa University
      Takamatu, Kagawa, Japan
    • Sungkyunkwan University
      • Samsung Medical Center
      Seoul, Seoul, South Korea
  • 2009–2012
    • Baylor College of Medicine
      • Parkinson's Disease Center and Movement Disorders Clinic
      Houston, Texas, United States
  • 1999–2010
    • University of Toronto
      • Division of Neurology
      Toronto, Ontario, Canada
    • University of Maryland, Baltimore
      Baltimore, Maryland, United States
  • 2008
    • Università degli Studi di Milano-Bicocca
      Milano, Lombardy, Italy
  • 1992–2005
    • Northern Inyo Hospital
      BIH, California, United States
  • 2004
    • University Hospital RWTH Aachen
      Aachen, North Rhine-Westphalia, Germany
  • 2002
    • University of Oxford
      • Department of Experimental Psychology
      Oxford, England, United Kingdom
  • 2001
    • The National Institute of Diabetes and Digestive and Kidney Diseases
      베서스다, Maryland, United States
  • 1995–1997
    • National Institute of Mental Health (NIMH)
      • • Laboratory of Systems Neuroscience
      • • Laboratory of Brain And Cognition
      베서스다, Maryland, United States
  • 1994
    • IMSA Amsterdam
      Amsterdamo, North Holland, Netherlands
  • 1989
    • Bulgarian Academy of Sciences
      Ulpia Serdica, Sofia-Capital, Bulgaria