Johns Hopkins Medical Institution

Cape Saint Claire, MD, United States

Johns Hopkins Medical Institution

Cape Saint Claire, MD, United States
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Cantarero G.,Johns Hopkins University | Lloyd A.,Johns Hopkins Medical Institution | Celnik P.,Johns Hopkins University | Celnik P.,Johns Hopkins Medical Institution
Journal of Neuroscience | Year: 2013

Plasticity of synaptic connections in the primary motor cortex (M1) is thought to play an essential role in learning and memory. Human and animal studies have shown that motor learning results in long-term potentiation (LTP)-like plasticity processes, namely potentiation of M1 and a temporary occlusion of additional LTP-like plasticity. Moreover, biochemical processes essential for LTP are also crucial for certain types of motor learning and memory. Thus, it has been speculated that the occlusion of LTP-like plasticity after learning, indicative of how much LTP was used to learn, is essential for retention. Here we provide supporting evidence of it in humans. Induction of LTP-like plasticity can be abolished using a depotentiation protocol (DePo) consisting of brief continuous theta burst stimulation. We used transcranial magnetic stimulation to assess whether application of DePo over M1 after motor learning affected (1) occlusion of LTP-like plasticity and (2) retention of motor skill learning. We found that the magnitude of motor memory retention is proportional to the magnitude of occlusion of LTP-like plasticity. Moreover, DePo stimulation over M1, but not over a control site, reversed the occlusion of LTP-like plasticity induced by motor learning and disrupted skill retention relative to control subjects. Altogether, these results provide evidence of a link between occlusion of LTP-like plasticity and retention and that this measure could be used as a biomarker to predict retention. Importantly, attempts to reverse the occlusion of LTP-like plasticity after motor learning comes with the cost of reducing retention of motor learning. © 2013 the authors.


Cantarero G.,Johns Hopkins Medical Institution | Spampinato D.,Johns Hopkins Medical Institution | Reis J.,Albert Ludwigs University of Freiburg | Ajagbe L.,Johns Hopkins Medical Institution | And 3 more authors.
Journal of Neuroscience | Year: 2015

The cerebellum is involved in the update of motor commands during error-dependent learning. Transcranial direct current stimulation (tDCS), a form of noninvasive brain stimulation, has been shown to increase cerebellar excitability and improve learning in motor adaptation tasks. Although cerebellar involvement has been clearly demonstrated in adaptation paradigms, a type of task that heavily relies on error-dependent motor learning mechanisms, its role during motor skill learning, a behavior that likely involves errordependent as well as reinforcement and strategic mechanisms, is not completely understood. Here, in humans, we delivered cerebellar tDCS to modulate its activity during novel motor skill training over the course of 3 d and assessed gains during training (on-line effects), between days (off-line effects), and overall improvement. We found that excitatory anodal tDCS applied over the cerebellum increased skill learning relative to sham and cathodal tDCS specifically by increasing on-line rather than off-line learning. Moreover, the larger skill improvement in the anodal group was predominantly mediated by reductions in error rate rather than changes in movement time. These results have important implications for using cerebellar tDCS as an intervention to speed up motor skill acquisition and to improve motor skill accuracy, as well as to further our understanding of cerebellar function. © 2015 the authors.


Wymbs N.F.,Johns Hopkins Medical Institution | Grafton S.T.,University of California at Santa Barbara
Cerebral Cortex | Year: 2015

Motor sequence learning is associated with increasing and decreasing motor system activity. Here, we ask whether sequence-specific activity is contingent upon the time interval and absolute amount of training over which the skill is acquired. We hypothesize that within each motor region, the strength of any sequence representation is a non-linear function that can be characterized by 3 timescales. We had subjects train for 6 weeks and measured brain activity with functional magnetic resonance imaging. We used repetition suppression (RS) to isolate sequence-specific representations while controlling for effects related to kinematics and general task familiarity. Following a baseline training session, primary and secondary motor regions demonstrated rapidly increasing RS. With continued training, there was evidence for skill-specific efficiency, characterized by a dramatic decrease in motor system RS. In contrast, after performance had reached a plateau, further training led to a pattern of slowly increasing RS in the contralateral sensorimotor cortex, supplementary motor area, ventral premotor cortex, and anterior cerebellum consistent with skill-specific specialization. Importantly, many motor areas show changes involving more than 1 of these 3 timescales, underscoring the capacity of the motor system to flexibly represent a sequence based on the amount of prior experience. © The Author 2014. Published by Oxford University Press. All rights reserved.


Galea J.M.,Johns Hopkins Medical Institution | Vazquez A.,Johns Hopkins University | Pasricha N.,Johns Hopkins University | Orban De Xivry J.-J.,Johns Hopkins University | And 2 more authors.
Cerebral Cortex | Year: 2011

Adaptation to a novel visuomotor transformation has revealed important principles regarding learning and memory. Computational and behavioral studies have suggested that acquisition and retention of a new visuomotor transformation are distinct processes. However, this dissociation has never been clearly shown. Here, participants made fast reaching movements while unexpectedly a 30-degree visuomotor transformation was introduced. During visuomotor adaptation, subjects received cerebellar, primary motor cortex (M1) or sham anodal transcranial direct current stimulation (tDCS), a noninvasive form of brain stimulation known to increase excitability. We found that cerebellar tDCS caused faster adaptation to the visuomotor transformation, as shown by a rapid reduction of movement errors. These findings were not present with similar modulation of visual cortex excitability. In contrast, tDCS over M1 did not affect adaptation, but resulted in a marked increase in retention of the newly learnt visuomotor transformation. These results show a clear dissociation in the processes of acquisition and retention during adaptive motor learning and demonstrate that the cerebellum and primary motor cortex have distinct functional roles. Furthermore, they show that is possible to enhance cerebellar function using tDCS. © 2011 The Authors.


Bassett D.S.,University of Pennsylvania | Yang M.,University of Pennsylvania | Wymbs N.F.,University of California at Santa Barbara | Wymbs N.F.,Johns Hopkins Medical Institution | Grafton S.T.,University of California at Santa Barbara
Nature Neuroscience | Year: 2015

Distributed networks of brain areas interact with one another in a time-varying fashion to enable complex cognitive and sensorimotor functions. Here we used new network-analysis algorithms to test the recruitment and integration of large-scale functional neural circuitry during learning. Using functional magnetic resonance imaging data acquired from healthy human participants, we investigated changes in the architecture of functional connectivity patterns that promote learning from initial training through mastery of a simple motor skill. Our results show that learning induces an autonomy of sensorimotor systems and that the release of cognitive control hubs in frontal and cingulate cortices predicts individual differences in the rate of learning on other days of practice. Our general statistical approach is applicable across other cognitive domains and provides a key to understanding time-resolved interactions between distributed neural circuits that enable task performance. © 2015 Nature America, Inc. All rights reserved.


Malayeri A.A.,Johns Hopkins Medical Institution
Journal of computer assisted tomography | Year: 2013

Adrenal masses are among the most common incidentally discovered lesions on cross-sectional imaging with estimated incidence of approximately 5%. In addition, adrenal lesions can also be detected as part of an endocrinology workup with suspicion of a functional adrenal mass. Regardless of the source of detection, it is crucial to differentiate a benign from a malignant process and furthermore utilize characteristic imaging appearance of different adrenal masses to facilitate diagnosis and guide management. There are numerous imaging protocols and postprocessing methods for evaluation of adrenal masses with high sensitivity and specificity with small differences between institutions. Currently, the most widely used imaging modality for evaluation of adrenal mass is computed tomography without and with contrast washout assessment. In this article, we review diagnostic approaches to adrenal masses using computed tomography and magnetic resonance imaging techniques and present imaging strategies utilized at our institution. The advantages and challenges of these imaging modalities for evaluation of adrenal pathologies are discussed.


Yousem D.M.,Johns Hopkins Medical Institution
Neuroimaging Clinics of North America | Year: 2012

Radiology benefits managers (RBMs) and computerized decision support offer different advantages and disadvantages in the efforts to provide appropriate use of radiology resources. RBMs are effective in their hard-stop ability to reject inappropriate studies, incur a significant cost, and interpose an intermediary between patient and physician. Decision support is a more friendly educational product, but has not been implemented for all clinical indications and its efficacy is still being studied. © 2012 Elsevier Inc.


Junkins-Hopkins J.M.,Johns Hopkins Medical Institution
Journal of the American Academy of Dermatology | Year: 2010

Dialogues in Dermatology, a monthly audio program from the American Academy of Dermatology, contains discussions between dermatologists on timely topics. Commentaries from Dialogues Editor-in-Chief Jacqueline M. Junkins-Hopkins, MD, are provided after each discussion as a topic summary and are provided here as a special service to readers of the Journal of the American Academy of Dermatology. © 2009 by the American Academy of Dermatology, Inc.


Junkins-Hopkins J.M.,Johns Hopkins Medical Institution
Journal of the American Academy of Dermatology | Year: 2011

Dialogues in Dermatology, a monthly audio program from the American Academy of Dermatology, contains discussions between dermatologists on timely topics. Commentaries from Dialogues Editor-in-Chief Jacqueline M. Junkins-Hopkins, MD, are provided after each discussion as a topic summary and are provided here as a special service to readers of the Journal of the American Academy of Dermatology. © 2009 by the American Academy of Dermatology, Inc.


Zulfiqar M.,Johns Hopkins Medical Institution | Yousem D.M.,Johns Hopkins Medical Institution | Lai H.,Johns Hopkins Medical Institution
American Journal of Roentgenology | Year: 2013

OBJECTIVE. The purpose of this article is to determine via meta-analysis whether apparent diffusion coefficient (ADC) predicts astrocytoma prognosis independent of grade. MATERIALS AND METHODS. Survival data were subjected to Mantel Haenszel analysis in four qualifying studies. Stratification by tumor grade was also performed. RESULTS. The survival rates of malignant astrocytomas, grade 3 and 4 (p, 0.004 and < 0.0001, respectively) were worse below a specific ADC value, independent of grade. CONCLUSION. Low ADC values correlate with poor survival in malignant astrocytomas independent of tumor grade. © American Roentgen Ray Socoety.

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