Moss Rehabilitation Research Institute

Elkins Park, PA, United States

Moss Rehabilitation Research Institute

Elkins Park, PA, United States
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News Article | May 12, 2017

People in a minimally conscious state have been “woken” for a whole week after a brief period of brain stimulation. The breakthrough suggests we may be on the verge of creating a device that can be used at home to help people with disorders of consciousness communicate with friends and family. People with severe brain trauma can fall into a coma. If they begin to show signs of arousal but not awareness, they are said to be in a vegetative state. If they then show fluctuating signs of awareness but cannot communicate, they are described as being minimally consciousness. In 2014, Steven Laureys at the University of Liège in Belgium and his colleagues discovered that 13 people with minimal consciousness and two people in a vegetative state could temporarily show new signs of awareness when given mild electrical stimulation. The people in the trial received transcranial direct current stimulation (tDCS), which uses low-level electrical stimulation to make neurons more or less likely to fire. This was applied once over an area of the brain called the prefrontal cortex, which is involved in “higher” cognitive functions such as consciousness. Soon after, they showed signs of consciousness, including moving their hands or following instructions using their eyes. Two people were even able to answer questions for 2 hours by moving their body, before drifting back into their previous state. Because the improvements in awareness lasted for only a few hours, the team wondered if more stimulation would extend this. They began a new trial, in which 16 people with brain damage received a 20-minute session of tDCS daily for five consecutive days, or a sham session, in which they received a low level of stimulation that had no effect on the brain. Later, they received the opposite treatment. Each participant had been in a minimally conscious state for at least three months before the start of the trial – meaning spontaneous recovery was unlikely. After the fifth day of the real treatment, nine of the 16 participants showed significant improvements in conscious awareness. This included being able to respond to commands, recognise objects and perform voluntary motor movements. What’s more, these improvements lasted at least a week after the final day of stimulation. Two of the participants even started to communicate. “They couldn’t speak but we could ask questions, such as “is your name David?” and they answered yes or no by moving a part of their body, like their tongue or their foot,” says Aurore Thibaut, also at the University of Liège, who led the study. “They correctly answered all of the questions we asked.” None of the participants showed any signs of improvement after the sham treatment. The stimulation targeted the prefrontal cortex, which is involved in consciousness. It is also linked to other vital hubs, such as the thalamus, which helps propagate electrical signals to wider areas of the brain. When a person is conscious, electrical activity spreads like a wave into brain areas that are never reached while we are unconscious. Thibaut says that as well as increasing activity in the immediate area, the stimulation likely also increased the communication between other areas of the brain – potentially helping to propagate this wave of “conscious” activity. “This is an encouraging development,” says John Whyte, director of the Moss Rehabilitation Research Institute in Elkins Park, Pennsylvania. “The study suggests that longer treatment intervals lead to more sustained improvements in consciousness.” However, we don’t know if the improvements from longer treatment will wear off eventually, says Whyte. The team says that the results are starting to look clinically relevant – meaning they are good enough to consider how to use the technique to treat patients away from the hospital. The stimulation device can be used at the bedside, and is relatively cheap to produce, so in theory the patient’s family could be taught how to use it at home. More trials will be needed before this happens, though. Although there were no side effects in the recent trial, Thibaut says it first needs to be determined whether using the device for months on end is safe or effective. “You can find similar devices online, but we don’t know the long-term effects yet,” she says. “We need to see what happens when we use it for perhaps five hours a day, or what happens if we apply it daily for three months. We need to be really careful.”

Tarhan L.Y.,Moss Rehabilitation Research Institute | Watson C.E.,Moss Rehabilitation Research Institute | Buxbaum L.J.,Moss Rehabilitation Research Institute
Journal of Cognitive Neuroscience | Year: 2015

The inferior frontal gyrus and inferior parietal lobe have been characterized as human homologues of the monkey “mirror neuron” system, critical for both action production (AP) and action recognition (AR). However, data from brain lesion patients with selective impairment on only one of these tasks provide evidence of neural and cognitive dissociations. We sought to clarify the relationship between AP and AR, and their critical neural substrates, by directly comparing performance of 131 chronic left-hemisphere stroke patients on both tasks—to our knowledge, the largest lesion-based experimental investigation of action cognition to date. Using voxel-based lesion-symptom mapping, we found that lesions to primary motor and somatosensory cortices and inferior parietal lobule were associated with disproportionately impaired performance on AP, whereas lesions to lateral temporo-occipital cortex were associated with a relatively rare pattern of disproportionately impaired performance on AR. In contrast, damage to posterior middle temporal gyrus was associated with impairment on both AP and AR. The distinction between lateral temporo-occipital cortex, critical for recognition, and posterior middle temporal gyrus, important for both tasks, suggests a rough gradient from modality-specific to abstract representations in posterior temporal cortex, the first lesion-based evidence for this phenomenon. Overall, the results of this large patient study help to bring closure to a longstanding debate by showing that tool-related AP and AR critically depend on both common and distinct left hemisphere neural substrates, most of which are external to putative human mirror regions. © 2015 Massachusetts Institute of Technology.

Medaglia J.D.,Moss Rehabilitation Research Institute | Lynall M.-E.,University of Cambridge | Lynall M.-E.,University of Oxford | Bassett D.S.,University of Pennsylvania
Journal of Cognitive Neuroscience | Year: 2015

Network science provides theoretical, computational, and empirical tools that can be used to understand the structure and function of the human brain in novel ways using simple concepts and mathematical representations. Network neuroscience is a rapidly growing field that is providing considerable insight into human structural connectivity, functional connectivity while at rest, changes in functional networks over time (dynamics), and how these properties differ in clinical populations. In addition, a number of studies have begun to quantify network characteristics in a variety of cognitive processes and provide a context for understanding cognition from a network perspective. In this review, we outline the contributions of network science to cognitive neuroscience. We describe the methodology of network science as applied to the particular case of neuroimaging data and review its uses in investigating a range of cognitive functions including sensory processing, language, emotion, attention, cognitive control, learning, and memory. In conclusion, we discuss current frontiers and the specific challenges that must be overcome to integrate these complementary disciplines of network science and cognitive neuroscience. Increased communication between cognitive neuroscientists and network scientists could lead to significant discoveries under an emerging scientific intersection known as cognitive network neuroscience. © 2015 Massachusetts Institute of Technology

Watson C.E.,Moss Rehabilitation Research Institute | Buxbaum L.J.,Moss Rehabilitation Research Institute
Cortex | Year: 2015

Tools pose a challenge to the need to select actions appropriate for task goals and environmental constraints. For many tools (e.g., calculator), actions for "using" and "grasping-to-move" conflict with each other and may compete during selection. To date, little is known about the mechanisms that enable selection between possible tool actions or their neural substrates. The study of patients with chronic left hemisphere stroke, many of whom are deficient in tool-use action (apraxic), provides an opportunity to elucidate these issues. Here, 31 such patients pantomimed or recognized tool use actions for "conflict" and "non-conflict" tools. Voxel-based lesion-symptom mapping (VLSM), lesion subtraction, and tractographic overlap analyses were used to determine brain regions necessary for selecting among tool-directed actions. Lesions to posterior middle temporal gyrus (pMTG) and anterior intraparietal sulcus (aIPS) tended to impair production of use actions similarly for both conflict and non-conflict tools. By contrast, lesions to the supramarginal gyrus (SMG), inferior frontal gyrus (IFG)/anterior insula, and superior longitudinal fasciculus (SLF) specifically impaired production of use actions for conflict tools. Patients' errors on conflict tools suggested inappropriate selection of grasping actions and difficulty selecting single actions. Use/grasp conflict had no effect on action recognition. We suggest that the SMG/SLF/IFG pathway implements biased competition between possible tool actions, while aIPS and pMTG compute the structure-based and skilled use actions, respectively, that constitute input to this competitive process. This is the first study to demonstrate a reliable link between a characteristic of single tools (i.e., their association with different use and grasp actions) and action selection difficulties. Additionally, the data allow us to posit an SMG-involved subtype of apraxia characterized by an inability to resolve action competition. © 2015 Elsevier Ltd.

Mirman D.,Moss Rehabilitation Research Institute | Graziano K.M.,Moss Rehabilitation Research Institute
Journal of Cognitive Neuroscience | Year: 2013

Theories of word production and word recognition generally agree that multiple word candidates are activated during processing. The facilitative and inhibitory effects of these "lexical neighbors" have been studied extensively using behavioral methods and have spurred theoretical development in psycholinguistics, but relatively little is known about the neural basis of these effects and how lesions may affect them. This study used voxel-wise lesion overlap subtraction to examine semantic and phonological neighbor effects in spoken word production following left hemisphere stroke. Increased inhibitory effects of near semantic neighbors were associated with inferior frontal lobe lesions, suggesting impaired selection among strongly activated semantically related candidates. Increased inhibitory effects of phonological neighbors were associated with posterior superior temporal and inferior parietal lobe lesions. In combination with previous studies, these results suggest that such lesions cause phonological-to-lexical feedback to more strongly activate phonologically related lexical candidates. The comparison of semantic and phonological neighbor effects and how they are affected by left hemisphere lesions provides new insights into the cognitive dynamics and neural basis of phonological, semantic, and cognitive control processes in spoken word production. © 2013 Massachusetts Institute of Technology.

Mirman D.,Moss Rehabilitation Research Institute | Graziano K.M.,Moss Rehabilitation Research Institute
Journal of Experimental Psychology: General | Year: 2012

Knowledge about word and object meanings can be organized taxonomically (fruits, mammals, etc.) on the basis of shared features or thematically (eating breakfast, taking a dog for a walk, etc.) on the basis of participation in events or scenarios. An eye-tracking study showed that both kinds of knowledge are activated during comprehension of a single spoken word, even when the listener is not required to perform any active task. The results further revealed that an individual's relative activation of taxonomic relations compared to thematic relations predicts that individual's tendency to favor taxonomic over thematic relations when asked to choose between them in a similarity judgment task. These results indicate that individuals differ in the relative strengths of their taxonomic and thematic semantic knowledge and suggest that meaning information is organized in 2 parallel, complementary semantic systems. © 2011 American Psychological Association.

Mirman D.,Moss Rehabilitation Research Institute
Cognitive, Affective and Behavioral Neuroscience | Year: 2011

One way to examine the dynamics of word processing is to investigate how processing is affected by the co-activation of similar words ("neighbors"). A unique prediction of attractor dynamicalmodels is that near neighbors should exert inhibitory effects and distant neighbors should exert facilitative effects. In study 1, data from 62 unselected chronic aphasia patients revealed a higher rate of semantic errors for words with many near semantic neighbors and fewer semantic errors for words with many distant semantic neighbors. In study 2, this basic result was replicated incontrols using a speeded picturenaming paradigm. Together, these two studies provide strong new evidence consistent with the attractor dynamics view of neighborhood effects. In addition, analyses of correlations between effect sizes and lesion locations, and comparisons with the existing literature on semantic deficits in aphasia and the speeded picture-naming paradigm, all provide converging evidence that the semantic error patterns found in the present studies were due to disruptions of cognitive control mechanisms. © Psychonomic Society, Inc. 2010.

Lupyan G.,University of Wisconsin - Madison | Mirman D.,Moss Rehabilitation Research Institute
Cortex | Year: 2013

In addition to its use in communication, language appears to have a variety of extra-communicative functions; disrupting language disrupts performance in seemingly non-linguistic tasks. Previous work has specifically linked linguistic impairments to categorization impairments. Here, we systematically tested this link by comparing categorization performance in a group of 12 participants with aphasia and 12 age- and education-matched control participants. Participants were asked to choose all of the objects that fit a specified criterion from sets of 20 pictured objects. The criterion was either " high-dimensional" (i.e., the objects shared many features, such as " farm animals") or " low-dimensional" (i.e., the objects shared one or a few features, such as " things that are green" ). Participants with aphasia were selectively impaired on low-dimensional categorization. This selective impairment was correlated with the severity of their naming impairment and not with the overall severity of their aphasia, semantic impairment, lesion size, or lesion location. These results indicate that linguistic impairment impacts categorization specifically when that categorization requires focusing attention and isolating individual features - a task that requires a larger degree of cognitive control than high-dimensional categorization. The results offer some support for the hypothesis that language supports cognitive functioning, particularly the ability to select task-relevant stimulus features. © 2012 Elsevier Ltd.

Whyte J.,Moss Rehabilitation Research Institute
Archives of Physical Medicine and Rehabilitation | Year: 2014

Scientific theory is crucial to the advancement of clinical research. The breadth of rehabilitation treatment requires that many different theoretical perspectives be incorporated into the design and testing of treatment interventions. In this article, the 2 broad classes of theory relevant to rehabilitation research and practice are defined, and their distinct but complementary contributions to research and clinical practice are explored. These theory classes are referred to as treatment theories (theories about how to effect change in clinical targets) and enablement theories (theories about how changes in a proximal clinical target will influence distal clinical aims). Treatment theories provide the tools for inducing clinical change but do not specify how far reaching the ultimate impact of the change will be. Enablement theories model the impact of changes on other areas of function but provide no insight as to how treatment can create functional change. Treatment theories are more critical in the early stages of treatment development, whereas enablement theories become increasingly relevant in specifying the clinical significance and practical effectiveness of more mature treatments. Understanding the differences in the questions these theory classes address and how to combine their insights is crucial for effective research development and clinical practice. © 2014 by the American Congress of Rehabilitation Medicine.

Schwartz M.F.,Moss Rehabilitation Research Institute
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2014

The cognitive analysis of adult language disorders continues to draw heavily on linguistic theory, but increasingly it reflects the influence of connectionist, spreading activation models of cognition. In the area of spoken word production, 'localist' connectionist models represent a natural evolution from the psycholingistic theories of earlier decades. By contrast, the parallel distributed processing framework forces more radical rethinking of aphasic impairments. This paper exemplifies these multiple influences in contemporary cognitive aphasiology. Topics include (i) what aphasia reveals about semantic-phonological interaction in lexical access; (ii) controversies surrounding the interpretation of semantic errors and (iii) a computational account of the relationship between naming and word repetition in aphasia. Several of these topics have been addressed using case series methods, including computational simulation of the individual, quantitative error patterns of diverse groups of patients and analysis of brain lesions that correlate with error rates and patterns. Efforts to map the lesion correlates of nonword errors in naming and repetition highlight the involvement of sensorimotor areas in the brain and suggest the need to better integrate models of word production with models of speech and action. © 2013 The Author(s) Published by the Royal Society. All rights reserved.

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