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.”
Nozari N.,University of Illinois at Urbana - Champaign |
Dell G.S.,University of Illinois at Urbana - Champaign |
Schwartz M.F.,Moss Rehabilitation Research Institute
Cognitive Psychology | Year: 2011
Despite the existence of speech errors, verbal communication is successful because speakers can detect (and correct) their errors. The standard theory of speech-error detection, the perceptual-loop account, posits that the comprehension system monitors production output for errors. Such a comprehension-based monitor, however, cannot explain the double dissociation between comprehension and error-detection ability observed in the aphasic patients. We propose a new theory of speech-error detection which is instead based on the production process itself. The theory borrows from studies of forced-choice-response tasks the notion that error detection is accomplished by monitoring response conflict via a frontal brain structure, such as the anterior cingulate cortex. We adapt this idea to the two-step model of word production, and test the model-derived predictions on a sample of aphasic patients. Our results show a strong correlation between patients' error-detection ability and the model's characterization of their production skills, and no significant correlation between error detection and comprehension measures, thus supporting a production-based monitor, generally, and the implemented conflict-based monitor in particular. The successful application of the conflict-based theory to error-detection in linguistic, as well as non-linguistic domains points to a domain-general monitoring system. © 2011 Elsevier Inc.
Harvey D.Y.,Rice University |
Harvey D.Y.,University of Pennsylvania |
Harvey D.Y.,Moss Rehabilitation Research Institute |
Schnur T.T.,Rice University
Cortex | Year: 2015
Naming pictures and matching words to pictures belonging to the same semantic category negatively affects language production and comprehension. By most accounts, semantic interference arises when accessing lexical representations in naming (e.g., Damian, Vigliocco, & Levelt, 2001) and semantic representations in comprehension (e.g., Forde & Humphreys, 1997). Further, damage to the left inferior frontal gyrus (LIFG), a region implicated in cognitive control, results in increasing semantic interference when items repeat across cycles in both language production and comprehension (Jefferies, Baker, Doran, & Lambon Ralph, 2007). This generates the prediction that the LIFG via white matter connections supports resolution of semantic interference arising from different loci (lexical vssemantic) in the temporal lobe. However, it remains unclear whether the cognitive and neural mechanisms that resolve semantic interference are the same across tasks. Thus, we examined which gray matter structures [using whole brain and region of interest (ROI) approaches] and white matter connections (using deterministic tractography) when damaged impact semantic interference and its increase across cycles when repeatedly producing and understanding words in 15 speakers with varying lexical-semantic deficits from left hemisphere stroke. We found that damage to distinct brain regions, the posterior versusanterior temporal lobe, was associated with semantic interference (collapsed across cycles) in naming and comprehension, respectively. Further, those with LIFG damage compared to those without exhibited marginally larger increases in semantic interference across cycles in naming but not comprehension. Lastly, the inferior fronto-occipital fasciculus, connecting the LIFG with posterior temporal lobe, related to semantic interference in naming, whereas the inferior longitudinal fasciculus (ILF), connecting posterior with anterior temporal regions related to semantic interference in comprehension. These neuroanatomical-behavioral findings have implications for models of the lexical-semantic language network by demonstrating that semantic interference in language production and comprehension involves different representations which differentially recruit a cognitive control mechanism for interference resolution. © 2015 Elsevier Ltd.
Hart T.,Moss Rehabilitation Research Institute |
Bagiella E.,Columbia University
Archives of Physical Medicine and Rehabilitation | Year: 2012
The growth of evidence-based medicine means that both researchers and clinicians must grasp the complex issues involved in implementing clinical trials, which are especially challenging for the behavioral (experience-based) treatments that predominate in rehabilitation. In this article we discuss selected issues germane to the design, implementation, and analysis of group-level clinical trials in rehabilitation. We review strengths, weaknesses, and best applications of 1-sample, between-subjects, and within-subjects study designs, including newer models such as practical clinical trials and point-of-care trials. We also discuss the selection of appropriate control conditions against which to test rehabilitation treatments, as well as issues related to trial blinding. In a section on treatment definition, we discuss the challenges of specifying the active ingredients in the complex interventions that are widely used in rehabilitation, and present an illustration of 1 approach to defining treatments via the learning mechanisms that underlie them. Issues related to treatment implementation are also discussed, including therapist allocation and training, and assessment of treatment fidelity. Finally we consider 2 statistical topics of particular importance to many rehabilitation trials: the use of multiple or composite outcomes, and factors that must be weighed in estimating sample size for clinical trials. © 2012 American Congress of Rehabilitation Medicine.
Buxbaum L.J.,Moss Rehabilitation Research Institute |
Kalenine S.,Moss Rehabilitation Research Institute
Annals of the New York Academy of Sciences | Year: 2010
Scientific interest in the relationship between cognition and action has increased markedly in the past several years, fueled by the discovery of mirror neurons in monkey prefrontal and parietal cortex and by the emergence of a movement in cognitive psychology, termed the embodied cognition framework, which emphasizes the role of simulation in cognitive representations. Guided by a functional neuroanatomic model called the Two Action Systems account, which posits numerous points of differentiation between structure- and function-based actions, we focus on two of the major issues under recent scrutiny: the relationship between representations for action production and recognition, and the role of action in object representations. We suggest that mirror neurons in humans are not critical for full action understanding, and that only function-based (and not structure-based) action is a component of embodied object concepts. © 2010 New York Academy of Sciences.
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.
Mirman D.,Moss Rehabilitation Research Institute |
Britt A.E.,Moss Rehabilitation Research Institute
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2014
Semantic impairments have been divided into storage deficits, in which the semantic representations themselves are damaged, and access deficits, in which the representations are intact but access to them is impaired. The behavioural phenomena that have been associated with access deficits include sensitivity to cueing, sensitivity to presentation rate, performance inconsistency, negative serial position effects, sensitivity to number and strength of competitors, semantic blocking effects, disordered selection between strong and weak competitors, correlation between semantic deficits and executive function deficits and reduced word frequency effects. Four general accounts have been proposed for different subsets of these phenomena: abnormal refractoriness, too much activation, impaired competitive selection and deficits of semantic control. A combination of abnormal refractoriness and impaired competitive selection can account for most ofthe behavioural phenomena, but there remain several open questions. In particular, it remains unclear whether access deficits represent a single syndrome, a syndrome with multiple subtypes or a variable collection of phenomena, whether the underlying deficit is domain-general or domain-specific, whether it is owing to disorders of inhibition, activation or selection, and the nature of the connection (if any) between access phenomena in aphasia and in neurologically intact controls. Computational models offer a promising approach to answering these questions. © 2013 The Author(s) Published by the Royal Society. All rights reserved.
Watson C.E.,Moss Rehabilitation Research Institute |
Buxbaum L.J.,Moss Rehabilitation Research Institute
Journal of Experimental Psychology: Human Perception and Performance | Year: 2014
Despite research suggesting that stored sensorimotor information about tool use is a component of the semantic representations of tools, little is known about the action features or organizing principles that underlie this knowledge. We used methods similar to those applied in other semantic domains to examine the "architecture" of action semantic knowledge. In Experiment 1, participants sorted photographs of tools into groups according to the similarity of their associated "use" actions and rated tools on dimensions related to action. The results suggest that the magnitude of arm movement, configuration of the hand, and manner of motion during tool use play a role in determining how tools cluster in action "semantic space." In Experiment 2, we validated the architecture uncovered in Experiment 1 using an implicit semantic task for which tool use knowledge was not ostensibly relevant (blocked cyclic word-picture matching). Using stimuli from Experiment 1, we found that participants performed more poorly during blocks of trials containing tools used with similar versus unrelated actions, and the amount of semantic interference depended on the magnitude of action similarity among tools. Thus, the degree of featural overlap between tool use actions plays a role in determining the overall semantic similarity of tools. © 2014 American Psychological Association.
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.