Laurel J Buxbaum

• Psy.D.
• Professor (Full) at Thomas Jefferson University

Increasing evidence indicates that focal lesions following stroke cause alterations in connectivity among func- tional brain networks. Functional connectivity between hemispheres has been shown to be particularly critical for predicting stroke-related behavioral deficits and recovery of motor function and attention. Much less is known, however, abo...

"Two route" theories of object-related action processing posit different temporal activation profiles of grasp-to-move actions (rapidly evoked based on object structure) versus skilled use actions (more slowly activated based on semantic knowledge). We capitalized on the exquisite temporal resolution and multidimensionality of Event-Related Potenti...

Our use of tools is situated in different contexts. Prior evidence suggests that diverse regions within the ventral and dorsal streams represent information supporting common tool use. However, given the flexibility of object concepts, these regions may be tuned to different types of information when generating novel or uncommon uses of tools. To i...

Up to 90% of amputees experience sensations in their phantom limb, often including strong, persistent phantom limb pain (PLP). Standard treatments do not provide relief for the majority of people who experience PLP, but virtual reality (VR) has shown promise. This study provides additional evidence that game-like training with low-cost immersive VR...

Limb apraxia is a heterogeneous disorder of skilled action and tool use that has long perplexed clinicians and researchers. It occurs after damage to various loci in a densely interconnected network of regions in the left temporal, parietal, and frontal lobes. Historically, a highly classificatory approach to the study of apraxia documented numerou...

Tool use is a complex motor planning problem. Prior research suggests that planning to use tools involves resolving competition between different action representations. We reasoned that competition may be exacerbated with tools for which the motions of the tool and the hand are incongruent, such as pinching the fingers to open a clothespin. If thi...

A vexing characteristic of motor disability after stroke is that many individuals fail to use their affected arm effectively despite having the capacity to do so, a phenomenon termed arm nonuse. Based on the hypothesis that nonuse is influenced by the competing cognitive demands of many daily activities, we examined the effects of cognitive load on...

Tulving characterized semantic memory as a vast repository of meaning that underlies language and many other cognitive processes. This perspective on lexical and conceptual knowledge galvanized a new era of research undertaken by numerous fields, each with their own idiosyncratic methods and terminology. For example, “concept” has different meaning...

Individuals who have experienced a left hemisphere cerebrovascular accident (LCVA) have been shown to make errors in naturalistic action tasks designed to assess the ability to perform everyday activities such as preparing a cup of coffee. Naturalistic action errors in this population are often attributed to limb apraxia, a common deficit in the re...

Stroke is a leading cause of disability worldwide which can cause significant and persistent upper limb (UL) impairment. It is difficult to predict UL motor recovery after stroke and to forecast the expected outcomes of rehabilitation interventions during the acute and subacute phases when using clinical data alone. Accurate prediction of response...

Daily life requires use of the arms for a variety of tasks under competing cognitive demands, such as reaching for objects in a visually-cluttered kitchen cabinet while holding a conversation. Prior studies have suggested that such demands may impact motor performance, including selection of the most efficient arm to use to reach to a target in a g...

Tulving (1972) characterized semantic memory as a vast repository of meaning that provides a substrate for language and many other cognitive processes. Tulving’s perspective resulted in a paradigm shift in the study of human conceptual knowledge. Semantic research has since evolved as a multidisciplinary endeavor advanced by fields with their own e...

Tulving (1972) characterized semantic memory as a vast repository of meaning that underlies language and many other cognitive processes. This perspective on lexical and conceptual knowledge galvanized a new era of research undertaken by numerous fields, each with their own idiosyncratic methods and terminology. For example, ‘concept’ has different...

The ability to select between potential actions is central to the complex process of tool use. After left hemisphere stroke, individuals with limb apraxia make more hand action errors when gesturing the use of tools with conflicting hand actions for grasping-to-move and use (e.g., screwdriver) relative to tools that are grasped-to-move and used wit...

Aphasia is a language disorder that often involves speech comprehension impairments affecting communication. In face-to-face settings, speech is accompanied by mouth and facial movements, but little is known about the extent to which they benefit aphasic comprehension. This study investigated the benefit of visual information accompanying speech fo...

Dual-route models of high-level (praxis) actions distinguish between an “indirect” semantic route mediating meaningful gesture imitation, and a “direct” sensory-motor route mediates meaningless gesture imitation. Similarly, dual-route language models distinguish between an indirect route mediating production and repetition of words, and a direct ro...

Primary progressive aphasia (PPA) is a neurodegenerative syndrome characterized by progressive language deficits. The main variants of PPA - semantic (svPPA), logopenic (lvPPA), and nonfluent (nfvPPA) - can be challenging to distinguish. Limb apraxia often co-occurs with PPA, but it is unclear whether PPA variants are associated with different apra...

The ability to select between potential actions is central to the complex process of tool use. After left hemisphere stroke, individuals with limb apraxia make more hand action errors when gesturing the use of tools with conflicting hand actions for grasping-to-move and use (e.g., screwdriver) relative to tools that are grasped-to-move and used wit...

This study investigates, using behavioral and lesion-symptom mapping methods, the impact of visual speech information for word comprehension in aphasia and the neuroanatomic substrates of any benefit.

Imitation is an important daily activity involved in social interactions, motor learning, and is commonly used for rehabilitation after stroke. Moreover, deficits in imitation of novel movements commonly occur after left hemisphere stroke (LCVA) in the syndrome of limb apraxia. In the current study, we used a novel virtual reality (VR) imitation pa...

Left inattention is common in individuals following right cerebrovascular accident (RCVA). In neurotypical adults, we have previously found prolonged rightward visual attention resulted in a subsequent increase in leftward attention. Here we applied the same method in neurological patients with RCVA and found improved post-intervention attention bo...

Dual-route models of high-level (praxis) actions distinguish between an “indirect” semantic route mediating meaningful gesture imitation, and a “direct” sensory-motor route mediates meaningless gesture imitation. Similarly, dual-route language models distinguish between an indirect route mediating production and repetition of words, and a direct ro...

The reliable identification of healthy versus damaged brain tissue is of primary importance in studies of brain-behavior relationships in patient populations. However, lesion appearance and boundaries are extremely inconsistent and can often vary based on the location in the brain, the appearance of surrounding tissue and structures, the scan type,...

Imitation is a significant daily activity involved in social interaction and motor learning. Imitation has been theorized to be performed in at least two ways. In posture-based imitation, individuals reproduce how the body should look and feel, and are sensitive to the relative positioning of body parts. In trajectory imitation, individuals mimic t...

Influential theories of skilled action posit that distinct cognitive mechanisms and neuroanatomic substrates support meaningless gesture imitation and tool use pantomiming, and poor performance on these tasks are hallmarks of limb apraxia. Yet prior research has primarily investigated brain-behavior relations at the group level; thus, it is unclear...

Influential theories of skilled action posit that distinct cognitive mechanisms and neuroanatomic substrates support meaningless gesture imitation and tool use pantomiming, and poor performance on these tasks are hallmarks of limb apraxia. Yet prior research has primarily investigated brain-behavior relations at the group level; thus, it is unclear...

The ability to imitate observed actions serves as an efficient method for learning novel movements and is specifically impaired (without concomitant gross motor impairments) in the neurological disorder of limb apraxia, a disorder common after left hemisphere stroke. Research with apraxic patients has advanced our understanding of how people imitat...

Background Phantom limb pain (PLP) is a common and in some cases debilitating consequence of upper- or lower-limb amputation for which current treatments are inadequate. Objective This small clinical trial tested whether game-like interactions with immersive VR activities can reduce PLP in subjects with transtibial lower-limb amputation. Methods...

Many individuals who undergo limb amputation experience persistent phantom limb pain (PLP), but the underlying mechanisms of PLP are unknown. The traditional hypothesis was that PLP resulted from maladaptive plasticity in sensorimotor cortex that degrades the neural representation of the missing limb. However, a recent study of individuals with upp...

Tools are ubiquitous in human environments and to think about them we use concepts. Increasingly, conceptual representation is thought to be dynamic and sensitive to the goals of the observer. Indeed, observer goals can reshape representational geometry within cortical networks supporting concepts. In the present study, we investigated the novel hy...

The ability to imitate observed actions serves as an efficient method for learning novel movements and is specifically impaired (without concomitant gross motor impairments) in the neurological disorder of limb apraxia, a disorder common after left hemisphere stroke. Research with apraxic patients has advanced our understanding of how people imitat...

Hand gestures, imagistically related to the content of speech, are ubiquitous in face-to-face communication. Here we investigated people with aphasia's (PWA) processing of speech accompanied by gestures using lesion-symptom mapping. Twenty-nine PWA and 15 matched controls were shown a picture of an object/action and then a video-clip of a speaker p...

Movement imitation is a significant daily activity involved in social interaction and motor 2 learning. Although imitation remains poorly understood, recent research suggests that it may be achieved in two distinct ways. In posture-based imitation, movements reproduce how the body should look and feel, and are sensitive to the relative positioning...

Many individuals who undergo limb amputation experience persistent phantom limb pain (PLP). The underlying mechanism of PLP is unknown, but the phenomenon has been associated with reorganization in sensorimotor cortex following amputation. The traditional view is that cortical reorganization degrades the missing limb’s representation. However, rece...

Producing a tool use gesture is a complex process drawing upon the integration of stored knowledge of tools and their associated actions with sensory-motor mechanisms supporting the planning and control of hand and arm actions. Understanding how sensory-motor systems in parietal cortex interface with semantic representations of actions and objects...

Background. Nonuse (NU) after stroke is characterized by failure to use the contralesional arm despite adequate capacity. It has been suggested that NU is a consequence of the greater effort and/or attention required to use the affected limb, but such accounts have not been directly tested, and we have poor understanding of the predictors of NU. Ob...

Limb apraxia is evident in approximately 50% of patients after left hemisphere cerebral vascular accident (LCVA) and increases disability and caregiver dependence. Individuals with apraxia exhibit abnormalities in spatio-temporal aspects of gesture production and/or in knowledge of tool-related actions (action semantics). This preliminary study of...

The sixth edition of the foundational reference on cognitive neuroscience, with entirely new material that covers the latest research, experimental approaches, and measurement methodologies. Each edition of this classic reference has proved to be a benchmark in the developing field of cognitive neuroscience. The sixth edition of The Cognitive Neuro...

Hand gestures, imagistically related to the content of speech, are ubiquitous in face-to-face communication. In the first study with people with aphasia (PWA) investigating speech-gesture processing in the brain using lesion-symptom mapping, we investigated the brain regions as well as the lexical-semantic and gesture recognition abilities associat...

Producing a tool use gesture is a complex process drawing upon the integration of stored knowledge of tools and their associated actions with sensory-motor mechanisms supporting the planning and control of hand and arm actions. Understanding how sensory-motor systems in parietal cortex interface with semantic representations of actions and objects...

Background The phenomenon of non-use after stroke is characterized by failure to use the contralesional arm despite adequate capacity. It has been suggested that non-use is a consequence of the greater effort and/or attention required to use the affected limb, but such accounts have not been tested, and we have poor understanding of the characteris...

When pantomiming the use of tools, patients with limb apraxia after left hemisphere stroke (LCVA) produce more spatiotemporal hand action errors with tools associated with conflicting actions for use versus grasp-to-pick-up (e.g., corkscrew) than tools having a single action for both use and grasp (e.g., hammer). There are two possible accounts for...

Interacting with manipulable objects (tools) requires the integration of diverse computations supported by anatomically remote regions. Previous functional neuroimaging research has demonstrated the left supramarginal (SMG) exhibits functional connectivity to both ventral and dorsal pathways, supporting the integration of ventrally‐mediated tool pr...

Humans are particularly good at copying novel and meaningless gestures. The mechanistic and anatomical basis for this specialized imitation ability remains largely unknown. One idea is that imitation occurs by matching body configurations. Here we propose an alternative route to imitation that depends on a body-independent representation of the tra...

When pantomiming the use of tools, patients with limb apraxia after left hemisphere stroke (LCVA) produce more spatiotemporal hand action errors with tools associated with conflicting actions for use versus grasp-to-pick-up (e.g., corkscrew) than tools having a single action for both use and grasp (e.g., hammer). There are two possible accounts for...

The mechanisms and brain regions underlying error monitoring in complex action are poorly understood, yet errors and impaired error correction in these tasks are hallmarks of apraxia, a common disorder associated with left hemisphere stroke. Accounts of monitoring of language posit an internal route by which production planning or competition betwe...

The mechanisms and brain regions underlying error monitoring in complex action are poorly understood, yet errors and impaired error correction in these tasks are hallmarks of apraxia, a common disorder associated with left hemisphere stroke. Accounts of monitoring of language posit an internal route by which production planning or competition betwe...

Humans are particularly good at copying novel and meaningless gestures. The mechanistic and anatomical basis for this specialized imitation ability remains largely unknown. One idea is that imitation occurs by matching body configurations. Here we propose an alternative route to imitation that depends on a body-independent representation of the tra...

Introduction. Non-use, an acquired, transiently reversible behavioral response to suppress movement of the paretic limb, is a persistent problem in stroke survivors, but it is unclear whether level of sensorimotor impairment, cognitive, and/or or psychological factors may influence its presence. We reasoned that paretic arm use may be modulated by...

Introduction. Non-use, an acquired, transiently reversible behavioral response to suppress movement of the paretic limb, is a persistent problem in stroke survivors, but it is unclear whether level of sensorimotor impairment, cognitive, and/or or psychological factors may influence its presence. We reasoned that paretic arm use may be modulated by...

The reasoning-based approach championed by Francois Osiurak and Arnaud Badets (Osiurak & Badets, 2016) denies the existence of sensory-motor memories of tool use except in limited circumstances, and suggests instead that most tool use is subserved solely by online technical reasoning about tool properties. In this commentary, I highlight the streng...

Objectives: Adaptive interaction with the environment requires the ability to predict both human and non-biological motion trajectories. Prior accounts of the neurocognitive basis for prediction of these two motion classes may generally be divided into those that posit that non-biological motion trajectories are predicted using the same motor plan...

The mirror illusion uses a standard mirror to create a compelling illusion in which movements of one limb seem to be made by the other hidden limb. In this paper we adapt a motor control framework to examine which estimates of the body’s configuration are affected by the illusion. We propose that the illusion primarily alters estimates related to u...

Converging evidence supports the existence of functionally and neuroanatomically distinct taxonomic (similarity-based; e.g., hammer-screwdriver) and thematic (event-based; e.g., hammer-nail) semantic systems. Processing of thematic relations between objects has been shown to selectively recruit the left posterior temporoparietal cortex. Similar pos...

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 dissociat...

A number of studies have explored the role of associative/event-based (thematic) and categorical (taxonomic) relations in the organization of object representations. Recent evidence suggests that thematic information may be particularly important in determining relationships between manipulable artifacts. However, although sensorimotor information...

Sir, It is intriguing that our article ‘Critical brain regions for tool-related and imitative actions: a componential analysis’ was the sole subject of a recent positive Scientific Commentary in Brain by Professor Georg Goldenberg ‘Challenging traditions in apraxia’ (Goldenberg, 2014) noting that the paper ‘excels by virtue of its methodical astut...

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...

Tactile cues generated from lightweight, wearable actuators can help users learn new motions by providing immediate feedback on when and how to correct their movements. We present a vibrotactile motion guidance system that measures arm motions and provides vibration feedback when the user deviates from a desired trajectory. A study was conducted to...

Numerous functional neuroimaging studies suggest that widespread bilateral parietal, temporal, and frontal regions are involved in tool-related and pantomimed gesture performance, but the role of these regions in specific aspects of gestural tasks remains unclear. In the largest prospective study of apraxia-related lesions to date, we performed vox...

A number of studies have explored the role of associative/event-based (thematic) and categorical (taxonomic) relations in the organization of object representations. Recent evidence suggests that thematic information may be particularly important in determining relationships between manipulable artifacts. However, although sensorimotor information...

Substantial evidence suggests that conceptual processing of manipulable objects is associated with potentiation of action. Such data have been viewed as evidence that objects are recognized via access to action features. Many objects, however, are associated with multiple actions. For example, a kitchen timer may be clenched with a power grip to mo...

Many tests of hemispatial neglect are insensitive to subtle (but clinically relevant) forms of the disorder. This study provides additional reliability and validity data on the Virtual Reality Lateralized Attention Test (VRLAT), an easy-to-administer computerized measure of hemispatial neglect that mimics the attentional demands of real-world tasks...

Semantic knowledge may be organized in terms of similarity relations based on shared features and/or complementary relations based on co-occurrence in events. Thus, relationships between manipulable objects such as tools may be defined by their functional properties (what the objects are used for) or thematic properties (e.g., what the objects are...

We report data from two left hemisphere stroke patients with moderate-to-severe ideomotor apraxia who exhibited deficits in positioning their hands to use 'conflict' objects (objects grasped and used with different hand postures) relative to controls and patients with mild apraxia. These novel data support the claim that actions to common objects a...

The current research aimed at specifying the activation time course of different types of semantic information during object conceptual processing and the effect of context on this time course. We distinguished between thematic and functional knowledge and the specificity of functional similarity. Two experiments were conducted with healthy older a...

Previous studies suggest that action representations are activated during object processing, even when task-irrelevant. In addition, there is evidence that lexical-semantic context may affect such activation during object processing. Finally, prior work from our laboratory and others indicates that function-based (“use”) and structure-based (“move”...

The past decade has seen increasing interest within the cognitive neuroscience community in understanding the psychological processes involved in representing the body, and in learning how these processes may be implemented within the brain. This special issue of Cognitive Neuroscience presents six new empirical papers that contribute to this rapid...

During gain adaptation, participants must learn to adapt to novel visuo-motor mappings in which the movement amplitudes they produce do not match the visual feedback they receive. The aim of the present study was to investigate the neural substrates of gain adaptation by examining its possible disruption following left hemisphere stroke. Thirteen c...

We present and evaluate an arm-motion guidance system that uses magnetic tracking sensors and low cost vibrotactile actuators. The system measures the movement of the user’s arm and provides vibration feedback at the wrist and elbow when they stray from the desired motion. An initial study was conducted to investigate whether adding tactile feedbac...

In this chapter, the authors use the computation, anatomy, and physiology (CAP) principles to consider the impact of common clinical problems on action. They focus on 3 major syndromes: paresis, apraxia, and ataxia. They also review mechanisms that could account for spontaneous recovery, using what is known about the best-studied clinical dysfuncti...

A number of conflicting claims have been advanced regarding the role of the left inferior frontal gyrus, inferior parietal lobe and posterior middle temporal gyrus in action recognition, driven in part by an ongoing debate about the capacities of putative mirror systems that match observed and planned actions. We report data from 43 left hemisphere...

Optic ataxia, a disorder of visually guided reaching, has been attributed to a failure in the transmission of visuospatial information to motor systems. This account fails to explain why many patients w ith optic ataxia misreach only when targets are presented in non-foveal vision, but not w hen targets are view ed directly. We present data from tw...

Apraxic stroke patients need to perform repetitive arm movements to regain motor functionality, but they struggle to process the visual feedback provided by typical virtual rehabilitation systems. Instead, we imagine a low cost sleeve that can measure the movement of the upper limb and provide tactile feedback at key locations. The feedback provide...

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 cogn...

Apraxic patients are known for deficits in producing and comprehending skilled movements. Two experiments tested their implicit and explicit knowledge about manipulable objects in order to examine whether such deficits accompany impairment in the conceptual representation of manipulation features. An eyetracking method was used to test implicit kno...

Viewing objects with the intention to act upon them may activate task-irrelevant motor responses. Many manufactured objects are associated with two action classes: grasping in accordance with object structure and skillful use consistent with object function. We studied the potential for within-object competition during action selection by comparing...

Apraxia is a common clinical disorder characterized by an inability to perform complex, familiar actions that cannot be attributed to weakness or elementary sensory loss. The disorder is usually associated with damage to the left parietal or frontal lobe. A variety of different types of apraxia have been identified, ranging from an impairment in de...

Fingertip force scaling for lifting objects frequently occurs in anticipation of finger contact. An ongoing question concerns the types of memories that are used to inform predictive control. Object-specific information such as weight may be stored and retrieved when previously encountered objects are lifted again. Alternatively, visual size and sh...