Lewis Wheaton

Publications

• 5.38

  Impact points

  Forming tool use representations: a neurophysiological investigation into tool exposure.

  John Christopher Mizelle, Teresa Tang, Nikta Pirouz, Lewis A Wheaton

  Journal of cognitive neuroscience. 03/2011; 23(10):2920-34.

  Prior work has identified a common left parietofrontal network for storage of tool-related information for various tasks. How these representations become established within this network on the basis of different modes of exposure is unclear. Here, healthy subjects engaged in physical practice (dire... [more] Prior work has identified a common left parietofrontal network for storage of tool-related information for various tasks. How these representations become established within this network on the basis of different modes of exposure is unclear. Here, healthy subjects engaged in physical practice (direct exposure) with familiar and unfamiliar tools. A separate group of subjects engaged in video-based observation (indirect exposure) of the same tools to understand how these learning strategies create representations. To assess neural mechanisms engaged for pantomime after different modes of exposure, a pantomime task was performed for both tools while recording neural activation with high-density EEG. Motor planning-related neural activation was evaluated using beta band (13-22 Hz) event-related desynchronization. Hemispheric dominance was assessed, and activation maps were generated to understand topography of activations. Comparison of conditions (effects of tool familiarity and tool exposure) was performed with standardized low-resolution brain electromagnetic tomography. Novel tool pantomime following direct exposure resulted in greater activations of bilateral parietofrontal regions. Activations following indirect training varied by tool familiarity; pantomime of the familiar tool showed greater activations in left parietofrontal areas, whereas the novel tool showed greater activations at right temporoparieto-occipital areas. These findings have relevance to the mechanisms for understanding motor-related behaviors involved in new tools that we have little or no experience with and can extend into advancing theories of tool use motor learning.
• 3.12

  Impact points

  Attenuation of corticomuscular coherence with additional motor or non-motor task.

  Ashley N Johnson, Lewis A Wheaton, Minoru Shinohara

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology. 02/2011; 122(2):356-63.

  The study aimed to compare beta (15-30 Hz) band corticomuscular coherence between a unilateral hand motor task and concurrent motor or non-motor tasks. Additionally, we examined the potential associations between corticomuscular coherence and fine motor performance. Ten healthy young right-handed ad... [more] The study aimed to compare beta (15-30 Hz) band corticomuscular coherence between a unilateral hand motor task and concurrent motor or non-motor tasks. Additionally, we examined the potential associations between corticomuscular coherence and fine motor performance. Ten healthy young right-handed adults performed unilateral, bilateral, concurrent motor-cognitive, and cognitive tasks. Electroencephalogram and electromyogram were recorded from the primary motor cortex and the first dorsal interosseous muscle, respectively, during steady contractions. Corticomuscular beta band coherence decreased (P<0.05) from the unilateral motor task with the right hand to the same extent in both the bilateral motor and motor-cognitive tasks. A decrease in corticomuscular coherence with concurrent tasks was also observed for the left hand (P<0.05). Beta band coherence was not associated with motor output steadiness or accuracy. Beta band coherence decreased during concurrent tasks irrespective of the additional task, most likely due to divided attention. There was no association between beta band coherence and fine motor performance during steady contractions. This study supports that attention divided by an additional motor or non-motor task influences beta band corticomuscular coherence that was not associated with fine motor performance. The results suggest clinical relevance to identify what might occur in clinical distracter tasks.

• Forming Tool Use Representations: A Neurophysiological Investigation into Tool Exposure.

  John Christopher Mizelle, Teresa Tang, Nikta Pirouz, Lewis A. Wheaton

  J. Cognitive Neuroscience. 01/2011; 23:2920-2934.
• 1.93

  Impact points

  Testing perceptual limits of functional units: Are there "automatic" tendencies to associate tools and objects?

  J C Mizelle, Lewis A Wheaton

  Neuroscience letters. 11/2010; 488(1):92-6.

  Prior work has demonstrated a unique network involving the insula, temporal cortex, and precuneus in evaluating appropriate relationships between tool-object pairings under instruction [20]. However, are there automatic tendencies to evaluate appropriate tool-object pairings? Using electroencephalog... [more] Prior work has demonstrated a unique network involving the insula, temporal cortex, and precuneus in evaluating appropriate relationships between tool-object pairings under instruction [20]. However, are there automatic tendencies to evaluate appropriate tool-object pairings? Using electroencephalography (EEG), we emulated our prior work to identify neural mechanisms that, in the absence of task-related consciousness, differentiate functionally matching from mismatching tool-object pairs. This was compared to any activation consistent with this using environmental image pairs. In addition, based on the paradigm we were able to discern any naïve processes that distinguish tools from non-tool environmental images. Results show that without task-related consciousness, the left occipitotemporal gyrus is preferentially active for tools compared to environmental images. Tool-object match and mismatch each versus control images show differences relative to a control image over the left temporal cortex, extending into the insula, yet there was no difference between tool-object match and mismatch. This suggests that there is no clear neural mechanism for continual evaluation of tool matching from mismatching, though there is for broad picture classifications. Taken together with our previous results, this creates a discussion for the role of intention when determining such relationships.
• 2.46

  Impact points

  Neural activation for conceptual identification of correct versus incorrect tool-object pairs.

  J C Mizelle, Lewis A Wheaton

  Brain research. 10/2010; 1354:100-12.

  Appropriate tool-object pairing is a natural part of our lives. When preparing to clean our teeth, we know that a toothbrush is useful, but not a screwdriver. The neural correlates of this pairing process remain unclear. We recorded 64-channel electroencephalography to determine neural correlates of... [more] Appropriate tool-object pairing is a natural part of our lives. When preparing to clean our teeth, we know that a toothbrush is useful, but not a screwdriver. The neural correlates of this pairing process remain unclear. We recorded 64-channel electroencephalography to determine neural correlates of identification of tool-object matches and mismatches. Subjects were shown a target tool (e.g. spoon) later paired with an object that was either a conceptual match (e.g. bowl) or mismatch (e.g. wood). To verify that activity was not related to general concept of match-mismatch, in a second condition subjects saw non-tool environmental items (e.g. bird) later paired with a conceptual match (e.g. nest) or mismatch (e.g. spider web). Analysis was focused on time bins after each picture, using standardized low-resolution brain electromagnetic tomography (sLORETA). Tool-object match versus mismatch revealed significant differences in the posterior cingulate, precuneus, left insula and superior temporal gyrus. These patterns were not present for environmental match versus mismatch. This work suggests a specific network in comprehending tool-based pairings, but not extensive to other pairings. The posterior cingulate, precuneus, insula and superior temporal gyrus preferentially differentiates tool-object matching and mismatching, identifying a potential locus related to impairments in comprehending appropriate and inappropriate tool-object relationships that arise after neural injury.
• 2.26

  Impact points

  Theta frequency band activity and attentional mechanisms in visual and proprioceptive demand.

  J C Mizelle, Larry Forrester, Mark Hallett, Lewis A Wheaton

  Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale. 07/2010; 204(2):189-97.

  In a companion manuscript we reported reduced electroencephalographic (EEG) activation at traditional sensorimotor areas in knee movements with high levels of task difficulty modulated by varying visual and proprioceptive sensory demands. Given that reduced cortical activity with more complex tasks ... [more] In a companion manuscript we reported reduced electroencephalographic (EEG) activation at traditional sensorimotor areas in knee movements with high levels of task difficulty modulated by varying visual and proprioceptive sensory demands. Given that reduced cortical activity with more complex tasks is counter-intuitive, we suggested that high order cognitive-motor areas may show increased EEG activation to compensate for the observed decrease in sensorimotor regions. To test this hypothesis, we evaluated theta band activation at anterior frontal regions in a secondary analysis of our previous data. Unlike activation at sensorimotor areas, anterior frontal responses increased with each level of task difficulty as modulated by precision of visual targeting and/or proprioceptive demands from adding masses to the leg. Activity was increased as both unimodal visual and proprioceptive requirements became more demanding, but showed greater sensitivity to visual over proprioceptive processing requirements. Each level of bimodal task demands showed increasing activation, which was consistently greater when modulated through visual demands. These results are consistent with our hypothesis of increased contribution of anterior frontal regions for motor control in lower extremity movements with increasing sensory demands and further support different mechanisms for internally and externally guided movement.
• 2.26

  Impact points

  Electroencephalographic reactivity to unimodal and bimodal visual and proprioceptive demands in sensorimotor integration.

  J C Mizelle, Larry Forrester, Mark Hallett, Lewis A Wheaton

  Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale. 06/2010; 203(4):659-70.

  We used electroencephalography to see how the brain deals with altered sensory processing demands in lower extremity movements. In unimodal conditions, sensory processing demands were altered with subjects performing movement to a small or large visual target, or with a small or large weight to modi... [more] We used electroencephalography to see how the brain deals with altered sensory processing demands in lower extremity movements. In unimodal conditions, sensory processing demands were altered with subjects performing movement to a small or large visual target, or with a small or large weight to modify proprioception. In bimodal conditions, both weight and targets needed to be met. We assessed activity over primary sensorimotor, premotor and parietal areas before and during knee movements. In unimodal conditions, the primary sensorimotor area showed the least sensitivity to the maximally increased sensory demand in both vision and proprioception, while the premotor region was most sensitive to proprioceptive demands, and the parietal region showed greatest sensitivity to visual demands. In bimodal conditions, intermediate levels of sensory processing demand maximally increased activation at premotor and parietal regions. However, when visual and proprioceptive demands were both maximal, activation decreased and was similar to that seen with the lowest level of sensory processing demand. As behavior was consistent across conditions while activation at these regions decreased, we suggest that additional brain areas, possibly high order cognitive and attentional regions, may be required to augment the function of the traditional sensorimotor network in lower extremity movements with increasingly difficult sensory processing demands.

• The Neuroscience of Storing and Molding Tool Action Concepts: How "Plastic" is Grounded Cognition?

  J C Mizelle, Lewis A Wheaton

  Frontiers in psychology. 01/2010; 1:195.

  Choosing how to use tools to accomplish a task is a natural and seemingly trivial aspect of our lives, yet engages complex neural mechanisms. Recently, work in healthy populations has led to the idea that tool knowledge is grounded to allow for appropriate recall based on some level of personal hist... [more] Choosing how to use tools to accomplish a task is a natural and seemingly trivial aspect of our lives, yet engages complex neural mechanisms. Recently, work in healthy populations has led to the idea that tool knowledge is grounded to allow for appropriate recall based on some level of personal history. This grounding has presumed neural loci for tool use, centered on parieto-temporo-frontal areas to fuse perception and action representations into one dynamic system. A challenge for this idea is related to one of its great benefits. For such a system to exist, it must be very plastic, to allow for the introduction of novel tools or concepts of tool use and modification of existing ones. Thus, learning new tool usage (familiar tools in new situations and new tools in familiar situations) must involve mapping into this grounded network while maintaining existing rules for tool usage. This plasticity may present a challenging breadth of encoding that needs to be optimally stored and accessed. The aim of this work is to explore the challenges of plasticity related to changing or incorporating representations of tool action within the theory of grounded cognition and propose a modular model of tool-object goal related accomplishment. While considering the neuroscience evidence for this approach, we will focus on the requisite plasticity for this system. Further, we will highlight challenges for flexibility and organization of already grounded tool actions and provide thoughts on future research to better evaluate mechanisms of encoding in the theory of grounded cognition.
• 1.55

  Impact points

  Why is that Hammer in My Coffee? A Multimodal Imaging Investigation of Contextually Based Tool Understanding.

  J C Mizelle, Lewis A Wheaton

  Frontiers in human neuroscience. 01/2010; 4:233.

  Appropriate tool-object pairing is a natural part of our lives. When preparing to stir coffee, we know that a hammer is useful for some tasks but that it is not appropriate in this behavioral context. The neural correlates of this context-tool pairing process remain unclear. In the current work, we ... [more] Appropriate tool-object pairing is a natural part of our lives. When preparing to stir coffee, we know that a hammer is useful for some tasks but that it is not appropriate in this behavioral context. The neural correlates of this context-tool pairing process remain unclear. In the current work, we used event-related electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) to determine neural correlates for differentiating contextually correct and incorrect tool use. Subjects were shown images depicting correct (e.g., spoon used to stir coffee) or incorrect (e.g., hammer used to stir coffee) tool use. We identified distinct regional and temporal activations for identifying incorrect versus correct tool use. The posterior cingulate, insula, and superior temporal gyrus preferentially differentiated incorrect tool-object usage, while occipital, parietal, and frontal areas were active in identifying correct tool use. Source localized EEG analysis confirmed the fMRI data and showed phases of activation, where incorrect tool-use activation (0-200 ms) preceded occipitotemporal activation for correct tool use (300-400 ms). This work extends our previous findings to better identify the neural substrate for contextual evaluation of tool use, and may contribute to our understanding of neurological disorders resulting in tool-use deficits.
• 4.87

  Impact points

  Kinematic improvement following Botulinum Toxin-A injection in upper limb spasticity due to stroke.

  Esteban Fridman, Marcos Crespo, Santiago Gomez Argüello, Lorena Degue, Mirta Villarreal, Stephan Bohlhalter, Lewis Wheaton, Mark Hallett

  Journal of neurology, neurosurgery, and psychiatry. 12/2009;

  Background and purpose: Focal spasticity is a significant motor disorder following stroke. Botulinum Toxin Type-A (BoNT-A) is a useful treatment for it. We evaluated kinematic modifications induced by spasticity, and whether or not there is an improvement following injection of BoNT-A. METHODS: Eigh... [more] Background and purpose: Focal spasticity is a significant motor disorder following stroke. Botulinum Toxin Type-A (BoNT-A) is a useful treatment for it. We evaluated kinematic modifications induced by spasticity, and whether or not there is an improvement following injection of BoNT-A. METHODS: Eight stroke patients with upper limb spasticity, showing a flexor pattern, were evaluated using kinematics before and after focal treatment with BoNT-A. A group of sex and age-matched normal volunteers acted as a control group. RESULTS: Repeated-measure ANOVA showed that stroke patients performed slower in comparison to the control group. Following treatment with BoNT-A there was a significant improvement in kinematics in stroke patients while in the control group performance remained unchanged. CONCLUSIONS: Focal treatment of spasticity with Botulinum Toxin Type-A leads to an adaptive change in the upper limb of spastic stroke patients.
• 3.12

  Impact points

  Left parietal activation related to planning, executing and suppressing praxis hand movements.

  Lewis Wheaton, Esteban Fridman, Stephan Bohlhalter, Sherry Vorbach, Mark Hallett

  Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology. 05/2009;

  OBJECTIVE: We sought to investigate the activity of bilateral parietal and premotor areas during a Go/No Go paradigm involving praxis movements of the dominant hand. METHODS: A sentence was presented which instructed subjects on what movement to make (S1; for example, "Show me how to use a hamm... [more] OBJECTIVE: We sought to investigate the activity of bilateral parietal and premotor areas during a Go/No Go paradigm involving praxis movements of the dominant hand. METHODS: A sentence was presented which instructed subjects on what movement to make (S1; for example, "Show me how to use a hammer."). After an 8-s delay, "Go" or "No Go" (S2) was presented. If Go, they were instructed to make the movement described in the S1 instruction sentence as quickly as possible, and continuously until the "Rest" cue was presented 3s later. If No Go, subjects were to simply relax until the next instruction sentence. Event-related potentials (ERP) and event-related desynchronization (ERD) in the beta band (18-22Hz) were evaluated for three time bins: after S1, after S2, and from -2.5 to -1.5s before the S2 period. RESULTS: Bilateral premotor ERP was greater than bilateral parietal ERP after the S2 Go compared with the No Go. Additionally, left premotor ERP was greater than that from the right premotor area. There was predominant left parietal ERD immediately after S1 for both Go and No Go, which was sustained for the duration of the interval between S1 and S2. For both S2 stimuli, predominant left parietal ERD was again seen when compared to that from the left premotor or right parietal area. However, the left parietal ERD was greater for Go than No Go. CONCLUSION: The results suggest a dominant role in the left parietal cortex for planning, executing, and suppressing praxis movements. The ERP and ERD show different patterns of activation and may reflect distinct neural movement-related activities. SIGNIFICANCE: The data can guide further studies to determine the neurophysiological changes occurring in apraxia patients and help explain the unique error profiles seen in patients with left parietal damage.
• 3.48

  Impact points

  Discrete parieto-frontal functional connectivity related to grasping.

  Noriaki Hattori, Hiroshi Shibasaki, Lewis Wheaton, Tao Wu, Masao Matsuhashi, Mark Hallett

  Journal of neurophysiology. 01/2009;

  The human inferior parietal lobule (IPL) is known to have neuronal connections with the frontal lobe, and these connections have been shown to be associated with sensorimotor integration to perform various types of movement such as grasping. The function of these anatomical connections has not been ... [more] The human inferior parietal lobule (IPL) is known to have neuronal connections with the frontal lobe, and these connections have been shown to be associated with sensorimotor integration to perform various types of movement such as grasping. The function of these anatomical connections has not been fully investigated. We studied the judgment of graspability of objects in an event-related functional MRI study in healthy subjects, and found activation in two different regions within IPL; one in the left dorsal IPL extending to the intraparietal sulcus and the other in the left ventral IPL. The former region was activated only in the judgment of graspable objects while the latter was activated in the judgment of both graspable and non-graspable objects although the activation was greater for the graspable objects. Psychophysiological interaction analysis showed that these regions had similar, but discrete functional connectivity to the lateral and medial frontal cortices. In relation to this particular task, the left dorsal IPL had functional connectivity to the left ventral premotor cortex, supplementary motor area (SMA) and right cerebellar cortex, whereas the left ventral IPL had functional connectivity to the left dorsolateral prefrontal cortex and pre-SMA. These findings suggest that the connection from the left dorsal IPL is associated specifically with automatic flow of information about grasping behavior. By contrast, the connection from the left ventral IPL might be related to motor imagination or enhanced external attention to the presented stimuli.
• 2.32

  Impact points

  Reliability of TMS motor evoked potentials in quadriceps of subjects with chronic hemiparesis after stroke.

  Lewis A Wheaton, Federico Villagra, Daniel F Hanley, Richard F Macko, Larry W Forrester

  Journal of the neurological sciences. 11/2008;

  Transcranial magnetic stimulation (TMS) non-invasively measures excitability of central motor pathways in humans and is used to characterize neuroplasticity after stroke. Using TMS to index lower extremity neuroplasticity after gait rehabilitation requires test-retest reliability. This study assesse... [more] Transcranial magnetic stimulation (TMS) non-invasively measures excitability of central motor pathways in humans and is used to characterize neuroplasticity after stroke. Using TMS to index lower extremity neuroplasticity after gait rehabilitation requires test-retest reliability. This study assesses the reliability of TMS-derived variables measured at bilateral quadriceps of chronic hemiparetic stroke survivors. Results support using measures of both paretic and nonparetic motor threshold, motor evoked potential (MEP) latencies; and nonparetic MEP amplitudes. Implications for longitudinal research are discussed.
• 1.93

  Impact points

  Cortico-cortical networks in patients with ideomotor apraxia as revealed by EEG coherence analysis.

  Lewis A Wheaton, Stephan Bohlhalter, Guido Nolte, Hiroshi Shibasaki, Noriaki Hattori, Esteban Fridman, Sherry Vorbach, Jordan Grafman, Mark Hallett

  Neuroscience letters. 04/2008; 433(2):87-92.

  We sought to determine whether coherent networks which circumvent lesioned cortex are seen in patients with ideomotor apraxia (IMA) while performing tool-use pantomimes. Five normal subjects and five patients with IMA (three patients with corticobasal degeneration and two with left hemisphere stroke... [more] We sought to determine whether coherent networks which circumvent lesioned cortex are seen in patients with ideomotor apraxia (IMA) while performing tool-use pantomimes. Five normal subjects and five patients with IMA (three patients with corticobasal degeneration and two with left hemisphere stroke) underwent 64-channel EEG recording while performing three tool-use pantomimes with their left hand in a self-paced manner. Beta band (20-22 Hz) coherence indicates that normal subjects have a dominant left hemisphere network responsible for praxis preparation, which was absent in patients. Corticobasal degeneration patients showed significant coherence increase between left parietal-right premotor areas. Left hemisphere stroke patients showed significant coherence increases in a right parietofrontal network. The right hemisphere appears to store useable praxis representations in IMA patients with left hemisphere damage.
• 1.56

  Impact points

  Treatment of limb apraxia: moving forward to improved action.

  Laurel J Buxbaum, Kathleen Y Haaland, Mark Hallett, Lewis Wheaton, Kenneth M Heilman, Amy Rodriguez, Leslie J Gonzalez Rothi

  American journal of physical medicine & rehabilitation / Association of Academic Physiatrists. 03/2008; 87(2):149-61.

  Limb apraxia is a common disorder of skilled, purposive movement that is frequently associated with stroke and degenerative diseases such as Alzheimer disease. Despite evidence that several types of limb apraxia significantly impact functional abilities, surprisingly few studies have focused on deve... [more] Limb apraxia is a common disorder of skilled, purposive movement that is frequently associated with stroke and degenerative diseases such as Alzheimer disease. Despite evidence that several types of limb apraxia significantly impact functional abilities, surprisingly few studies have focused on development of treatment paradigms. Additionally, although the most disabling types of apraxia reflect damage to gesture and/or object memory systems, existing treatments have not fully taken advantage of principles of experience known to affect learning and neural plasticity. We review the current state of the art in the rehabilitation of limb apraxia, indicate possible points of contact with the learning literature, and generate suggestions for how translational principles might be applied to the development of future research on treatment of this disabling disorder.
• 1.37

  Impact points

  Exercise-mediated locomotor recovery and lower-limb neuroplasticity after stroke.

  Larry W Forrester, Lewis A Wheaton, Andreas R Luft

  Journal of rehabilitation research and development. 02/2008; 45(2):205-20.

  Assumptions that motor recovery plateaus within months after stroke are being challenged by advances in novel motor-learning-based rehabilitation therapies. The use of lower-limb treadmill (TM) exercise has been effective in improving hemiparetic gait function. In this review, we provide a rationale... [more] Assumptions that motor recovery plateaus within months after stroke are being challenged by advances in novel motor-learning-based rehabilitation therapies. The use of lower-limb treadmill (TM) exercise has been effective in improving hemiparetic gait function. In this review, we provide a rationale for treadmill exercise as stimulus for locomotor relearning after stroke. Recent studies using neuroimaging and neurophysiological measures demonstrate central nervous system (CNS) influences on lower-limb motor control and gait. As with studies of upper limbs, evidence shows that rapid transient CNS plasticity can be elicited in the lower limb. Such effects observed after short-term paretic leg exercises suggest potential mechanisms for motor learning with TM exercise. Initial intervention studies provide evidence that long-term TM exercise can mediate CNS plasticity, which is associated with improved gait function. Critical needs are to determine the optimal timing and intensities of TM therapy to maximize plasticity and learning effects.
• 2.26

  Impact points

  Preparatory band specific premotor cortical activity differentiates upper and lower extremity movement.

  Lewis A Wheaton, Mackenzie Carpenter, J C Mizelle, Larry Forrester

  Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale. 02/2008; 184(1):121-6.

  Event related desynchronization (ERD) allows evaluation of brain signals in multiple frequency dimensions. The purpose of this study was to determine left hemispheric non-primary motor cortex differences at varying frequencies of premovement ERD for similar movements by end-effectors of the upper an... [more] Event related desynchronization (ERD) allows evaluation of brain signals in multiple frequency dimensions. The purpose of this study was to determine left hemispheric non-primary motor cortex differences at varying frequencies of premovement ERD for similar movements by end-effectors of the upper and lower extremities. We recorded 32-channel electroencephalography (EEG) while subjects performed self-paced right ankle dorsiflexion and wrist extension. Electromyography (EMG) was recorded over the tibialis anterior and extensor carpi ulnaris. EEG was analyzed for premovement ERD within the alpha (8-12 Hz), low beta (13-18 Hz) and high beta (18-22 Hz) frequencies over the premotor, motor, and sensory areas of the left and mesial cortex from -1.5 to 0 s before movement. Within the alpha and high beta bands, wrist movements showed limited topography, but greater ERD over posterior premotor cortex areas. Alpha ERD was also significantly greater over the lateral motor cortex for wrist movements. In the low beta band, wrist movements provided extensive ERD differences to include the left motor and mesial/lateral premotor areas, whereas ankle movements showed only limited ERD activity. Overall, alpha and high beta activity demonstrated distinctions that are consistent with mapping of wrist and ankle representations over the sensorimotor strip, whereas the low beta representation demonstrated the clearest distinctions between the limbs over widespread brain areas, particularly the lateral premotor cortex. This suggests limited leg premovement activity at the dorsolateral premotor cortex. Low beta ERD may be reflect joint or limb specific preparatory activity in the premotor area. Further work is required to better evaluate the extent of this low beta activity for multiple comparative joints.
• 2.32

  Impact points

  Ideomotor apraxia: a review.

  Lewis A Wheaton, Mark Hallett

  Journal of the neurological sciences. 10/2007; 260(1-2):1-10.

  Ideomotor apraxia (IMA) is a disorder traditionally characterized by deficits in properly performing tool-use pantomimes (e.g., pretending to use a hammer) and communicative gestures (e.g., waving goodbye). These deficits are typically identified with movements made to verbal command or imitation. Q... [more] Ideomotor apraxia (IMA) is a disorder traditionally characterized by deficits in properly performing tool-use pantomimes (e.g., pretending to use a hammer) and communicative gestures (e.g., waving goodbye). These deficits are typically identified with movements made to verbal command or imitation. Questions about this disorder relate to its diagnosis, anatomical correlates, physiological mechanisms involved, and the patients in whom IMA is best characterized. In this review, utilizing information presented at an international workshop, we summarize the present state of knowledge about IMA. We include insights on how to distinguish IMA from the other motor apraxias and confounding disorders. We discuss testing for IMA and the need for more rigorous tests that examine more elements, such as imitation, actual use, task selection, and recognizing proper use. From neurophysiological insights, we propose hypotheses of the necessity of networks in praxis performance. We also point out that more neurophysiological knowledge in humans might lead to a better understanding of how different brain structures may aid in the rehabilitation of praxis. While little is known about exactly how rehabilitation may be pursued, biological evidence warrants the further exploration of this issue.
• 2.26

  Impact points

  How does the brain respond to unimodal and bimodal sensory demand in movement of the lower extremity?

  Lewis A Wheaton, J C Mizelle, Larry W Forrester, Ou Bai, Hiroshi Shibasaki, Richard F Macko

  Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale. 07/2007; 180(2):345-54.

  Numerous electroencephalography (EEG) studies have shown that neurophysiological signals change in response to visual and sensory adaptations in upper extremity tasks. However, this has not been clearly studied in the lower extremity. In this study, we evaluated how sensory loading affects brain act... [more] Numerous electroencephalography (EEG) studies have shown that neurophysiological signals change in response to visual and sensory adaptations in upper extremity tasks. However, this has not been clearly studied in the lower extremity. In this study, we evaluated how sensory loading affects brain activations related to knee movement. Thirty-two channel EEG was recorded while ten subjects performed knee extension in four different conditions: no weight and no visual target (NWNT), weight affixed to the ankle and no visual target (WNT), no weight and a visual target (NWT), and both weight and target (WT). Surface electromyography (EMG) was recorded from the vastus medialis and vastus lateralis muscles to determine onset of the movement. EEG was epoched from -4.5 s before to 1 s after EMG onset. Epochs were averaged to acquire movement-related cortical potentials (MRCPs) of each task condition. MRCP amplitude during the pre-movement period from -2 s to EMG onset was evaluated at electrodes over motor, sensory, frontal, and parietal areas. The amplitude of the pre-movement potentials for the conditions was different across areas of interest. Over the motor area, NWNT had lower amplitude than any other condition and WT had higher amplitude than any other condition. There was no difference between unimodal NWT and WNT conditions. Mesial frontal and parietal areas showed larger MRCP to the bimodal condition than either unimodal or NWNT conditions. The parietal cortex was the only region that showed a difference between unimodal conditions with greater amplitude for NWT condition. Information concerning added sensory demand is processed by the motor cortex in a way that may be indifferent to the type of modality, but is influenced by the quantity of modalities at the level of the knee. Other brain structures such as parietal and premotor cortices respond based on the modality type to help plan appropriate strategies for motor control in response to sensory manipulations. This suggests that additional task demands in motor training may create a rich sensory environment that may be beneficial in promoting optimal neuromotor recovery.
• 7.18

  Impact points

  Parietal representations for hand-object interactions.

  Lewis A Wheaton

  The Journal of neuroscience : the official journal of the Society for Neuroscience. 02/2007; 27(5):969-70.