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Petreska B.,Ecole Polytechnique Federale de Lausanne | Billard A.,Ecole Polytechnique Federale de Lausanne | Hermsdorfer J.,Clinical Neuropsychology Research Group EKN | Goldenberg G.,Bogenhausen Hospital | Goldenberg G.,TU Munich

Callosal disconnection can reveal asymmetrical contributions of the two brain hemispheres to praxis. In this paper, we revisit a study of a patient with callosal disconnection (Goldenberg et al., 2001, Neuropsychologia, 39:1432-1443), who perfectly imitated meaningless gestures when imitation was controlled only by the left hemisphere, but was severely impaired when the right hemisphere was in charge of motor control. We decomposed the gestures into a set of geometric variables that were to be reproduced, such as the orientation of the hand and the position of contact between the hand and the face. Whereas orientation of the hand in extrinsic coordinates was replicated correctly by both hemispheres, only the left hemisphere reproduced correctly the position of contact between the hand and the face. This goal-dissociation as well as several partial perseveration errors speak against the hypothesis of a direct route from perception to motor replication of gestures, as interruption of a direct route would probably impair all the features of the gesture. We speculate that incorrect coordination between the reproductions of multiple goals may be the core deficit underlying callosal apraxia. © 2010 Elsevier Ltd. Source

Brendel B.,University of Tubingen | Erb M.,University of Tubingen | Riecker A.,University of Ulm | Grodd W.,University of Tubingen | And 2 more authors.
Motor Control

The present study combines functional magnetic resonance imaging (fMRI) and reaction time (RT) measurements to further elucidate the influence of syllable frequency and complexity on speech motor control processes, i.e., overt reading of pseudowords. Tying in with a recent fMRI-study of our group we focused on the concept of a mental syllabary housing syllable sized ready-made motor plans for high- (HF), but not low-frequency (LF) syllables. The RT-analysis disclosed a frequency effect weakened by a simultaneous complexity effect for HF-syllables. In contrast, the fMRI data revealed no effect of syllable frequency, but point to an impact of syllable structure: Compared with CV-items, syllables with a complex onset (CCV) yielded higher hemodynamic activation in motor "execution" areas (left sensorimotor cortex, right inferior cerebellum), which is at least partially compatible with our previous study. We discuss the role of the syllable in speech motor control. © 2011 Human Kinetics, Inc. Source

Hermsdorfer J.,TU Munich | Hermsdorfer J.,Clinical Neuropsychology Research Group EKN | Li Y.,TU Munich | Randerath J.,University of Oregon | And 2 more authors.

Studying the characteristics of movements performed under different action conditions may foster the understanding of disturbed tool use in apraxia and may enhance the knowledge about the links between states of action representations.We registered hand and arm movements during a hammering action executed under three task conditions: pantomime, demonstration with the hammer only, and actual execution with hammer and nail. Various movement parameters were calculated to characterize the kinematic aspects of the hammering movements. An apraxia score that reflects conceptual errors was derived from video-evaluation of pantomiming. Twenty-three patients with left brain damage (LBD), 10 patients with right brain damage (RBD), and 19 control subjects were tested. Patients performed with the non-paretic ipsilesional hand.Four apraxic LBD patients failed to perform the task due to severe conceptual errors. The remaining LBD patients frequently produced movements that were slower, shorter, and less vertical than those of control subjects in all task conditions. Lesion analyses for the LBD patients suggested that inferior frontal areas were particularly responsible for impaired performance. RBD patients performed normally in most kinematic task aspects. Although the conditions differed characteristically in geometry and kinematics, correlations of performance measures indicated that individual patterns in patients as well as in control subjects were stable across the conditions.Performance stability across conditions and the overlapping neural network both support the concept of a general action prototype that is adapted flexibly to environmental constraints. Findings in patients show that LBD can affect the execution of an actual hammering action also in the absence of conceptual errors. It remains to be shown however whether conceptual errors and abnormalities of movement kinematics have a common cause or are two independent manifestations of damage to the motor-dominant brain. © 2011 Elsevier Ltd. Source

Hogrefe K.,Clinical Neuropsychology Research Group EKN | Ziegler W.,Clinical Neuropsychology Research Group EKN | Weidinger N.,Clinical Neuropsychology Research Group EKN | Goldenberg G.,Clinical Neuropsychology Research Group EKN | Goldenberg G.,TU Munich

Patients suffering from severe aphasia have to rely on non-verbal means of communication to convey a message. However, to date it is not clear which patients are able to do so. Clinical experience indicates that some patients use non-verbal communication strategies like gesturing very efficiently whereas others fail to transmit semantic content by non-verbal means. Concerns have been expressed that limb apraxia would affect the production of communicative gestures. Research investigating if and how apraxia influences the production of communicative gestures, led to contradictory outcomes. The purpose of this study was to investigate the impact of limb apraxia on spontaneous gesturing. Further, linguistic and non-verbal semantic processing abilities were explored as potential factors that might influence non-verbal expression in aphasic patients. Twenty-four aphasic patients with highly limited verbal output were asked to retell short video-clips. The narrations were videotaped. Gestural communication was analyzed in two ways. In the first part of the study, we used a form-based approach. Physiological and kinetic aspects of hand movements were transcribed with a notation system for sign languages. We determined the formal diversity of the hand gestures as an indicator of potential richness of the transmitted information. In the second part of the study, comprehensibility of the patients' gestural communication was evaluated by naive raters. The raters were familiarized with the model video-clips and shown the recordings of the patients' retelling without sound. They were asked to indicate, for each narration, which story was being told and which aspects of the stories they recognized. The results indicate that non-verbal faculties are the most important prerequisites for the production of hand gestures. Whereas results on standardized aphasia testing did not correlate with any gestural indices, non-verbal semantic processing abilities predicted the formal diversity of hand gestures while apraxia predicted the comprehensibility of gesturing. © 2011 Elsevier Srl. Source

Schneider A.S.,Schon Klinik Munich Harlaching | Schneider A.S.,Clinical Neuropsychology Research Group EKN | Furholzer W.,Clinical Neuropsychology Research Group EKN | Marquardt C.,Clinical Neuropsychology Research Group EKN | Hermsdorfer J.,TU Munich
Clinical Neurophysiology

Objective: Writer's cramp is defined as a task specific focal dystonia generating hypertonic muscle co-contractions during handwriting resulting in impaired writing performance and exaggerated finger force. However, little is known about the generalisation of grip force across tasks others than writing. The aim of the study was to directly compare regulation of grip forces during handwriting with force regulation in other fine-motor tasks in patients and control subjects. Methods: Handwriting, lifting and cyclic movements of a grasped object were investigated in 21 patients and 14 controls. The applied forces were registered in all three tasks and compared between groups and tasks. In addition, task-specific measures of fine-motor skill were assessed. Results: As expected, patients generated exaggerated forces during handwriting compared to control subjects. However there were no statistically significant group differences during lifting and cyclic movements. The control group revealed a generalisation of grip forces across manual tasks whereas in patients there was no such correlation. Conclusion: We conclude that increased finger forces during handwriting are a task-specific phenomenon that does not necessarily generalise to other fine-motor tasks. Significance: Force control of patients with writer's cramp in handwriting and other fine-motor tasks is characterised by individualised control strategies. © 2013 International Federation of Clinical Neurophysiology. Source

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