Biomedical subjects

Joachim Hermsdörfer

Publications and source records attributed to Joachim Hermsdörfer.

At least 19 recordsLinked to original sources

PubMed2006

Dexterity in cerebellar agenesis.

Given the well established role of the cerebellum in motor control, deficient motor performance during life time appears to be common in cerebellar agenesis. However, behavioural data on motor performance in living subjects with cerebellar agenesis are scarce. Dexterity during object manipulation was comparatively investigated in a 63-year old female with cerebellar agenesis and three healthy age- and gender-matched control subjects. Participants performed a transport task with an instrumented object and caught a weight that was dropped into a hand-held receptacle either expectedly from the opposite hand or unexpectedly from the experimenter's hand. Compared to healthy subjects, the subject with cerebellar agenesis generated greater grasping forces. For the transport task the patient showed a clear impairment of the predictive adjustment of grasping forces to the differential loading requirements of movement direction. For the weight-catching task, the patient established an accurate reactive mode of control when the weight was dropped unexpectedly. In case the weight was dropped expectedly from the opposite hand, predictive control mechanisms were severely disturbed in the subject with cerebellar agenesis. These data highlight the role of the cerebellum for predictive force control and are interpreted within the concept of internal models reflecting the causal relationship between actions and their consequences.

Aged↗

PubMed2006

Modified pen grip in the treatment of Writer's Cramp.

Writer's Cramp (WC) is a focal, action-related dystonia, which induces hypertonic co-contractions and severely impairs handwriting. One behavioral treatment approach is the handwriting training developed by Mai and Marquardt (1999), [Mai, N., & Marquardt, C. (1999). Schreibtraining in der neurologischen Rehabilitation. In EKN-Materialien für die Rehabilitation. Dortmund: Borgmann] which includes among various motor exercises the use of a modified pen grip (stabilized between index and middle finger). This pen grip has proven particularly successful in clinical practice. The current study aims at elucidating the immediate effects of the modified pen grip on writing in 23 WC patients and 11 healthy controls. All participants wrote a sentence with their usual and also with the modified pen grip. Movement and pressure were recorded with a digitizing tablet. Pressure, movement time for the whole sentence, script size and writing fluency were analyzed. When writing with their usual pen grip, pressure in the WC patients was elevated, and writing speed was decreased compared to healthy controls. Changing over to the modified pen grip reduced the pressure significantly in WC patients and controls, but left other aspects of their writing unaffected. This shows that the use of the modified pen grip is an effective way to normalize pen pressure in WC patients, thereby providing the best conditions for the training of speed and fluency.

Adult↗

PubMed2006

Spatial and kinematic features of apraxic movement depend on the mode of execution.

Knowledge about the dependency of apraxic movements on the mode of execution may enhance the understanding of apraxia and of the cerebral representation of actions. We examined a common tool-use action in nine patients with left hemisphere damage and apraxia. Arm movements during the use of a handsaw were measured and tested in three different modes of execution: pantomime, pantomime with a bar shaped like the handle of the saw, and actual sawing. Analysis concentrated on spatial and kinematic features of the wrist trajectories during these repetitive movements. In healthy control subjects, both pantomime conditions differed from actual use mainly by larger amplitudes during miming. Apraxic patients executed large proportions of their pantomiming movements in an incorrect direction away from the appropriate anteroposterior direction, while other movement features were normal. The availability of the handle-like bar did not improve performance. During actual use, movement direction was constraint by mechanical demands. In this condition patients moved with moderately decreased velocity. However, this deficit was not related to the errors in movement direction characteristic of pantomiming. These data suggest that pantomiming and actual execution of an action are dictated by different external requirements and constraints, pantomiming serves to convey information, while actual use has to obey the mechanical demands of the task. Due to these differences, spatial and kinematic movement features in healthy subjects vary between the modes of execution, movements are differently vulnerable to apraxia, and deficits in patients may dissociate.

Adult↗

PubMed2006

Predictive and reactive control of grasping forces: on the role of the basal ganglia and sensory feedback.

We comparatively investigated predictive and reactive grip force behaviour in 12 subjects with basal ganglia dysfunction (six subjects with Parkinson's disease, six subjects with writer's cramp), two subjects chronically lacking all tactile and proprioceptive sensory feedback and 16 sex- and age-matched control subjects. Subjects held an instrumented receptacle between the index finger and thumb. A weight was dropped into the receptacle either unexpectedly from the experimenter's hand with the subject being blindfolded or expectedly from the subject's opposite hand. This paradigm allowed us to study predictive and reactive modes of grip force control. All patients generated an overshoot in grip force, irrespective of whether the weight was dropped expectedly or unexpectedly. When the weight was dropped from the experimenter's hand, a reactive grip force response lagged behind the load perturbation at impact in patients with basal ganglia dysfunction and healthy controls. When the weight was dropped expectedly from the subject's opposite hand, patients with basal ganglia dysfunction and healthy subjects started to increase grip force prior to the release of the weight, indicating a predictive mode of control. We interpret these data to support the notion that the motor dysfunction in basal ganglia disorders is associated with deficits of sensorimotor integration. Both deafferented subjects did not show a reactive mode of force control when the weight was dropped unexpectedly, underlining the importance of sensory feedback to initiate reactive force responses. Also in the predictive mode, grip force processing was severely impaired in deafferented subjects. Thus, at least intermittent sensory information is necessary to establish and update predictive modes of grasping force control.

Adult↗

PubMed2005

Objective evaluation of manual performance deficits in neurological movement disorders.

Impaired hand function is a frequent finding in movement disorders. The skilled control of prehensile finger forces is an essential feature of tool use in daily life. In healthy subjects, grip force is precisely adjusted to the mechanical object properties, such as weight and surface friction. Grip force is accurately scaled to be only a small amount higher than the minimum necessary to prevent a hand-held object from slipping. When an object is lifted and moved around in space, grip force is modulated in parallel with the movement-induced fluctuations in load. The absence of a temporal delay between grip and load force profiles implies that the central nervous system is able to predict the load variations before the intended manipulation. Sensory information is used to adjust the level of applied finger forces efficiently to the requirements of the mechanical object properties and the task at hand. The characteristics of impaired finger force control include inefficient grip force scaling and imprecision of the temporal coupling between grip and load force profiles. Here, we review the characteristics of deficient grip force behavior in movement disorders, e.g. Parkinson's disease, task-specific dystonia, Gille de la Tourette's syndrome and cerebellar disease. Grip force analysis is a highly sensitive method to document even subtle impairments of finger force control and may be used both as a diagnostic tool and for the objective evaluation of treatment in neurological movement disorders.

Fingers↗

PubMed2005

Preserved and impaired aspects of predictive grip force control in cerebellar patients.

OBJECTIVE: To analyze preserved and impaired aspects of feedforward grip force control during cyclic arm movements with a hand-held object after cerebellar damage. METHODS: We tested eight subjects with unilateral or bilateral cerebellar pathologies and eight healthy control subjects. Participants performed cyclic vertical arm movements with a hand held instrumented object at three different speeds. RESULTS: Compared to controls, patients excerted increased grip forces. The minimum force ratio between grip force and load force was constant across all movement frequencies, suggesting that patients anticipated speed-related changes in load magnitudes by adjusting the grip force. Thus the scaling of grip force level to self-generated load magnitudes was preserved. The coupling between grip and load profiles was assessed by cross correlation analysis. Patients exhibited significantly decreased maximum coefficients of cross correlation implicating impaired anticipation of inertial load fluctuations. However feedforward control could be preserved, as obvious from zero time lags of the maximum cross correlation coefficient. CONCLUSIONS: Our findings suggest that cerebellar lesions affect the processing of predictive grip force modulation in anticipation of inertial loads. Our results add further evidence to the theoretical concept that the cerebellum implements internal feedforward models. However, preserved functions may indicate compensatory mechanisms or extra-cerebellar aspects of grip and load force regulation. SIGNIFICANCE: The observed dissociation of performance deficits may have direct clinical implication and may guide the development of individual therapeutic strategies for patients with cerebellar disorders.

Adult↗

PubMed2005

Left inferior parietal dominance in gesture imitation: an fMRI study.

The inability to imitate gestures is an essential feature of apraxia. However, discrepancies exist between clinical studies in apraxic patients and neuroimaging findings on imitation. We therefore aimed to investigate: (1) which areas are recruited during imitation under conditions similar to clinical tests for apraxic deficits; (2) whether there are common lateralized areas subserving imitation irrespective of the acting limb side; and also (3) whether there are differences between hand and finger gestures. We used fMRI in 12 healthy, right handed subjects to investigate the imitation of four types of variable gestures that were presented by video clips (16 different finger and 16 different hand gestures with either the right or the left arm). The respective control conditions consisted of stereotyped gestures (only two gestures presented in pseudorandom order). Subtraction analysis of each type of gesture imitation (variable>stereotyped) revealed a bilateral activation pattern including the inferior parietal cortex Brodmann Area (BA 40), the superior parietal cortex, the inferior frontal cortex (opercular region), the prefrontal motor cortex, the lateral occipito-temporal junction, and the cerebellum. These results were supported by statistical conjunction of all four subtraction analyses and by the common analysis of all four types of gesture imitation. The direct comparison of the right and left hemispheric activation revealed a lateralization to the left only of the inferior parietal cortex. Comparisons between different types of gesture imitation yielded no significant results. In conclusion, gesture imitation recruits bilateral fronto-parietal regions, with significant lateralization of only one area, namely the left inferior parietal cortex. These in vivo data indicate left inferior parietal dominance for gesture imitation in right handers, confirming lesion-based theories of apraxia.

Adult↗

PubMed2005

Grip force behavior during object manipulation in neurological disorders: toward an objective evaluation of manual performance deficits.

The control of prehensile finger forces is an essential feature of skilled manual performance. The basic aspects of healthy grip force behavior have been well documented. In healthy subjects, grip force is precisely adjusted to the mechanical object properties. Grip force is always slightly higher than the minimum necessary to prevent the object from slipping. When we move a hand-held object, grip force is modulated in parallel with movements-induced load fluctuations without an obvious delay. The absence of a temporal delay between grip and load force profiles suggests that the central nervous system is able to predict the load variations before the intended manipulation and consequently regulates grip force in anticipation. Feedback from the grasping fingertips is used to adjust the level of applied fingertip force efficiently to the actual loading requirements. Pathologic grip force control affects the efficiency of produced force and the precision of the temporal coupling between grip and load force profiles. Here, we review the characteristics of pathologic grip force behavior in various neurological disorders. Detailed examination of grip force control is simple and well suited for the objective evaluation of impaired motor function of the hand and its rehabilitation.

Biomechanical Phenomena↗

PubMed2005

Impaired generalization of weight-related information during grasping in cerebellar degeneration.

When we repetitively lift an object, the balance between grip force normal to the object's surface and load force tangential to the object's surface is accurately programmed to match the physical object properties within a few lifts. Here, we ask if the accuracy of grip force scaling to object weight and the transfer of weight-related information from one hand to the other is impaired in cerebellar degeneration. Subjects with generalized cerebellar degenerative disorders were tested. Subjects first repeatedly lifted a constant weight with the dominant hand, followed by a series of lifts of the same weight with the opposite hand. The experiments were performed with a light and a heavy weight. Patients and controls scaled the grip force output differentially to different weight. The comparison of grip force scaling for the first and last lifts with a constant weight demonstrated that healthy subjects and cerebellar patients adjusted grip forces more accurately to a specific weight with increasing number of lifts performed at each hand. The ability to transfer weight-related information from one hand to the other was analyzed by comparing the last lift with a constant weight of the dominant hand with the first lift of the same weight performed by the opposite hand. Healthy subjects scaled the grip force output precisely to a given weight immediately after a change in hand, suggesting that they succeeded to transfer weight-related information in between both hemispheres. In contrast, cerebellar patients produced an inaccurate grip force overshoot when lifting a given weight with the opposite hand. Our data suggest that the cerebellum plays a major role for the generalization of weight-related information during object manipulation.

Aged↗

PubMed2005

It takes the whole brain to make a cup of coffee: the neuropsychology of naturalistic actions involving technical devices.

Left hemisphere dominance has been established for use of single familiar tools and tool/object pairs, but everyday action in natural environment frequently affords multi-step actions with more or less novel technical devices. One purpose of our study was to find out whether left hemisphere dominance extends to such naturalistic action. Another aim was to analyze the cognitive components contributing to success or failure. Patients with LBD and aphasia, patients with RBD, and healthy controls were examined on experimental tests assessing retrieval of functional knowledge from semantic memory, inference of function from structure, and solution of mechanical and non-mechanical multi-step problems, and were confronted with two naturalistic tasks involving technical devices: preparing coffee with a drip coffee maker and fixing a cassette recorder. Both patient groups were about equally impaired on both naturalistic actions. Analysis of the experimental tests and their correlations to naturalistic actions suggested that different cognitive deficits caused failure in both patient groups, and that in LBD patients there were also different causes for failure on both naturalistic actions. The main difficulty of RBD patients seemed to reside in the demand to keep track of multi-step actions. In aphasic LBD patients difficulties with making coffee but not the cassette recorder were correlated with aphasia and defective retrieval of functional knowledge from semantic memory, whereas the cassette recorder correlated more strongly with a test probing solution of multi-step mechanical problems. Inference of function from structure which had been shown to be important for use of single familiar tools or tool/objects pairs [Goldenberg, G., Hagmann, S. (1998). AT Tool use and mechanical problem solving in apraxia. Neuropsychologia, 36, 581-589] appeared to play only a subordinate role for naturalistic actions involving technical devices.

Activities of Daily Living↗

PubMed2005

Manual and hemispheric asymmetries in the execution of actual and pantomimed prehension.

Impairments of the ipsilesional hand after brain damage have been reported in goal-directed motor acts and in pantomimes; the relationship between both movement conditions is largely unknown. In the presented study, pantomimed and actual prehension was examined in 29 stroke patients with left brain damage (LBD) or right brain damage (RBD) as well as in 21 control subjects. Kinematic analyses revealed various performance differences between the conditions of movement execution and the subject groups. The differences depended on the hand tested and on the side of the brain lesion. During actual prehension deviations from normal performance were obvious in the peak velocity of the transport component of the movement, which was reduced in RBD patients, and in the duration of the final adjustment phase, which was prolonged in both patient groups. Pantomime changed various features of movement execution. The transport component was particularly altered in the groups performing with the right hand. Hand aperture was significantly smaller during pantomime than during actual movement execution in all groups. However, this effect was particularly obvious in LBD patients, in whom the hand aperture was even completely absent during many of their pantomimes. Actual movement execution immediately preceding the pantomimes did not change the characteristic features of pantomimes. Thus, the cerebral processes for actually executed and pantomimed motor acts differ. Actual movements seem to be governed by external affordances and constraints; whereas, pantomimes may represent a symbolic act. During prehension, differences in grip formation reveal most directly this dichotomy. We argue that the left hemisphere plays a special role in the generation of the symbolic act; a lesion may abolish grip formation and causes the clinical symptom of apraxia.

Adult↗

PubMed2004

Moving objects in a rotating environment: rapid prediction of Coriolis and centrifugal force perturbations.

Grip force adaptation to Coriolis and centrifugal force perturbations was tested in healthy subjects. Eight subjects were seated in a rotating chamber in a rotating axis position. They each grasped an instrumented object resting on the thumb, which was stabilized by the other fingers from above. Subjects performed horizontal point-to-point movements with the grasped object away and towards the trunk. These movements were directed in a nonparallel fashion towards the axis of rotation prior (40 pre-rotational movements), during (80 per-rotational movements) and following (40 post-rotational movements) clockwise body rotation. During pre- and post-rotational movements two load force peaks of similar magnitude occurred during the acceleratory and deceleratory phases of the movements. Accordingly, a Coriolis force, which was orthogonal and proportional to the linear velocity of the moving arm, as well as a centrifugal force proportional to the system's squared angular velocity and movement amplitude developed during per-rotational movements. The load perturbations altered the load force profile in a characteristic way. The first 10 per-rotational movement sequence revealed that there was a less precise coupling between grip and load force magnitudes and a reduced temporo-spatial co-ordination between grip and load force profiles. With increasing number of per-rotational movements, there was significant improvement in the temporo-spatial co-ordination and in the coupling in force magnitude between grip and load force profiles, indicating an ongoing adaptation process. The coupling between grip and load forces proved to be similarly precise for the last 10 per-rotational movements and for pre-rotational movements, suggesting complete adaptation. Significant effects were observed for the first post rotational movements following adaptation to the per-rotational load characteristics both for the temporal co-ordination between grip and load forces and for the coupling in force magnitudes. However, the last 10 post-rotational movements proved to be similarly precise with comparison to pre-rotational performance in terms of grip force regulation with movement-induced loads. The results are discussed within the context of the CNS ability to use internal models when planning and processing anticipatory grip force adjustments during manipulative tasks.

Acoustic Stimulation↗

PubMed2004

Memory for fingertip forces: passive hand muscle vibration interferes with predictive grip force scaling.

When subjects repetitively lift an object, the grip force they select is influenced by the mechanical object properties of the preceding lift. Similar effects on grip force scaling are observed whether the subsequent lift is performed with the same hand or the hand contralateral to the preceding lift. Here we demonstrate that passive vibration of the hand muscles involved in the generation of grip force in the interval between two blocks of lifting trials interferes with predictive grip force scaling. Following ten trials in which subjects lifted an object with constant mechanical properties with the dominant hand, muscle vibration was given to the first interosseus and adductor pollicis muscles of the dominant hand during a 10-min rest period. Compared with the last lift preceding vibration, peak rates of grip force increase and peak grip forces were scaled too high during the first lift following vibration whether the lift was made with the dominant or non-dominant hand. Subjects scaled grip force accurately to the object properties within three lifts following vibration. If subjects rested for 10 min after the first ten trials and received no vibration, then there was no significant difference in the peak grip force or its rate of increase between the last lift preceding rest and the first lift following it. We suggest that vibration impairs the memory processes responsible for predictive grip force scaling. Our data are consistent with the recent suggestion that these memory processes are neither specific for a certain motor action nor do they reflect internal representations of mechanical object properties.

Adult↗

PubMed2004

[Analysis of grip force during object manipulation. Method for the objective measurement of physiological normal and impaired hand function].

The control of prehensile finger forces is an essential feature of all skilled manual performance. The basic aspects of healthy grip force control have been well documented within the past two decades. In healthy subjects, grip force is accurately adjusted to the mechanical object properties such as weight, surface friction, and shape: when we move a hand-held object, grip force is modulated in parallel with movement-induced load fluctuations without an apparent temporal delay. At all phases of the movement, grip force is always slightly higher than the minimum necessary to prevent the object from slipping. The absence of a temporal delay between grip and load force profiles implies that the central nervous system is able to predict load variations precisely before the intended manipulation, and consequently regulates grip force in anticipation. Feedback from the grasping fingertips is used to adjust the force level efficiently to the actual load requirements. Pathologic grip force control affects the efficiency of the forces produced and the predictive temporal coupling between grip and load force profiles. Here we demonstrate pathologic grip force control in various neurologic disorders. The analysis of grip force control is simple and highly sensitive for detecting healthy and pathologic motor behaviour. The examination of grip force control is well suited for an objective evaluation of therapy during sensorimotor rehabilitation of deficient hand function.

Diagnosis, Computer-Assisted↗

PubMed2004

Deficits of anticipatory grip force control after damage to peripheral and central sensorimotor systems.

Healthy subjects adjust their grip force economically to the weight of a hand-held object. In addition, inertial loads, which arise from arm movements with the grasped object, are anticipated by parallel grip force modulations. Internal forward models have been proposed to predict the consequences of voluntary movements. Anesthesia of the fingers impairs grip force economy but the feedforward character of the grip force/load coupling is preserved. To further analyze the role of sensory input for internal forward models and to characterize the consequences of central nervous system damage for anticipatory grip force control, we measured grip force behavior in neurological patients. We tested a group of stroke patients with varying degrees of impaired fine motor control and sensory loss, a single patient with complete and permanent differentation from all tactile and proprioceptive input, and a group of patients with amyotrophic lateral sclerosis (ALS) that exclusively impairs the motor system without affecting sensory modalities. Increased grip forces were a common finding in all patients. Sensory deficits were a strong but not the only predictor of impaired grip force economy. The feedforward mode of grip force control was typically preserved in the stroke patients despite their central sensory deficits, but was severely disturbed in the patient with peripheral sensory deafferentation and in a minority of stroke patients. Moderate deficits of feedforward control were also obvious in ALS patients. Thus, the function of the internal forward model and the precision of grip force production may depend on a complex anatomical and functional network of sensory and motor structures and their interaction in time and space.

Afferent Pathways↗

PubMed2004

Predictive and reactive finger force control during catching in cerebellar degeneration.

We investigated how patients with cerebellar degeneration control fingertip forces to resist a perturbation imposed on a handheld load. Patients and healthy sex- and age-matched control subjects held an instrumented receptacle between the index finger and thumb. A weight was dropped into the receptacle either unexpectedly from the experimenter's hand with the subject being blindfolded or expectedly from the subject's opposite hand. This paradigm allowed us to study predictive and reactive modes of finger force control. Patients generated an overshoot of grip force, irrespective of whether the weight was dropped expectedly or unexpectedly. When the weight was dropped from the experimenter's hand, grip force lagged behind the load perturbation at impact in patients and controls. When the weight was dropped expectedly from the subject's opposite hand, healthy subjects started to increase grip force prior to the release of the weight. This observation is indicative for a predictive mode of force control. In contrast, the grip force profile of cerebellar patients was not processed in anticipation of the time of impact when the weight was dropped from the opposite hand. Our data suggest involvement of cerebellar circuits in a predictive, but less in a reactive, mode of fingertip force control during manipulative behavior.

Acceleration↗

PubMed2003

Predictability influences finger force control when catching a free-falling object.

We studied grip force control when catching a free-falling object with the dominant hand. An instrumented object was dropped either from the subjects' opposite hand or expectedly from the experimenter's hand. Following digit-object contact, triggered responses were observed in the load and grip force profiles. The peak rates of load force increase and the peak load forces produced at the time the catching fingers made contact with the object were of similar magnitude for the experimenter- and self-release conditions. However, the peak rates of grip force development and the peak grip forces were more pronounced when the object was dropped by the experimenter. These findings suggest that the prediction of the load magnitude was less precise when the object was dropped from the experimenter's hand. In addition, a correlation analysis between maximum grip and load force rates revealed a less precise coupling between the force rates in the experimenter-release condition. The time lags between maximum force rates and maximum forces were longer for the experimenter-release than for the self-release condition. These observations may indicate a less precise temporal coupling between grip and load force profiles in the experimenter-release condition. As observed during other manipulative tasks, the co-ordination between grip and load forces is a prerequisite to cope with collision forces when catching free-falling objects. Grip force control during catching is both highly automatic and flexible depending on the predictability of the task.

Adult↗

PubMed2003

Grip force efficiency in long-term deprivation of somatosensory feedback.

A subject with complete and chronic absence of cutaneous and proprioceptive feedback applied inefficiently elevated grip forces to lift and hold instrumented objects of varying weight. However, the ability to differentially scale grip forces according to various weights (0.36 kg, 0.61 kg and 0.86 kg) was mainly maintained when the subject was allowed to lift a constant weight repeatedly under constant visual control. The normally very precise temporal coupling between grip and load forces was substantially disturbed for lifts performed by the deafferented subject. In particular, maximum grip force lagging some 100 ms behind maximum load, suggesting rather feedback-based than predictive grip force control. Our findings demonstrate the importance of cutaneous and proprioceptive afferents for predictive regulation of prehensile finger forces. However, alternative sensory signals, e.g. from visual cues, small myelinated and unmyelinated muscle afferents or neck proprioception, may provide some provisional grip force control in the absence of cutaneous and proprioceptive feedback.

Adult↗