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M Wiesendanger

Publications and source records attributed to M Wiesendanger.

At least 37 records · Page 2Linked to original sources
PubMed1999

Eye-hand coordination in uni- and bimanual goal-oriented tasks.

Two different drawer tasks were investigated with the aim of assessing the role of eye movements in well-coordinated hand movements. In an unimanual step-tracking task, which had a predictive and an unpredictive movement, a two-way repeated-measures ANOVA showed a significant effect of prediction on the onset of grip-force (GF) rate (300+/-39 ms for the predictive condition versus 394+/-53 ms for the non-predictive condition, P<0.0001). Correlation coefficients, computed from the eye and the hand movements were low for the right and the left hand. The saccade was more coupled with the visual step change than with the action of the hand per se. In a second bimanual pull-and-pick task, the instruction was to pull a drawer with the left hand from a closed position to a LED-cued open position and then to grasp and reinsert a small peg in the drawer with the right hand. Correlation coefficients, computed from the latencies of saccades and of the leading left hand or of the right hand, were significant in four of five subjects. Intermanual correlations were significant in all five subjects. In conclusion, we found that the initial saccade in the unimanual task was best related with the visual step change, but was poorly correlated with the pulling/pushing hand. In the bimanual task, a moderate, but significant temporal coupling between the eyes and hand events was observed. This coupling was, however, less tight than that between both hands.

Acoustic Stimulation↗
PubMed1999

Time structure of a goal-directed bimanual skill and its dependence on task constraints.

The aim of the study was to elucidate the underlying principles of bimanual coordination and to establish quantitative coordination criteria. Healthy human subjects were instructed to open a loaded drawer with the left hand and to grasp, lift and reinsert with the right hand a small peg in the drawer recess. This bimanual goal-oriented task was executed promptly and consistently after a few trials. The temporal structure of the individual limb actions was assessed for computing interlimb synchronization and temporal correlation. In all subjects, both hands were well synchronized at the goal with high intermanual correlation in reaching the goal (event times of drawer opening and grasping the peg). This temporal goal-invariance was independent of movement speed and of the highly variable timing of the individual hands and persisted when subjects were blindfolded. Unilateral loading of the pulling hand and cutaneous anesthesia of the left index finger and thumb used for grasping the drawer handle significantly increased the pull-phase. This slowing of the left hand was matched by an adaptive delay of the right non-disturbed hand, thus preserving goal invariance. As a working hypothesis, we propose that multimodal sensory signals generated in the leading arm be transmitted centrally to re-parameterize the non-disturbed arm.

Adult↗
PubMed1999

Neural activity of supplementary and primary motor areas in monkeys and its relation to bimanual and unimanual movement sequences.

A chronic single-unit study of motor cortical activity was undertaken in two monkeys trained to perform a bimanually coordinated task. The hypothesis was tested that the supplementary motor area plays a specific role in coordinating the two hands for common goal-oriented actions. With this objective, a special search was made for neurons that might exhibit properties exclusively related to bimanual task performance. Monkeys learned to reach for and to pull open a spring-loaded drawer with one hand, while the other hand reached out to grasp food from the drawer recess. The two hands were precisely coordinated for achievement of this goal. Monkeys also performed, in separate blocks of trials, only the pulling or grasping movements, using the same hands as in the bimanual task. Task-related activity of 348 neurons from the supplementary motor area and 341 neurons from the primary motor area, each examined in the bimanual and in both unimanual tasks, was recorded in the two hemispheres. Most neurons from the supplementary motor area were recorded within its caudal microexcitable portion. Contrary to expectation, the proportion of neurons with activity patterns related exclusively to the bimanual task was small, but somewhat higher in the supplementary motor area (5%) than in the primary motor cortex (2%). Another group of neurons that were equally modulated during the bimanual as well as to both unimanual task components might also contribute in controlling bimanual actions. Such "task-dependent" rather than "effector-dependent" activity patterns were more common in neurons of the supplementary motor area (19%) than of the primary motor cortex (5%). Bilateral receptive fields were also more numerous among the supplementary motor area neurons. However, a large majority of neurons from primary and supplementary motor areas had activity profiles clearly related only to contralateral hand movements (65% in the primary motor and 51% in the supplementary motor area). A similar group of neurons showed an additional slight modulation with ipsilateral movements; they were equally common in the two areas (14% and 16%, respectively) and their significance for bimanual coordination is questionable. Summed activity profiles of all neurons recorded in the primary and supplementary motor areas of the same hemisphere were compared. The modulations of the three histograms, corresponding to the two unimanual and the bimanual tasks, were similar for the two motor areas, i.e. prominent with bimanual and contralateral movements and weak with ipsilateral movements. It is concluded that the supplementary motor area is likely to contribute to bimanual coordination, perhaps more than the primary motor cortex, but that it is not a defining function for the former cortical area. Instead, it is suggested that the supplementary motor area is part of a callosally interconnected and distributed network of frontal and parietal cortical areas that together orchestrate bimanual coordination.

Animals↗
PubMed1999

Role of the cerebellum in tuning anticipatory and reactive grip force responses.

The aim of our study was to determine if load perturbations that could destabilize grasp control are adequately controlled by cerebellar patients. We examined patients with unilateral cerebellar lesions who had largely recovered from their initial symptoms and compared grip force regulation for the affected and unaffected hand during a drawer-opening task. Two experimental paradigms were included: (1) a brief load perturbation during a self-stopped drawer pull and (2) a loading impact when the drawer was pulled out to the mechanical stop. The results showed that when a self-stopped movement was perturbed during its trajectory, anticipatory grip force increase was smaller for the affected than for the unaffected hand, illustrating a disturbed gain control due to cerebellar dysfunction. When the mechanical stop arrested the movement, the amount of grip force did not differ significantly between the affected and unaffected side; however, both hands used different control strategies. Whereas the unaffected hand anticipated the load perturbation by a ramp-like increase of grip force toward the impending impact, the affected hand increased grip force at movement onset to a default level and maintained this value until the task was ended. In addition, the latency between impact and reactive peak in grip force was prolonged for the affected hand, suggesting a delayed cerebellar transmission of reactive responses. In conclusion, these findings demonstrate that the cerebellum is involved in anticipatory and reactive mechanisms dealing with load perturbations during goal-directed behavior.

Adaptation, Physiological↗
PubMed1998

Effects of lesions in the mesial frontal cortex on bimanual co-ordination in monkeys.

The hypothesis was tested that the mesial frontal cortex, including the supplementary motor area, is engaged in bimanual co-ordination. Three monkeys, trained in a well-co-ordinated bimanual pull-and-grasp task, were subjected to unilateral or bilateral lesions of the mesial frontal cortex. With unilateral lesions, the deficit consisted in a delay in movement initiation of the contralateral arm. With a bilateral lesion, the deficit was more pronounced with marked bilateral delays in movement onset and slowing in reaching. However, in the three monkeys bimanual co-ordination at the moment of goal achievement remained intact with an excellent temporal co-variation of the two limbs. In the two unilateral cases, an adaptive strategy developed after a few sessions, either by catching up during reaching with the limb contralateral to the lesion (monkey M1) or by delaying movement initiation of the limb ipsilateral to the lesion (monkey M2). This outcome is discussed in terms of Lashley's principle of motor equivalence, i.e. invariant goal achievement with variable means. Bilateral lesions led to a transient and near-total impairment in movement self-initiation when all external cues were absent. It is concluded that in monkeys the mesial frontal cortex does not play a crucial role in bimanual co-ordination but rather in movement initiation, especially when sensory cues are absent.

Animals↗
PubMed1998

Dexterity in adult monkeys following early lesion of the motor cortical hand area: the role of cortex adjacent to the lesion.

Infant monkeys were subjected to unilateral lesions of the motor cortex (mainly its hand representation). After maturation, they showed normal use of the contralateral hand for global grip movements. However, as compared with the ipsilateral hand, precision grip tasks requiring relatively independent finger movements were performed with less dexterity, particularly if adjustments of the wrist position were necessary. The purpose of this study was to investigate mechanisms which may be responsible for the rather well, although not complete, preservation of manipulative behaviour of these adult monkeys. To this end, the hand representations were mapped bilaterally with intracortical microstimulation in the mature monkeys, and the dexterity of both hands assessed quantitatively in a precision grip task. The behavioural effects of reversible inactivations of the primary (M1) and supplementary (SMA) motor cortical areas were then tested. The following were found. (i) The hand contralateral to the lesion exhibited subtle but significant dexterity deficits, as compared with the ipsilateral hand; the deficit was essentially for complex movements requiring dissociation of the thumb-index finger pinch from the other digits, involving also an arm rotation. (ii) Reversible inactivation of the M1 hand representation in the intact hemisphere dramatically impaired dexterity of the opposite hand without affecting the ipsilateral hand (contralateral to the early lesion). (iii) A relatively complete hand representation was found to occupy a new territory, medial to the old lesion. (iv) The role of this new displaced representation was crucial for the preserved dexterity of the opposite hand, as evidenced by its functional inactivation. In contrast, inactivation of both SMA cortices did not interfere with the manipulative behaviour. It is thus concluded that the preserved functional capacity of manipulations with the hand opposite the early lesion can be essentially attributed to a cortical reorganization around the old lesion. Under the present experimental conditions, contributions from either the SMA or the intact M1 appear not to be crucial.

Animals↗
PubMed1995

[The doctrine of brain localization and its development in the 20th century].

The discovery of the cerebral motor cortex in the last third of the 19th century has decisively influenced the doctrine of cerebral localization. It has dominated brain research from there on. Its considerable practical importance for focalized local diagnosis was recognized from the clinical point of view. As a consequence, interdisciplinary institutions for brain research developed in Europe and in the USA for the study of functional localization in the brain by means of cyto- and myeloarchitecture, electrical brain stimulation and lesion experiments in close connection with clinico-neurologic centers. From this research resulted the cerebral cortical maps with more or less numerous areas linked to either sensory, motor or 'higher' psychic functions. An intensive, emotional critique developed against the brain-localization theory from its onset. This article demonstrates that the arguments of the anti-localizationists gave rise in part to new knowledge about some principles of cerebral function. Some of these are the concept of 'diaschisis' (distant effects of acute lesions and functional recovery, von Monakow, 1902), the concept of 'motor equivalence' (Lashley, 1930) and of neuronal plasticity of the cerebral cortex (Cajal, 1911). Furthermore, modern imaging techniques (position emission tomography, functional nuclear spin resonance) show that complex functions in particular, such as the natural, targeted arm and grasp synergy, are not 'localized' within a small area of the cortex but do activate multiple neuronal networks interconnected dynamically and in alternating composition in the process of movement initiation and execution.

Brain↗
PubMed1994

Cerebellothalamocortical and pallidothalamocortical projections to the primary and supplementary motor cortical areas: a multiple tracing study in macaque monkeys.

The goal of the present study was to clarify whether the primary motor cortex (M1) and the supplementary motor cortex (SMA) both receive, via the motor thalamus, input from cerebellar and basal ganglia output nuclei. This is the first investigation that explores the problem by direct comparison, in the same animal, of thalamic zones that 1) project to M1 and SMA and 2) receive cerebellar-nuclear (CN) and pallidal (GP) afferents. These four zones were mapped in two monkeys by means of two retrograde tracers for M1 and SMA injections and of two anterograde tracers for CN and GP injections. All injections were performed under electrophysiological control (microstimulation and multiunit recordings). Injections in cortical areas were restricted to the hand/arm representation; in the SMA, the tracer deposit was within the "SMA-proper" (or "area F3") and did not include its rostral extension ("pre-SMA" or "area F6"). It was found that zones of all four types formed a number of highly complex patches of labeling that were usually not confined to one cytoarchitectonically defined thalamic nucleus. The overlap of clusters of labeled terminals and perikarya was evaluated morphometrically (area measurements) on a number of coronal sections along the anteroposterior extent of the motor thalamus. In line with previous studies, the thalamic territories innervated by CN and GP afferents rarely overlapped. However, zones projecting to M1 and/or to SMA included thalamic regions receiving CN as well as GP projections, providing the first evidence of such overlap from individual animals. The present observations support the previous conclusion from this laboratory (based on transsynaptic labeling) that the SMA receives, apart from its strong pallidal transthalamic input, a CN transthalamic input. These present findings that both M1 and SMA are recipients of transthalamic inputs from GP and CN thus support the concept that a mixed subcortical input consisting of weighted contributions from cerebellum, basal ganglia, substantia nigra, and spinothalamic tract is directed to each functional component of the sensorimotor cortex.

Animals↗
PubMed1994

Temporal structure of a bimanual goal-directed movement sequence in monkeys.

The aim of the present investigation was to assess a bimanual goal-oriented movement sequence with particular emphasis on its temporal structure. The three monkeys (Macaca fascicularis) used in this study chose the left arm as the leading and more postural arm to reach out and pull back a spring-loaded drawer containing a food morsel. The right arm followed the left and picked up the food with a precision grip. Video recordings, trajectory recordings of the two index fingers, drawer displacement and the measurements of discrete events of the left and right hand revealed a considerable trial-by-trial variability in the temporal and spatial domain. The variability of latencies progressively increased from the initiation of the bimanual sequence to the left-hand and right-hand events defining goal achievement. The main result was that, in spite of this variability in each of the two limbs, there was an invariant left-right goal-related synchronization. The timing of the goal-related event pairs covaried and showed high correlation coefficients. Covariation of the two hands resulting in an invariant synchronization was particularly striking when monkeys performed the task without vision, and timing of right and left movement components was delayed with further increase in variability. The results indicate that, in the present bimanual skill, kinaesthetic signals may be sufficient to coordinate the two limbs in a goal-oriented unitary action in accord with a memorized plan.

Acoustic Stimulation↗
PubMed1994

Transcallosal connections of the distal forelimb representations of the primary and supplementary motor cortical areas in macaque monkeys.

The goal of the present neuroanatomical study in macaque monkeys was twofold: (1) to clarify whether the hand representation of the primary motor cortex (M1) has a transcallosal projection to M1 of the opposite hemisphere; (2) to compare the topography and density of transcallosal connections for the hand representations of M1 and the supplementary motor area (SMA). The hand areas of M1 and the SMA were identified by intracortical microstimulation and then injected either with retrograde tracer substances in order to label the neurons of origin in the contralateral motor cortical areas (four monkeys) or, with an anterograde tracer, to establish the regional distribution and density of terminal fields in the opposite motor cortical areas (two monkeys). The main results were: (1) The hand representation of M1 exhibited a modest homotopic callosal projection, as judged by the small number of labeled neurons within the region corresponding to the contralateral injection. A modest heterotopic callosal projection originated from the opposite supplementary, premotor, and cingulate motor areas. (2) In contrast, the SMA hand representation showed a dense callosal projection to the opposite SMA. The SMA was found to receive also dense heterotopic callosal projections from the contralateral rostral and caudal cingulate motor areas, moderate projections from the lateral premotor cortex, and sparse projections from M1. (3) After injection of an anterograde tracer (biotinylated dextran amine) in the hand representation of M1, only a few small patches of axonal label were found in the corresponding region of M1, as well as in the lateral premotor cortex; virtually no label was found in the SMA or in cingulate motor areas. Injections of the same anterograde tracer in the hand representation of the SMA, however, resulted in dense and widely distributed axonal terminal fields in the opposite SMA, premotor cortex, and cingulate motor areas, while labeled terminals were clearly less dense in M1. It is concluded that the hand representations of the SMA and M1 strongly differ with respect to the strength and distribution of callosal connectivity with the former having more powerful and widespread callosal connections with a number of motor fields of the opposite cortex than the latter. These anatomical results support the proposition of the SMA being a bilaterally organized system, possibly contributing to bimanual coordination.

Animals↗
PubMed1994

The problem of bimanual coupling: a reaction time study of simple unimanual and bimanual finger responses.

The properties of the sensorimotor system controlling finger movements were investigated in the simple uni- and bimanual reaction time (RT) paradigm, with emphasis on the problem of interhemispheric transfer of sensory and motor information. Unimanual and bimanual responses of the index fingers were elicited by stimulation of either left or right hand and resulting reaction times were compared to assess the degree of right-left differences and thus also of crossed-uncrossed differences (CUD). The response consisted of a force pulse (first dorsal interosseus muscle) which was elicited by a non-painful electrical stimulus applied to the base of the middle finger. In unimanual experiments, the population analysis showed that RTs obtained with contralateral stimuli were significantly longer (6 msec) than RTs elicited with ipsilateral stimuli. However, inter-subject differences were large and sometimes pointed in the non-expected direction (crossed < uncrossed). Statistically significant right-left differences in RT were detected in the bimanual response paradigm, but these differences occurred in both directions with the crossed RT either longer or shorter than uncrossed RT. The analysis of the correlation structure of bimanual RT suggested the presence of stimulus-related asymmetries of the hands. These observations provide some support for the notion of an additional processing time related to interhemispheric transmission of sensory and/or motor signals. In addition, it turned out that factors other than callosal transmission can also produce asymmetries in RTs of the two hands. Thus some subjects had consistent right-left differences which were unrelated to callosal transmission. Asymmetries were also introduced by changing the stimulation side. In the light of this multi-factorial influence, we argue that the underlying mechanisms leading to intermanual asymmetries in RT cannot be attributed exclusively to callosal transmission.

Adult↗
PubMed1994

Temporal coordination in bimanual actions.

The issue of bimanual temporal coordination in human subjects is discussed for three selected movement paradigms: (i) simple, symmetric, bimanual finger movements, (ii) bimanual unloading, and (iii) a complex bimanual pull and grasp task. Temporal synchronization was found for all three experiments and was least variable for the first experiment. In the second experiment, synchronization concerned unloading with the index finger of one hand (electromyographic activation of the first dorsal interosseus muscle) and the postural adjustment of the load-bearing index finger of the other hand (electromyographic deactivation of the first dorsal interosseus muscle). In the third experiment, a goal-related temporal invariance was observed, even in the absence of visual guidance. Possible neural mechanisms for the observed temporal coordination of the three types of bimanual movements are discussed, as well as the concepts of goal invariance and motor equivalence.

Fingers↗
PubMed1994

Epidemiology of IDDM in Switzerland. Increasing incidence rate and rural-urban differences in Swiss men born 1948-1972.

OBJECTIVE: To determine the incidence of insulin-dependent diabetes mellitus (IDDM) in Switzerland by undertaking a retrospective analysis of the registry of the Swiss army, which contains updated medical files for all male Swiss citizens. Nation-wide data for IDDM epidemiology have not been available in Switzerland. RESEARCH DESIGN AND METHODS: Every male Swiss citizen is obliged to enlist in the Swiss military service at 19 years of age, when a personal, continuously updated medical file is established. Diabetes is an exclusion condition for military service and is clearly marked in the file. A total number of 514,747 files, corresponding to birth year cohorts 1948-1950, 1955-1957, 1962-1964, and 1970-1972, have been manually checked for the diagnosis of IDDM. RESULTS: IDDM was identified in 926 cases in the four groups of three age-cohorts. The incidence at < or = 15 years (per 100,000/year) was 4.5 in the age cohorts 1948-1950 and 7.2 in the age cohorts 1970-1972 (P < 0.005). An additive age-cohort Poisson regression model fits the nationwide incidences adequately, neither a period effect nor age x cohort interactions being required. In the oldest age cohorts, the age-specific incidence of IDDM was calculated up to the age of 43 and was approximately 7/100,000/year in men between 20 and 40. In these age cohorts, we found an approximately 50% higher risk to develop IDDM at age < or = 19 for men living in an urban region and a significantly (P < 0.005) increased incidence between 20 and 40 years in rural regions compared with urban regions. CONCLUSIONS: The incidence of IDDM in Switzerland is comparable to other countries in central Europe and has been increasing in the last 20 years. This is in accordance to most recent epidemiological studies worldwide. In addition, the data suggest exogenous factors inducing IDDM at a younger age in urban regions.

Adolescent↗
PubMed1993

Modulation of sustained electromyographic activity by single intracortical microstimuli: comparison of two forelimb motor cortical areas of the rat.

In rats, a rostral and a caudal forelimb motor area (RFA and CFA, respectively) have been distinguished on the basis of intracortical microstimulation effects (see Neafsey et al., 1986, for a review). The goal of the present study was to assess and compare their relative connectional strength with target motor units of the forelimb. This was achieved by averaging modulation responses of sustained electromyographic (EMG) activity triggered by single intracortical microstimuli (S-ICMS) of relatively low intensity (mostly below 35 microA) to minimize both direct and transsynaptic current spread. In chronically prepared and ketamine-sedated rats, this method produced prominent peaks and troughs in the averaged EMG at short latencies with S-ICMS currents as low as 5 microA. S-ICMS at 30-50 microA in CFA sometimes even elicited visible twitches and an EMG burst of the contralateral wrist or digits following each stimulation pulse. Increasing S-ICMS currents to about 1.5 mA revealed a sudden shortening of EMG response latencies, which was most likely induced by current spread to brainstem motor centers. S-ICMS at near-threshold intensity in the majority of effective sites in both CFA and RFA produced modulation responses in more than one group of forelimb muscles, frequently also including muscles of the ipsilateral forelimb. Usually the ipsilateral responses were weaker, as were the suppression effects. Comparison of CFA and RFA revealed similar effects in terms of the number of modulated muscle groups and the response latencies. In contralateral wrist/digit muscles, facilitation responses were elicited at latencies of 9.7 +/- 1.8 msec (CFA) and 9.6 +/- 1.9 msec (RFA), with the shortest latencies around 6 msec. However, modulations by S-ICMS in RFA had significantly smaller amplitudes, had slower rates of buildup, and required higher thresholds than those obtained from S-ICMS in CFA. It is concluded, on the basis of the S-ICMS method, that both the CFA and the RFA exert a prominent and relatively direct influence on forelimb motoneurons. The present findings, together with calculations of conduction time, suggest that a contingent of corticospinal axons of the rat has oligosynaptic and possibly even monosynaptic connections with forelimb motoneurons. The recruitment of a relatively large number of muscles, including those of the ipsilateral forelimb, by S-ICMS in both areas may be explained by the prominent divergence of corticospinal axons. Further investigations are required to understand the relative positions and roles of the two areas in motor control and their possible homology with primary and nonprimary motor areas of primates.

Animals↗
PubMed1992

Feedforward postural stabilization in a distal bimanual unloading task.

The aim of the present study was to investigate postural adjustments and positional stability in a bimanual unloading task, involving essentially the index finger, in order to test whether proactive adjustments are also observed in distal body segments. A second goal of the study was to evaluate the concept of a central command that would be responsible for coupling movement and posture. The positional disturbance of the right load-bearing index finger of healthy human subjects was studied under two types of manipulations: passive, i.e., imposed, unloading and active unloading, by the subject's left index finger. It was found that, in such a distal task, positional stabilization of the load-bearing finger was much better (by a factor of 6) in the active situation than the passive situation. This improvement was greater than previously reported for a proximal task. An electromyogram (EMG) analysis of the mostly implicated dorsal interosseous muscles revealed a typical unloading reflex in the passive situation (reactive mode) and a suppression of EMG before unloading onset in the active situation (proactive mode). Averaged records showed an almost perfect synchronization between the EMG suppression in the load-bearing interosseous muscle and the onset of the EMG burst of the unloading index finger. A trial-by-trial analysis, however, revealed a considerable scatter in intervals of the two EMG events, with a tendency of the activity burst in the left finger to occur slightly before the suppression of EMG in the load-bearing muscle. No positive correlation was found between the precision of synchronization (intervals near zero time) and the accuracy of performance, i.e., positional stability of the unloaded finger. Although the trial-by-trial variability was large, it is suggested that at least some of this variability is caused by a nonsteady state of motoneuronal excitability. In view of the low-pass property of the muscle, the observed variability in synchronization may be sufficiently precise to maintain the hypothesis of a central temporal coupling of the events in the two hands through a common command. However, the lack of a correlation between the degree of synchronization and the performance in stability argues rather in favor of separate commands to the two hands that select the parameters in the spatial domain. Finally, an intermanual EMG or torque analysis is proposed that might be useful in assessing the accuracy in goal achievement, i.e., the maintenance of a stable finger position in spite of the "internal" perturbation.

Electromyography↗