Biomedical subjects

C Dohle

Publications and source records attributed to C Dohle.

13 recordsLinked to original sources

PubMed2001

The effect of the Ebbinghaus illusion on grasping behaviour of children.

Within the context of the Ebbinghaus illusion, adults regularly misjudge the physical size of a centre disc, yet scale their hand aperture according to its actual size. Separate visual pathways for perception and action are assumed to account for this finding. The dorsal visual stream is said to elaborate on egocentric (visuomotor), while the ventral stream is involved in allocentric transformations (object recognition). This study examines the ontogenetic development of this dissociation between perception and action in 35 children between the ages of 5 and 12 years. We report four major results. First, when children judged object size without grasping the disc, their judgements were deceived by the illusion to the same extent as adults. However, when asked to estimate size and then to grasp the disc, young children's (5-7 years) perceptual judgements became unreliable, while adults were still reliably deceived by the illusion in 80% of their trials. Second, the younger the children, the more their aperture was affected by the illusional surround. Discs of the same size were grasped with a smaller aperture when surrounded by a small annulus, although they were perceived as being larger. Third, young children used the largest safety margin during grasping. Fourth, the reliance on visual feedback decreased with increasing age, which was documented by shorter movement times and earlier maximum hand opening during grasping in the older children (feedforward control). Our results indicate that grasping behaviour in children is subject to an interaction between ventral and dorsal processes. Both pathways seem not to be functionally segregated in early and middle childhood. The data are inconclusive about whether young children predominantly use a specific visual stream for either a perceptual or motor task. However, our data demonstrate that children were relying on both visual processing streams during perceptual as well as visuomotor tasks. We found that children used egocentric cues to make perceptual judgements, while their grasping gestures were not exclusively shaped by viewer-centred but also by object-centred information.

Aging↗

PubMed2001

Motor impairment in patients with parietal lesions: disturbances of meaningless arm movement sequences.

The execution of meaningless movement sequences was studied in 12 patients with lesions of the parietal cortex in comparison to the performance of age- and sex-matched controls. Five sequences of increasing complexity had to be performed by imitation and after verbal instruction. The performance errors were qualitatively scored by means of four error categories (temporal or spatial error, addition or omission of movement components). This study examined whether the error scores depended on instruction modality, movement complexity or lesion side. Patients with left parietal lesions produced more errors than those with right parietal lesions and control subjects. While additions or omissions of movement components occurred almost equally in all groups, temporal and spatial errors were more frequent in patients with left parietal lesions only. In addition, only the latter group showed a significant increase of error rates with increasing movement complexity. There were no significant differences between the contra- and ipsilesional hand in any group. These results demonstrate that lesions in the left parietal lobe lead to a disturbed spatio-temporal organisation of movement that becomes increasingly prominent for more complex movements.

Adult↗

PubMed2000

Different coupling for the reach and grasp components in bimanual prehension movements.

In this study on functional coupling in bimanual grasping movements, nine normal subjects had to reach and grasp two different objects simultaneously. Both objects could be either small or large, resulting in four different conditions of bimanual grasping. The main dependent variables were the coupling coefficients calculated either between the hand displacements or between the grip apertures of both hands, serving as variables for the coupling of the reach and the grasp component respectively. The correlation was significantly higher for the reach component than for the grasp component, with only the latter one changing significantly with variation of object size. These findings suggest different temporo-spatial coupling modes for the reach and the grasp components of bimanual grasping movements.

Adult↗

PubMed2000

Zinc sulphate induces metallothionein in pancreatic islets of mice and protects against diabetes induced by multiple low doses of streptozotocin.

AIMS/HYPOTHESIS: Diabetes is induced by multiple low doses of streptozotocin (MLD-STZ) in male mice of susceptible strains. In this model beta-cell injury and T-cell-mediated inflammatory reactions are induced. Probably, reactive oxygen species (ROS) participate in the destruction of beta cells. The effects of ROS can be counterbalanced by several antioxidant systems. One of these is metallothionein (MT), cytosolic proteins that are induced by zinc ions (Zn2+) and scavenge hydroxyl radicals (OH). The effect of Zn2+ on MLD-STZ-diabetes was studied. METHODS: We gave C57BL/6 and (C57BL/6 x SJL)F1 hybrid mice either MLD-STZ or in addition Zn2+-enriched drinking water. We analysed metallothionein ex vivo in pancreatic islets for protein and mRNA concentration for the isoforms 1 and 2. Pancreatic sections were examined by immunohistochemistry for metallothionein and histologically for insulitis. RESULTS: In both strains, Zn2+-enriched drinking water significantly up-regulated metallothionein and prevented MLD-STZ-diabetes and loss of beta-cell function. In the F1 hybrid mice a variant of MLD-STZ-diabetes was observed. These mice developed hyperglycaemia 10 weeks after the first injection of STZ (in contrast to 2 weeks observed in other mouse strains) and pronounced insulitis. The mRNA of the metallothionein isoforms 1 and 2 were constitutively expressed and slightly up-regulated by Zn2+-enriched drinking water. All islets cells stained for metallothionein. CONCLUSIONS/INTERPRETATIONS: Drinking water enriched with Zn2+ significantly up-regulated metallothionein production in pancreatic islets of mice and prevented diabetes induced with MLD-STZ.

Animals↗

PubMed1999

Mirror agnosia and mirror ataxia constitute different parietal lobe disorders.

We describe two new clinical syndromes, mirror agnosia and mirror ataxia, both characterized by the deficit of reaching for an object through a mirror in association with a lesion of either parietal lobe. Clinical investigation of 13 patients demonstrated that the impairments affected both sides of the body. In mirror agnosia, the patients always reached toward the virtual object in the mirror and they were not capable of changing their behavior even after presentation of the position of the object in real visual space. In mirror ataxia (resembling optic ataxia) although some patients initially tended to reach for the virtual object in the mirror, they soon learned to guide their arms toward the real object, all of them producing many directional errors. Both patient groups performed poorly on mental rotation, but only the patients with mirror agnosia were impaired in line orientation. Only 1 of the patients suffered from neglect and 3 from apraxia. Magnetic resonance imaging showed that in mirror agnosia the common zone of lesion overlap was scattered around the posterior angular gyrus/superior temporal gyrus and in mirror ataxia around the postcentral sulcus. We propose that both these clinical syndromes may represent different types of dissociation of retinotopic space and body scheme, or likewise, of allocentric and egocentric space normally adjusted in the parietal lobe.

Adult↗

PubMed1999

The role of ventral medial wall motor areas in bimanual co-ordination. A combined lesion and activation study.

Two patients with midline tumours and disturbances of bimanual co-ordination as the presenting symptoms were examined. Both reported difficulties whenever the two hands had to act together simultaneously, whereas they had no problems with unimanual dexterity or the use of both hands sequentially. In the first patient the lesion was confined to the cingulate gyrus; in the second it also invaded the corpus callosum and the supplementary motor area. Kinematic analysis of bimanual in-phase and anti-phase movements revealed an impairment of both the temporal adjustment between the hands and the independence of movements between the two hands. A functional imaging study in six volunteers, who performed the same bimanual in-phase and anti-phase tasks, showed strong activations of midline areas including the cingulate and ventral supplementary motor area. The prominent activation of the ventral medial wall motor areas in the volunteers in conjunction with the bimanual co-ordination disorder in the two patients with lesions compromising their function is evidence for their pivotal role in bimanual co-ordination.

Adult↗

PubMed1998

Force regulation is deficient in patients with parietal lesions: a system-analytic approach.

By means of a quantitative system-analytic investigation strategy, the postural motor control of the fingers was evaluated, to characterise the possible deficit of force regulation in patients with parietal lesions. In spite of a normal response to short torque pulses, the parietal-lesion patients had difficulties in returning to the preload level after the application of an additional step torque load to fingers II-IV of their left or right hands. The control offset (measured 500 ms after step torque application) was significantly larger in the patient group. This deficit in the investigated patients with parietal lesions to compensate for step torque loads was not due to a paresis, but rather resulted from a disturbance in the generation of a sufficient counterforce against the applied step torque within an adequate time window and motor pattern. This distinct force-regulation deficit was found in patients with left- and right-sided parietal lesions.

Adult↗

PubMed1998

Human anterior intraparietal area subserves prehension: a combined lesion and functional MRI activation study.

It has been shown in nonhuman primates that the posterior parietal cortex is involved in coordination of arm and eye movements in space, whereas the anterior intraparietal area in the anterior lateral bank of the intraparietal sulcus plays a crucial role in fine finger movements, such as grasping. In this study we show by optoelectronic movement recordings that patients with cortical lesions involving the anterior lateral bank of the intraparietal sulcus have selective deficits in the coordination of finger movements required for object grasping, whereas reaching is much less disturbed. Patients with parietal lesions sparing the cortex lining the anterior intraparietal sulcus showed intact grasping behavior. Complementary evidence was obtained from functional MRI in normal control subjects showing a specific activation of the anterior lateral bank of the intraparietal sulcus during grasping. In conclusion, this combined lesion and activation study suggests that the anterior lateral bank of the intraparietal sulcus, possibly including the human homologue of the anterior intraparietal area, mediates the processing of sensorimotor integration of precisely tuned finger movements in humans.

Adult↗

PubMed1996

Virtual holography in diagnosis and therapy of sensorimotor disturbances.

It has been shown that VR techniques can be usefully applied in the field of sensorimotor disturbances. Virtual scenarios can be created in which patients perform specific motor tasks. Using an optoelectronic position tracking system for motion recording as well as for interaction with virtual objects, and using Virtual Holography as an adequate visualization technique, we are now developing and testing suitable scenarios. Furthermore, an advanced visualization and animation tool using VR technology for diagnosis purpose and therapy planning has been developed, which the physician can profit from during motion analysis.

Computer Graphics↗

PubMed1995

Ataxic breathing during alternating forearm movements of various frequencies in cerebellar patients.

Breathing was analyzed at rest and during sinusoidal tracking movements of the forearm of the dominant side at various frequencies in 11 patients with a cerebellar impairment and in 9 healthy subjects. In the patients, breathing movements were always rhythmical as in normal subjects during rest, but sometimes were interrupted by intermittent breathing-arrests during tracking (breathing ataxia). In 9 of the 11 cerebellar patients, the normal phase relationships between breathing and forearm movements at target frequencies in the spontaneous breathing rate range were absent. Thus patients with cerebellar lesions not only show disturbed skeletomotor movements, but also show an impaired coordination between breathing and limb movements.

Adult↗

PubMed1995

Virtual reality for physically disabled people.

This paper demonstrates how physically disabled people can benefit from the innovative virtual reality techniques. Several specific examples show the applicability of virtual reality to the therapy and rehabilitation of people with various disabilities. In addition, the paper describes how physicians can use virtual reality as an advanced visualization tool for the diagnosis of physical disabilities. Finally, possible display techniques and input devices for diagnosis and rehabilitation purposes are discussed briefly.

Attitude of Health Personnel↗

PubMed1993

Prevention of high- and low-dose STZ-induced diabetes with D-glucose and 5-thio-D-glucose.

To induce hyperglycemia in mice by administration of STZ, two experimental protocols that involve different pathogenic pathways are being used. First, the intraperitoneal injection of a single high dose (HD-STZ) exerts direct toxicity on beta-cells, which results in necrosis within 48-72 h and overt permanent hyperglycemia. Second, injections of multiple low doses of STZ (LD-STZ), administered intraperitoneally on 5 consecutive days, induce both beta-cytotoxic effects and STZ-specific T-cell-dependent immune reactions. In LD-STZ models, only a combination of toxic and immunological effects result in gradually increasing hyperglycemia, provided male mice of susceptible strains are being used. In this study, we found that 5-T-G, a glucose analogue that has sulfur for oxygen in the pyranose ring, prevented, in a dose-dependent way, both HD-STZ- and LD-STZ-induced hyperglycemia and that D-G, which was only tested in the LD-STZ system, was also protective, albeit somewhat less so than 5-T-G. This protective effect was achieved by intraperitoneally injecting 5-T-G and D-G, respectively, right before each STZ injection. Protection against hyperglycemia was already achieved with a total of 3 injections of 5-T-G, 1 injection each given before the first 3 of 5 LD-STZ injections. By means of OGTT, it was determined that pretreatment with 5-T-G afforded protection from substantial beta-cell damage in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

T cell-dependent class II major histocompatibility complex antigen expression in vivo induced by the diabetogen streptozotocin.

Immune reactions are involved in the low-dose streptozotocin (STZ)-model of hyperglycemia (1). By means of the popliteal lymph node assay, we demonstrated that T cell-dependent lymphoproliferation can be evoked by STZ (2). The present report shows that class II MHC antigen expression is readily inducible in multiple organs by a single dose of STZ injected subcutaneously (s.c.) into BALB/cJ mice. An increment of class II-positive cells of the lymphocyte and monocyte/macrophage lineage is discernible in the endocrine pancreas, kidney, and liver, but not the brain. In addition, renal tubular and bile duct epithelium express strong class II positivity. Class II antigens are not visible on pancreatic endocrine cells and hepatocytes. These immune phenomena are T cell-dependent, as assessed in tissues from BALB/cJ nu/nu recipients and their +/nu counterparts. STZ-induced class II antigens develop transiently and are not necessarily associated with organ dysfunction. The present STZ-induced MHC class II antigen aberrancies are in agreement with observations described recently by COCKFIELD et al. (3). In addition, we found that injection of methylnitrosourea, the aglycone of STZ, also resulted in class II MHC molecule induction in the liver, whereas the diabetogen alloxan failed to exert any effect on class II antigens.

Alloxan↗