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Biomedical subjects

A Straube

Publications and source records attributed to A Straube.

At least 19 recordsLinked to original sources
PubMed2001

Mislocalization of peripheral targets during fixation.

To investigate the effect of the visual stimulus configuration on localization when oculomotor performance is excluded, we evaluated the errors made when subjects compare the horizontal location of two sequentially presented peripheral targets while looking at a visual or memorized fixation spot. Eye position was monitored by means of an infrared eye tracker. Significant localization errors were observed. As long as the fixation spot stayed on or off during the entire presentation time of both peripheral targets, the localization error did not depend on the presence or absence of the fixation spot. A significant change in the localization error was observed only if the fixation spot was presented together with the first peripheral target but disappeared before the presentation of the second one. The localization error did not depend on: (1) the visual asymmetry (unilateral versus bilateral target presentation); (2) the distribution of visual attention (cued versus non-cued test location); or (3) the time interval between the two targets. These results suggest that the mislocalization observed during fixation is partially due to a mismatch between egocentric and exocentric localization mechanisms.

Analysis of Variance↗
PubMed2000

A placebo-controlled crossover trial of creatine in mitochondrial diseases.

To test the efficacy and safety of creatine (Cr) monohydrate in mitochondrial diseases, 16 patients with chronic progressive external ophthalmoplegia or mitochondrial myopathy were randomized in a crossover design to receive double-blind placebo or 20 g Cr/day for 4 weeks. Cr was well tolerated, but there were no significant effects with regard to exercise performance, eye movements, or activities of daily life. The power of this pilot study was limited and future multicenter trials are needed.

Adult↗
PubMed2000

Nicotine-induced nystagmus: three-dimensional analysis and dependence on head position.

Two- and three-dimensional analyses of nicotine-induced eye movements were performed in 53 subjects to evaluate whether they were primarily of vestibular or ocular motor origin. Nicotine-induced nystagmus was detected in 27 subjects (51%); in 25 of these (93%) it was modulated by otolith input. Three-dimensional analysis of nicotine-induced nystagmus revealed that it violates Listing's law. Taken together, these findings suggest that nicotine induces an imbalance in the vestibulo-ocular reflex.

Adult↗
PubMed2000

Indomethacin reduces CSF pressure in intracranial hypertension.

The CSF-pressure-lowering effects of indomethacin in seven patients with idiopathic intracranial hypertension and one patient with symptomatic intracranial hypertension due to a non-space-occupying meningioma are reported. CSF opening pressure between 350 and 500 mm H2O (mean 400 mm H2O) was promptly reduced by 80 to 200 mm H2O (mean reduction, 139 mm H2O) for at least 10 minutes in all patients after IV administration of 50 mg indomethacin. Four patients had mild and transient side effects (dizziness). Indomethacin might be an alternative drug for treatment of intracranial hypertension.

Adult↗
PubMed2000

Size distortion in spatial neglect.

One of the suggested theories to explain some aspects of neglect in patients with right parietal lesions is the spatial distortion hypothesis. To determine whether a distorted representation of space can account for the performance of neglect patients in visuospatial tasks we asked 27 neglect patients to compare the width of two horizontally aligned bars. The bars were presented symmetric to the body midline or either on the left or right side of egocentric space. The size comparison data are in accordance with the hypothesis of a distorted egocentric representation based on a dynamic remapping of space. The results support the idea that the abnormalities observed in the size comparison tasks are due to a distorted internal representation of the outside world. There are some hints that this distortion could be based on a dynamic mapping of space determined by the distribution of visuospatial attention.

Aged↗
PubMed2000

Increased anti-streptococcal antibodies in patients with Tourette's syndrome.

Infection or postinfectious phenomena have been postulated to play a role in the pathogenesis of children afflicted with the typical symptoms of Tourette's syndrome (TS). We investigated whether an increase of titers of antistreptococcal antibodies can be reproduced in our children with TS, and whether this increase is restricted to children. We examined the titers of two different antistreptococcal antibodies, antistreptolysin (ASL) and anitDNase B, both in children and adults. Titer s of ASO and antiDNase B were measured (1) in 13 children/adolescents suffering from TS and in an aged-matched comparison group;(2) in 23 adult patients, a comparison group of 23 aged-matched controls, and in another group of 17 aged-matched, non-medicated acute schizophrenics. ASO and antiDNase B titers were determined by laser nephelometry using a commercially available kit. Two antistreptococcal cut-off levels were compared (> 250 U/ml and 400 U/ml). As expected, increases ASO titers (>400 IU/ml) were found in a higher portion of children/adolescents with TS compared to controls. Regarding adults, titers >250 U/ml for both antistreptococcal antigens were found in significantly more TS patients than in schizophrenic patients or healthy control subjects. The mean values of ASO and antiDNase titers were significantly higher in both groups of TS patients compared to control children/adolescents, to the comparison groups of healthy adults and to schizophrenics. No difference in antistreptococcal titers was found between schizophrenics and the group of healthy adults. TS patients exhibited higher antistreptococcal titers than age-matched comparison groups of both children/adolescents and adults using different types of calculation. Our findings support the theory that a postinfectious immune mechanism may play a role in the pathogenesis of TS. The mechanism still needs to be elucidated.

Adolescent↗
PubMed2000

Learning to write letters: transfer in automated movements indicates modularity of motor programs in human subjects.

Many automatic movements are open-loop, feed-forward motor programs (MP) that are kinematically well characterized by smooth speed and acceleration curves. However, it is unclear whether their internal representation consists of monolithic blocks or subroutines. This question was investigated using a learning paradigm of a writing task. Fifty-nine normal subjects were presented with two similar, but different new letters. Every subject practiced each letter in a series of 60 trials, with the order of letter series randomized. Every session was continuously recorded by a digitizing tablet. Using kinematic analysis, we measured the number of vertical acceleration peaks as an indication of the number of corrective movements (COM). Since COM declined as automatization was approached, we could quantitatively infer progress in motor learning under natural learning conditions. In the case of modular storage of MP, transfer in-between letters was expected due to the re-use of pre-learned motor subroutines. Statistical analysis showed that the exponential model described the data much better than the linear model (residual error: P<0.88 and P<0.00001, respectively), as expected for a learning paradigm. There was no difference between letters per se (P<0.77). Motor improvement differed significantly (P<0.02) between the first and the second series; there was a much greater reduction of COM in the second series (50.1 vs. 41.1%). This difference can be logically ascribed to transfer, indicating that automated movements are stored in motor subroutines.

Biomechanical Phenomena↗
PubMed2000

["Inner perilymph fistula" of the anterior semicircular canal. A new disease picture with recurrent attacks of vertigo].

In 1998 Minor et al. described a new variant of perilymphatic fistula: the "superior canal dehiscence syndrome". This syndrome is clinically characterized by recurrent attacks of vertigo and oscillopsia induced by loud noises or stimuli that result in changes in intracranial or middle ear pressure. It is caused by a dehiscence of bone overlying the superior (anterior) semicircular canal. Due to this dehiscence, a third, mobile window (in addition to the round and oval windows) is formed, and changes in pressure are pathologically transduced to the anterior semicircular canal. Although the superior canal dehiscence syndrome is not a rare condition, no other cases have yet been reported. Therefore, we describe a typical patient who suffered for many years from recurrent attacks of vertigo and oscillopsia induced by coughing and Valsalva's maneuvers. High resolution temporal bone CT scan showed a defect in the bone overlying the left anterior semicircular canal. Three-dimensional eye movement recordings using the search coil technique and subsequent vector analysis demonstrated that the eye movements were induced by excitation of the left anterior semicircular canal. We conclude that superior canal dehiscence syndrome is an important differential diagnosis in patients suffering from symptoms of a perilymphatic fistula, especially since it can be successfully treated by "plugging" of the affected semicircular canal. Such patients are thus spared unnecessary surgery of the middle ear.

Diagnosis, Differential↗
PubMed2000

[Neurological complications after organ transplantation].

Following organ transplantation, 30-60% of patients develop neurologic complications which can be classified as pre-existing deficits due to the underlying disease, complications during surgery, metabolic encephalopathies, neurotoxicity of immunosuppressant agents, opportunistic CNS infections, and secondary malignomas as indirect side effects of immunosuppression. While encephalopathies, seizures, or CNS infection can occur in all types of transplantation, some specific neurological complications exist for different types of organ transplantation. In this review, the clinical symptoms and treatment of both the common neurological complications as well as the particular neurological syndromes after liver, heart, and bone marrow transplantation are discussed.

Acute Disease↗
PubMed2000

[Symptomatic cluster headache. Expression of multiple sclerosis relapse with magnetic resonance tomography detection of pontomedullary lesion in the ipsilateral trigeminal nucleus area].

We describe a 25-year-old male who developed, in the course of an acute exacerbation of his multiple sclerosis, cluster headache-like attacks which responded to oxygen therapy. Magnetic resonance imaging revealed a lesion in the area of the ipsilateral pontomedullary trigeminal nuclei. This symptomatic case and other published cases are most probably explained by an activation of the trigeminovascular system as it is assumed for primary headache syndromes.

Adult↗
PubMed2000

Spatial and temporal aspects of eye-hand coordination across different tasks.

The way in which saccadic eye movements are elicited influences their latency and accuracy. Accordingly, different tasks elicit different types of saccades. Using the tasks steps, gap, memory, scanning and antisaccade, we analyzed combined eye and hand movements to determine whether both motor systems share control strategies. Errors and latencies were measured to examine whether changes in eye motor behavior are reflected in hand motor behavior. Directional and variable errors of eye and hand changed differently according to the tasks. Moreover, errors of the two systems did not correlate for any of the tasks investigated. Contrary to errors, mean latencies of eye movements were organized in the same pattern as hand movements. A correlation of latencies indicates that both motor systems rely on common information to initiate movement. Temporal coupling was stronger for intentional tasks than for reflexive tasks.

Adult↗
PubMed2000

The role of the attention focus in the visual information processing underlying saccadic adaptation.

Three experiments were performed to determine how an error signal for driving saccadic adaptation is derived from visual information processing. The first experiment demonstrated that an intrasaccadic displacement of a visual background does not influence saccadic adaptation when a small foveal target is used. The second experiment showed that when a different type of target, a 4.8 deg annulus, is used an intrasaccadic background shift influences the adaptive process. The third experiment showed that the size of the saccade target determines the size of the attention focus around the time of a saccade. These findings suggest that the attention focus selects the visual information used for a trans-saccadic comparison in order to generate the error signal.

Adaptation, Physiological↗
PubMed2000

Motor cortex excitability in patients with migraine with aura and hemiplegic migraine.

We studied the excitability of the motor cortex using transcranial magnetic stimulation (TMS) in 12 patients with migraine with aura (MA) and nine patients with familial hemiplegic migraine (FHM). Motor thresholds at rest, the duration of the cortical and peripheral silent period and intracortical inhibition and facilitation using paired-pulse TMS at intervals of 2 to 15 ms were measured with patients free of attacks for at least 48 h. In contrast to previous reports we could not find any significant differences between patient groups and compared to controls (n=17) in the parameters tested. The results suggest that there are no interictal changes of excitability of the motor cortex in migraine. This study does not support the concept of general cortical hyperexcitability in migraine secondary to a genetic predisposition or a structural alteration of inhibitory interneurones in the cortex due to repeated parenchymal insults during attacks.

Adult↗
PubMed2000

Relation between the metrics of the presaccadic attention shift and of the saccade before and after saccadic adaptation.

A shift of the visual attention focus is known to precede saccades. However, how the metrics of both this presaccadic attention shift and the saccade are coupled is still unclear. We altered the saccade size by short-term saccadic adaptation to determine whether the attention focus would still be shifted to the location of the saccade target or to the modified postsaccadic eye position. The results showed that saccadic adaptation had no influence on the presaccadic attention shift. Thus either different processes determine the metrics of the attention shift and of the saccade or saccadic adaptation causes only modifications on a lower hierarchical level of saccade programming, thereby not influencing the metrics of the attention shift.

Adaptation, Physiological↗