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Johannes Noth

Publications and source records attributed to Johannes Noth.

At least 19 recordsLinked to original sources
PubMed2006

Excitability of human motor and visual cortex before, during, and after hyperventilation.

In humans, hyperventilation (HV) has various effects on systemic physiology and, in particular, on neuronal excitability and synaptic transmission. However, it is far from clear how the effects of HV are mediated at the cortical level. In this study we investigated the effects of HV-induced hypocapnia on primary motor (M1) and visual cortex (V1) excitability. We used 1) motor threshold (MT) and phosphene threshold (PT) and 2) stimulus-response (S-R) curves (i.e., recruitment curves) as measures of excitability. In the motor cortex, we additionally investigated 3) the intrinsic inhibitory and facilitatory neuronal circuits using a short-interval paired-pulse paradigm. Measurements were performed before, during, and after 10 min of HV (resulting in a minimum end-tidal Pco(2) of 15 Torr). HV significantly increased motor-evoked potential (MEP) amplitudes, particularly at lower transcranial magnetic stimulation (TMS) intensities. Paired-pulse stimulation indicated that HV decreases intracortical inhibition (ICI) without changing intracortical facilitation. The results suggestthat low Pco(2) levels modulate, in particular, the intrinsic neuronal circuits of ICI, which are largely mediated by neurons containing gamma-aminobutyric acid. Modulation of MT probably resulted from alterations of Na(+) channel conductances. A significant decrease of PT, together with higher intensity of phosphenes at low stimulus intensities, furthermore suggested that HV acts on the excitability of M1 and V1 in a comparable fashion. This finding implies that HV also affects other brain structures besides the corticospinal motor system. The further exploration of these physiological mechanisms may contribute to the understanding of the various HV-related clinical phenomenona.

Adult↗
PubMed2006

The effect of subthalamic nucleus deep brain stimulation on precision grip abnormalities in Parkinson's disease.

We have studied grip force performance in a group of 10 patients who were in a stable state after implantation of bilateral stimulating electrodes in the subthalamic nuclei (Stn) to counter drug-resistant or drug-induced symptoms of advanced Parkinson's disease. The patients were required to use a precision grip to lift an object which recorded grip force development and lift dynamics. Lifting was performed with stimulation on and with stimulation off under optimal medication. Post-operatively, dyskinesia was absent in all patients in both conditions, but in the 'off' state the patients showed the profound bradykinesia and excessive levels of grip force development associated with Parkinson's disease from its early stages. In the stimulation 'on' state both the rate of grip force development and the speed of the lifting phase were increased significantly. The excessive levels of grip force present in the stimulation 'off' state, and present from the early stages of the disease, however, were even more marked with Stn stimulation on. It is suggested that this results from a failure to modify stored motor programs developed over a long period under the influence of bradykinesia, leading to an inappropriately prolonged duration of grip force development when this influence is removed by Stn stimulation. Thus although Stn stimulation achieved a dramatic improvement in the mobility of the patients in general, and in the dynamics of hand movements specifically, by improving rates of force development and lifting dynamics, it does not restore, and may even worsen, the ability to match lifting parameters to actual conditions.

Aged↗
PubMed2006

Processing the spatial configuration of complex actions involves right posterior parietal cortex: An fMRI study with clinical implications.

The left hemispheric dominance for complex motor behavior is undisputed. Clinical observations of complex motor deficits in patients with right hemispheric lesions, however, suggest an additional contribution of the right hemisphere to higher motor control. We assessed, using functional MRI (fMRI), which brain regions are implicated in processing the spatial aspects of complex, object-related actions. Using a blocked, factorial design, 17 healthy volunteers were asked to detect either spatial or sequential errors (factor ERROR) in complex activities of daily living, presented as video sequences with the appropriate object(s) or as pantomimes (factor STIMULUS). Observing complex actions (irrespective of stimulus type) activated a bilateral frontoparietal network. Observing actions with objects (relative to pantomimes) differentially increased neural activity in the fusiform gyrus and inferior occipital cortex bilaterally. Observing pantomimes, i.e., the same actions but without any object, differentially activated right prefrontal cortex, anterior cingulate cortex, the precuneus, and left cerebellum. The left cingulate cortex was differentially activated when subjects assessed the sequencing of actions. By contrast, assessing the spatial configuration of complex actions differentially increased neural activity in right posterior parietal cortex. A significant interaction of ERROR and STIMULUS was revealed for the right inferior parietal cortex only. These findings suggest a specific role of the right hemisphere, especially of right posterior parietal cortex, in processing spatial aspects of complex actions and thus provide a physiological basis for the observed apraxic motor deficits in patients with right hemispheric damage.

Activities of Daily Living↗
PubMed2006

On-demand deep brain stimulation for essential tremor: a report on four cases.

Deep brain stimulation (DBS) is an established therapy for essential tremor (ET), but loss of efficacy due to tolerance can occur. Our objective was to evaluate if it is feasible to use DBS only on-demand and if this would prevent tolerance. We report on the effects of left-side thalamic DBS in 4 ET patients who were instructed to switch on stimulation only when using their right hand for motor tasks and were followed-up to 30 months after surgery. The patients were capable of using DBS only on-demand (DBS use of 22.0+/-13.5%/day). DBS led to a stable suppression of right arm tremor throughout the follow-up. No problems associated with tolerance such as tremor rebound or late therapy failure occurred. In comparison to publications stating that ET patients had been using DBS continuously during the daytime, the use of on-demand DBS saves battery life, which delays surgical replacement of the stimulator. Thus, on-demand DBS saves money, may help to prevent tolerance, and should be adopted for the long-term treatment of ET patients.

Adult↗
PubMed2006

Unusual form of proprioceptive facilitation during recovery from hemiplegia.

Proprioceptive facilitation (PF) is a phenomenon occasionally seen during motor restoration following acute hemiplegia. At an early stage of recovery, a number of brief passive muscle stretches can facilitate voluntary contraction in the stretched muscles. Here we present a patient who during early recovery from a left hemispheric stroke causing right hemiplegia was able to develop maximum isometric arm force if, during this effort, large-amplitude passive stretches of the elbow were applied as conditioning stimuli. Based on clinical and positron emission tomography findings, possible physiological mechanisms of PF and the role of proprioception in stroke recovery are discussed.

Hemiplegia↗
PubMed2004

Regulation of stearoyl-CoA desaturase-1 after central and peripheral nerve lesions.

BACKGROUND: Interruption of mature axons activates a cascade of events in neuronal cell bodies which leads to various outcomes from functional regeneration in the PNS to the failure of any significant regeneration in the CNS. One factor which seems to play an important role in the molecular programs after axotomy is the stearoyl Coenzyme A-desaturase-1 (SCD-1). This enzyme is needed for the conversion of stearate into oleate. Beside its role in membrane synthesis, oleate could act as a neurotrophic factor, involved in signal transduction pathways via activation of protein kinases C. RESULTS: In situ hybridization and immunohistochemistry demonstrated a strong up-regulation of SCD at mRNA and protein level in regenerating neurons of the rat facial nucleus whereas non-regenerating Clarke's and Red nucleus neurons did not show an induction of this gene. CONCLUSION: This differential expression points to a functionally significant role for the SCD-1 in the process of regeneration.

Animals↗
PubMed2004

Grip force abnormalities in de novo Parkinson's disease.

In recent years it has been shown that a variety of movement disorders are associated with abnormalities of the fine motor control of the hand. In Parkinson's disease (PD), these changes consist of a slowing of the rate of grip force development and the use of abnormally large grip forces both during lifting and static holding of an object. It has been suggested, however, that these changes are a direct effect of the patient's levodopa medication or associated with levodopa induced dyskinesias. Accordingly, we examined the performance of de novo Parkinson patients in a precision lifting task. All patients (n = 6) were newly diagnosed and showed rigidity, bradykinesia, or both, but were unaffected by tremor or dyskinesia. None of the patients had received antiparkinson medication. Grip force was abnormally high in both the lifting and hold phases. This exaggeration was equal in magnitude to that observed previously in medicated patients. Thus we conclude that the abnormalities in grip force observed here are intrinsic features of PD and not the result of dopamine medication or its side effects.

Aged↗
PubMed2004

[Fulminant meningoencephalitis associated with Mycoplasma pneumoniae infection in adults. Aggressive treatment enabled a good outcome].

Mycoplasma pneumoniae (M. pn.) commonly causes respiratory tract infections in humans. In a certain percentage of cases it may also be associated with various peripheral and central nervous system manifestations. We report a case of a 38-year-old previously healthy man who presented with hemiplegia and somnolence after he had suffered from a febrile respiratory infection 10 days earlier. Clinical features and laboratory investigations supported the diagnosis of an acute M. pneumoniae-associated meningoencephalitis. He was treated by an aggressive antibiotic and immunomodulatory regimen over the course of several weeks in the neurocritical care unit. Decompressive hemicraniectomy was performed due to life-threatening raised intracranial pressure. However, the patient recovered almost completely and presented with a mild neurological deficit after 3 months. Based on this case we give a review of the literature and discuss potential pathomechanisms and diagnostic approaches.

Adult↗
PubMed2004

Neural basis of pantomiming the use of visually presented objects.

UNLABELLED: Neuropsychological studies of patients suffering from apraxia strongly imply a left hemisphere basis for skillful object use, the neural mechanisms of which, however, remain to be elucidated. We therefore carried out a PET study in 14 healthy human volunteers with the aim to isolate the neural mechanisms underlying the sensorimotor transformation of object-triggers into skilled actions. We employed a factorial design with two factors ( RESPONSE: naming, pantomiming; and TRIGGER: actions, objects) and four conditions (IA: imitating the observed pantomime; IO: pantomiming the use of the object shown; NA: naming the observed pantomime; NO: naming the object shown). The design thus mainly aims at investigating the interaction [i.e. (IO-IA)-(NO-NA)] which allows the assessment of increased neural activity specific to the sensorimotor transformation of object-triggers into skilled actions. The results (P < 0.05, corrected) showed that producing a wide range of skilled actions triggered by objects (controlled for perceptual, motor, semantic, and lexical effects) activated left inferior parietal cortex. The data provide an explanation for why patients with lesions including left parietal cortex suffer from ideational apraxia as assessed by impaired object use and pantomining to visually presented objects.

Adult↗
PubMed2004

CT findings and clinical features as markers for patient outcome in primary pontine hemorrhage.

BACKGROUND AND PURPOSE: The overall mortality rate of primary pontine hemorrhage (PPH) in recent studies is 40-50%. The aim of the present study was to analyze the predictive value of clinical and neuroradiologic parameters concerning the outcome of patients with PPH. METHODS: We reviewed the clinical data of 29 consecutive patients (mean age, 59 +/- 13.5 years; 12 women, 17 men) with PPH. National Institutes of Health Stroke Scale (NIHSS) and Glasgow Coma Scale (GCS) scores were assessed on admission, and NIHSS, GCS, and Glasgow Outcome Scale (GOS) scores were assessed on discharge. The hemorrhage volume was calculated by using a previously published formula. Clinical manifestations, outcome, and volume and location of the bleeding were correlated. RESULTS: The mean GCS score on admission was 6.8 +/- 3.9 and increased to 9.0 +/- 3.9 on discharge. The NIHSS score improved from 29.1 +/- 12.5 to 12.1 +/- 7.3. Nine patients (31%) died as a result of PPH after 5 +/- 3 days. The mean GOS score was 3.0 +/- 1.5 (3.9 +/- 0.8 for patients who survived). Arterial hypertension was the most common risk factor (90%); other causes were anticoagulation therapy (7%) and amyloid angiopathy (3%). A high correlation was observed between a poor outcome (GOS score < 4) and hematoma volume greater than 4 mL (P =.006), ventral hemorrhage (P <.001), and necessity for mechanical ventilation (P <.001). Patients with dorsally located hematomas less than 4 mL in volume had a significantly better outcome. CONCLUSION: The prognosis of PPH is better than commonly expected. Most patients with moderate neurologic deficits on admission and dorsally located small hematomas are able to survive PPH with minor neurologic deficits.

Adult↗
PubMed2003

Identification of regeneration-associated genes after central and peripheral nerve injury in the adult rat.

BACKGROUND: It is well known that neurons of the peripheral nervous system have the capacity to regenerate a severed axon leading to functional recovery, whereas neurons of the central nervous system do not regenerate successfully after injury. The underlying molecular programs initiated by axotomized peripheral and central nervous system neurons are not yet fully understood. RESULTS: To gain insight into the molecular mechanisms underlying the process of regeneration in the nervous system, differential display polymerase chain reaction has been used to identify differentially expressed genes following axotomy of peripheral and central nerve fibers. For this purpose, axotomy induced changes of regenerating facial nucleus neurons, and non-regenerating red nucleus and Clarke's nucleus neurons have been analyzed in an intra-animal side-to-side comparison. One hundred and thirty five gene fragments have been isolated, of which 69 correspond to known genes encoding for a number of different functional classes of proteins such as transcription factors, signaling molecules, homeobox-genes, receptors and proteins involved in metabolism. Sixty gene fragments correspond to genomic mouse sequences without known function. In situ-hybridization has been used to confirm differential expression and to analyze the cellular localization of these gene fragments. Twenty one genes (approximately 15%) have been demonstrated to be differentially expressed. CONCLUSIONS: The detailed analysis of differentially expressed genes in different lesion paradigms provides new insights into the molecular mechanisms underlying the process of regeneration and may lead to the identification of genes which play key roles in functional repair of central nervous tissues.

Animals↗
PubMed2003

Retrograde reactions of Clarke's nucleus neurons after human spinal cord injury.

Successful axon regeneration depends on the expression of regeneration-associated genes by axotomized neurons. Here, we demonstrate, for the first time to our knowledge, the expression of regeneration-associated genes by axotomized human CNS neurons. In situ hybridization and immunohistochemistry showed a transient induction of GAP-43 and c-jun in Clarke's nucleus neurons caudal to traumatic human spinal cord injury. These results support experimental data that nonregenerating central nervous system neurons can temporarily upregulate regeneration-associated genes, reflecting a transient regenerative capacity that fails over time.

Caspase 3↗
PubMed2003

Left inferior parietal cortex integrates time and space during collision judgments.

Left inferior parietal lobe lesions can cause perturbation of the space-time plans underlying skilled actions. But does the perceptual integration of spatiotemporal information use the same neural substrate or is the role of the left inferior parietal cortex restricted to visuomotor transformations? We use fMRI and a collision judgment paradigm to examine whether the left inferior parietal cortex integrates temporal and spatial variables in situations in which no complex action and no visuomotor transformation is required. We used a perceptual task in which healthy subjects indicated by simple button presses whether two moving objects (of the same or different size) would or would not collide with each other. This task of interest was contrasted with a control task that employed the same stimuli and identical motor responses but in which the size of the two moving objects had to be compared. To assess putative differential eye-movement effects both tasks were performed with and without central fixation. Analysis of the fMRI data (employing a random-effects model and SPM99) showed that collision judgments (relative to size judgments) provoked a significant increase in neural activity in the left inferior parietal cortex (supramarginal gyrus) only. These results show that left inferior parietal cortex is involved in the integration of perceptual spatiotemporal information and thus provide a neural correlate for the use of space-time plans (whose perturbation can lead to apraxia as originally hypothesized by Liepmann). Furthermore, the data suggest that the left supramarginal gyrus combines temporal and spatial variables more widely than previously supposed.

Adolescent↗
PubMed2002

Huntington's disease transgenic mice are resistant to global cerebral ischemia.

Excitotoxicity plays a key role in ischemic neuronal death and is also one of the candidate mechanisms contributing to neurodegeneration in Huntington's disease (HD). Unexpectedly we have now found that transgenic mice expressing exon 1 of a mutant human HD gene (R6/1) are protected against global cerebral ischemia (GCI), installed by temporary bilateral occlusion of the carotid arteries. Whereas wild type mice showed a substantial neuronal damage in the hippocampus following 15, 20 and 60 min of GCI, transgenic mice were partially protected after 15 and 20 minutes of hypoxemia. This tolerance to ischemia is not blocked by pretreatment of mice with cycloheximide, an unspecific protein synthesis inhibitor. We conclude that this form of tolerance to ischemia in HD transgenic mice--although somewhat reminiscent of ischemic tolerance after ischemic preconditioning--is therefore independent of short term expression of endogenous neuroprotective proteins.

Animals↗
PubMed2002

Modification of a functional motor task by non-consciously perceived sensory stimuli.

In recent years it has been suggested that processing of visual information is divided between a ventral stream, responsible for object recognition and conscious processing of object properties, and a dorsal stream mediating automatic integration of visual information into a motor task. We used metacontrast masking to prevent conscious perception of visual cues concerning the load of an object to be lifted in a precision grip. It was found that when such non-consciously perceived cues warned of a load change, they allowed the subjects to produce the grip force profile appropriate to the new load. It is concluded that non-consciously perceived visual information can be utilised to adapt a functional motor task to actual conditions.

Adult↗
PubMed2002

Contrast-enhanced three-dimensional transcranial color-coded sonography of intracranial stenoses.

BACKGROUND AND PURPOSE: Intracranial stenoses are associated with a considerable number of strokes each year. The clinical value of a workstation-based three-dimensional (3D) reconstruction system for transcranial color-coded sonography was evaluated in patients with intracranial stenosis or occlusion. METHODS: Twenty-six patients (13 men, 13 women; mean age, 57 years +/- 12 [SD]) with 36 intracranial stenoses or occlusions, as detected at two-dimensional (2D) color Doppler imaging (CDI) and digital subtraction angiography (DSA), underwent Levovist-enhanced power Doppler imaging (PDI), with subsequent 3D reconstruction. A workstation connected to a magnetic sensor capable of spatial localization of the probe was used to reconstruct 3D images of the circle of Willis from serial PDI images. RESULTS: At DSA, seven (19%) stenoses were estimated to less than 50%, 24 (67%) were 50% or more, and five (14%) were occluded. DSA and 3D-PDI estimates of the degree of stenosis agreed in 33 cases (92%), with a weighted kappa value of 0.86. Disagreement occurred with two subtotal basilar artery stenoses and one subtotal middle cerebral artery stenosis, which were evaluated as being complete occlusions at 3D-PDI. Interobserver agreement between two experienced 3D investigators in estimating the percentage of stenosis was high (correlation coefficient,.98). CONCLUSION: 3D-PDI enables the investigator to reconstruct virtually any arbitrary viewing angle. Compared with conventional CDI, 3D-PDI offers easier spatial assessment of intracranial stenoses, and its findings are sufficiently correlated with angiographic findings. Because different investigators can postprocess the same 3D data, improving reproducibility and reducing investigator dependency in transcranial color-coded sonography may be possible.

Aged↗