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Martin Tegenthoff

Publications and source records attributed to Martin Tegenthoff.

At least 19 recordsLinked to original sources
PubMed2006

Age-related attenuation of dominant hand superiority.

BACKGROUND: The decline of motor performance of the human hand-arm system with age is well-documented. While dominant hand performance is superior to that of the non-dominant hand in young individuals, little is known of possible age-related changes in hand dominance. We investigated age-related alterations of hand dominance in 20 to 90 year old subjects. All subjects were unambiguously right-handed according to the Edinburgh Handedness Inventory. In Experiment 1, motor performance for aiming, postural tremor, precision of arm-hand movement, speed of arm-hand movement, and wrist-finger speed tasks were tested. In Experiment 2, accelerometer-sensors were used to obtain objective records of hand use in everyday activities. PRINCIPAL FINDINGS: Our data confirm previous findings of a general task-dependent decline in motor performance with age. Analysis of the relationship between right/left-hand performances using a laterality index showed a loss of right hand dominance with advancing age. The clear right-hand advantage present at younger ages changed to a more balanced performance in advanced age. This shift was due to a more pronounced age-related decline of right hand performance. Accelerometer-sensor measurements supported these findings by demonstrating that the frequency of hand use also shifted from a clear right hand preference in young adults to a more balanced usage of both hands in old age. Despite these age-related changes in the relative level of performance in defined motor tasks and in the frequency of hand use, elderly subjects continued to rate themselves as unambiguous right-handers. CONCLUSION: The discrepancy between hand-specific practical performance in controlled motor tests as well as under everyday conditions and the results of questionnaires concerning hand use and hand dominance suggests that most elderly subjects are unaware of the changes in hand dominance that occur over their lifespan, i.e., a shift to ambidexterity.

Adult↗
PubMed2006

Patterns of cortical reorganization parallel impaired tactile discrimination and pain intensity in complex regional pain syndrome.

In the complex regional pain syndrome (CRPS), several theories proposed the existence of pathophysiological mechanisms of central origin. Recent studies highlighted a smaller representation of the CRPS-affected hand on the primary somatosensory cortex (SI) during non-painful stimulation of the affected side. We addressed the question whether reorganizational changes can also be found in the secondary somatosensory cortex (SII). Moreover, we investigated whether cortical changes might be accompanied by perceptual changes within associated skin territories. Seventeen patients with CRPS of one upper limb without the presence of peripheral nerve injuries (type I) were subjected to functional magnetic resonance imaging (fMRI) during electrical stimulation of both index fingers (IFs) in order to assess hemodynamic signals of the IF representation in SI and SII. As a marker of tactile perception, we tested 2-point discrimination thresholds on the tip of both IFs. Cortical signals within SI and SII were significantly reduced contralateral to the CRPS-affected IF as compared to the ipsilateral side and to the representation of age- and sex-matched healthy controls. In parallel, discrimination thresholds of the CRPS-affected IF were significantly higher, giving rise to an impairment of tactile perception within the corresponding skin territory. Mean sustained, but not current pain levels were correlated with the amount of sensory impairment and the reduction in signal strength. We conclude that patterns of cortical reorganization in SI and SII seem to parallel impaired tactile discrimination. Furthermore, the amount of reorganization and tactile impairment appeared to be linked to characteristics of CRPS pain.

Adult↗
PubMed2006

Tactile coactivation resets age-related decline of human tactile discrimination.

OBJECTIVE: For young subjects, it is well-documented that training and practice improve sensorimotor performance. However, little is known about how the typically observed age-related decline of sensorimotor abilities can be ameliorated by sensory stimulation. METHODS: As an alternative approach to training, we have introduced a tactile coactivation protocol involving Hebbian synaptic plasticity to improve tactile performance on a short timescale of a few hours. RESULTS: By applying coactivation on the index finger to drive perceptual learning, we demonstrate that in the elderly, aged 65 to 89 years, the age-related impairment of tactile two-point discrimination can be mitigated substantially. In elderly adults, tactile-acuity thresholds increased to 3.5mm compared with 1.5mm found in young adults, whereas 50-year-old subjects showed intermediate performance. As a result of coactivation, discrimination thresholds of the 80-year-old adults came to match those typically found at an age of 50, demonstrating that age-related decline in tactile performance is not irreversible, but rather subject to considerable restoration by specific stimulation protocols. INTERPRETATION: Because the preservation of sufficient tactile acuity into advanced age is an important prerequisite for the maintenance of autonomous living, we believe that the concept of coactivation might turn out to be beneficial in preserving everyday sensorimotor competence in the elderly through new forms of therapeutic interventions.

Adult↗
PubMed2006

Efficacy of acupuncture for the prophylaxis of migraine: a multicentre randomised controlled clinical trial.

BACKGROUND: Our aim was to assess the efficacy of a part-standardised verum acupuncture procedure, in accordance with the rules of traditional Chinese medicine, compared with that of part-standardised sham acupuncture and standard migraine prophylaxis with beta blockers, calcium-channel blockers, or antiepileptic drugs in the reduction of migraine days 26 weeks after the start of treatment. METHODS: This study was a prospective, randomised, multicentre, double-blind, parallel-group, controlled, clinical trial, undertaken between April 2002 and July 2005. Patients who had two to six migraine attacks per month were randomly assigned verum acupuncture (n=313), sham acupuncture (n=339), or standard therapy (n=308). Patients received ten sessions of acupuncture treatment in 6 weeks or continuous prophylaxis with drugs. Primary outcome was the difference in migraine days between 4 weeks before randomisation and weeks 23-26 after randomisation. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN52683557. FINDINGS: Of 1295 patients screened, 960 were randomly assigned to a treatment group. Immediately after randomisation, 125 patients (106 from the standard group) withdrew their consent to study participation. 794 patients were analysed in the intention-to-treat popoulation and 443 in the per-protocol population. The primary outcome showed a mean reduction of 2 .3 days (95% CI 1.9-2.7) in the verum acupuncture group, 1.5 days (1.1-2.0) in the sham acupuncture group, and 2.1 days (1.5-2.7) in the standard therapy group. These differences were statistically significant compared with baseline (p<0.0001), but not across the treatment groups (p=0.09). The proportion of responders, defined as patients with a reduction of migraine days by at least 50%, 26 weeks after randomisation, was 47% in the verum group, 39% in the sham acupuncture group, and 40% in the standard group (p=0.133). INTERPRETATION: Treatment outcomes for migraine do not differ between patients treated with sham acupuncture, verum acupuncture, or standard therapy.

Acupuncture Therapy↗
PubMed2005

Improvement of tactile discrimination performance and enlargement of cortical somatosensory maps after 5 Hz rTMS.

Repetitive transcranial magnetic stimulation (rTMS) is increasingly used to investigate mechanisms of brain functions and plasticity, but also as a promising new therapeutic tool. The effects of rTMS depend on the intensity and frequency of stimulation and consist of changes of cortical excitability, which often persists several minutes after termination of rTMS. While these findings imply that cortical processing can be altered by applying current pulses from outside the brain, little is known about how rTMS persistently affects learning and perception. Here we demonstrate in humans, through a combination of psychophysical assessment of two-point discrimination thresholds and functional magnetic resonance imaging (fMRI), that brief periods of 5 Hz rTMS evoke lasting perceptual and cortical changes. rTMS was applied over the cortical representation of the right index finger of primary somatosensory cortex, resulting in a lowering of discrimination thresholds of the right index finger. fMRI revealed an enlargement of the right index finger representation in primary somatosensory cortex that was linearly correlated with the individual rTMS-induced perceptual improvement indicative of a close link between cortical and perceptual changes. The results demonstrate that repetitive, unattended stimulation from outside the brain, combined with a lack of behavioral information, are effective in driving persistent improvement of the perception of touch. The underlying properties and processes that allow cortical networks, after being modified through TMS pulses, to reach new organized stable states that mediate better performance remain to be clarified.

Adult↗
PubMed2005

The NMDA antagonist memantine affects training induced motor cortex plasticity--a study using transcranial magnetic stimulation.

BACKGROUND: Training of a repetitive synchronised movement of two limb muscles leads to short-term plastic changes in the primary motor cortex, which can be assessed by transcranial magnetic stimulation (TMS) mapping. We used this paradigm to study the effect of memantine, a NDMA antagonist, on short-term motor cortex plasticity in 20 healthy human subjects, and we were especially interested in possible differential effects of different treatment regimens. In a randomised double-blinded cross over study design we therefore administered placebo or memantine either as a single dosage or as an ascending dosage over 8 days. Before and after one hour of motor training, which consisted of a repetitive co-contraction of the abductor pollicis brevis (APB) and the deltoid muscle, we assessed the motor output map of the APB muscle by TMS under the different conditions. RESULTS: We found a significant medial shift of the APB motor output map after training in the placebo condition, indicating training-induced short-term plastic changes in the motor cortex. A single dosage of memantine had no significant effect on this training-induced plasticity, whereas memantine administered in an ascending dosage over 8 days was able to block the cortical effect of the motor training. The memantine serum levels after 8 days were markedly higher than the serum levels after a single dosage of memantine, but there was no individual correlation between the shift of the motor output map and the memantine serum level. Besides, repeated administration of a low memantine dosage also led to an effective blockade of training-induced cortical plasticity in spite of serum levels comparable to those reached after single dose administration, suggesting that the repeated administration was more important for the blocking effect than the memantine serum levels. CONCLUSION: We conclude that the NMDA-antagonist memantine is able to block training-induced motor cortex plasticity when administered over 8 days, but not after administration of a single dose. This differential effect might be mainly due to the prolonged action of memantine at the NMDA receptor. These findings must be considered if clinical studies are designed, which aim at evaluating the potency of memantine to prevent "maladaptive" plasticity, e.g. after limb amputation.

Adult↗
PubMed2005

Sensorimotor retuning [corrected] in complex regional pain syndrome parallels pain reduction.

Patients with complex regional pain syndrome (CRPS) and intractable pain showed a shrinkage of cortical maps on primary (SI) and secondary somatosensory cortex (SII) contralateral to the affected limb. This was paralleled by an impairment of the two-point discrimination thresholds. Behavioral treatment over 1 to 6 months consisting of graded sensorimotor retuning led to a persistent decrease in pain intensity, which was accompanied by a restoration of the impaired tactile discrimination and regaining of cortical map size in contralateral SI and SII. This suggests that the reversal of tactile impairment and cortical reorganization in CRPS is associated with a decrease in pain.

Behavior Therapy↗
PubMed2004

Sustained increase of somatosensory cortex excitability by 5 Hz repetitive transcranial magnetic stimulation studied by paired median nerve stimulation in humans.

Repetitive transcranial magnetic stimulation (rTMS) has been shown to alter cortical processing within primary motor cortex dependent on the choice of stimulation variables. However, little is known about the effects of TMS in other cortical areas such as the primary somatosensory cortex (SI). Here we asked whether high-frequency (5 Hz) rTMS applied over the left SI evokes sustained changes in cortical excitability. To assess excitability changes, we applied a paired-pulse protocol consisting of paired electrical stimulation of the median nerve using an interstimulus interval of 30 ms and recordings of somatosensory evoked potentials. For ipsilateral SI we found that 1 h after termination of 5 Hz rTMS applied over the left SI with a figure-of-eight coil there was a sustained suppression of the normally present paired-pulse inhibition. Latencies and N20 amplitudes of the first peak remained unchanged. No changes of paired-pulse behavior were observed in the contralateral SI that was not TMS stimulated. The sustained excitability enhancement in SI is discussed in respect to previous findings regarding an improvement of tactile discrimination behavior by rTMS.

Adult↗
PubMed2004

Repetitive transcranial magnetic stimulation of the motor cortex attenuates pain perception in complex regional pain syndrome type I.

In complex regional pain syndrome (CRPS) many clinical symptoms suggest involvement of the central nervous system. Neuropathic pain as the leading symptom is often resistant to therapy. In the present study we investigated the analgesic efficiency of repetitive transcranial magnetic simulation (rTMS) applied to the motor cortex contralateral to the CRPS-affected side. Seven out of ten patients reported decreased pain intensities. Pain relief occurred 30 s after stimulation, whereas the maximum effect was found 15 min later. Pain re-intensified increasingly 45 min after rTMS. In contrast, sham rTMS did not alter pain perception. These findings provide evidence that in CRPS I pain perception can be modulated by repetitive motor cortex stimulation.

Adult↗
PubMed2004

Mean sustained pain levels are linked to hemispherical side-to-side differences of primary somatosensory cortex in the complex regional pain syndrome I.

Chronic back pain as well as phantom-limb pain is characterized by a close relationship between the amount of cortical reorganization and the magnitude of pain. In patients with positively assessed complex regional pain syndrome type I (CRPS I), we found a positive correlation between representational changes of primary somatosensory cortex (SI) and mean sustained pain levels. We investigated seven right-handed patients with CRPS I of one upper limb by means of somatosensory evoked potential (SSEP) mapping. Cortical representation of the CRPS-affected hand was significantly smaller than that of the contralateral healthy hand, giving rise to a substantial side difference. Subjective pain levels experienced over the last 4 weeks were estimated according to the visual analogue scale (VAS). Individual expansion of hand representation contralateral to the CRPS-affected limb was significantly correlated with mean pain intensity. Accordingly, low pain levels were linked to small representational side-to-side differences, while subjects with a distinctive hemispherical asymmetry reported the highest pain levels. Follow-up studies using functional imaging methods might be instrumental in providing a better understanding of this issue.

Adult↗
PubMed2004

Fluoxetine facilitates use-dependent excitability of human primary motor cortex.

OBJECTIVES: In poststroke patients, fluoxetine, a selective serotonin-reuptake inhibitor, as an adjunct to physical therapy provided a better functional recovery from motor deficits. The aim of this study was to investigate the effect of a single dose of 20 mg fluoxetine on motor learning and associated cortical changes in healthy right-handed subjects in order to get deeper insight into its facilitating influence on human motor cortex. METHODS: Subjects performed a motor task consisting of a simultaneous co-contraction of the abductor pollicis brevis (APB) and the deltoid muscle with and without fluoxetine in a placebo-controlled double-blinded crossover study design. Immediately before and after motor learning motor output maps of the APB muscle were assessed in order to get insight into plastic changes of the muscle representation. RESULTS: We found a significantly improved motor performance under both conditions without having substantial differences between placebo and fluoxetine. After the completion of the motor task there was a medial shift of the APB muscle motor output map. Only after the administration of fluoxetine the sum of MEP amplitudes (SOA) increased and the motor output map enlarged. CONCLUSIONS: These findings provide evidence for a use-dependent facilitating effect of fluoxetine on cortical excitability but not on motor performance. SIGNIFICANCE: Our findings are not in line with previous experiments in poststroke patients. However, long-term treatment with fluoxetine may additionally improve motor function by upregulating serotonergic receptors. Further studies investigating the influence of long-term treatment on cortical excitability and psychophysics may therefore provide deeper insight into a possible therapeutical efficiency of fluoxetine in poststroke patients.

Adult↗
PubMed2003

Functional imaging of perceptual learning in human primary and secondary somatosensory cortex.

Cellular mechanisms underlying synaptic plasticity are in line with the Hebbian concept. In contrast, data linking Hebbian learning to altered perception are rare. Combining functional magnetic resonance imaging with psychophysical tests, we studied cortical reorganization in primary and secondary somatosensory cortex (SI and SII) and the resulting changes of tactile perception before and after tactile coactivation, a simple type of Hebbian learning. Coactivation on the right index finger (IF) for 3 hr lowered its spatial discrimination threshold. In parallel, blood-oxygen level-dependent (BOLD) signals from the right IF representation in SI and SII enlarged. The individual threshold reduction was linearly correlated with the enlargement in SI, implying a close relation between altered discrimination and cortical reorganization. Controls consisting of a single-site stimulation did not affect thresholds and cortical maps. Accordingly, changes within distributed cortical networks based on Hebbian mechanisms alter the individual percept.

Adult↗
PubMed2003

Reorganization in the ipsilateral motor cortex of patients with lower limb amputation.

The aim of the present study was to assess reorganization in the motor cortex of patients with lower limb amputation. We studied seven patients with traumatic lower limb amputation, and six healthy controls, using transcranial magnetic stimulation mapping, with recordings from the quadriceps femoris muscle on both sides. Motor threshold, sum of amplitudes, area and the amplitude-weighted centre of gravity (COG) of the motor output map were assessed. We found a significant lateral displacement of the COG on the hemisphere contralateral to the healthy leg, whereas other parameters did not differ significantly between sides. This finding might be indicative of cortical reorganization in the hemisphere ipsilateral to the amputation. It is discussed with respect to an altered peripheral input to this hemisphere, and to transcallosal interactions from the deafferented hemisphere.

Adaptation, Physiological↗
PubMed2003

GABAergic mechanisms gate tactile discrimination learning.

In contrast to mechanisms mediating synaptic plasticity, the pharmacological basis of perceptual learning remains to be clarified. Here we report that a specific form of perceptual learning is influenced by GABAergic mechanisms. We induced perceptual learning by Hebbian co-activation of the skin of the tip of the right index fingers in human subjects. Under placebo conditions, tactile 2-point discrimination was improved on the co-activated, but not on the left, index finger. This augmentation was completely eliminated by lorazepam, a GABAA receptor agonist. No drug effects were found on the left index finger indicating that the drugs had no effect per se on performance. The results demonstrate that perceptual learning is subject to pharmacological gating by basic mechanisms known to mediate and modulate synaptic plasticity.

Adult↗
PubMed2003

Combination of 5 Hz repetitive transcranial magnetic stimulation (rTMS) and tactile coactivation boosts tactile discrimination in humans.

A combination of 5 Hz repetitive transcranial magnetic stimulation (rTMS) over the left primary somatosensory cortex together with tactile coactivation applied to the right index-finger representation (coac + rTMS) boosted tactile discrimination ability tested on the right index-finger. Applying coactivation alone caused a 0.25 mm lowering in tactile discrimination thresholds. In contrast, after coac + rTMS we found a significant further improvement of discrimination thresholds in comparison to the coactivation-induced perceptual changes alone. We demonstrate that the individual further improvement after coac + rTMS depended on the effectiveness of the coactivation protocol when applied alone. Subjects, who showed little gain in tactile performance after coactivation alone, showed the largest improvement after coac + rTMS implying that the combined application was selective for poor learners. The selective effects of coac + rTMS are discussed in respect to N-methyl-D-aspartate receptor activation.

Adult↗
PubMed2003

Pharmacological modulation of perceptual learning and associated cortical reorganization.

The pharmacological basis of perceptual learning and associated cortical reorganizations remains elusive. We induced perceptual learning by Hebbian coactivation of the skin of the tip of the right index finger in humans. Under placebo, tactile two-point discrimination was improved on the coactivated but not on the left index finger. This augmentation was blocked by an N-methyl-D-aspartate-receptor blocker, but doubled by amphetamine. No drug effects were found on the left index finger. The individual amount of cortical reorganization as assessed by mapping of somatosensory evoked potentials was linearly correlated with the pharmacological modulation of discrimination thresholds, implying that perceptual learning and associated cortical changes are controlled by basic mechanisms known to mediate and modulate synaptic plasticity.

Adult↗