Biomedical subjects

Alain Kaelin-Lang

Publications and source records attributed to Alain Kaelin-Lang.

15 recordsLinked to original sources

PubMed2006

An integrative transcranial magnetic stimulation mapping technique using non-linear curve fitting.

The aim of this study is to develop a new simple method for analyzing one-dimensional transcranial magnetic stimulation (TMS) mapping studies in humans. Motor evoked potentials (MEP) were recorded from the abductor pollicis brevis (APB) muscle during stimulation at nine different positions on the scalp along a line passing through the APB hot spot and the vertex. Non-linear curve fitting according to the Levenberg-Marquardt algorithm was performed on the averaged amplitude values obtained at all points to find the best-fitting symmetrical and asymmetrical peak functions. Several peak functions could be fitted to the experimental data. Across all subjects, a symmetric, bell-shaped curve, the complementary error function (erfc) gave the best results. This function is characterized by three parameters giving its amplitude, position, and width. None of the mathematical functions tested with less or more than three parameters fitted better. The amplitude and position parameters of the erfc were highly correlated with the amplitude at the hot spot and with the location of the center of gravity of the TMS curve. In conclusion, non-linear curve fitting is an accurate method for the mathematical characterization of one-dimensional TMS curves. This is the first method that provides information on amplitude, position and width simultaneously.

Adult↗

PubMed2006

Estimating the number of motor units using random sums with independently thinned terms.

The problem of estimating the numbers of motor units N in a muscle is embedded in a general stochastic model using the notion of thinning from point process theory. In the paper a new moment type estimator for the numbers of motor units in a muscle is denned, which is derived using random sums with independently thinned terms. Asymptotic normality of the estimator is shown and its practical value is demonstrated with bootstrap and approximative confidence intervals for a data set from a 31-year-old healthy right-handed, female volunteer. Moreover simulation results are presented and Monte-Carlo based quantiles, means, and variances are calculated for N in{300,600,1000}.

Adult↗

PubMed2005

Effects of somatosensory stimulation on use-dependent plasticity in chronic stroke.

BACKGROUND AND PURPOSE: There is a need to develop strategies to enhance the beneficial effects of motor training, including use-dependent plasticity (UDP), in neurorehabilitation. Peripheral nerve stimulation (PNS) modulates motor cortical excitability in healthy humans and could influence training effects in stroke patients. METHODS: We compared the ability of PNS applied to the (1) arm, (2) leg, and (3) idle time to influence training effects in the paretic hand in 7 chronic stroke patients. The end point measure was the magnitude of UDP. RESULTS: UDP was more prominent with arm stimulation (increased by 22.8%) than with idle time (by 2.9%) or leg stimulation (by 6.4%). CONCLUSIONS: PNS applied to the paretic limb paired with motor training enhances training effects on cortical plasticity in stroke patients.

Aged↗

PubMed2005

Modulation of parvalbumin expression in the motor cortex of parkinsonian rats.

Dopamine deficiency in Parkinson's disease leads to numerous molecular changes in basal ganglia. However, the consequences of these changes on the motor cortex remain unclear. Here we show that the immunoreactivity of parvalbumin, which is expressed in GABAergic interneurons, increases in the primary motor cortex of parkinsonian rats. This increase can be reversed by a subsequent lesion of the subthalamic nucleus. These results suggest that dopamine deficiency induces reversible changes in GABAergic cortical cells, which might be linked with parkinsonian symptoms.

Animals↗

PubMed2004

Role of voluntary drive in encoding an elementary motor memory.

Motor training consisting of repetitive thumb movements results in encoding of motor memories in the primary motor cortex. It is not known if proprioceptive input originating in the training movements is sufficient to produce this effect. In this study, we compared the ability of training consisting of voluntary (active) and passively-elicited (passive) movements to induce this form of plasticity. Active training led to successful encoding accompanied by characteristic changes in corticomotor excitability, while passive training did not. These results support a pivotal role for voluntary motor drive in coding motor memories in the primary motor cortex.

Adult↗

PubMed2004

Localization of DJ-1 mRNA in the mouse brain.

DJ-1 is mutated in autosomal recessive, early onset Parkinson's disease but the exact localization of the DJ-1 gene product in the mammalian brain is largely unknown. We aimed to evaluate the DJ-1 mRNA expression pattern in the mouse brain. Serial coronal sections of brains of five male and five female adult mice were investigated by using in situ hybridization with a DJ-1 specific 35S-labeled oligonucleotide probe. Hybridized sections were analyzed after exposure to autoradiography films and after coating with a photographic emulsion. DJ-1 was heterogeneously expressed throughout the mouse central nervous system. A high expression of DJ-1 mRNA was detected in neuronal and non-neuronal populations of several structures of the motor system such as the substantia nigra, the red nucleus, the caudate putamen, the globus pallidus, and the deep nuclei of the cerebellum. Furthermore, DJ-1 mRNA was also highly expressed in non-motor structures including the hippocampus, the olfactory bulb, the reticular nucleus of the thalamus, and the piriform cortex. The high expression of DJ-1 mRNA in brain regions involved in motor control is compatible with the occurrence of parkinsonian symptoms after DJ-1 mutations. However, expression in other regions indicates that a dysfunction of DJ-1 may contribute to additional clinical features in patients with a DJ-1 mutation.

Animals↗

PubMed2004

Impact of coil position and electrophysiological monitoring on determination of motor thresholds to transcranial magnetic stimulation.

OBJECTIVE: We compared motor and movement thresholds to transcranial magnetic stimulation (TMS) in healthy subjects and investigated the effect of different coil positions on thresholds and MEP (motor-evoked potential) amplitudes. METHODS: The abductor pollicis brevis (APB) 'hot spot' and a standard scalp position were stimulated. APB resting motor threshold (APB MEP-MT) defined by the '5/10' electrophysiological method was compared with movement threshold (MOV-MT), defined by visualization of movements. Additionally, APB MEP-MTs were evaluated with the '3/6 method,' and MEPs were recorded at a stimulation intensity of 120% APB MEP-MT at each position. RESULTS: APB MEP-MTs were significantly lower by stimulation of the 'hot spot' than of the standard position, and significantly lower than MOV-MTs (n=15). There were no significant differences between the '3/6' and the '5/10' methods, or between APB MEP amplitudes by stimulating each position at 120% APB MEP-MT. CONCLUSIONS: Coil position and electrophysiological monitoring influenced motor threshold determinations. Performing 6 instead of 10 trials did not produce different threshold measurements. Adjustment of intensity according to APB MEP-MT at the stimulated position did not influence APB MEP amplitudes. SIGNIFICANCE: Standardization of stimulation positions, nomenclature and criteria for threshold measurements should be considered in design and comparison of TMS protocols.

Adult↗

PubMed2003

Multiple effects of adenosine in the arterially perfused mammalian eye. Possible mechanisms for the neuroprotective function of adenosine in the retina.

It has been postulated that the major physiological role of adenosine is protection of the central nervous system in conditions such as ischemia, hypoxia, or prolonged neuronal excitation. Under these conditions adenosine is released, and exerts multiple effects, including vasodilation, inhibition of neuronal activity, and enhancement of glycogenolysis, resulting in neuroprotection. In this article, published as well as unpublished data on the multiple effects of exogenous adenosine and application of adenosine-related agents, performed using the arterially perfused cat eye, will be reviewed and discussed within the framework of the neuroprotective role of adenosine. The isolated, arterially perfused eye preparation has the advantage of combining integrity of the eye structure, exact control of arterial concentration and timing of applied pharmacological agents, and access to electrophysiological parameters of both retina and optic nerve, as well as the ability to control and monitor perfusate flow. The absence of red blood cells in the perfusate prevents adenosine from being metabolized prior to reaching the eye.

Adenosine↗

PubMed2002

Excitability of the ipsilateral motor cortex during phasic voluntary hand movement.

We investigated the influence of self-paced, phasic voluntary hand movement on the excitability of the ipsilateral motor cortex. Single- and paired-pulse transcranial magnetic stimulation (TMS) was applied to the right motor cortex triggered by EMG onset of self-paced movements of individual right hand fingers at intervals ranging from 13 to 2,000 ms. Motor evoked potentials (MEPs) were evaluated in several left arm muscles. Significant suppression of MEP amplitudes was observed when TMS was applied between 35 and 70 ms after EMG onset. This inhibition was diffuse, affecting "adjacent" muscles (those near the homologous muscle in the same extremity) as well as homologous muscles, but more inhibition was observed in adjacent and distal muscles than homologous and proximal muscles. Significant inhibition of ipsilateral motor cortex was produced by index finger movements (both the extensor indicis proprius and the first dorsal interosseus), but not by little finger movement (the abductor digiti minimi). Paired-pulse TMS (at 2- and 10-ms interstimulus intervals) showed a significant increase in intracortical facilitation (ICF) selectively in the homologous muscle when triggered by self-paced movement of the opposite hand, but no change was observed in intracortical inhibition. When stimulation was triggered by self-paced movements, the silent period of the homologous muscle was significantly shortened, but the F-wave and compound muscle action potential were unchanged. Our findings demonstrate that voluntary hand movement exerts an inhibitory influence on a diffuse area of the ipsilateral motor cortex. This inhibitory influence is both time and movement dependent. The inhibitory influence is nonselective, while the facilitatory influence (enhancing ICF) appears to act selectively on the homologous muscles. These effects are most likely mediated by a transcallosal pathway.

Adult↗

PubMed2002

Modulation of human corticomotor excitability by somatosensory input.

In humans, somatosensory stimulation results in increased corticomotoneuronal excitability to the stimulated body parts. The purpose of this study was to investigate the underlying mechanisms. We recorded motor evoked potentials (MEPs) to transcranial magnetic stimulation (TMS) from abductor pollicis brevis (APB), first dorsal interosseous (FDI), and abductor digiti minimi (ADM) muscles. MEP amplitudes, recruitment curves (RC), intracortical inhibition (ICI), intracortical facilitation (ICF), resting (rMT) and active motor thresholds (aMT) were recorded before and after a 2-h period of ulnar nerve electrical stimulation at the wrist. Somatosensory input was monitored by recording somatosensory evoked potentials. To differentiate excitability changes at cortical vs. subcortical sites, we recorded supramaximal peripheral M-responses and MEPs to brainstem electrical stimulation (BES). In order to investigate the involvement of GABAergic mechanisms, we studied the influence of lorazepam (LZ) (a GABA(A) receptor agonist) relative to that of dextromethorphan (DM) (an NMDA receptor antagonist) and placebo in a double-blind design. We found that somatosensory stimulation increased MEP amplitudes to TMS only in the ADM, confirming a previous report. This effect was blocked by LZ but not by either DM or placebo and lasted between 8 and 20 min in the absence of (i) changes in MEPs elicited by BES, (ii) amplitudes of early somatosensory-evoked potentials or (iii) M-responses. We conclude that somatosensory stimulation elicited a focal increase in corticomotoneuronal excitability that outlasts the stimulation period and probably occurs at cortical sites. The antagonistic effect of LZ supports the hypothesis of GABAergic involvement as an operating mechanism.

Adolescent↗

PubMed2002

Modulation of rodent cortical motor excitability by somatosensory input.

It is assumed that somatosensory input is required for motor learning and recovery from focal brain injury. In rodents and other mammals, corticocortical projections between somatosensory and motor cortices are modified by patterned input. Whether and how motor cortex function is modulated by somatosensory input to support motor learning is largely unknown. Recent human evidence suggests that input changes motor excitability. Using transcranial magnetic stimulation (TMS), this study tested whether motor cortex excitability is affected by patterned somatosensory stimulation in rodents. Motor potentials evoked in gastrocnemius muscles in response to TMS (MEP(TMS)) and to cervical electrical stimulation (MEP(CES)) were recorded bilaterally. Initially, the first negative peak of the MEP(TMS) was identified as a cortical component because it disappeared after decortication in three animals. Subsequently, we studied the effects of 2 h of electrical stimulation of one sciatic nerve on the cortical component of the MEP(TMS), i.e., on motor cortex excitability. After stimulation, its amplitude increased by 117 +/- 45% ( P<0.01) in the stimulated limb. A significantly smaller effect was found in the unstimulated limb ( P<0.02) and no effect was observed in unstimulated control animals. The subcortically evoked MEP(CES) were not affected by stimulation. It is concluded that somatosensory input increases motor excitability in rat. This increase outlasts the stimulation period and is mediated by supraspinal structures, likely motor cortex. Modulation of motor cortex excitability by somatosensory input may play a role in motor learning and recovery from lesion.

Action Potentials↗

PubMed2002

Effect of levetiracetam on rapid motor learning in humans.

BACKGROUND: The human motor cortex (M1) has a role in motor learning. Antiepileptic drugs that suppress M1 excitability may affect learning, presumably by inhibiting long-term potentiation. Levetiracetam, a new antiepileptic drug with a unique preclinical profile, also suppresses M1 excitability, but in a way that is different from other antiepileptic drugs. The effect of levetiracetam on motor learning has yet to be addressed. OBJECTIVE: To investigate whether levetiracetam alters rapid motor learning in humans. METHODS: We measured pinch force and acceleration and motor excitability before and after 30 minutes of pinch practice at 0.5 Hz in 10 healthy volunteers. Either 3000 mg of levetiracetam or placebo was administered 1 hour before the experiment. RESULTS: After practice, pinch acceleration was significantly increased with placebo, but not with levetiracetam. All other measures showed no significant change. CONCLUSION: Levetiracetam interferes with rapid motor learning; this is consistent with a negative influence on long-term potentiation.

Adult↗

PubMed2002

Increase in hand muscle strength of stroke patients after somatosensory stimulation.

It has been proposed that somatosensory input in the form of peripheral nerve stimulation can influence functional measures of motor performance. We studied the effects of median nerve stimulation on pinch muscle strength (a function mediated predominantly by median nerve innervated muscles) in the affected hand of chronic stroke patients. A 2-hour period of median nerve stimulation elicited an increase in pinch strength that outlasted the stimulation period. The improvement in muscle strength correlated with stimulus intensity and was identified in the absence of motor training. These results suggest that somatosensory stimulation may be a promising adjuvant to rehabilitation of the motor deficits in stroke patients.

Adult↗

PubMed2002

Cortical excitability changes induced by deafferentation of the contralateral hemisphere.

Short-term deprivation of sensory input by ischaemic nerve block (INB) leads to functional reorganization in the deafferented motor cortex. Here, we show that INB also elicits functional changes in homotopic regions of the cortex contralateral to the deafferented one. We measured motor evoked potential (MEP) amplitudes elicited by transcranial magnetic stimulation (TMS) in small hand and biceps brachii muscles before, during and after INB of the right hand. INB increased excitability of the cortical representation of (i) the intact hand and (ii) body parts proximal to the deafferented hand (upper arm), in the absence of excitability changes in other body part representations such as thorax or leg muscles. This effect persisted throughout the entire period of deafferentation and returned to baseline values afterward. Motor responses to brainstem electrical stimulation remained unchanged during INB, indicating that the effect is probably of cortical origin. Lorazepam, a GABA(A) receptor agonist, blocked this increased excitability. Interhemispheric inhibition between hand muscles decreased during INB. After chronic deafferentation in amputees, MEP amplitudes and motor output curves in small hand muscles were depressed and motor thresholds were elevated compared with aged-matched controls. These results indicate that acute hand deafferentation can elicit a focal increase in excitability in the hand motor representation contralateral to the deafferented cortex that is influenced by transcallosal interactions and GABAergic transmission, and is balanced in the setting of chronic deafferentation.

Adult↗

PubMedDate not supplied

Protein synthesis inhibition blocks consolidation of an acrobatic motor skill.

To investigate whether motor skill learning depends on de novo protein synthesis, adult rats were trained in an acrobatic locomotor task (accelerating rotarod) for 7 d. Animals were systemically injected with cycloheximide (CHX, 0.5 mg/kg, i.p.) 1 h before sessions 1 and 2 or sessions 2 and 3. Control rats received vehicle injections before sessions 1, 2, and 3. Although CHX did not affect improvement of performance within session 1, between-session improvement was impaired. In overtrained animals, comparable injections of CHX had no effect on rotarod performance. These findings suggest that consolidation of motor skills requires protein synthesis.

Analysis of Variance↗