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C Gerloff

Publications and source records attributed to C Gerloff.

At least 19 recordsLinked to original sources
PubMed2006

Developing somatosensory projections bypass periventricular brain lesions.

The authors studied four hemiparetic patients with large unilateral periventricular brain lesions acquired during the early third trimester of pregnancy. fMRI and magnetoencephalography demonstrated that the primary somatosensory representation of their paretic hands was nevertheless located in the contralateral rolandic cortex. Thus, outgrowing thalamocortical somatosensory projections had apparently bypassed the lesion to reach their original cortical destination. Such somatosensory projections curving around the lesion were effectively visualized by magnetic resonance diffusion tractography.

Adult↗
PubMed2006

Moderate therapeutic efficacy of positron emission tomography-navigated repetitive transcranial magnetic stimulation for chronic tinnitus: a randomised, controlled pilot study.

BACKGROUND: Tinnitus has been shown to respond to modulations of cortical activity by high-frequency and low-frequency repetitive transcranial magnetic stimulation (rTMS). OBJECTIVE: To determine the tinnitus-attenuating effects of a 2-week daily regimen of rTMS, navigated to the maximum of tinnitus-related increase in regional cerebral blood flow. METHODS: Six patients with chronic tinnitus were enrolled in this sham-controlled crossover study and treated with 2x2 weeks of suprathreshold 1 Hz rTMS (30 min) applied to the region with maximal tinnitus-related increase in regional cerebral blood flow delineated by functional imaging with [15O]H2O positron emission tomography and a control area. Tinnitus-related distress was assessed before and after each treatment and 2 weeks after the end of the 4-week course of stimulation using a validated tinnitus questionnaire. Additional self-assessment scores of tinnitus change, loudness and annoyance were obtained. RESULTS: In five of six patients, rTMS induced greater reduction of the tinnitus questionnaire score than sham stimulation. In two patients, all parameters measured (tinnitus change score, tinnitus loudness, tinnitus annoyance) showed unequivocal improvement. At the group level, the degree of response in the tinnitus questionnaire score was correlated with tinnitus-associated activation of the anterior cingulate cortex. Two weeks after the final stimulation, tinnitus had returned to baseline in all patients but one. CONCLUSION: Tinnitus can be attenuated by low-frequency rTMS navigated to each person's maximum tinnitus-related cortical hyperactivity. The effects are only moderate; interindividual responsiveness varies and the attenuation seems to wear off within 2 weeks after the last stimulation session. Notably, tinnitus-related anterior cingulate cortex activation seems to predict the response to rTMS treatment.

Aged↗
PubMed2001

Noradrenergic modulation of human cortex excitability by the presynaptic alpha(2)-antagonist yohimbine.

The objective of this study was to determine if yohimbine, a central norepinephrine enhancing drug, increases cortico-motoneuronal excitability in intact humans. Transcranial magnetic stimulation was used to assess excitability of the motor system reflected in the parameters motor threshold, recruitment curve, intracortical inhibition and intracortical facilitation before and after oral administration of 20 and 40 mg yohimbine. Oral intake of 40 but not 20 mg yohimbine increased slope and plateau of the recruitment curve and intracortical facilitation. Motor threshold and intracortical inhibition remained unchanged. The data show that pharmacological enhancement of central norepinephrine in humans is effective to increase the cortico-motoneuronal excitability. Since cortical excitability is closely linked to neuroplasticity, this observation might be of possible relevance for strategies to enhance rehabilitative processes after cortical lesions by pairing noradrenergic drugs with motor training.

Adrenergic alpha-Antagonists↗
PubMed2001

Event-related desynchronization in reaction time paradigms: a comparison with event-related potentials and corticospinal excitability.

OBJECTIVES: To study cortical activity in different motor tasks, we compared event-related desynchronization (ERD) and event-related potentials (ERPs) in different reaction time (RT) paradigms with the time course of corticospinal excitability. METHODS: Nine right-handed, normal subjects performed right or left thumb extensions in simple, choice and go/no go auditory RT paradigms. Eight subjects had participated in a previous study evaluating changes in corticospinal excitability during the same paradigms. Twenty-nine EEG channels with electrooculogram and bilateral EMG monitoring were collected. ERPs and ERD of 10 and 18-22 Hz bands were obtained with respect to tone administration and EMG onset. RESULTS: Trials with movement showed lateralized ERP components, corresponding to the motor potential (MP), both in the averages on the tone and on EMG. The MP corresponded well in time and location to the rise in corticospinal excitability on the moving side observed in the previous study. Sensorimotor ERD, followed by event-related synchronization (ERS), was present for trials with movements and for the no go. ERD was present contralaterally during movement preparation and in no go trials, while it was bilateral during motor execution. No go ERD was followed more rapidly by ERS than in trials with movement. This finding suggests that in no go trials, there is a brief active process in the sensorimotor areas. ERD and ERS do not correspond, respectively, in time and location to increases and decreases in corticospinal excitability. In fact, ERD is bilateral during movement execution, when corticospinal inhibition of the side at rest is observed. Contralateral no go ERS occurs later than corticospinal inhibition, which is bilateral. CONCLUSIONS: These findings may suggest that ERD is compatible with both corticospinal activation and inhibition, ERS indicating the removal of either, resulting in cortical idling.

Acoustic Stimulation↗
PubMed2000

The influence of normal aging on the cortical processing of a simple motor task.

OBJECTIVE: To assess the influence of normal aging on the cortical physiology of motor behavior. METHODS: The authors studied cortical activation in eight elderly (55 to 76 years of age) and eight younger (18 to 27 years of age) healthy subjects while they performed a simple motor task. A 28-channel EEG was recorded; task-related power changes associated with repetitive, metronome-paced (1 Hz) finger movements were computed as a measure of cortical activation. RESULTS: Distinct, age-dependent activation patterns were expressed in four distinct frequency ranges: low-alpha (10 to 11 Hz), high-alpha (12 to 13 Hz), low-beta (16 to 17 Hz), and high-beta (22 to 23 Hz) bands. The main findings were a greater overall activation and, more specifically, a pronounced bilateral activation of sensorimotor regions in elderly subjects for both alpha bands. Additionally, in the elderly subjects there was increased activation of the mesial frontocentral cortex (supplementary motor area region) in the high-beta band, whereas younger volunteers had a prominent activation of the left lateral premotor and sensorimotor region in this frequency range. CONCLUSIONS: These findings demonstrate that the functional anatomy of the human motor system changes during normal aging. It appears that, for a given motor task, the aging brain recruits additional primary sensorimotor and premotor regions of both hemispheres.

Adolescent↗
PubMed2000

Electroencephalographic measurement of motor cortex control of muscle activity in humans.

OBJECTIVE: To detect and measure correlation between cortical and muscle activities, coherence analysis was used. METHODS: The electroencephalogram (EEG) and electromyogram (EMG) were recorded in 9 normal volunteers during tonic contraction of upper and lower limb muscles on the right side. Coherence between EEG and EMG was computed to analyze their linear association. RESULTS: EEG over the contralateral sensorimotor area was coherent with EMG, with peak coherence at 11-36 Hz (mean, 22 Hz). For the abductor pollicis brevis (APB) muscle, peak coherence, as determined by functional brain mapping with focal transcranial magnetic stimulation (TMS), was over or slightly posterior to the hand area on the primary motor cortex determined by focal transcranial magnetic stimulation (TMS). Peak coherence over the scalp was somatotopically organized. The temporal relation between EEG and EMG was analyzed with a new model for interpreting the phase shift ('constant phase shift plus constant time lag' model). For the APB muscle, the phase relation between cortical and muscular oscillations differed in the frequency ranges of 3-13 Hz and 14-50 Hz, respectively, suggesting that different coupling mechanisms operate in different bands. Only the phase shift between cortical and motoneuronal firing at 14-50 Hz was reliably estimated by a linear model. At 14-50 Hz, motoneuronal firing was led by surface-negative cortical activity with a constant time lag that depended on the cortical-muscular distance. For the APB muscle, the time lag was slightly shorter than the cortical-muscular conduction time determined by TMS. Vibratory stimulation (100 Hz) of a muscle tendon during tonic contraction had no significant effect on cortical-muscular coherence, indicating that cortical oscillation reflected motor rather than sensory activity. CONCLUSIONS: The present findings suggest temporal coding of the oscillatory motor control system (3-13 Hz vs. 14-50 Hz), and confirm the functional importance of cortical beta and gamma rhythms in the motor efferent command. Cortical-muscular synchronization is most likely mediated by the direct corticospinal pathway within the frequency range of 14-50 Hz.

Adult↗
PubMed1999

PET study of visually and non-visually guided finger movements in patients with severe pan-sensory neuropathies and healthy controls.

Although patients with sensory neuropathies and normal muscle power are rare, they have been extensively studied because they are a model for dissociating the sensory and motor components of movement. We have examined these patients to determine the cerebral functional anatomy of movement in the absence of proprioceptive input. In addition, the disabling symptoms of these patients can be substantially improved by visually monitoring their movements. We hypothesized that, during visually guided movements, these patients would show overactivity of regions specialized for visuomotor control with the possible additional involvement of areas that normally process somatosensory information. We used positron emission tomography (PET) and the tracer H(2)(15)O to determine the functional anatomy of visually and non-visually guided finger movements in three patients with long-standing pan-sensory neuropathies and normal muscle power and six healthy controls. Five conditions were performed with the right hand: a sequential finger movement task under visual guidance, the same motor task without observation of the hand, monitoring a video of the same sequential finger movement, a passive visual task observing a reversing checkerboard, and an unconstrained rest condition. Data were analyzed using conventional subtraction techniques with a statistical threshold of z>2.33 with corrections for multiple comparisons. When compared with the control group, activation was not deficient in any brain areas of the patient cohort in any of the contrasts tested. In particular, in the non-visually guided movement task, in which meaningful visual and proprioceptive input was absent, the patient group activated primary motor, premotor, and cerebellar regions. This suggests that these areas are involved in motor processing independent of sensory input. In all conditions involving visual observation of hand movements, there was highly significant overactivity of the left parietal operculum (SII) and right parieto-occipital cortex (PO) in the patient group. Recent non-human primate studies have suggested that the PO region contains a visual representation of hand movements. Overactivity of this area and the activation of SII by visual input appear to indicate that compensatory overactivity of visual areas and cross-modal plasticity of somatosensory areas occur in deafferented patients. These processes may underlie their ability to compensate for their proprioceptive deficits.

Aged↗
PubMed1999

Functional coupling of human cortical sensorimotor areas during bimanual skill acquisition.

Bimanual co-ordination of skilled finger movements is a high-level capability of the human motor system and virtually always requires training. Little is known about the physiological processes underlying successful bimanual performance and skill acquisition. In the present study, we used task-related coherence (TRCoh) and task-related power (TRPow) analysis of multichannel surface EEG to investigate the functional coupling and regional activation of human sensorimotor regions during bimanual skill acquisition. We focused on changes in interhemispheric coupling associated with bimanual learning. TRCoh and TRPow were estimated during the fusion of two overlearned unimanual finger-tapping sequences into one novel bimanual sequence, before and after a 30-min training period in 18 normal volunteers. Control experiments included learning and repetition of complex and simple unimanual finger sequences. The main finding was a significant increase in interhemispheric TRCoh selectively in the early learning stage (P < 0.0001). Interhemispheric TRCoh was also present during the unimanual control tasks, but with lower magnitude, even if learning was involved. Training improved bimanual sequence performance (from 58.3+/-24.1 to 83.7+/-15.3% correct sequences). After training, interhemispheric (bimanual) TRCoh decreased again, thereby approaching levels similar to those in the unimanual controls. We propose that the initial increase in TRCoh reflects changes in interhemispheric communication that are specifically related to bimanual learning and may be relayed through the corpus callosum. The present data might also offer a neurophysiological explanation for the clinical observation that patients with lesions of the corpus callosum may show deficits in the acquisition of novel bimanual tasks but not necessarily in the execution of previously learned bimanual activities.

Adult↗
PubMed1999

Coherence of sequential movements and motor learning.

The analysis of oscillatory EEG phenomena such as interregional coherence (task-related coherence [TRCoh] or event-related coherence) has advanced our knowledge of neurophysiological processes underlying the performance and learning of skilled finger movements. It has become clear that various types of higher task demands are reflected by changes in the functional coupling of different cortical areas and not only by changes in regional activation. Neuroscientists are merely starting to understand how coherent oscillations might encode information in the human motor system ("sensorimotor binding") and how well this can be measured from the surface EEG. However, interregional coherence is a potentially independent mechanism that can, up to now, only be investigated with electrophysiological techniques such as EEG and MEG. The studies reviewed below focus on coherence of finger movements and motor learning: increasing complexity of a movement sequence, internal rhythm generation, visuomotor integration, deficits in interhemispheric coupling, and bimanual coordination. Evidence is presented for a special functional significance of TRCoh in the beta frequency range (13 to 21 Hz) for information processing in large-scale sensorimotor networks during motor tasks.

Electroencephalography↗
PubMed1999

Movement-related cerebellar activation in the absence of sensory input.

Movement-related cerebellar activation may be due to sensory or motor processing. Ordinarily, sensory and motor processing are obligatorily linked, but in patients who have severe pansensory neuropathies with normal muscle strength, motor activity occurs in isolation. In the present study, positron emission tomography and functional magnetic resonance imaging in such patients showed no cerebellar activation with passive movement, whereas there was prominent movement-related cerebellar activation despite absence of proprioceptive or visual input. The results indicate that motor processing occurs within the cerebellum and do not support the recently advanced view that the cerebellum is primarily a sensory organ.

Aged↗
PubMed1998

Inhibitory influence of the ipsilateral motor cortex on responses to stimulation of the human cortex and pyramidal tract.

1. The ability of the primary motor cortex (M1) to modulate motor responses in ipsilateral hand muscles seems to be important for normal motor control and potentially also for recovery after brain lesions. It is not clear which pathways mediate this ipsilateral modulation. Transcallosal connections have been proposed, but are known to be sparse between cortical hand motor representations in primates. The present study was performed to determine whether descending ipsilateral modulation of motor responses might also be mediated below the cortical level in humans. 2. A paired-pulse protocol was used, in which motor-evoked potentials (MEPs) were produced by cortical transcranial magnetic stimulation (cTMS) or by electrical stimulation of the pyramidal tract at the level of the pyramidal decussation (pdTES), in both preactivated and relaxed hand muscles. Paired stimuli were applied at various interstimulus intervals (ISIs) between 2 and 100 ms. The conditioning stimulus (CS) was always magnetic, and delivered to the M1 ipsilateral to the target hand, prior to the test stimulus (TS). The magnetic TS was delivered to the M1 contralateral to the target hand; the electrical TS was applied through electrodes placed over the mastoid process bilaterally. Further experiments included cortical electrical stimulation and H-reflexes. The MEP amplitudes were averaged separately for each ISI and the control condition (no CS), and expressed as a percentage of the unconditioned response. 3. Conditioning stimulation of the ipsilateral M1 resulted in significant inhibition of magnetically evoked MEPs, and also of MEPs produced by pdTES. Inhibition occurred at ISIs between 6 and 50 ms, and was observed in preactivated and relaxed muscles. Higher CS intensities caused greater inhibition of both cTMS- and pdTES-evoked MEPs. 4. While the conditioning effects on magnetically evoked muscle responses could be explained by a transcallosal mechanism, the effects on pdTES-evoked MEPs cannot, because they are elicited subcortically and are therefore not susceptible to inhibitory mechanisms transmitted at the cortico-cortical level. 5. In conclusion, the present results provide novel evidence that the inhibitory influence of the human M1 on ipsilateral hand muscles is to a significant extent mediated below the cortical level, and not only through cortico-cortical transcallosal connections. They point to a concept of inhibitory interaction between the two primary motor cortices that is relayed at multiple levels along the neuroaxis, thus perhaps providing a structurally redundant system which may become important in case of lesions.

Adult↗
PubMed1998

Cutaneous withdrawal reflexes of the upper extremity.

We characterized reflexes of the upper limb elicited by electrical stimulation of the fingers. Surface electromyogram (EMG) was recorded from several upper extremity muscles, and a finger was stimulated through paired ring electrodes. A train of 4-10 shocks at a frequency of 300 Hz and an intensity 4-6 times the perceptual threshold was the most effective stimulus for evoking EMG activity in relaxed arm muscles. Habituation was prominent. Latencies of EMG activity were <100 ms for most proximal and forearm muscles, and at least 40 ms prior to voluntary withdrawal movements. The timing of EMG activity in arm muscles was similar to that of the E2 component of the cutaneomuscular reflex evoked in these same muscles during contraction, and coincided with a silent period in active hand muscles. We conclude that cutaneous stimuli to the fingers activate a complex motor pattern that tends to withdraw the hand at the same time the grasp is released.

Adult↗
PubMed1998

Abnormal somatosensory homunculus in dystonia of the hand.

Abnormalities of the sensory system have been proposed as causative factors for dystonia By mapping the human cortical hand somatosensory area of 6 patients with focal dystonia of the hand, we found an abnormality of the normal homuncular organization of the finger representations in the primary somatosensory cortex (S1). Although a remote antecedent event or even a developmental anomaly cannot entirely be ruled out, our findings may support the concept that abnormal plasticity is involved in the development of dystonia.

Brain↗
PubMed1998

Task-related coherence and task-related spectral power changes during sequential finger movements.

In order to investigate the activity of cortical regions in the control of complex movements, we studied task-related coherence (TRCoh) and task-related spectral power (TRPow) changes in 8 right-handed subjects during the execution of 4 different finger movement sequences of increasing complexity. All sequences were performed with the right hand and were paced by a metronome at 2 Hz. EEG power spectra and coherence values were computed within alpha (8-12 Hz) and beta (13-20 Hz) frequency bands for 29 scalp EEG positions during the execution of the sequences and were compared with values obtained during a rest (control) condition. Movement sequences were associated with TRPow decreases in the alpha and beta frequency bands over bilateral sensorimotor and parietal areas, with a preponderance over the contralateral hemisphere. Increases of TRCoh occurred over bilateral frontocentral regions. TRCoh decreases were present over the temporal and occipital areas. The spatial extent and the magnitude of TRPow decreases and TRCoh increases in both frequency bands were greater for sequential movements of higher complexity than for simpler ones. These results are consistent with previous findings of bilateral activation of sensorimotor areas during sequential finger movements. Moreover, the present results indicate an active intercommunication between bilateral and mesial central and prefrontal regions which becomes more intense with more complex sequential movements.

Adult↗
PubMed1998

Cortical activation during fast repetitive finger movements in humans: steady-state movement-related magnetic fields and their cortical generators.

OBJECTIVE: To study the cortical physiology of fast repetitive finger movements. METHODS: We recorded steady-state movement-related magnetic fields (ssMRMFs) associated with self-paced, repetitive, 2-Hz finger movements in a 122-channel whole-head magnetometer. The ssMRMF generators were determined by equivalent current dipole (ECD) modeling and co-registered with anatomical magnetic resonance images (MRIs). RESULTS: Two major ssMRMF components occurred in proximity to EMG onset: a motor field (MF) peaking at 37+/-11 ms after EMG onset, and a postmovement field (post-MF), with inverse polarity, peaking at 102+/-13 ms after EMG onset. The ECD for the MF was located in the primary motor cortex (M1), and the ECD for the post-MF in the primary somatosensory cortex (S1). The MF was probably closely related to the generation of corticospinal volleys, whereas the post-MF most likely represented reafferent feedback processing. CONCLUSIONS: The present data offer further evidence that the main phasic changes of cortical activity occur in direct proximity to repetitive EMG bursts in the contralateral M1 and S1. They complement previous electroencephalography (EEG) findings on steady-state movement-related cortical potentials (ssMRCPs) by providing more precise anatomical information, and thereby enhance the potential value of ssMRCPs and ssMRMFs for studying human sensorimotor cortex activation non-invasively and with high temporal resolution.

Adult↗
PubMed1998

Functional coupling and regional activation of human cortical motor areas during simple, internally paced and externally paced finger movements.

We studied the activation and interaction of cortical motor regions during simple, internally paced and externally paced right-hand finger extensions in healthy volunteers. We recorded EEGs from 28 scalp electrodes and analysed task-related coherence, task-related power and movement-related cortical potentials. Task-related coherence reflects inter-regional functional coupling of oscillatory neuronal activity, task-related power reflects regional oscillatory activity of neuronal assemblies and movement-related cortical potentials reflect summated potentials of apical dendrites of pyramidal cells. A combination of these three analytical techniques allows comprehensive evaluation of different aspects of information processing in neuronal assemblies. For both externally and internally paced finger extensions, movement-related regional activation was predominant over the contralateral premotor and primary sensorimotor cortex, and functional coupling occurred between the primary sensorimotor cortex of both hemispheres and between the primary sensorimotor cortex and the mesial premotor areas, probably including the supplementary motor area. The main difference between the different types of movement pacing was enhanced functional coupling of central motor areas during internally paced finger extensions, particularly inter-hemispherically between the left and right primary sensorimotor cortexes and between the contralateral primary sensorimotor cortex and the mesial premotor areas. Internally paced finger extensions were also associated with additional regional (premovement) activation over the mesial premotor areas. The maximal task-related coherence differences between internally and externally paced finger extensions occurred in the frequency range of 20-22 Hz rather than in the range of maximal task-related power differences (9-11 Hz). This suggests that important aspects of information processing in the human motor system could be based on network-like oscillatory cortical activity and might be modulated on at least two levels, which to some extent can operate independently from each other: (i) regional activation (task-related power) and (ii) inter-regional functional coupling. We propose that internal pacing of movement poses higher demands on the motor system than external pacing, and that the motor system responds not only by increasing regional activation of the mesial premotor system, including the supplementary motor area, but also by enhancing information flow between lateral and mesial premotor and sensorimotor areas of both hemispheres, even if the movements are simple and unimanual.

Adult↗