共查询到20条相似文献,搜索用时 234 毫秒
1.
Wang Y Xiang J Kotecha R Vannest J Liu Y Rose D Schapiro M Degrauw T 《Brain topography》2008,21(2):75-85
The present study investigated the spatial and frequency differences of neuromagnetic activities between the perception of
open- and closed-class words by using a 275-channel whole head magnetoencephalography (MEG) system. Two groups of words, 110
open-class and 110 closed-class, were presented visually and auditorily simultaneously. The data of 12 healthy subjects were
analyzed with synthetic aperture magnetometry (SAM) which can identify the frequency-dependent volumetric distribution of
evoked magnetic fields (EMFs). Both vocabulary classes elicited spectral power changes in the left inferior frontal gyrus
(Broca’s area) and left posterior-superior temporal gyrus (Wernicke’s area) within 70–120 Hz. However, the open-class words
elicited event-related desynchronization (ERD) while the closed-class words elicited event-related synchronization (ERS) in
the two areas within 70–120 Hz. In addition, the open-class words also elicited ERS in the right inferior frontal gyrus, right
middle frontal gyrus and right inferior parietal lobe within 1–8 Hz, but the closed-class words only elicited ERD in the right
inferior frontal gyrus within 1–8 Hz. Furthermore, there were ERD in the right posterior-superior temporal gyrus within 120–200 Hz
for the open-class words, but not for the closed-class words. These results indicate that open- and closed-class words are
processed differently in the brain, not only in the anatomical substrates, but also in the frequency range of neuromagnetic
activity. 相似文献
2.
Minoru Hoshiyama R. Kakigi P. Berg Sachiko Koyama Yoshihiro Kitamura Motoko Shimojo Shoko Watanabe A. Nakamura 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1997,115(1):6-14
We investigated the movement-related cortical fields (MRCFs) recorded by magnetoencephalography (MEG) to identify the motor
and sensory brain activities at the instant of the unilateral finger movement using six normal subjects. We focused our investigation
on the source analysis of the events tightly linked to movement onset, and we used brain electric source analysis (BESA) to
model the sources generating MRCFs during the interval from 200 ms before to 150 ms after the movement onset. Four sources
provided satisfactory solutions for MRCF activities in this interval. Sources 1 and 2, which were located in the pre-central
regions in the hemisphere contralateral and ipsilateral to the moved finger, respectively, generated the readiness fields
(RF), but source 1 was predominant just before movement onset. The motor field (MF), the peak of which was just after movement
onset, was mainly generated by source 1. Sources 3 and 4 were located in the post-central regions in the hemisphere contralateral
and ipsilateral to the moved finger, respectively. The first motor evoked field (MEF-I), the peak of which was about 80 ms
after the movement, was mainly generated by source 3, but with the participation of sources 1, 2 and 4. The results indicated
that the activities of both pre -and post-central regions in bilateral hemispheres were related to voluntary movements, although
the predominant areas varied over time. This is the first noninvasive study to clarify the complex spatiotemporal activities
relating movements in humans using a multi-channel MEG system.
Received: 8 January 1996 / Accepted: 3 December 1996 相似文献
3.
Calmels C Hars M Holmes P Jarry G Stam CJ 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2008,190(4):389-400
The main aim of this study was to examine the temporal aspects of neuronal changes during the observation and execution of
simple and complex tasks to gain a greater understanding of the mirror neuron system’s involvement in complex motor tasks.
Eleven right-handed subjects observed simple and complex finger movement sequences. Electroencephalograms were recorded from
19 electrodes. Activity was considered in four frequency bands (8–10, 10–13, 13–20, and 20–30 Hz) using a new measure, synchronization
likelihood. The results show that motor tasks of different levels of complexity did not have a significant influence on cortical
synchronization. The results also provide additional indirect evidence for mirror neuron activity associated with intransitive
tasks. Data are discussed in the light of recent findings from the cognitive and behavioral neuroscience literature. 相似文献
4.
Verstynen T Diedrichsen J Albert N Aparicio P Ivry RB 《Journal of neurophysiology》2005,93(3):1209-1222
Functional imaging studies have revealed recruitment of ipsilateral motor areas during the production of sequential unimanual finger movements. This phenomenon is more prominent in the left hemisphere during left-hand movements than in the right hemisphere during right-hand movements. Here we investigate whether this lateralization pattern is related specifically to the sequential structure of the unimanual action or generalizes to other complex movements. Using event-related fMRI, we measured activation changes in the motor cortex during three types of unimanual movements: repetitions of a sequence of movements with multiple fingers, repetitive "chords" composed of three simultaneous key presses, and simple repetitive tapping movements with a single finger. During sequence and chord movements, strong ipsilateral activation was observed and was especially pronounced in the left hemisphere during left-hand movements. This pattern was evident for both right-handed and, to a lesser degree, left-handed individuals. Ipsilateral activation was less pronounced in the tapping condition. The site of ipsilateral activation was shifted laterally, ventrally, and anteriorly with respect to that observed during contralateral movements and the time course of activation implied a role in the execution rather than planning of the movement. A control experiment revealed that strong ipsilateral activity in left motor cortex is specific to complex movements and does not depend on the number of required muscles. These findings indicate a prominent role of left hemisphere in the execution of complex movements independent of the sequential nature of the task. 相似文献
5.
Muthukumaraswamy SD 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2011,212(4):623-633
In recent years, the use of non-invasive techniques (EEG/MEG) to measure the ~80 Hz (“gamma”) oscillations generated by the
primary motor cortex during motor control has been well validated. However, primary motor cortex gamma oscillations have yet
to be systematically compared with lower frequency (30–50 Hz, ‘piper’) corticomuscular coherence in the same tasks. In this
paper, primary cortex gamma oscillations and piper corticomuscular coherence are compared for three types of movements: simple
abductions of the index finger, repetitive abductions of the index finger of different extents and frequencies and static
abduction of the index finger at two different force levels. For simple movements, piper coherence and gamma amplitude followed
very similar time courses with coherence appearing at approximately half the frequency of cortical gamma oscillations. No
evidence of 2:1 phase–phase coupling was observed. A similar pattern of results was observed for repetitive movements varying
in size and frequency; however, during the production of static force, the time courses became dissociated. During these movements,
EMG piper amplitude was sustained for the entire contraction; gamma power showed a burst at onset but no piper corticomuscular
coherence was observed. For these data, this dissociation suggests that while primary motor cortex gamma oscillations and
piper corticomuscular coherence may often co-occur during the production of dynamic movements, they probably reflect different
functional processes in motor control. 相似文献
6.
Hermer-Vazquez R Hermer-Vazquez L Srinivasan S Chapin JK 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2007,180(2):217-235
A major question in neuroscience concerns how widely separated brain regions coordinate their activity to produce unitary
cognitive states or motor actions. To investigate this question, we employed multisite, multielectrode recording in rats to
study how olfactory and motor circuits are coupled prior to the execution of an olfactory-driven, GO/NO-GO variant of a skilled,
rapidly executed (∼350–600 ms) reaching task. During task performance, we recorded multi-single units and local field potentials
(LFPs) simultaneously from the rats’ olfactory cortex (specifically, the posterior piriform cortex) and from cortical and
subcortical motor sites (the caudal forepaw M1, and the magnocellular red nucleus, respectively). Analyses on multi-single
units across areas revealed an increase in beta-frequency spiking (12–30 Hz) during a ∼100 ms window surrounding the Final Sniff of the GO cue before lifting the arm (the “Sniff-GO window”) that was seldom seen when animals sniffed the NO-GO cue. Also
during the Sniff-GO window, LFPs displayed a striking increase in beta, low-gamma, and high-gamma energy (12–30, 30–50, and
50–100 Hz, respectively), and oscillations in the high gamma band appeared to be coherent across the recorded sites. These
results indicate that transient, multispectral coherence across cortical and subcortical brain sites is part of the coordination
process prior to sensory-guided movement initiation.
Raymond Hermer-Vazquez, Linda Hermer-Vazquez these two authors contributed equally. 相似文献
7.
Novakovic V Sanguineti V 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2011,209(3):425-436
In many robot-assisted rehabilitation and motor skill learning applications, robots generate forces that facilitate movement
performance. While there is some evidence that assistance is beneficial, the underlying mechanisms of action are largely unknown,
and it is unclear what force patterns are more effective. Here, we investigate how reaching movements (and their neural correlates)
are altered by ‘assistive’ forces. Subjects performed center-out reaching movements, under the influence of a robot-generated
force, constant in magnitude and always directed toward the target. The experimental protocol included three phases: (1) baseline
(no forces), (2) force field (with two different force levels, 3 N and 6 N, applied in random order), and (3) after-effect
(no forces). EEG activity was recorded from motor and frontal cortical areas. In both movement kinematics and EEG activity,
we looked at the effects of forces, of adaptation to such forces and at the aftereffects of such adaptation. Assistive forces
initially induced a degraded performance and in general alterations in movement kinematics. However, subjects quickly adapted
to the perturbation by improving their performance. With regard to EEG activity, we found (1) an increased beta band synchronization
just before movements and an alpha band synchronization in the ipsilateral hemisphere, both proportional to force magnitude;
(2) a gradual decrease in alpha band synchronization with practice in the contralateral hemisphere; (3) an increase in theta
band synchronization in the later stage of the force epochs; and (4) an ipsilateral to contralateral shift (from baseline
to aftereffect) of theta band synchronization. These results point to the need for a careful design of assistive forces to
effectively facilitate motor performance and motor learning. Moreover, EEG signals exhibit distinct features related to force
and adaptation. Therefore, at least in principle, the latter might be used to monitor the learning process and/or to regulate
the amount of assistance. 相似文献
8.
Teo WP Rodrigues JP Mastaglia FL Thickbroom GW 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2012,216(1):41-49
Transcranial magnetic stimulation has been used to study changes in central excitability associated with motor tasks. Recently,
we reported that a finger flexion–extension task performed at a maximal voluntary rate (MVR) could not be sustained and that
this was not due to muscle fatigue, but was more likely a breakdown in central motor control. To determine the central changes
that accompany this type of movement task, we tracked motor-evoked potential (MEP) amplitude from the first dorsal interosseous
(FDI) and abductor pollicis brevis (APB) muscles of the dominant hand in normal subjects for 20 min after a 10 sec index finger
flexion–extension task performed at MVR and at a moderate sustainable rate (MSR) and half the MSR (MSR/2). The FDI MEP amplitude was reduced for up to 6–8 min after each of the tasks but there was a greater and longer-lasting
reduction after the MSR and MSR/2 tasks compared to the MVR task. There was a similar reduction in the amplitude of the FDI MEP after a 10 sec cyclic index
finger abduction–adduction task when the FDI was acting as the prime mover. The amplitude of the MEP recorded from the inactive
APB was also reduced after the flexion–extension tasks, but to a lesser degree and for a shorter duration. Measurements of
short-interval cortical inhibition revealed an increase in inhibition after all of the finger flexion–extension tasks, with
the MSR task being associated with the greatest degree of inhibition. These findings indicate that a demanding MVR finger
movement task is followed by a period of reduced corticomotor excitability and increased intracortical inhibition. However,
these changes also occur with and are greater with slower rates of movement and are not specific for motor demand, but may
be indicative of adaptive changes in the central motor pathway after a period of repetitive movement. 相似文献
9.
Po-Lei Lee Li-Zen Shang Yu-Te Wu Chih-Hung Shu Jen-Chuen Hsieh Yung-Yang Lin Chi-Hsun Wu Yu-Lu Liu Chia-Yen Yang Chia-Wei Sun Kuo-Kai Shyu 《Annals of biomedical engineering》2009,37(8):1683-1700
This study presents a method based on empirical mode decomposition (EMD) and a spatial template-based matching approach to
extract sensorimotor oscillatory activities from multi-channel magnetoencephalographic (MEG) measurements during right index
finger lifting. The longitudinal gradiometer of the sensor unit which presents most prominent SEF was selected on which each
single-trial recording was decomposed into a set of intrinsic mode functions (IMFs). The correlation between each IMF of the
selected channel and raw data on other channels were created and represented as a spatial map. The sensorimotor-related IMFs
with corresponding correlational spatial map exhibiting large values on primary sensorimotor area (SMI) were selected via
spatial-template matching process. Trial-specific alpha and beta bands were determined in sensorimotor-related oscillatory
activities using a two-spectrum comparison between the spectra obtained from baseline period (−4 to −3 s) and movement-onset
period (−0.5 to 0.5 s). Sensorimotor-related oscillatory activities were filtered within the trial-specific frequency bands
to resolve task-related oscillatory activities. Results demonstrated that the optimal phase and amplitude information were
preserved not only for alpha suppression (event-related desynchronization) and beta rebound (event-related synchronization)
but also for profound analysis of subtle dynamics across trials. The retention of high SNR in the extracted oscillatory activities
allow various methods of source estimation that can be applied to study the intricate brain dynamics of motor control mechanisms.
The present study enables the possibility of investigating cortical pathophysiology of movement disorder on a trial-by-trial
basis which also permits an effective alternative for participants or patients who can not endure lengthy procedures or are
incapable of sustaining long experiments. 相似文献
10.
Summary This article deals with the estimation of event-related coherence (ERCoh) and its application to the planning and execution of self-paced index finger movement. ERCoh estimation complements the event-related desynchronization (ERD) measurements of rhythms within the alpha band. ERCoh yields information of the functional relationships between different brain areas as a function of time. The time resolution is 125 msec. Before movement onset a contralateral ERCoh increase was found between premotor and motor areas. This coherence increase was accompanied by an ERCoh decrease in parallel to the ERD over the contralateral centro-temporal areas. During movement, the ERD became bilaterally symmetrical. Simultaneously, interhemispheric coherence between contralateral and ipsilateral sensori-motor areas increased.Supported by the Austrian Fonds zur Förderung der wissenschaftlichen Forschung project S 49/02. 相似文献
11.
The stochastic behavior of the phase synchronization index (SI) in different EEG bands was examined for noninvasive localization
of the epileptogenic areas from the short duration (30–60 s), seizure-free and spike-free high density (256 channel) scalp
EEG data. We also examined the cross-frequency and cross-electrode coupling in different EEG bands. EEG data of four subjects
was used. The seizure areas were localized with subdural recordings with an 8×8 grid electrode array. It was found that the
stochastic behavior of the SI in low gamma band (30–50 Hz) was higher in epileptogenic areas. The beta (12–30 Hz) band also
showed similar tendencies. The stochastic behavior in theta (3–7 Hz) band was depressed in the seizure area while it was widespread
in large areas over the scalp in the alpha (7–12 Hz) band. The stochastic behavior of the cross-frequency and cross-electrode
couplings in theta–gamma, alpha–gamma and beta–gamma bands were decreased in the seizure areas for all four subjects. These
findings suggest that it is possible to localize the epileptogenic areas from the short duration seizure-free and spike-free
high density scalp EEG data. 相似文献
12.
Several studies have suggested that the cerebellum has an important role in timing of subsecond intervals. Previous studies using transcranial magnetic stimulation (TMS) to test this hypothesis directly have produced inconsistent results. Here we used 1-Hz repetitive TMS (rTMS) for 10 min over the right or left cerebellar hemisphere to interfere transiently with cerebellar processing to assess its effect on the performance of a finger-tapping task. Subjects tapped with their right index finger for 1 min (synchronization phase) with an auditory or visual cue at 0.5, 1, or 2 Hz; they continued for a further 1 min at the same rate with no cues (continuation phase). The blocks of trials were performed in a random order. rTMS of the cerebellum ipsilateral to the movement increased the variability of the intertap interval but only for movements at 2 Hz that were made while subjects were synchronizing with an auditory cue. There was no effect on the continuation phase of the task when the cues were no longer present or on synchronization with a visual cue. Similar results were seen after stimulation over the contralateral dorsal premotor cortex but not after rTMS over supplementary motor area. There was no effect after rTMS over the ipsilateral right cervical nerve roots or over the ipsilateral primary motor cortex. The results support the hypothesis of neural network for event-related timing in the subsecond range that involves a cerebellar-premotor network. 相似文献
13.
Shim JK Karol S Hsu J de Oliveira MA 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2008,186(3):443-456
The aim of this study was to investigate the contralateral motor overflow in children during single-finger and multi-finger
maximum force production tasks. Forty-five right handed children, 5–11 years of age produced maximum isometric pressing force
in flexion or extension with single fingers or all four fingers of their right hand. The forces produced by individual fingers
of the right and left hands were recorded and analyzed in four-dimensional finger force vector space. The results showed that
increases in task (right) hand finger forces were linearly associated with non-task (left) hand finger forces. The ratio of
the non-task hand finger force magnitude to the corresponding task hand finger force magnitude, termed motor overflow magnitude
(MOM), was greater in extension than flexion. The index finger flexion task showed the smallest MOM values. The similarity
between the directions of task hand and non-task hand finger force vectors in four-dimensional finger force vector space,
termed motor overflow direction (MOD), was the greatest for index and smallest for little finger tasks. MOM of a four-finger
task was greater than the sum of MOMs of single-finger tasks, and this phenomenon was termed motor overflow surplus. Contrary
to previous studies, no single-finger or four-finger tasks showed significant changes of MOM or MOD with the age of children.
We conclude that the contralateral motor overflow in children during finger maximum force production tasks is dependent upon
the task fingers and the magnitude and direction of task finger forces. 相似文献
14.
Chen Y Ding M Kelso JA 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2003,148(1):105-116
We analyzed a set of full-head (66 channels, CTF Inc.) magnetoencephalography (MEG) data recorded when 5 subjects performed
rhythmic right index-finger flexion and extension movements on the beat (synchronization) or off the beat (syncopation) with
a visual metronome at 1 Hz. Neuromagnetic activities in the alpha (8–14 Hz), beta (15–30 Hz) and gamma (30–50 Hz) ranges were
shown to correlate with different aspects of the task. Specifically, we found that, compared with the control condition in
which subjects only looked at the visual metronome without making any movement, all the movement conditions were accompanied
by a decrease of power in the alpha range (8–14 Hz) in sensorimotor channels of both hemispheres, and an increase of coherence
among a subset of these channels. The same comparison showed that power changes in the beta range differentiate task conditions
by exhibiting power increases for synchronization and power decreases for syncopation. Changes in the gamma range power were
found to be related to the kinematics of movement trajectories (flexion versus extension). These results suggest that three
important cortical oscillations play different functional roles in a visuomotor timing task.
Electronic Publication 相似文献
15.
Kidgell DJ Sale MV Semmler JG 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2006,175(4):745-753
The purpose of the study was to quantify the strength of motor unit synchronization and coherence from pairs of concurrently active motor units before and after short-term (4–8 weeks) strength training of the left first dorsal interosseous (FDI) muscle. Five subjects (age 24.8 ± 4.3 years) performed a training protocol three times/week that consisted of six sets of ten maximal isometric index finger abductions, whereas three subjects (age 27.3 ± 6.7 years) acted as controls. Motor unit activity was recorded from pairs of intramuscular electrodes in the FDI muscle with two separate motor unit recording sessions obtained before and after strength training (trained group) or after 4 weeks of normal daily activities that did not involve training (control group). The training intervention resulted in a 54% (45.2 ± 8.3 to 69.5 ± 13.8 N, P = 0.001) increase in maximal index finger abduction force, whereas there was no change in strength in the control group. A total of 163 motor unit pairs (198 single motor units) were examined in both subject groups, with 52 motor unit pairs obtained from 10 recording sessions before training and 51 motor unit pairs from 10 recording sessions after training. Using the cross-correlation procedure, there was no change in the strength of motor unit synchronization following strength training (common input strength index; 0.71 ± 0.41 to 0.67 ± 0.43 pulses/s). Furthermore, motor unit coherence z scores at low (0–10 Hz; 3.9 ± 0.3 before to 4.4 ± 0.4 after) or high (10–30 Hz; 1.7 ± 0.1 before to 1.9 ± 0.1 after) frequencies were not influenced by strength training. These motor unit data indicate that increases in strength following several weeks of training a hand muscle are not accompanied by changes in motor unit synchronization or coherence, suggesting that these features of correlated motor unit activity are not important in the expression of muscle strength.Dawson J. Kidgell and Martin V. Sale contributed equally to the study. 相似文献
16.
Ron Levy Andres M. Lozano Anthony E. Lang Jonathan O. Dostrovsky 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2010,206(1):1-13
Multiple system atrophy (MSA) is a progressive neurodegenerative disease characterized by parkinsonism (MSA-P), cerebellar
and autonomic deficits. In Parkinson’s disease (PD), an impaired modulation of motor cortical mu and beta range oscillations
may be related to the pathophysiology of bradykinesia. Event-related desynchronization (ERD) of these oscillations occur for
1–2 s preceding a voluntary movement in normal subjects and patients with PD treated with levodopa while only lasting around
0.5 s in untreated patients. Motor cortical rhythms were recorded from subdural strip electrodes in three patients with MSA-P
while taking their regular dopaminergic medications. Following a ready cue, patients performed an externally cued wrist extension
movement to a go cue. In addition, recordings were obtained during imagined wrist extension movements to the same cues and
during self-paced wrist extensions. ERD and event-related synchronization were examined in subject-specific frequency bands.
All patients showed movement-related ERD in subject-specific frequency bands below ~40 Hz in both externally cued and self-paced
conditions. Preparatory ERD latency preceding self-cued movement was 900 ms in one patient and at or after movement onset
in the other two patients. In the externally cued task, a short lasting (<1.3 s) ready cue-related ERD that was not sustained
to movement onset was observed in two patients. Imagined movements resulted in go cue-related ERD with a smaller magnitude
in the same two patients. These results indicate that the modulation of motor cortical oscillations in patients with MSA that
are treated with levodopa is similar to that occurring in untreated patients with PD. The findings suggest that cortical activation
in patients with MSA is diminished, may be related to pathophysiological changes occurring in the basal ganglia and correlates
with the poor clinical response that these patients typically obtain with dopaminergic therapy. 相似文献
17.
This study investigated the neuromagnetic spatial and frequency differences between recognizing concrete and abstract words
using a 275 channel whole head magnetoencephalography (MEG) system. The stimuli consisted of 100 concrete words and 100 abstract
words which were presented visually and auditorily simultaneously. The data of 12 right-handed healthy subjects in six different
frequency bands were analyzed with synthetic aperture magnetometry (SAM) which can identify the frequency-dependent volumetric
distribution of the evoked magnetic field. Concrete and abstract words evoked a very similar neuromagnetic activation pattern
in the primary visual and auditory cortices. However, concrete words evoked stronger synchronization in the right hemisphere
and abstract words evoked stronger synchronization in the left hemisphere in 1–8 Hz. In addition, concrete words evoked more
desynchronization in the left posterior temporal and parietal cortex; while abstract words evoked a clear synchronization
in the left posterior temporal cortex and desynchronization in the left inferior frontal cortex in 70–120 Hz. Furthermore,
concrete words evoked clear desynchronization in the left inferior frontal cortex while abstract words evoked strong synchronization
in the left posterior temporal cortex in 200–300 Hz. These findings suggested that concrete words and abstract words are processed
differently in the brain not only in anatomical substrates, but also in the frequency band of neural activation. 相似文献
18.
Kato Y Endo H Kizuka T Asami T 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2006,168(1-2):51-61
The stimulus–response (S–R) compatibility effect refers to the difference in performance due to the spatial S–R relationship
in choice reaction time. We investigated the mechanism of neural activities in S–R compatibility at the level of the primary
motor cortices for upper and lower limbs responses using magnetoencephalography (MEG). In the S–R compatible task, subjects
were required to respond on the same side of the stimulus light using either an upper or lower limb. In the incompatible task,
subjects were required to respond in the reverse manner. Premotor times of upper and lower limbs were faster for the compatible
response than for the incompatible response. The neuromagnetic brain activities related to response execution were estimated
using a multi-dipole model. Stimulus-locked MEG indicated that the current moments of motor dipoles for both effectors occurred
bilaterally and reached the first peak at a constant delay irrespective of whether the task was compatible or incompatible.
This indicates that the neural activation of the primary motor cortex is automatically synchronized with the stimulus onset.
Response-locked MEG showed that the peak current moment of the motor dipole contralateral to the response was stronger for
the compatible task than for the incompatible one regardless of whether the responses were made using the upper or lower limbs.
The MEG results suggest that automatic motor activation facilitates imperative motor activation for a compatible response,
whereas it is not sufficient to prime imperative motor activation for an incompatible response. 相似文献
19.
In light of the interplay between limb oscillatory outputs and the outcome performance of movement effectors, this study was undertaken to investigate neuromotor control in the upper limb during position tracking and posture holding. Sixteen volunteers conducted a postural pointing task and two index tracking maneuvers at 0.3 and 0.6 Hz with an outstretched arm. Limb acceleration in the index finger, hand, forearm, arm, and C7 spinal process were monitored to correlate functionally with the accuracy of index rhythmic displacements. The results showed that index oscillatory activity multiplied with tracking speed, but hand oscillatory activity declined during tracking movement. The tracking maneuvers also altered spectral distribution of the tremulous activities in the context of a lower spectral peak in the range of 8–12 Hz and suppression of spectral peaks at 2–4 Hz, in reference to that already presented in posture tremor. Consisting of three local maxima around 2–4, 8–12, and 18–22 Hz, the coherence of tremulous activity between the finger and hand during position tracking was nearly identical, but inferior to high coherence below 12 Hz during posture holding. Functionally, better tracking performance was associated with a smaller tremulous activity in the finger and hand, entailing sophisticated release of mechanical couplings in the finger-hand and hand-forearm. In conclusion, inversely related to tracking performance, limb tremulous movements were task-dependently organized, and speed-invariant coherence of limb tremulous movement specified an inter-segmental coordination, which is physiological evidence of the generalized motor program for position tracking. 相似文献
20.
Julian P. Rodrigues Frank L. Mastaglia Gary W. Thickbroom 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2009,196(4):557-563
Exploring the limits of the motor system can provide insights into the mechanisms underlying performance deterioration, such
as force loss during fatiguing isometric muscle contraction, which has been shown to be due to both peripheral and central
factors. However, the role of central factors in performance deterioration during dynamic tasks has received little attention.
We studied index finger flexion/extension movement performed at maximum voluntary rate (MVR) in ten healthy subjects, measuring
movement rate and amplitude over time, and performed measures of peripheral fatigue. During 20 s finger movements at MVR,
there was a decline in movement rate beginning at 7–9 s and continuing until the end of the task, reaching 73% of baseline
(P < 0.001), while amplitude remained unchanged. Isometric maximum voluntary contraction force and speed of single ballistic
flexion and extension finger movements remained unchanged after the task, indicating a lack of peripheral fatigue. The timing
of finger flexor and extensor EMG burst activity changed during the task from an alternating flexion/extension pattern to
a less effective co-contraction pattern. Overall, these findings suggest a breakdown of motor control rather than failure
of muscle force generation during an MVR task, and therefore that the mechanisms underlying the early decline in movement
rate are central in origin. 相似文献