Showing papers on "Motor imagery published in 1999"
TL;DR: The results of cortical activity support the hypothesis that motor imagery and motor performance possess similar neural substrates as well as the assumption that the posterior cerebellum is involved in the inhibition of movement execution during imagination.
Abstract: Brain activation during executed (EM) and imagined movements (IM) of the right and left hand was studied in 10 healthy right-handed subjects using functional magnetic resonance imagining (fMRI). Low electromyographic (EMG) activity of the musculi flexor digitorum superficialis and high vividness of the imagined movements were trained prior to image acquisition. Regional cerebral activation was measured by fMRI during EM and IM and compared to resting conditions. Anatomically selected regions of interest (ROIs) were marked interactively over the entire brain. In each ROI activated pixels above a t value of 2.45 (p < 0.01) were counted and analyzed. In all subjects the supplementary motor area (SMA), the premotor cortex (PMC), and the primary motor cortex (M1) showed significant activation during both EM and IM; the somatosen sory cortex (S1) was significantly activated only during EM. Ipsilateral cerebellar activation was decreased during IM compared to EM. In the cerebellum, IM and EM differed in their foci of maximal activation: Highest ipsilateral activation of the cerebellum was observed in the anterior lobe (Larsell lobule H IV) during EM, whereas a lower maximum was found about 2-cm dorsolateral (Larsell lobule H VII) during IM. The prefrontal and parietal regions revealed no significant changes during both conditions. The results of cortical activity support the hypothesis that motor imagery and motor performance possess similar neural substrates. The differential activation in the cerebellum during EM and IM is in accordance with the assumption that the posterior cerebellum is involved in the inhibition of movement execution during imagination.
903 citations
TL;DR: Motor imagery corresponds to a subliminal activation of the motor system, a system that appears to be involved not only in producing movements, but also in imagining actions, recognising tools and learning by observation, as well as in understanding the behaviour of other people.
553 citations
TL;DR: It is suggested that motor imagery can have dynamic effects on the excitability of motor cortex similar to those seen during actual motor performance.
Abstract: We investigated temporal changes in the amplitudes of motor-evoked potentials (MEPs) induced by transcranial magnetic stimulation over the left motor cortex during motor imagery. Nine subjects were instructed to imagine repetitive wrist flexion and extension movements at 1 Hz, in which the flexion timing was cued by a tone signal. Electromyographs (EMGs) were recorded from the first dorsal interosseous, flexor carpi radialis and extensor carpi radialis muscles of the right hand, and magnetic stimulation was delivered at 0, 250, 500 and 750 ms after the auditory cue. On average, the evoked EMG responses were larger in the flexor muscle during the phase of imagined flexion than during extension, whilst the opposite was true for the extensor muscle. There were no consistent changes in the amplitudes of MEPs in the intrinsic hand muscle (first dorsal interosseous). The EMG remained relaxed in all muscles and did not show any significant temporal changes during the test. The H-reflex in the flexor muscle was obtained in four subjects. There was no change in its amplitude during motor imagery. These observations lead us to suggest that motor imagery can have dynamic effects on the excitability of motor cortex similar to those seen during actual motor performance.
252 citations
TL;DR: EEG feedback studies demonstrate that human subjects can learn to regulate electrocortical activity over the sensorimotor cortex and self-induced EEG changes could serve as control signals for a Brain Computer Interface.
Abstract: EEG feedback studies demonstrate that human subjects can learn to regulate electrocortical activity over the sensorimotor cortex. Such self-induced EEG changes could serve as control signals for a Brain Computer Interface. The experimental task of the current study was to imagine either right-hand or left-hand movement depending on a visual cue stimulus on a computer monitor. The performance of this imagination task was controlled on-line by means of a feedback bar that represented the current EEG pattern. EEG signals recorded from left and right central recording sites were used for on-line classification. For the estimation of EEG parameters, an adaptive autoregressive model was applied, and a linear discriminant classifier was used to discriminate between EEG patterns associated with left and right motor imagery. Four trained subjects reached 85% to 95% classification accuracy in the course of the experimental sessions. To investigate the impact of continuous feedback presentation, time courses of band power changes were computed for subject-specific frequency bands. The EEG data revealed a significant event-related desynchronization over the contralateral central area in all subjects. Two subjects simultaneously displayed synchronization of EEG activity (event-related synchronization) over the ipsilateral side. During feedback presentation the event-related desynchronization/event-related synchronization patterns showed increased hemispheric asymmetry compared to initial control sessions without feedback.
239 citations
TL;DR: The hypothesis that cortical brain structures responsible for execution and imagination of memorized saccadic eye movements are similar is supported.
195 citations
TL;DR: Asymmetries arising from motor dominance in real movements also occurred for imagined movements, which support the hypothesis that real and imagined movements are represented within the same neurocognitive networks but suggest that asymmetries in performance related to handedness are greater for imagining movements.
130 citations
TL;DR: The data support the hypothesis that similar neural structures, including the primary motor cortex, are activated during both mental simulation and actual execution of motor activities.
99 citations
TL;DR: The results suggest that perception of the visual cue stimulus modifies oscillations in sensorimotor areas specific to the indicated hand starting as soon as 250-500 ms after stimulus onset.
76 citations
TL;DR: Investigating a functional hemispheric asymmetry of the human motor system between right- and left-handed subjects using motor evoked potentials in first dorsal interosseous (FDI) produced by transcranial magnetic stimulation found right-handers' MEP amplitudes were significantly larger than those induced by mental imagery of left finger movement.
73 citations
TL;DR: How non-intuitive but clinically tractable methods can emerge out of systematic application of cognitive neuroscience to the problem of how to foster dynamic change and recovery in the damaged brain is shown.
TL;DR: Two hypotheses are proposed to explain the differences in cortical processing between movement and imagery and between injury groups: first, cortical motor processes are altered by the absence of kinesthetic feedback during attempted movement of a deafferented limb as well as during imagery; and second, inhibitory processes, present during imagined movements of an intact limb, may be weakened by a spinal cord injury so that movement and image processes appear isomorphic.
TL;DR: Blood oxygenation level dependent functional magnetic resonance imaging (BOLD fMRI), because of its superior resolution and unlimited repeatability, can be particularly useful in studying functional aspects of the human motor system, especially plasticity, and somatotopic and temporal organization.
TL;DR: There were no substantial correlations between the performance on the visual imagery tasks and the improvement of motor performance through motor imagery, which indicates that visual and motor imagery are independent processes.
TL;DR: The authors found that left-facing heads are more likely to be remembered correctly by right-handed participants than right-facing faces by left-handed ones, while right-face faces are less likely to recall correctly than left-face heads.
Abstract: The assumption that cognitive processes are independent of handedness was questioned. Five experiments with left-handed and right-handed participants centered on investigating recognition memory for the orientation of heads. Their results provided consistent evidence of a general contralateral handedness effect: Left-facing heads are more likely to be remembered correctly by right-handed participants, whereas right-facing heads are more likely to be remembered correctly by left-handed participants. Motor imagery and hemispheric differences explanations were compared. The results supported the hypothesis that the effect is a consequence of differences between handedness groups in terms of specific patterns of underlying motor activation rather than in terms of more general differences in function between cerebral hemispheres. The possibility of a chiral psychology of cognition that takes note of a person's handedness is considered.
10 Jul 1999
TL;DR: The results suggest that combinations of different task pairings and dynamic neural network models have the potential to drastically reduce the time it takes for a new user to learn to use an EEG-based computer interface.
Abstract: The overall aim of this research is to develop an EEG-based computer interface. We report on an offline analysis of EEG data recorded from 7 subjects performing two different pairs of cognitive tasks; motor imagery versus a baseline task and motor imagery versus a maths task. For the imagery versus baseline pairing, discrimination was good in three subjects, marginal in two and not possible in the other two. For the imagery versus maths pairing, discrimination was very good in two subjects, good in 4 and marginal in one. The data was analysed using lagged-AR feature vectors and a Bayesian logistic regression classifier with temporal smoothing. Enhanced spectra are shown highlighting differential spectral activity for each task pairing. The results suggest that combinations of different task pairings and dynamic neural network models have the potential to drastically reduce the time it takes for a new user to learn to use an EEG-based computer interface.
02 Jun 1999
TL;DR: Sensorimotor EEG rhythms are affected by motor imagery and can be used as input signals for an EEG-based brain-computer interface (BCI) when multiple EEG recordings are made and the method of common spatial patterns is used for parameter estimation.
Abstract: Sensorimotor EEG rhythms are affected by motor imagery and can, therefore, be used as input signals for an EEG-based brain-computer interface (BCI). Satisfactory classification rates of imagery-related EEG patterns can be activated when multiple EEG recordings and the method of common spatial patterns is used for parameter estimation. Data from 3 BCI experiments with and without feedback are reported.
TL;DR: Although the tegmental involvement raises the question of an insufficient cortical motor arousal, preserved motor imagery suggested a normal cortical motor area activation.
Abstract: Motor evoked potentials (MEPs) to transcranial magnetic stimulation were evaluated in a case of locked-in syndrome due to a large pontine infarction. In this patient, magnetic resonance imaging (MRI) and somatosensory evoked potentials demonstrated a tegmental involvement. One month after the attack, no MEP could be recorded from the right abductor digiti minimi (ADM) or either tibialis anterior muscle. On the contrary, MEPs were obtained from the left ADM, although with a prolonged latency and a reduced amplitude. When the patient was requested to think about the abduction of her paralyzed left little finger, the latency and the elicitability of these responses improved as compared with the relaxed condition. These severe MEP alterations correctly predicted a poor recovery of motor function in the chronic stage. However, although the tegmental involvement raises the question of an insufficient cortical motor arousal, preserved motor imagery suggested a normal cortical motor area activation.
TL;DR: This technique has proved useful to deepen the understanding of the neural basis of motor imagery, demonstrating increased activity in the primary motor cortex during mental representation of sequential finger movements.
Abstract: Non-invasive functional magnetic resonance imaging (fMRI) mapping techniques sensitive to the local changes of blood flow, blood volume, and blood oxygenation which accompany neuronal activation have been widely used over the last few years to investigate the functional organization of human cortical motor systems, and specifically of the primary motor cortex. Validation studies have demonstrated a good correspondence between quantitative and topographic aspects of data acquired by fMRI and positron emission tomography. The spatial and temporal resolution affordable by fMRI has allowed to achieve new important information on the distributed representation of hand movements in multiple functional modules, and on the intensity and spatial extent of neural activation in the contralateral and ipsilateral primary motor cortex in relation to parametric and nonparametric aspects of movement and to the degree of handedness. Neural populations with different functional characteristics have been identified in anatomically defined regions, and the temporal aspects of the activation during voluntary movement tracked in different components of the motor system. Finally, this technique has proved useful to deepen our understanding of the neural basis of motor imagery, demonstrating increased activity in the primary motor cortex during mental representation of sequential finger movements.
01 Jan 1999