Showing papers on "Motor imagery published in 2001"
TL;DR: The hypothesis that the motor system is part of a simulation network that is activated under a variety of conditions in relation to action, either self-intended or observed from other individuals, will be developed.
2,043 citations
01 Jul 2001
TL;DR: At this time, a tetraplegic patient is able to operate an EEG-based control of a hand orthosis with nearly 100% classification accuracy by mental imagination of specific motor commands.
Abstract: Motor imagery can modify the neuronal activity in the primary sensorimotor areas in a very similar way as observable with a real executed movement. One part of EEG-based brain-computer interfaces (BCI) is based on the recording and classification of circumscribed and transient EEG changes during different types of motor imagery such as, e.g., imagination of left-hand, right-hand, or foot movement. Features such as, e.g., band power or adaptive autoregressive parameters are either extracted in bipolar EEG recordings overlaying sensorimotor areas or from an array of electrodes located over central and neighboring areas. For the classification of the features, linear discrimination analysis and neural networks are used. Characteristic for the Graz BCI is that a classifier is set up in a learning session and updated after one or more sessions with online feedback using the procedure of "rapid prototyping." As a result, a discrimination of two brain states (e.g., leftversus right-hand movement imagination) can be reached within only a few days of training. At this time, a tetraplegic patient is able to operate an EEG-based control of a hand orthosis with nearly 100% classification accuracy by mental imagination of specific motor commands.
1,638 citations
TL;DR: Neuroimaging studies, combined with other methods, are revealing the ways in which imagery draws on mechanisms used in other activities, such as perception and motor control.
Abstract: Mental imagery has, until recently, fallen within the purview of philosophy and cognitive psychology. Both enterprises have raised important questions about imagery, but have not made substantial progress in answering them. With the advent of cognitive neuroscience, these questions have become empirically tractable. Neuroimaging studies, combined with other methods (such as studies of brain-damaged patients and of the effects of transcranial magnetic stimulation), are revealing the ways in which imagery draws on mechanisms used in other activities, such as perception and motor control. Because of its close relation to these basic processes, imagery is now becoming one of the best understood 'higher' cognitive functions.
1,521 citations
TL;DR: In this article, an evidence-based, 7-point checklist that includes: physical, environmental, task, timing, learning, emotional, and perspective elements of imagery delivery highlighting the minimum requirement areas in which sport psyc...
Abstract: This paper supports the contention that the brain stores memories in the form of a central representation that is accessed by both physical preparation and execution and, more importantly, by motor imagery associated with this preparation and execution. Considerable evidence in support of shared central and vegetative structures suggests that sport psychologists should consider more closely aspects of the performer's responses to the physical skill when providing imagery interventions and not rely on “traditional,” more clinically orientated, methods of delivery. Many texts provide a schedule of factors and techniques for psychologists, athletes, and coaches to consider but with a limited theoretical explanation of why these factors are the crucial concerns. We, therefore, propose an evidence-based, 7-point checklist that includes: physical, environmental, task, timing, learning, emotional, and perspective elements of imagery delivery highlighting the minimum requirement areas in which sport psyc...
558 citations
TL;DR: The rationale for investigating mental practice as a means of promoting motor recovery in patients with a neurologic disorder is discussed and evidence supporting the existence of a similarity between executed and imagined actions is presented using data from psychophysical, neurophysiologic, and brain imaging studies.
520 citations
TL;DR: This work investigates the performance, by normal individual and subjects with a selective impairment in either motor or visual imagery, of an imagery task involving a mental rotation, and highlights the distinct but complementary contribution of covert motor and visual processes during mental rotation.
Abstract: Recent studies indicate that covert mental activities, such as simulating a motor action and imagining the shape of an object, involve shared neural representations with actual motor performance and with visual perception, respectively. Here we investigate the performance, by normal individual and subjects with a selective impairment in either motor or visual imagery, of an imagery task involving a mental rotation. The task involved imagining a hand in a particular orientation in space and making a subsequent laterality judgement. A simple change in the phrasing of the imagery instructions (first-person or third-person imagery) and in actual hand posture (holding the hands on the lap or in the back) had a strong impact on response time (RT) in normal subjects, and on response accuracy in brain-damaged subjects. The pattern of results indicates that the activation of covert motor and visual processes during mental imagery depends on both top-down and bottom-up factors, and highlights the distinct but complementary contribution of covert motor and visual processes during mental rotation.
344 citations
TL;DR: Six key issues for this integrative approach are reviewed, including arguments for the value and greater use of: rigorous quantitative meta-analyses of neuroimaging studies; stereotactic coordinate-based data; standardized vocabularies capturing the elementary component operations of cognitive and behavioral tasks.
155 citations
21 Aug 2001
TL;DR: A "virtual keyboard" (VK) is a letter spelling device operated for example by spontaneous electroencephalogram (EEG), whereby the EEC is modulated by mental hand and leg motor imagery.
Abstract: A 'Virtual Keyboard' (VK) is a letter spelling device operated by spontaneous EEG, whereby the EEG is modulated by mental hand and leg motor imagery. We report on a tetraplegic patient initially trained on an EEG-based orthosis control system operating the VK. He achieved an outstanding ability in the use of the VK and can operate it with 0.95 letters per minute.
124 citations
Dissertation•
01 Feb 2001
107 citations
TL;DR: The results support the notion that underfunctioning of mesial frontal and dorsolateral prefrontal cortex may underlie motor preparation in Parkinson's disease but also suggest that akinesia may occur in the absence of impaired Mesial frontal cortex activation.
Abstract: Motor imagery paradigms can be used to investigate motor preparation We used positron emission tomography to compare regional cerebral blood flow (rCBF) in patients with Parkinson's disease and normal controls under three conditions: rest, motor imagery and motor execution In controls, imagery activated bilateral dorsolateral and mesial frontal cortex, inferior parietal cortex and precuneus Motor execution additionally activated primary motor cortex (p < 0001) Between-group, for imagery there was relative reduction in dorsolateral and mesial frontal activation in the patient group (p<001) For execution, there was impaired activation of right dorsolateral frontal cortex and basal ganglia (p<001) Our results support the notion that underfunctioning of mesial frontal and dorsolateral prefrontal cortex may underlie motor preparation in Parkinson's disease but also suggest that akinesia may occur in the absence of impaired mesial frontal cortex activation
56 citations
TL;DR: The presence of a tonic hyperactivation of motor cortical circuitry in PD in conjunction with an abnormality of either motor imagery or the process by which motor imagery engages the sensorimotor cortices in the clinically affected hemisphere is demonstrated.
Abstract: Background: The motor impairment in Parkinson’s disease (PD) could partly reflect a failure to activate processes of motor imagery. Objective: To verify any selective changes of motor output during motor imagery, lateralized to the hemisphere contralateral to the clinically affected side of hemiparkinsonian patients. Methods: Transcranial magnetic stimulation (TMS) was used to map the cortical representations of the contralateral abductor digiti minimi muscle (ADM) during rest, contraction, and motor imagery in a group of patients with hemi-PD and in a group of healthy volunteers. Seven patients with hemi-PD and seven healthy subjects were examined. Focal TMS was applied over a grid of 20 scalp positions on each hemiscalp. Maps were characterized by area (number of excitable positions), volume (the sum of motor evoked potential amplitudes at all scalp positions), and center of gravity (a map position representing an amplitude-weighted calculation of the excitable area). Results: In healthy control subjects, the area of cortical representation of ADM was symmetrically increased in both hemispheres by mental simulation of movement and real muscle contraction. In patients with hemi-PD, there was a hemispheric asymmetry in the area of cortical representation elicited by motor imagery. The area was reduced in the clinically affected hemisphere. The volume of cortical representation was increased under all conditions and in both hemispheres in patients with PD. However, largely because the volume was so high at rest in patients, the increment in volume associated with contraction was smaller than in control subjects. Conclusion: This study demonstrates the presence of a tonic hyperactivation of motor cortical circuitry in PD in conjunction with an abnormality of either motor imagery or the process by which motor imagery engages the sensorimotor cortices in the clinically affected hemisphere.
TL;DR: Results are consistent with previous studies in the upper limb and suggest that corticospinal excitability can be enhanced during motor imagery to facilitate responses in specific lower limb muscles.
Abstract: In this study, we investigated corticospinal excitability during mental simulation of a leg extension movement with the technique of transcranial magnetic stimulation. Motor evoked potentials were recorded in both knee extensors (quadriceps) and e exors (biceps femoris) in 19 trained participants (healthy volunteers). The amplitude and latency of motor evoked potentials were compared in three conditions: (1) at rest, (2) during motor imagery, and (3) at rest, immediately after motor imagery. The results showed a signie cant effect ( p < 0.001) of conditions on motor evoked potentials amplitude in the quadriceps but not in the biceps femoris. During motor imagery, the size of motor evoked potentials in the quadriceps increased signie cantly ( p < 0.001) compared with rest and postimagery conditions. Changes in motor evoked potentials latency across conditions were not signie cant, however. These results are consistent with previous studies in the upper limb and suggest that corticospinal excitability can be enhanced during motor imagery to facilitate responses in specie c lower limb muscles.
TL;DR: General slowing of motor initiation is suggested, due to impaired functioning of explicit, intentional processes in patients with conversion paralysis, and is strongest in the most severely affected limb.
Abstract: Introduction : Motor imagery was implicitly and explicitly cued in patients with conversion paralysis. Patients' explicit motor imagery of affected limbs was expected to be slowed. Methods : Six patients and six healthy controls performed an implicit mental motor rotation task (a hand and foot judgement task), an explicit mental motor rotation task, and two control reaction time (RT) tasks. Results : On the implicit task patients showed a significantly larger increase in RT per degree of rotation (RTR) than controls. There was a nonsignificant trend showing a larger RTR for the most severely affected limb in patients. This effect was stronger for the explicit hand rotation task, in which patients’ RTR was larger for the most severely affected arm. Furthermore, in 9% of the explicit hand rotation trials and in 51% of the explicit foot rotation trials patients showed a complete inability to form a mental image of their most severely affected limb. Patients were also slower on two control RT tasks. Conclusio...
01 Nov 2001
TL;DR: A significant improvement of 9% is demonstrated for the classification accuracy for the asymmetric classifiers of the electroencephalogram during motor imagery of the left or right hand.
Abstract: Classification of the electroencephalogram (EEG) during motor imagery of the left or right hand can be performed using a classifier comprising two hidden Markov models (HMMs) describing the spatio-temporal patterns related to the imagination. Due to the known asymmetries during motor imagery of rightand left-hand movement, an HMM-based classifier allowing asymmetrical structures is introduced. The comparison between such a system and a symmetrical one is based on the error rate of classification. The results for EEG data collected during 20 sessions from five subjects demonstrate a significant improvement of 9% for the classification accuracy for the asymmetric classifiers. The selection of the DAM for classification is done using a variant of genetic algorithms (GAs); namely, the adaptive reservoir genetic algorithm (ARGA).
TL;DR: Although techniques like functional brain imaging undeniably hold considerable promise, the important contribution that other methods—such as cognitive neuropsychology—make to cognitive neuroscience should not be so easily discounted.
Abstract: (2001). Single case studies of neurological disorders: Their contribution to the cognitive neuroscience of vision. Visual Cognition: Vol. 8, No. 2, pp. 263-272.
TL;DR: Two studies using both event-related fMRI and PET imaging suggest that the brain mechanisms of visual orienting and motor orienting are subserved by two dissociable processes in the brain, and suggest that covert visual attention and motor attention play similar roles in their respective modalities.
01 Jan 2001
TL;DR: In this paper, the authors trace the history of visual imagery, beginning with cognitive psychology and extending into the cognitive neuroscience approach of the last two decades, and discuss issues concerning the relation between perception and imagery, the brain localization of imagery, and the neural systems underlying visual image generation.
Abstract: This article traces the history of the study of visual imagery, beginning with cognitive psychology and extending into the cognitive neuroscience approach of the last two decades. Issues concerning the relation between perception and imagery, the brain localization of imagery, and the neural systems underlying visual image generation are discussed. Diverse sources of evidence, including reaction time studies, patient-based behavioral studies, event-related potentials, and functional neuroimaging are reviewed.
01 Jan 2001
TL;DR: In this article, the authors propose a 7-point checklist that includes: physical, environmental, task, timing, learning, emotional and perspective elements of imagery delivery highlighting the minimum requirement areas in which sport psychologists should monitor the equivalence to the physical task in order to enhance the efficacy of their practice.
Abstract: This paper supports the contention that the brain stores memories in the form of a central representation that is accessed by both physical preparation and execution and, more importantly, by motor imagery associated with this preparation and execution. Considerable evidence in support of shared central and vegetative structures suggests that sport psychologists should consider more closely aspects of the performer’s responses to the physical skill when providing imagery interventions and not rely on “traditional,” more clinically orientated, methods of delivery. Many texts provide a schedule of factors and techniques for psychologists, athletes, and coaches to consider but with a limited theoretical explanation of why these factors are the crucial concerns. We, therefore, propose an evidencebased, 7-point checklist that includes: physical, environmental, task, timing, learning, emotional, and perspective elements of imagery delivery highlighting the minimum requirement areas in which sport psychologists should monitor the equivalence to the physical task in order to enhance the efficacy of their practice.