Showing papers on "Motor imagery published in 1996"

Possible involvement of primary motor cortex in mentally simulated movement : a functional magnetic resonance imaging study

Abstract: The role of the primary motor cortex (M1) during mental simulation of movement is open to debate. In the present study, functional magnetic resonance imaging (fMRI) signals were measured in normal right-handed subjects during actual and mental execution of a finger-to-thumb opposition task with either the right or the left hand. There were no significant differences between the two hands with either execution or simulation. A significant involvement of contralateral M1 (30% of the activity found during execution) was detected in four of six subjects. Premotor cortex (PM) and the rostral part of the posterior SMA were activated bilaterally during motor imagery. These findings support the hypothesis that motor imagery involves virtually all stages of motor control.

Movement-related potentials associated with movement preparation and motor imagery

Abstract: Movement-related potentials (MRPs), reflecting cortical activity associated with voluntary movement, typically show a slowly increasing negative potential beginning between 1 and 2 s prior to movement, which most likely reflects motor preparatory processes. Studies of regional cerebral blood flow implicate the supplementary motor area in such preparatory processes; however, the contribution of the supplementary motor area to premovement activity observed in MRPs is debated. It is possible to examine MRPs relating to movement preparation alone, in the absence of movement execution, by recording MRPs associated with imagined movements. In this study, MRPs were recorded from 11 healthy control subjects while performing a sequential button-pressing task in response to external cues, and while imaging performance of the same task in response to the same cues. The early component of MRPs was found not to differ in amplitude, onset time, or topography when performing compared with imagining movement, indicating that both movement execution and motor imagery involve similar pre-movement preparatory processes generated in the same cortical area-most likely the supplementary motor area. It is therefore concluded that the early component of the MRP reflects activity arising pre-dominantly from the supplementary motor area and is associated with pre-movement motor preparatory processes which occur relatively independently of actual movement execution.

An increase in cortical excitability with no change in spinal excitability during motor imagery

Abstract: During motor imagery, to estimate changes in excitability of flexor carpi radialis muscle motoneurons of the spinal and cortical levels, electrical stimuli for recording H-reflex and transcranial m

Motor imagery—Anatomical representation and electrophysiological characteristics

Abstract: Experience and results of neuropsychological studies have shown that motor imagery can improve motor performance and enhance motor learning. In recent years several electro-physiological and functional imaging studies have investigated the physiological basis for this observation. In the present essay we review two of our recent studies, in which we compared motor imagery with motor preparation and motor execution. In the first we used positron emission tomography to describe their functional anatomy and in the second we employed electromyography, H-reflexes and transcranial magnetic stimulation to delineate their electrophysiological characteristics. Both studies demonstrated that motor imagery shares some characteristics with motor preparation and other, additional ones with motor execution. Thus it can be seen as a special form of motor behaviour, similar but distinct from both motor preparation and execution. This combination of mutual and distinct characteristics may be the key to its successful role in motor learning.

Motor representations: One or many?

Abstract: Two issues have been raised. The first concerns whether consciousness is attached to a given type of action. It is argued that purposive actions are represented before being executed and that motor representations can either remain implicit or become explicit according to the task. The second issue concerns whether or not mental imagery of action is independent from action. Recent evidence showing the commonality of neural mechanisms for motor imagery and action, respectively, goes against the idea of independent processes.

Functional Activity Mapping of the Perirolandic Cortex During Motor Performance and Motor Imagery

Abstract: The development of noninvasive magnetic resonance imaging (MRI) techniques sensitive to the local changes of blood flow, volume, and oxygenation which accompany neuronal activation has provided the scientific community with a new and powerful tool for investigating the spatio-temporal dynamics of human brain function [1,2]. One of the most exciting application of brain mapping techniques, such as single photon emission tomography (SPET), positron emission tomography (PET), and functional MRI (fMRI) is the study of neural correlates of mental activity, such as the internal representation of sensory events or motor acts. It is still debated to what extent brain networks activated during mental rehearsal of, for instance, a visual scene or a motor sequence (visual or motor imagery) overlap those involved in the perception of visual stimuli or the preparation and execution of motor acts, respectively [3]. With regard to the motor system, the results of previous SPET and PET studies have demonstrated the activation of higher-order motor areas (such as the supplementary motor cortex) during motor imagery, whereas no change was found in the primary sensory-motor cortex [4]. However, the relatively poor spatial resolution of the employed techniques may have prevented the detection of areas characterized by less intense activation. The present study was therefore undertaken to evaluate by high-resolution fMRI the activity pattern of the perirolandic region (including pre- and postcentral gyri) during execution and imagery of a sequential motor task.

Alternative origins of motor images

Abstract: This paper concerns how motor actions are neurally represented and coded. Action planning and motor preparation can be studied using a specific type of representational activity, motor imagery. A close functional equivalence between motor imagery and motor preparation is suggested by the positive effects of imagining movements on motor learning, the similarity between the neural structures involved, and the similar physiological correlates observed in both imaging and preparing. The content of motor representations can be inferred from motor images at a macroscopic level, based on global aspects of the action (the duration and amount of effort involved) and the motor rules and constraints which predict the spatial path and kinematics of movements. A more microscopic neural account calls for a representation of object-oriented action. Object attributes are processed in different neural pathways depending on the kind of task the subject is performing. During object-oriented action, a pragmatic representation is activated in which object affordances are transformed into specific motor schemas (independently of other tasks such as object recognition). Animal as well as human clinical data implicate the posterior parietal and premotor cortical areas in schema instantiation. A mechanism is proposed that is able to encode the desired goal of the action and is applicable to different levels of representational organization.