Last posts on mental simulation

Inducing a virtual hand ownership illusion through a brain-computer interface

2009-10-20T17:43:00+02:00

Inducing a virtual hand ownership illusion through a brain-computer interface.

Neuroreport. 2009 Apr 22;20(6):589-594

Authors: Perez-Marcos D, Slater M, Sanchez-Vives MV

The apparently stable brain representation of our bodies is easily challenged. We have recently shown that the illusion of ownership of a three-dimensional virtual hand can be evoked through synchronous tactile stimulation of a person's hidden real hand and that of the virtual hand. This reproduces the well-known rubber-hand illusion, but in virtual reality. Here we show that some aspects of the illusion can also occur through motor imagery used to control movements of a virtual hand. When movements of the virtual hand followed motor imagery, the illusion of ownership of the virtual hand was evoked and muscle activity measured through electromyogram correlated with movements of the virtual arm. Using virtual bodies has a great potential in the fields of physical and neural rehabilitation, making the understanding of ownership of a virtual body highly relevant.

Neurofeedback-based motor imagery training for brain-computer interface

2009-06-24T18:48:12+02:00

Neurofeedback-based motor imagery training for brain-computer interface (BCI).

J Neurosci Methods. 2009 Apr 30;179(1):150-6

Authors: Hwang HJ, Kwon K, Im CH

In the present study, we propose a neurofeedback-based motor imagery training system for EEG-based brain-computer interface (BCI). The proposed system can help individuals get the feel of motor imagery by presenting them with real-time brain activation maps on their cortex. Ten healthy participants took part in our experiment, half of whom were trained by the suggested training system and the others did not use any training. All participants in the trained group succeeded in performing motor imagery after a series of trials to activate their motor cortex without any physical movements of their limbs. To confirm the effect of the suggested system, we recorded EEG signals for the trained group around sensorimotor cortex while they were imagining either left or right hand movements according to our experimental design, before and after the motor imagery training. For the control group, we also recorded EEG signals twice without any training sessions. The participants' intentions were then classified using a time-frequency analysis technique, and the results of the trained group showed significant differences in the sensorimotor rhythms between the signals recorded before and after training. Classification accuracy was also enhanced considerably in all participants after motor imagery training, compared to the accuracy before training. On the other hand, the analysis results for the control EEG data set did not show consistent increment in both the number of meaningful time-frequency combinations and the classification accuracy, demonstrating that the suggested system can be used as a tool for training motor imagery tasks in BCI applications. Further, we expect that the motor imagery training system will be useful not only for BCI applications, but for functional brain mapping studies that utilize motor imagery tasks as well.

Effect of Motor Imagery in the Rehabilitation of Burn Patients

2009-06-24T18:45:10+02:00

Effect of Motor Imagery in the Rehabilitation of Burn Patients.

J Burn Care Res. 2009 Jun 5;

Authors: Guillot A, Lebon F, Vernay M, Girbon JP, Doyon J, Collet C

Although there is ample evidence that motor imagery (MI) improves motor performance after CNS injury, it is still unknown whether MI may enhance motor recovery after peripheral injury and most especially in the rehabilitation of burn patients. This study aimed to investigate the effects of a 2-week MI training program combined with conventional rehabilitation on the recovery of motor functions in handed burn patients. Fourteen patients admitted to the Medical Burn Center were requested to take part in the study and were randomly assigned to the imagery or the control group. Behavioral data related to the ability to perform each successive step of three manual motor sequences were collected at five intervals during the medical procedure. The results provided evidence that MI may facilitate motor recovery, and the belief in the effectiveness of MI was strong in all patients. MI may substantially contribute to improve the efficacy of conventional rehabilitation programs. Hence, this technique should be considered as a reliable alternative method to help burn patients to recover motor functions.

How does visual thinking work in the mind of a person with autism?

2009-06-17T16:06:58+02:00

How does visual thinking work in the mind of a person with autism? A personal account.

Philos Trans R Soc Lond B Biol Sci. 2009 May 27;364(1522):1437-42

Authors: Grandin T

My mind is similar to an Internet search engine that searches for photographs. I use language to narrate the photo-realistic pictures that pop up in my imagination. When I design equipment for the cattle industry, I can test run it in my imagination similar to a virtual reality computer program. All my thinking is associative and not linear. To form concepts, I sort pictures into categories similar to computer files. To form the concept of orange, I see many different orange objects, such as oranges, pumpkins, orange juice and marmalade. I have observed that there are three different specialized autistic/Asperger cognitive types. They are: (i) visual thinkers such as I who are often poor at algebra, (ii) pattern thinkers such as Daniel Tammet who excel in math and music but may have problems with reading or writing composition, and (iii) verbal specialists who are good at talking and writing but they lack visual skills.

Facilitation of motor imagery through movement-related cueing

2009-05-03T21:15:41+02:00

Facilitation of motor imagery through movement-related cueing.

Brain Res. 2009 Apr 27;

Authors: Heremans E, Helsen WF, De Poel HJ, Alaerts K, Meyns P, Feys P

In the past few years, the use of motor imagery as an adjunct to other forms of training has been studied extensively. However, very little attention has been paid to how imagery could be used to greatest effect. It is well known that the provision of external cues has a beneficial effect on motor skill acquisition and performance during physical practice. Since physical execution and mental imagery share several common mechanisms, we hypothesized that motor imagery might be affected by external cues in a similar way. To examine this, we compared the motor imagery performance of three groups of 15 healthy participants who either physically performed or imagined performing a goal-directed cyclical wrist movement in the presence or the absence of visual and/or auditory external cues. As outcome measures, the participants' imagery vividness scores and eye movements were measured during all conditions. We found that visual movement-related cues improved the spatial accuracy of the participants' eye movements during imagery, while auditory cues specifically enhanced their temporal accuracy. Furthermore, both types of cues significantly improved the participants' imagery vividness. These findings indicate that subjects may imagine a movement in a better way when provided with external movement-related stimuli, which may possibly be useful with regard to the efficiency of mental practice in (clinical) training protocols.

Does erotic stimulus presentation design affect brain activation patterns?

2008-07-28T13:18:47+02:00

Does erotic stimulus presentation design affect brain activation patterns? Event-related vs. blocked fMRI designs.

Behav Brain Funct. 2008 Jul 22;4(1):30

Authors: Buehler M, Vollstaedt-Klein S, Klemen J, Smolka MN

ABSTRACT: BACKGROUND: Existing brain imaging studies, investigating sexual arousal via the presentation of erotic pictures or film excerpts, have mainly used blocked designs with long stimulus presentation times. METHODS: To clarify how experimental functional magnetic resonance imaging (fMRI) design affects stimulus-induced brain activity, we compared brief event-related presentation of erotic vs. neutral stimuli with blocked presentation in 10 male volunteers. RESULTS: Brain activation differed depending on design type in only 10% of the voxels showing task related brain activity. Differences between blocked and event-related stimulus presentation were found in occipitotemporal and temporal regions (Brodmann Area (BA) 19, 37, 48), parietal areas (BA 7, 40) and areas in the frontal lobe (BA 6, 44). CONCLUSIONS: Our results suggest that event-related designs might be a potential alternative when the core interest is the detection of networks associated with immediate processing of erotic stimuli. Additionally, blocked, compared to event-related, stimulus presentation allows the emergence and detection of non-specific secondary processes, such as sustained attention, motor imagery and inhibition of sexual arousal.

Motor imagery: A window into the mechanisms and alterations of the motor system

2008-04-10T15:03:22+02:00

Motor imagery: A window into the mechanisms and alterations of the motor system.

Cortex. 2008 May;44(5):494-506

Authors: de Lange FP, Roelofs K, Toni I

Motor imagery is a widely used paradigm for the study of cognitive aspects of action control, both in the healthy and the pathological brain. In this paper we review how motor imagery research has advanced our knowledge of behavioral and neural aspects of action control, both in healthy subjects and clinical populations. Furthermore, we will illustrate how motor imagery can provide new insights in a poorly understood psychopathological condition: conversion paralysis (CP). We measured behavioral and cerebral responses with functional magnetic resonance imaging (fMRI) in seven CP patients with a lateralized paresis of the arm as they imagined moving the affected or the unaffected hand. Imagined actions were either implicitly induced by the task requirements, or explicitly instructed through verbal instructions. We previously showed that implicitly induced motor imagery of the affected limb leads to larger ventromedial prefrontal responses compared to motor imagery of the unaffected limb. We interpreted this effect in terms of greater self-monitoring of actions during motor imagery of the affected limb. Here, we report new data in support of this interpretation: inducing self-monitoring of actions of both the affected and the unaffected limb (by means of explicitly cued motor imagery) abolishes the activation difference between the affected and the unaffected hand in the ventromedial prefrontal cortex. Our results show that although implicit and explicit motor imagery both entail motor simulations, they differ in terms of the amount of action monitoring they induce. The increased self-monitoring evoked by explicit motor imagery can have profound cerebral consequences in a psychopathological condition.

Cognitive processing and motor skill learning in motor-handicapped teenagers

2008-03-26T15:14:52+01:00

Cognitive processing and motor skill learning in motor-handicapped teenagers: effects of learning method.

Somatosens Mot Res. 2007 Dec;24(4):163-9

Authors: Deviterne D, Gauchard GC, Lavisse D, Perrin PP

This study aimed to assess the efficiency of a motor skill learning method intended to promote learning course personalization through an increase in cognitive processing deployment in motor-handicapped persons. Thirty-three secondary school students volunteered to participate in an archery motor skill learning session, 11 motor-handicapped (MH(1)) and 11 able-bodied (AB) teenagers following a standard learning method, and 11 motor-handicapped teenagers following a cognitive enriched learning method (MH(2)) based on the use of an individually written and illustrated document. The results showed that MH(1) displayed lower performances than AB, both in terms of the mental representations of the movements expected and performed and of efficiency of the movement. On the other hand, MH(2) performances were higher than MH(1) for all these parameters, and similar to those of AB at the end of the learning session. Personalization of the learning course allowed optimization of the learning potential in motor-handicapped teenagers to resolve the difficulties inherent to their handicap.

Action verbs and the primary motor cortex: A comparative TMS study

2008-03-13T19:18:15+01:00

Action verbs and the primary motor cortex: A comparative TMS study of silent reading, frequency judgments, and motor imagery.

Neuropsychologia. 2008 Feb 2;

Authors: Tomasino B, Fink GR, Sparing R, Dafotakis M, Weiss PH

Single pulse transcranial magnetic stimulation (TMS) was applied to the hand area of the left primary motor cortex or, as a control, to the vertex (STIMULATION: TMS(M1) vs. TMS(vertex)) while right-handed volunteers silently read verbs related to hand actions. We examined three different tasks and time points for stimulation within the same experiment: subjects indicated with their left foot when they (i) had finished reading, (ii) had judged whether the corresponding movement involved a hand rotation after simulating the hand movement, and (iii) had judged whether they would frequently encounter the action verb in a newspaper (TASK: silent reading, motor imagery, and frequency judgment). Response times were compared between TMS(M1) and TMS(vertex), both applied at different time points after stimulus onset (DELAY: 150, 300, 450, 600, and 750ms). TMS(M1) differentially modulated task performance: there was a significant facilitatory effect of TMS(M1) for the imagery task only (about 88ms), with subjects responding about 10% faster (compared to TMS(vertex)). In contrast, response times for silent reading and frequency judgments were unaffected by TMS(M1). No differential effect of the time point of TMS(M1) was observed. The differential effect of TMS(M1) when subjects performed a motor imagery task (relative to performing silent reading or frequency judgments with the same set of verbs) suggests that the primary motor cortex is critically involved in processing action verbs only when subjects are simulating the corresponding movement. This task-dependent effect of hand motor cortex TMS on the processing of hand-related action verbs is discussed with respect to the notion of embodied cognition and the associationist theory.

Effect of mental imagery on the development of skilled motor actions

2008-02-11T22:36:45+01:00

Effect of mental imagery on the development of skilled motor actions.

Percept Mot Skills. 2007 Dec;105(3 Pt 1):803-26

Authors: Fontani G, Migliorini S, Benocci R, Facchini A, Casini M, Corradeschi F

To test the effect of imagery in the training of skilled movements, an experiment was designed in which athletes learned a new motor action and trained themselves for a month either by overt action or by mental imagery of the action. The experiment was carried out with 30 male karateka (M age = 35 yr., SD = 8.7; M years of practice = 6, SD = 3) instructed to perform an action (Ura-Shuto-Uchi) that they had not previously learned. The athletes were divided into three groups: Untrained (10 subjects who did not perform any training), Action Trained (10 subjects who performed Ura-Shuto-Uchi training daily for 16 minutes), and Mental Imagery (10 subjects who performed mental imagery training of Ura-Shuto-Uchi daily for 16 minutes). The subjects were tested five times, once every 7 days. During each test, they performed a series of 60 motor action trials. In Tests 1, 3, and 5, they also performed a series of 60 mental imagery trials. During the trials, an electroencephalogram (EEG), electromyography (EMG), muscle strength and power, and other physiological parameters were recorded. The results differed by group. Untrained subjects did not show significant effects. In the Action Trained group, training had an effect on reactivity and movement speed, with a reduction of EMG activation and reaction times. Moreover, muscle strength, power, and work increased significantly. The Mental Imagery group showed the same effects on muscle strength, power, and work, but changes in reactivity were not observed. In the Mental Imagery group, the study of Movement Related Brain Macropotentials indicated a progressive modification of the profile of the waves from Test 1 to Test 5 during imagery, showing significant variations of the amplitude of the waves related to the premotor and motor execution periods. Results show that motor imagery can influence muscular abilities such as strength and power and can modify Movement Related Brain Macropotentials, the profile of which potentially could be used to verify the effectiveness of motor imagery training.

Effect of mental imagery on the development of skilled motor actions

2008-02-11T22:35:49+01:00

Effect of mental imagery on the development of skilled motor actions.

Percept Mot Skills. 2007 Dec;105(3 Pt 1):803-26

Authors: Fontani G, Migliorini S, Benocci R, Facchini A, Casini M, Corradeschi F

The suppressive influence of SMA on M1 in motor imagery

2008-02-11T22:34:34+01:00

The suppressive influence of SMA on M1 in motor imagery revealed by fMRI and dynamic causal modeling.

Neuroimage. 2007 Dec 8;

Authors: Kasess CH, Windischberger C, Cunnington R, Lanzenberger R, Pezawas L, Moser E

Although motor imagery is widely used for motor learning in rehabilitation and sports training, the underlying mechanisms are still poorly understood. Based on fMRI data sets acquired with very high temporal resolution (300 ms) under motor execution and imagery conditions, we utilized Dynamic Causal Modeling (DCM) to determine effective connectivity measures between supplementary motor area (SMA) and primary motor cortex (M1). A set of 28 models was tested in a Bayesian framework and the by-far best-performing model revealed a strong suppressive influence of the motor imagery condition on the forward connection between SMA and M1. Our results clearly indicate that the lack of activation in M1 during motor imagery is caused by suppression from the SMA. These results highlight the importance of the SMA not only for the preparation and execution of intended movements, but also for suppressing movements that are represented in the motor system but not to be performed.

Mental rotation of congenitally absent hands

2007-12-16T14:05:47+01:00

Mental rotation of congenitally absent hands.

J Int Neuropsychol Soc. 2008 Jan;14(1):81-9

Authors: Funk M, Brugger P

We compared motor imagery performance of normally limbed individuals with that of individuals with one or both hands missing since birth (i.e., hand amelia). To this aim, 14 unilaterally and 2 bilaterally amelic participants performed a task requiring the classification of hands depicted in different degrees of rotation as either a left or a right hand. On the same task, 24 normally limbed participants recapitulated previously reported effects; that is, that the hand motor dominance and, more generally, a lifelong use of hands are important determinants of left-right decisions. Unilaterally amelic participants responded slower to hands corresponding to their absent, compared with their existing, hand. Moreover, left and right hand amelic participants showed prolonged reaction times to hands (whether left or right) depicted in unnatural orientations compared with natural orientations. Among the bilateral amelics, the individual with phantom sensations, but not the one without, showed similar differentiation. These findings demonstrate that the visual recognition of a hand never physically developed is prolonged, but still modulated by different rotation angles. They are further compatible with the view that phantom limbs in hand amelia may constrain motor imagery as much as do amputation phantoms.

The emergence of motor imagery in children

2007-12-08T18:13:24+01:00

The emergence of motor imagery in children.

J Exp Child Psychol. 2007 Nov 28;

Authors: Molina M, Tijus C, Jouen F

A total of 80 children (40 5-year-olds and 40 7-year-olds) took part in an experiment to evaluate their capacity to mentally evoke a motor image of their own displacement. Using a chronometry paradigm, movement duration was compared in a task where children were asked to move in order to take a puppet back to its home (actual) and to think about themselves executing the same action (virtual). Movement durations for actual and virtual displacements were obtained in two conditions, where either no information was provided about the weight of the puppet to be displaced (standard situation) or the puppet was described as being heavy (informed situation). A significant correlation between actual and virtual walking durations was observed for 7-year-olds in the informed condition. This result provides evidence for a motor imagery process emerging in 7-year-olds when children are required to think about themselves in action.

Motor imagery for pathologic pain

2007-01-22T21:48:04+01:00

Graded motor imagery for pathologic pain: a randomized controlled trial.

Neurology. 2006 Dec 26;67(12):2129-34

Authors: Moseley GL

BACKGROUND: Phantom limb and complex regional pain syndrome type 1 (CRPS1) are characterized by changes in cortical processing and organization, perceptual disturbances, and poor response to conventional treatments. Graded motor imagery is effective for a small subset of patients with CRPS1. OBJECTIVE: To investigate whether graded motor imagery would reduce pain and disability for a more general CRPS1 population and for people with phantom limb pain. METHODS: Fifty-one patients with phantom limb pain or CRPS1 were randomly allocated to motor imagery, consisting of 2 weeks each of limb laterality recognition, imagined movements, and mirror movements, or to physical therapy and ongoing medical care. RESULTS: There was a main statistical effect of treatment group, but not diagnostic group, on pain and function. The mean (95% CI) decrease in pain between pre- and post-treatment (100 mm visual analogue scale) was 23.4 mm (16.2 to 30.4 mm) for the motor imagery group and 10.5 mm (1.9 to 19.2 mm) for the control group. Improvement in function was similar and gains were maintained at 6-month follow-up. CONCLUSION: Motor imagery reduced pain and disability in these patients with complex regional pain syndrome type I or phantom limb pain, but the mechanism, or mechanisms, of the effect are not clear.

Motor imagery and stroke rehabilitation

2007-01-21T23:42:07+01:00

Motor imagery and stroke rehabilitation: a critical discussion.

J Rehabil Med. 2007 Jan;39(1):5-13

Authors: de Vries S, Mulder T

Motor disorders are a frequent consequence of stroke and much effort is invested in the re-acquisition of motor control. Although patients often regain some of their lost function after therapy, most remain chronically disabled. Functional recovery is achieved largely through reorganization processes in the damaged brain. Neural reorganization depends on the information provided by sensorimotor efferent-afferent feedback loops. It has, however, been shown that the motor system can also be activated "offline" by imagining (motor imagery) or observing movements. The discovery of mirror neurones, which fire not only when an action is executed, but also when one observes another person performing the same action, also show that our action system can be used "online" as well as offline. It is an intriguing question as to whether the information provided by motor imagery or motor observation can lead to functional recovery and plastic changes in patients after stroke. This article reviews the evidence for motor imagery or observation as novel methods in stroke rehabilitation

The neural basis of narrative imagery

2007-01-21T23:40:00+01:00

The neural basis of narrative imagery: emotion and action.

Prog Brain Res. 2006;156:93-103

Authors: Sabatinelli D, Lang PJ, Bradley MM, Flaisch T

It has been proposed that narrative emotional imagery activates an associative network of stimulus, semantic, and response (procedural) information. In previous research, predicted response components have been demonstrated through psychophysiological methods in peripheral nervous system. Here we investigate central nervous system concomitants of pleasant, neutral, and unpleasant narrative imagery with functional magnetic resonance imaging. Subjects were presented with brief narrative scripts over headphones, and then imagined themselves engaged in the described events. During script perception, auditory association cortex showed enhanced activation during affectively arousing (pleasant and unpleasant), relative to neutral imagery. Structures involved in language processing (left middle frontal gyrus) and spatial navigation (retrosplenium) were also active during script presentation. At the onset of narrative imagery, supplementary motor area, lateral cerebellum, and left inferior frontal gyrus were initiated, showing enhanced signal change during affectively arousing (pleasant and unpleasant), relative to neutral scripts. These data are consistent with a bioinformational model of emotion that considers response mobilization as the measurable output of narrative imagery.

Motor imagery of gait: a quantitative approach

2007-01-15T22:52:25+01:00

Motor imagery of gait: a quantitative approach.

Exp Brain Res. 2007 Jan 9;

Authors: Bakker M, de Lange FP, Stevens JA, Toni I, Bloem BR

Motor imagery (MI) is widely used to study cognitive aspects of the neural control of action. Prior studies were mostly centred on hand and arm movements. Recently a few studies have used imagery tasks to explore the neurophysiology of human gait, but it remains unclear how to ascertain whether subjects actually perform imagery of gait as requested. Here we describe a new experimental protocol to quantify imagery of gait, by behaviourally distinguishing it from visual imagery (VI) processes and by showing its temporal correspondence with actual gait. Fourteen young healthy subjects performed two imagery tasks and an actual walking (AW) task. During both imagery tasks subjects were sitting on a chair and faced a computer screen that presented photographs of walking trajectories. During one task (MI), subjects had to imagine walking along the walking trajectory. During the other task (VI), subjects had to imagine seeing a disc moving along the walking trajectory. During the AW task, subjects had to physically walk along the same walking trajectory as presented on the photographs during the imagery tasks. We manipulated movement distance by changing the length of the walking trajectory, and movement difficulty by changing the width of the walking trajectory. Subjects reported onset and offset of both actual and imagined movements with a button press. The time between the two button presses was taken as the imagined or actual movement time (MT). MT increased with increasing path length and decreasing path width in all three tasks. Crucially, the effect of path width on MT was significantly stronger during MI and AW than during VI. The results demonstrate a high temporal correspondence between imagined and AW, suggesting that MI taps into similar cerebral resources as those used during actual gait. These results open the possibility of using this protocol for exploring neurophysiological correlates of gait control in humans.

Adolescent development of motor imagery

2007-01-02T22:58:27+01:00

Adolescent development of motor imagery in a visually guided pointing task.

Conscious Cogn. 2006 Dec 28;

Authors: Choudhury S, Charman T, Bird V, Blakemore SJ

The development of action representation during adolescence was investigated using a visually guided pointing motor task (VGPT) to test motor imagery. Forty adolescents (24 males; mean age 13.1 years) and 33 adults (15 males; mean age 27.5 years) were instructed to both execute and imagine hand movements from a starting point to a target of varying size. Reaction time (RT) was measured for both Execution (E) and Imagery (I) conditions. There is typically a close association between time taken to execute and image actions in adults because action execution and action simulation rely on overlapping neural circuitry. Further, representations of actions are governed by the same speed-accuracy trade-off as real actions, as expressed by Fitts' Law. In the current study, performance on the VGPT in both adolescents and adults conformed to Fitts' Law in E and I conditions. However, the strength of association between E and I significantly increased with age, reflecting a refinement in action representation between adolescence and adulthood.

Kinesthetic but not visual imagery assists in normalizing the CNV in Parkinson's disease

2006-12-18T17:48:59+01:00

Kinesthetic but not visual imagery assists in normalizing the CNV in Parkinson's disease.

Clin Neurophysiol. 2006 Oct;117(10):2308-14

Authors: Lim VK, Polych MA, Holländer A, Byblow WD, Kirk IJ, Hamm JP

OBJECTIVE: This study investigated whether kinesthetic and/or visual imagery could alter the contingent negative variation (CNV) for patients with Parkinson's disease (PD). METHODS: The CNV was recorded in six patients with PD and seven controls before and after a 10min block of imagery. There were two types of imagery employed: kinesthetic and visual, which were evaluated on separate days. RESULTS: The global field power (GFP) of the late CNV did not change after the visual imagery for either group, nor was there a significant difference between the groups. In contrast, kinesthetic imagery resulted in significant group differences pre-, versus post-imagery GFPs, which was not present prior to performing the kinesthetic imagery task. In patients with PD, the CNV amplitudes post-, relative to pre-kinesthetic imagery, increased over the dorsolateral prefrontal regions and decreased in the ipsilateral parietal regions. There were no such changes in controls. CONCLUSIONS: A 10-min session of kinesthetic imagery enhanced the GFP amplitude of the late CNV for patients but not for controls. SIGNIFICANCE: While the study needs to be replicated with a greater number of participants, the results suggest that kinesthetic imagery may be a promising tool for investigations into motor changes, and may potentially be employed therapeutically, in patients with Parkinson's disease.

Modulation of corticospinal excitability during both actual and imagined movements

2006-12-18T17:46:38+01:00

Movement-specific enhancement of corticospinal excitability at subthreshold levels during motor imagery.

Exp Brain Res. 2006 Dec 8;

Authors: Li S

This study examined modulation of corticospinal excitability during both actual and imagined movements. Seven young healthy subjects performed actual (3-50% maximal voluntary contractions) and imagined index finger force production, and rest. Individual responses to focal transcranial magnetic stimulation (TMS) in four fingers (index, middle, ring, and little) were recorded for all three tested conditions. The force increments at the threshold of activation were predicted from regression analysis, representing the TMS-induced response at the threshold activation of the corticospinal pathways. The measured increment in the index finger during motor imagery was larger than that at rest, but smaller than the predicted increment at the threshold of activation. On the other hand, the measured increment in the uninstructed (middle, ring, and little), slave fingers during motor imagery was larger than that at rest, but not different from the predicted increment at the threshold of activation. These contrasting results suggest that the degree of imagery-induced enhancement in corticospinal excitability was significantly less than what could be predicted for threshold levels from regression analysis, but only for the index finger, and not the adjacent slave fingers. It is concluded that corticospinal excitability for the explicitly instructed index finger is specifically enhanced at subthreshold levels during motor imagery.

Motor imagery practice in gait rehabilitation of chronic post-stroke hemiparesis

2006-11-22T09:28:07+01:00

Motor imagery practice in gait rehabilitation of chronic post-stroke hemiparesis: four case studies.

Int J Rehabil Res. 2006 Dec;29(4):351-356

Authors: Dunsky A, Dickstein R, Ariav C, Deutsch J, Marcovitz E

The aim of this series of pilot case studies was to examine the feasibility of enhancing the walking of individuals with post-stroke hemiparesis through the imagery practice of gait activities at home. Four persons with chronic hemiparesis received imagery gait practice, 3 days a week for 6 weeks. The intervention addressed gait impairments of the affected lower limb and task-specific gait training. Pre-intervention, mid-term, post-intervention and follow-up evaluations were performed. At 6 weeks from the beginning of treatment, the participants increased walking speed, stride length, cadence and single-support time on the affected lower limb, while decreasing double-support time. The findings appear to justify the institution of a larger-scale study in order to better delineate the contribution of motor imagery practice to gait performance in individuals with post-stroke hemiparesis.