Imagined Walking Research Articles

Cortical activation during imagined walking for people with lower limb loss: a pilot study.

Each year in Canada, a substantial number of adults undergo limb amputation, with lower limb amputation (LLA) the most prevalent. Enhancing walking ability is crucial for optimizing rehabilitation outcomes, promoting participation, and facilitating community reintegration. Overcoming challenges during the acute post-amputation phase and sub-acute rehabilitation necessitates alternative approaches, such as motor imagery and mental practice, to maximize rehabilitation success. However, the current evidence on activation patterns using motor imagery in individuals with LLA is limited. The primary objective was to assess the feasibility of observing brain activation during imagined walking in individuals with LLA utilizing 3T functional magnetic resonance imaging (fMRI). Eight individuals with LLA and 11 control subjects participated. Consistent with representations of the lower limbs, both control and amputee groups demonstrated bilateral activation in the medial surface of the primary motor and somatosensory cortices. However, individuals with lower limb amputations exhibited significantly greater activation during imagined walking, particularly in frontal regions and the medial surface of the primary motor and supplementary motor cortices. Furthermore, the volume of activation in the bilateral primary motor cortices was higher for participants with amputations compared to controls. The protocol developed in this study establishes a foundation for evaluating the effects of a gait training program that incorporates mental imagery alongside conventional rehabilitation practices, in contrast to standard care alone. This pilot investigation holds potential to enhance our understanding of brain plasticity in individuals with LLA and pave the way for more effective rehabilitation strategies to optimize functional recovery and community reintegration.

Changes in prefrontal cortical activation during motor imagery of precision gait with age and task difficulty

Previous studies have shown that imagined walking ability decreases with age in a similar manner as actual walking ability; however, little is known about the neural mechanisms underlying this aging effect. The present study investigates this issue, focusing on the effect of task difficulty and the involvement of the prefrontal cortex (PFC). Twenty healthy right-handed older adults (mean age 74.5 ± 3.3 years) participated in two experiments. In Experiment 1, the time participants took for actual and imagined walking along a 5-m walkway of three different path widths (15, 25, and 50 cm) were compared. In Experiment 2, the participants imagined walking along the aforementioned paths while PFC activity was measured using functional near-infrared spectroscopy. At the behavioral level, older adults exhibited longer mental and actual walking times for narrower paths and tended to overestimate their imagined walking times over their actual ones. However, overall, the magnitude of the overestimation did not differ by task difficulty. Regarding brain activity, older adults who overestimated mental walking times to a greater degree in the narrowest path exhibited decreased activation in the bilateral PFC. Moreover, compared with young adults in our previous study (Kotegawa et al., 2020), older adults with higher gait ability exhibited the same or smaller mental/actual walking times as well as decreased bilateral PFC activation in the most difficult condition. These results suggest that older adults, especially those with higher gait ability, can utilize neural mechanisms that are different from those of young adults when generating gait motor imagery.

Functional magnetic resonance brain imaging of imagined walking to study locomotor function after stroke

ObjectiveImagined walking has yielded insights into normal locomotor control and could improve understanding of neurologic gait dysfunction. This study evaluated brain activation during imagined walking in chronic stroke. MethodsTen persons with stroke and 10 matched controls completed a walking test battery and a magnetic resonance imaging session including imagined walking and knee extension tasks. Brain activations were compared between tasks and groups. Associations between activations and composite gait score were also calculated, while controlling for lesion load. ResultsStroke and worse gait score were each associated with lesser overall brain activation during knee extension but greater overall activation during imagined walking. During imagined walking, the stroke group significantly activated the primary motor cortex lower limb region and cerebellar locomotor region. Better walking function was associated with less activation of these regions and greater activation of medial superior frontal gyrus area 9. ConclusionsCompared with knee extension, imagined walking was less sensitive to stroke-related deficits in brain activation but better at revealing compensatory changes, some of which could be maladaptive. SignificanceThe identified associations for imagined walking suggest potential neural mechanisms of locomotor adaptation after stroke, which could be useful for future intervention development and prognostication.

Measuring egocentric distance perception in virtual reality: Influence of methodologies, locomotion and translation gains.

Virtual reality has become a popular means to study human behavior in a wide range of settings, including the role of pedestrians in traffic research. To understand distance perception in virtual environments is thereby crucial to the interpretation of results, as reactions to complex and dynamic traffic scenarios depend on perceptual processes allowing for the correct anticipation of future events. A number of approaches have been suggested to quantify perceived distances. While previous studies imply that the selected method influences the estimates’ accuracy, it is unclear how the respective estimates depend on depth information provided by different perceptual modalities. In the present study, six methodological approaches were compared in a virtual city scenery. The respective influence of visual and non-visual cues was investigated by manipulating the ratio between visually perceived and physically walked distances. In a repeated measures design with 30 participants, significant differences between methods were observed, with the smallest error occurring for visually guided walking and verbal estimates. A linear relation emerged between the visual-to-physical ratio and the extent of underestimation, indicating that non-visual cues during walking affected distance estimates. This relationship was mainly evident for methods building on actual or imagined walking movements and verbal estimates.

Imagine All The Synchrony: The effects of actual and imagined synchronous walking on attitudes towards marginalised groups.

Stereotyping is a pervasive societal problem that impacts not only minority groups but subserves individuals who perpetuate stereotypes, leading to greater distance between groups. Social contact interventions have been shown to reduce prejudice and stereotyping, but optimal contact conditions between groups are often out of reach in day to day life. Therefore, we investigated the effects of a synchronous walking intervention, a non-verbal embodied approach to intergroup contact that may reduce the need for optimal contact conditions. We studied attitude change towards the Roma group in Hungary following actual and imagined walking, both in a coordinated and uncoordinated manner. Results showed that coordinated walking, both imagined and in vivo, led to explicit and implicit reductions in prejudice and stereotyping towards both the Roma individual and the wider Roma social group. This suggests that coordinated movement could be a valuable addition to current approaches towards prejudice reduction.

Imagined Walking fMRI to Study Locomotor Control Post-Stroke

Previous stroke studies have largely used single-joint movements during functional MRI (fMRI) to assess brain locomotor control, but such movements typically elicit unilateral brain activation and may not optimally represent locomotion. Imagined walking activates similar bilateral brain regions compared to actual walking and has been the primary means of studying locomotor control in healthy populations, but has not been tested post-stroke. The objective of this fMRI study was to evaluate brain activation during imagined walking in chronic stroke.

Motor imagery of walking and walking while talking: a pilot randomized-controlled trial protocol for older adults.

Over a third of community-residing elderly have clinical gait abnormalities, and gait impairment is associated with morbidity, mortality and dementia. Motor imagery - envisioning motor actions without actual execution - has been used to improve gait in Parkinson's disease and poststroke, but the efficacy of motor imagery in healthy elderly is unknown. This single-blind pilot randomized-controlled trial aims to establish feasibility and explore the efficacy of a 3-month, telephone-based motor imagery intervention - that involves imagined walking, imagined talking and imagined walking while talking for improving gait in 48 healthy elderly. The primary outcomes will be gait speed during actual walking and walking while talking. Secondary outcomes will include cognitive performance during actual talking and walking while talking, and functional neuroplasticity during imagined walking and walking while talking. This clinical trial has been registered on clinicaltrials.gov (identifier NCT02762604).

The influences of tropical climate on imagined walking time

ABSTRACTThis study investigated the effects of a Tropical Climate (TC) on actual and imagined walking times. Participants had to execute and imagine walking 3 distances with or without a 10-kg weight in either a TC or an Air Conditioning (AC) condition. The motor imagery quality was evaluated by computing the isochrony index. The results revealed that movement times were shorter for imagined walking than for actual walking and increased with the distance of the paths in both cases. By contrast, the effect of the load increased actual walking times for the 10- and 15-meter distances without affecting imagined walking times. Importantly, the isochrony index was negatively affected by the increase in load and distance and the effects of distance were amplified in a TC. These findings showed that the environmental climate in which motor imagery arises can modulate the subject’s ability to build up the temporal characteristics of simulated actions.

Altered brain activation in complex walking conditions in patients with Parkinson's disease

IntroductionBehavioral studies suggest that deficits in cognitive domains and sensory-motor processes associated with Parkinson's disease (PD) impair the ability to walk in complex environments. However, the neural correlates of locomotion in complex environments are still unclear. MethodsTwenty healthy older adults (mean age 69.7 ± 1.3 yrs) and 20 patients with PD (mean age 72.9 ± 1.6 yrs; disease duration: 6.8 ± 1.3 yrs; UPDRSIII: 29.8 ± 2.4) were asked to imagine themselves walking while in the MRI scanner. Three imagined walking tasks, i.e., usual walking, obstacle negotiation, and navigation were performed. Watching the same virtual scenes without imagining walking served as control tasks. Whole brain analyses were used. ResultsCompared to usual walking, both groups had increased activation during obstacle negotiation in middle occipital gyrus (MOG) (pFWEcorr<0.001), middle frontal gyrus (MFG) (pFWEcorr<0.005), and cerebellum (pFWEcorr<0.001). Healthy older adults had higher activation in precuneus and MOG (pFWEcorr<0.023) during navigation, while no differences were observed in patients with PD. Between group comparisons revealed that patients with PD had a significantly higher activation in usual walking and obstacle negotiation (pFWEcorr<0.039) while during navigation task, healthy older adults had higher activation (pFWEcorr<0.047). ConclusionsPatients with PD require greater activation during imagined usual walking and obstacle negotiation than healthy older adults. This increased activation may reflect a compensatory attempt to overcome inefficient neural activation in patients with PD. This increased activation may reduce the functional reserve needed during more demanding tasks such as during navigation which may contribute to the high prevalence of falls and dual tasking difficulties among patients with PD.

Subthalamic nucleus stimulation improves Parkinsonian gait via brainstem locomotor centers

Subthalamic deep brain stimulation (STN-DBS) can ameliorate gait disturbances in Parkinson's disease (PD). Using motor imagery and positron emission tomography (PET), we investigated how STN-DBS interacts with supraspinal locomotor centers in PD. Ten PD patients with bilateral STN-DBS actually walked or stood still under STN-DBS ON or OFF conditions. Directly thereafter, subjects imagined walking or standing while changes in regional cerebral blood flow were measured by PET. Independent of STN-DBS, imagined walking distance correlated with imagery duration. Compared with STN-DBS OFF, STN-DBS ON improved actual gait and increased imagined walking distance. Imagery of gait (vs. stance) induced activity in the supplementary motor area and the right superior parietal lobule for both STN-DBS conditions. The improvement of imagined gait during STN-DBS ON led to activity changes in the pedunculopontine nucleus/mesencephalic locomotor region (PPN/MLR). Data suggest that STN-DBS improves Parkinsonian gait by modulating PPN/MLR activity.

Development of the Correspondence Between Real and Imagined Fine and Gross Motor Actions

The development of the correspondence between real and imagined motor actions was investigated in 2 experiments. Experiment 1 evaluated whether children imagine body position judgments of fine motor actions in the same way as they perform them. Thirty-two 8-year-old children completed a task in which an object was presented in different orientations, and children were asked to indicate the position of their hand as they grasped and imagined grasping the object. Children’s hand position was almost identical for the imagined- and real-grasping trials. Experiment 2 replicated this result with 8-year-olds as well as 6-year-olds and also assessed the development of the correspondence of the chronometry of real and imagined gross motor actions. Sixteen 6-year-old children and seventeen 8-year-old children participated in the fine motor grasping task from Experiment 1 and a gross motor task that measured the time it took for children to walk and imagine walking different distances. Six-year-olds showed more of a difference between real and imagined walking than did 8-year-olds. However, there were strong correlations between real and imagined grasping and walking for both 6- and 8-year-old children, suggesting that by at least 6 years of age, motor imagery and real action may involve common internal representations and that motor imagery is important for motor control and planning.

Neuroimaging of mobility in aging: a targeted review.

The relationship between mobility and cognition in aging is well established, but the relationship between mobility and the structure and function of the aging brain is relatively unknown. This, in part, is attributed to the technological limitations of most neuroimaging procedures, which require the individual to be immobile or in a supine position. Herein, we provide a targeted review of neuroimaging studies of mobility in aging to promote (i) a better understanding of this relationship, (ii) future research in this area, and (iii) development of applications for improving mobility. A systematic search of peer-reviewed studies was performed using PubMed. Search terms included (i) aging, older adults, or elderly; (ii) gait, walking, balance, or mobility; and (iii) magnetic resonance imaging, voxel-based morphometry, fluid-attenuated inversion recovery, diffusion tensor imaging, positron emission tomography, functional magnetic resonance imaging, electroencephalography, event-related potential, and functional near-infrared spectroscopy. Poor mobility outcomes were reliably associated with reduced gray and white matter volume. Fewer studies examined the relationship between changes in task-related brain activation and mobility performance. Extant findings, however, showed that activation patterns in the cerebellum, basal ganglia, parietal and frontal cortices were related to mobility. Increased involvement of the prefrontal cortex was evident in both imagined walking conditions and conditions where the cognitive demands of locomotion were increased. Cortical control of gait in aging is bilateral, widespread, and dependent on the integrity of both gray and white matter.

Behavioral and neural correlates of imagined walking and walking‐while‐talking in the elderly

Cognition is important for locomotion and gait decline increases the risk for morbidity, mortality, cognitive decline, and dementia. Yet, the neural correlates of gait are not well established, because most neuroimaging methods cannot image the brain during locomotion. Imagined gait protocols overcome this limitation. This study examined the behavioral and neural correlates of a new imagined gait protocol that involved imagined walking (iW), imagined talking (iT), and imagined walking-while-talking (iWWT). In Experiment 1, 82 cognitively-healthy older adults (M=80.45) walked (W), iW, walked while talking (WWT) and iWWT. Real and imagined walking task times were strongly correlated, particularly real and imagined dual-task times (WWT and iWWT). In Experiment 2, 33 cognitively-healthy older adults (M=73.03) iW, iT, and iWWT during functional magnetic resonance imaging. A multivariate Ordinal Trend (OrT) Covariance analysis identified a pattern of brain regions that: (1) varied as a function of imagery task difficulty (iW, iT and iWWT), (2) involved cerebellar, precuneus, supplementary motor and other prefrontal regions, and (3) were associated with kinesthetic imagery ratings and behavioral performance during actual WWT. This is the first study to compare the behavioral and neural correlates of imagined gait in single and dual-task situations, an issue that is particularly relevant to elderly populations. These initial findings encourage further research and development of this imagined gait protocol as a tool for improving gait and cognition among the elderly.

Walking execution is not affected by divided attention in patients with multiple sclerosis with no disability, but there is a motor planning impairment

We analysed the cognitive influence on walking in multiple sclerosis (MS) patients, in the absence of clinical disability. A case-control study was conducted with 12 MS patients with no disability and 12 matched healthy controls. Subjects were referred for completion a timed walk test of 10 m and a 3D-kinematic analysis. Participants were instructed to walk at a comfortable speed in a dual-task (arithmetic task) condition, and motor planning was measured by mental chronometry. Scores of walking speed and cadence showed no statistically significant differences between the groups in the three conditions. The dual-task condition showed an increase in the double support duration in both groups. Motor imagery analysis showed statistically significant differences between real and imagined walking in patients. MS patients with no disability did not show any influence of divided attention on walking execution. However, motor planning was overestimated as compared with real walking.

Freezing of gait is associated with a mismatch between motor imagery and motor execution in narrow doorways, not with failure to judge doorway passability

BackgroundMany patients with Parkinson's disease (PD) develop freezing of gait (FoG), which may manifest as a hesitation or “getting stuck” when they attempt to pass through a doorway. In two experiments, we asked whether FoG is associated with (1) a deficit in internal representation of one's body size with respect to a doorway and (2) a mismatch between imagined and actual walking times when passing through a doorway. Methods23 subjects with PD (11 with and 13 without FoG) and 10 control subjects of similar age completed two experiments. In the Passability experiment, subjects judged the passability of doorways with different apertures scaled to their body widths. We compared passability estimates across groups. In the Imagery experiment, subjects timed themselves while: (1) imagining walking through doorways of different apertures and from different distances and (2) actually walking in the same conditions they had just imagined. We compared imagined and actual walking durations across groups and conditions. ResultsIn the Passability experiment, the estimated just-passable doorway was wider, relative to body width, in PD subjects than in control subjects, but there was no difference between PD subjects with and without FoG. In the Imagery experiment, subjects in all groups walked more slowly through narrow doorways than though wide doorways, and subjects with FoG walked much more slowly through the narrowest doorways. PD subjects with FoG showed a large discrepancy between actual and imagined time to pass through narrow doorways, unlike PD subjects without FoG and control subjects. ConclusionsThe equivalent passability judgments in PD subjects with and without FoG indicate that FoG is not specifically associated with a deficit in ability to internally represent space with reference to body size. However, the large difference in duration between actual and imagined walking through narrow doorways in subjects with FoG suggests that PD subjects with FoG did not know how much they would slow down to pass through narrow doorways. The observed discrepancy between imagined and actual walking times may point to a specific problem that contributes to the occurrence of FoG. These results also suggest that caution should be used when interpreting brain imaging results from locomotor imagery studies with PD subjects who have FoG.

Hemispheric specialization during mental imagery of brisk walking

Brisk walking, a sensitive test to evaluate gait capacity in normal and pathological aging such as parkinsonism, is used as an alternative to classical fitness program for motor rehabilitation and may help to decrease the risk of cognitive deterioration observed with aging. In this study, we aimed to identify brain areas normally involved in its control. We conducted a block-design blood oxygen level dependent function magnetic resonance imaging (BOLD fMRI) experiment in 18 young healthy individuals trained to imagine themselves in three main situations: brisk walking in a 25-m-long corridor, standing or lying. Imagined walking time (IWT) was measured as a control of behavioral performance during fMRI. The group mean IWT was not significantly different from the actual walking time measured during a training session prior to the fMRI study. Compared with other experimental conditions, mental imagery (MI) of brisk walking was associated with stronger activity in frontal and parietal regions mainly on the right, and cerebellar hemispheres, mainly on the left. Presumed imagined walking speed (2.3 ± 0.4 m/s) was positively correlated with activity levels in the right dorsolateral prefrontal cortex and posterior parietal lobule along with the vermis and the left cerebellar hemisphere. A new finding in this study is that MI of brisk walking in young healthy individuals strongly involves processes lateralized in right fronto-parietal regions along with left cerebellum. These results show that brisk walking might be a non automatic locomotor activity requiring a high-level supraspinal control.

How does presentation method and measurement protocol affect distance estimation in real and virtual environments?

We conducted two experiments that compared distance perception in real and virtual environments in six visual presentation methods using either timed imagined walking or direct blindfolded walking, while controlling for several other factors that could potentially impact distance perception. Our presentation conditions included unencumbered real world, real world seen through an HMD, virtual world seen through an HMD, augmented reality seen through an HMD, virtual world seen on multiple, large immersive screens, and photo-based presentation of the real world seen on multiple, large immersive screens. We found that there was a similar degree of underestimation of distance in the HMD and large-screen presentations of virtual environments. We also found that while wearing the HMD can cause some degree of distance underestimation, this effect depends on the measurement protocol used. Finally, we found that photo-based presentation did not help to improve distance perception in a large-screen immersive display system. The discussion focuses on points of similarity and difference with previous work on distance estimation in real and virtual environments.

Real versus imagined locomotion: A [18F]-FDG PET-fMRI comparison

The cortical, cerebellar and brainstem BOLD-signal changes have been identified with fMRI in humans during mental imagery of walking. In this study the whole brain activation and deactivation pattern during real locomotion was investigated by [18F]-FDG-PET and compared to BOLD-signal changes during imagined locomotion in the same subjects using fMRI. Sixteen healthy subjects were scanned at locomotion and rest with [18F]-FDG-PET. In the locomotion paradigm subjects walked at constant velocity for 10 min. Then [18F]-FDG was injected intravenously while subjects continued walking for another 10 min. For comparison fMRI was performed in the same subjects during imagined walking. During real and imagined locomotion a basic locomotion network including activations in the frontal cortex, cerebellum, pontomesencephalic tegmentum, parahippocampal, fusiform and occipital gyri, and deactivations in the multisensory vestibular cortices (esp. superior temporal gyrus, inferior parietal lobule) was shown. As a difference, the primary motor and somatosensory cortices were activated during real locomotion as distinct to the supplementary motor cortex and basal ganglia during imagined locomotion. Activations of the brainstem locomotor centers were more prominent in imagined locomotion. In conclusion, basic activation and deactivation patterns of real locomotion correspond to that of imagined locomotion. The differences may be due to distinct patterns of locomotion tested. Contrary to constant velocity real locomotion (10 min) in [18F]-FDG-PET, mental imagery of locomotion over repeated 20-s periods includes gait initiation and velocity changes. Real steady-state locomotion seems to use a direct pathway via the primary motor cortex, whereas imagined modulatory locomotion an indirect pathway via a supplementary motor cortex and basal ganglia loop.

Evidence for motor simulation in imagined locomotion.

A series of experiments examined the role of the motor system in imagined movement, finding a strong relationship between imagined walking performance and the biomechanical information available during actual walking. Experiments 1 through 4 established the finding that real and imagined locomotion differ in absolute walking time. We then tested whether executed actions could provide a basis for imagined walking rate using 2 approaches. Experiments 5 and 6 used a perceptual-motor recalibration paradigm, finding that after physically walking in a treadmill virtual reality environment, actors recalibrated the time to imagine walking to a previously viewed target. This finding mirrors previous perceptual-motor recalibration work measuring actual walking to previously viewed targets. Experiments 7 and 8 used a dual-task paradigm in which actions performed concurrently with imagined walking increased the similarity between real and imagined walking time, but only when they were biomechanically consistent with the act of walking. The striking influence of biomechanical information on imagined locomotion provides evidence for shared motor systems in imagined and executed movements and is also directly relevant to the mechanisms involved in egocentric spatial updating of environmental layout.

Motor imagery of foot dorsiflexion and gait: Effects on corticospinal excitability

Objective We examined how corticospinal excitability was affected by motor imagery of foot dorsiflexion and motor imagery of gait. Methods Transcranial magnetic stimulation was applied over the primary motor cortex of 16 young healthy subjects while they performed imaginary foot dorsiflexions (Experiment I) and imaginary walking (Experiment II). Motor-evoked potentials (MEPs) were recorded from the tibialis anterior (TA) and first dorsal interosseus (FDI). MEPs recorded during motor imagery were compared to those recorded during a matched visual imagery task. Results Imagined foot dorsiflexions increased MEP areas in both TA and FDI. The increase in TA was stronger than in FDI. Overall, imagined walking did not change MEP areas. However, subjects with larger increases in TA during imagined foot dorsiflexion also showed larger increases in TA during imagined walking. Conclusions Imagined foot dorsiflexions increase corticospinal excitability in both a task-related muscle (TA) and a task-unrelated muscle (FDI), with larger increases in the task-related muscle. Imagined gait only increases corticospinal excitability in those subjects with the largest increments during imagined foot dorsiflexion. Significance Imagery of a simple lower extremity movement evokes increases in corticospinal excitability. Furthermore, corticospinal effects of a simple motor imagery task can predict corticospinal effects of a more complex motor imagery task involving the same muscle.