Effects of Motor Imagery on Cognitive Function and Prefrontal Cortex Activity in Normal Adults Evaluated by NIRS

Effects of trunk training using motor imagery on trunk control ability and balance function in patients with stroke

OBJECTIVE

To explore the effects of trunk training using motor imagery on trunk control and balance function in patients with stroke.

METHODS

One hundred eligible stroke patients were randomly divided into a control group and trial group. The control group was given routine rehabilitation therapy, while the trial group was given routine rehabilitation therapy and trunk training using motor imagery.

RESULTS

Prior to treatment, there was no significant difference between the two groups (P > 0.05) in Sheikh's trunk control ability, Berg rating scale (BBS), Fugl-Meyer assessment (FMA), movement length, movement area, average front-rear movement speed, average left-right movement speed, and surface electromyography (sEMG) signal of the bilateral erector spinae and rectus abdominis. After treatment, Sheikh's trunk control ability, FMA, and BBS in the two groups were significantly higher than those before treatment (P < 0.05). The movement length, movement area, the average front-rear movement speed, and the average left-right movement speed in the two groups decreased significantly (P < 0.05). The differences of these indicators between the two groups were statistically significant (P < 0.05). After treatment, the rectus abdominis and erector spinae on the affected side of the two groups improved when compared with those before treatment (P < 0.05). The rectus abdominis and erector spinae on the healthy side of the trial group descended after treatment (P < 0.05), while little changes were observed on the healthy side of the control group after treatment (P > 0.05). The rectus abdominis and erector spinae on the affected side of the trial group improved when compared with those in the control group (P < 0.05). There was no significant difference between the two groups in the decline of abdominalis rectus and erector spinal muscle on the healthy side.

CONCLUSION

Trunk training using motor imagery can significantly improve the trunk control ability and balance function of stroke patients and is conducive to promoting the recovery of motor function.

Estimation Error Consisting of Motor Imagery and Motor Execution in Patients with Stroke

Previous studies demonstrate that the difference between motor imagery and actual tasks (estimation error) is related to cognitive and physical functions and that a large estimation error (LE) is related to motor imagery ability, including cognitive and physical functions in healthy subjects. The purpose of this study investigated whether estimation error is related to physical and cognitive function in patients with stroke. The study included 60 patients with stroke. The Timed Up and Go Test (TUGT) was employed to assess estimation error. First, the imagined TUGT (iTUGT) was performed; thereafter, the actual TUGT was performed. The estimation error was calculated by subtracting TUGT from iTUGT, with conversion to the absolute value. The patients were classified into the small estimation error (SE) and LE groups, with comparisons of various clinical scores (Mini-Mental State Examination, Berg Balance Scale, 10-m walking speed, Brunnstrom Recovery Stage, and Functional Independence Measure). As a result, the estimation error was significantly larger in the LE group than in the SE group. Cognitive function and balance ability were significantly lower in the LE group than in the SE group. In conclusion, the estimation error was related to physical and cognitive functions in patients with stroke.

TMS over dorsolateral prefrontal cortex affects the timing of motor imagery but not overt action: Further support for the motor-cognitive model

The Motor-Cognitive model suggests a functional dissociation between motor imagery and overt action, in contrast to the Functional Equivalence view of common processes between the two behaviours. According to the Motor-Cognitive model, motor imagery differs from overt action primarily through the use of executive resources to monitor and elaborate a motor image during execution, which can result in a lack of correspondence between motor imagery and its overt action counterpart. The present study examined the importance of executive resources in motor imagery by using TMS to impair the function of the dorsolateral prefrontal cortex while measuring the time to complete imagined versus overt actions. In two experiments, TMS over the dorsolateral prefrontal cortex slowed motor imagery but did not affect overt actions. TMS over the same region also interfered with performance of a mental calculation task, though it did not reliably affect less demanding cognitive tasks also thought to rely on executive functions. Taken together, these results were consistent with the Motor-Cognitive model but not with the idea of functional equivalence. The implications of these results for the theoretical understanding of motor imagery, and potential applications of the Motor-Cognitive model to the use of motor imagery in training and rehabilitation, are discussed.

Motor Imagery and Frontal Head Oxygenation: An fNIRS Study

Motor imagery (MI) is a manifestation of mental movements, but it cannot be identified visually. Therefore, to a large extent, MI assessment has not yet been established. The present study aimed to investigate whether frontal oxy-Hb changes and cardiac autonomic nervous system activity during MI are associated with the psychometric scale assessment of MI and clarify the utility of each index in MI assessment. Thirty-one healthy men and women were included in this study, and Pocket NIRS Duo was used to assess frontal oxygenated hemoglobin levels during walking MI. Simultaneously, heart rate and sympathetic index (low and high frequency (LF/HF) during MI were evaluated using Chiryou Meijin, a heart rate frequency analyser. In addition, a psychometric scale evaluation was carried out in MC and VAS, and its correlation with oxy-Hb levels, heart rate (HR), and LF/HF was investigated. HRs and LF/HF during MI were significantly increased compared with those at rest. However, oxy-Hb levels during MI were not increased. There was a significant correlation between right oxy-Hb levels and mental chronometry (MC) during MI (r = -0.3, p < 0.05). HR and LF/HF were not correlated with MC. VAS was not correlated with oxy-Hb levels, HR, or LF/HF. The results of this study confirm an association between MI performance and frontal oxy-Hb changes and that brain activity is not necessarily elevated during MI. HR were significantly increased but did not show any association with MC.

Executive functions in motor imagery: support for the motor-cognitive model over the functional equivalence model

The motor-cognitive model holds that motor imagery relies on executive resources to a much greater extent than do overt actions. According to this view, engaging executive resources with an interference task during motor imagery or overt actions will lead to a greater lengthening of the time required to imagine a movement than to execute it physically. This model is in contrast to a currently popular view, the functional equivalence model, which holds that motor imagery and overt action use identical mental processes, and thus should be equally affected by task manipulations. The two competing frameworks were tested in three experiments that varied the amount and type of executive resources needed to perform an interference task concurrent with either an overt or imagined version of a grasping and placing action. In Experiment 1, performing a concurrent calculation task led to a greater lengthening of the time required to execute motor imagery than overt action relative to a control condition involving no interference task. Further, an increase in the number of responses used to index performance affected the timing of motor imagery but not overt actions. In Experiment 2, a low-load repetition task interfered with the timing of motor imagery, but less so than a high load calculation task; both tasks had much smaller effects on overt actions. In Experiment 3, a word generation task also interfered with motor imagery much more than with overt actions. The results of these experiments provide broad support for the motor-cognitive model over the functional equivalence model in showing that interfering with executive functions had a much greater impact on the timing of motor imagery than on overt actions. The possible roles of different executive processes in motor imagery are discussed.

Physical, cognitive and psychosocial effects of telerehabilitation-based motor imagery training in people with multiple sclerosis: A randomized controlled pilot trial

INTRODUCTION

Motor imagery training delivered at home via telerehabilitation is a novel rehabilitation concept. The aim was to investigate the effects of telerehabilitation-based motor imaging training (Tele-MIT) on gait, balance and cognitive and psychosocial outcomes in people with multiple sclerosis (pwMS).

METHODS

This randomized, controlled pilot trial included pwMS and healthy individuals. pwMS were randomly divided into two groups, intervention and control. The intervention group received Tele-MIT twice a week for 8 weeks. The control group was a wait-list group without any additional specific treatment. Healthy participants served as a baseline comparison. The Dynamic Gait Index, used to assess dynamic balance during walking, was the primary outcome. Secondary outcomes included assessments of walking speed, endurance and perceived ability, balance performance assessed by a computerized posturography device, balance confidence, cognitive functions, fatigue, anxiety, depression and quality of life.

RESULTS

Baseline comparisons with healthy individuals revealed that motor imagery abilities were preserved in pwMS (p > 0.05). The intervention group exhibited significant improvements in dynamic balance during walking (p = 0.002), walking speed (p = 0.007), perceived walking ability (p = 0.008), balance confidence (p = 0.002), most cognitive functions (p = 0.001-0.008), fatigue (p = 0.001), anxiety (p = 0.001), depression (p = 0.005) and quality of life (p = 0.002). No significant changes were observed in the control group in any of the outcome measures (p > 0.05).

DISCUSSION

Tele-MIT is a novel method that proved feasible and effective in improving dynamic balance during walking, walking speed and perceived walking ability, balance confidence, cognitive functions, fatigue, anxiety, depression and quality of life in pwMS.