Age-Related Differences in Strategy in the Hand Mental Rotation Task.

Mental imagery of movement is a potentially valuable rehabilitation task, but its therapeutic efficacy may depend on the specific cognitive strategy employed. Individuals use two main strategies to perform the hand mental rotation task (HMRT), which involves determining whether a visual image depicts a left or right hand. One is the motor imagery (MI) strategy, which involves mentally simulating one's own hand movements. In this case, task performance as measured by response time (RT) is subject to a medial-lateral effect wherein the RT is reduced when the fingertips are directed medially, presumably as the actual motion would be easier. The other strategy is to employ visual imagery (VI), which involves mentally rotating the picture and is not subject to this medial-lateral effect. The rehabilitative benefits of the HMRT are thought to depend on the MI strategy (mental practice), so it is essential to examine the effects of individual factors such as age, image perspective (e.g., palm or back of the hand), and innate ability (as indicated by baseline RT) on the strategy adopted. When presented with pictures of the palm, all subjects in the current study used the MI strategy, regardless of age and ability. In contrast, when subjects were presented with pictures of the back of the hand, the VI strategy predominated among the young age group regardless of performance, while the strategy used by middle-age and elderly groups depended on performance ability. In the middle-age and elderly groups, the VI approach predominated in those with high performance skill, whereas the MI strategy predominated among those with low performance skill. Thus, higher-skill middle-aged and elderly individuals may not necessarily form a motion image during the HMRT, potentially limiting rehabilitation efficacy.

Variation in Performance Strategies of a Hand Mental Rotation Task on Elderly.

A hand mental rotation task (HMRT) is a task wherein a person judges whether an image of a rotated hand is of the right or left hand. Two performance strategies are expected to come into play when performing these tasks: a visual imagery (VI) strategy, in which an image is mentally rotated, and a motor imagery (MI) strategy, in which the movement of a person's own hand is simulated. Although elderly people generally take some time to perform these tasks, ability differs greatly between individuals. The present study hypothesizes that there is a relationship between differences in task performance strategy and performance ability, and it compares performance strategy among elderly people divided into groups with a short mental rotation time and a long mental rotation time. In response to images of the palm, both groups displayed a medial-lateral effect in which responses were faster for images where the third finger was rotated toward the midline of the body than images rotated in the opposite direction, and we inferred that an MI strategy was primarily employed. Meanwhile, in response to images of the back of the hand, a medial-lateral effect was also observed in the group with a long mental rotation time and not in the group with the shortest mental rotation time (VI strategy). These results suggest that different strategies for performing HMRT task are used by elderly people with a short mental rotation time and those with a long mental rotation time.

Response time differences between men and women during hand mental rotation.

This study explored gender differences in correct response rates and response times on a task involving left or right arrow selection and another involving the transformation of mental rotation of the hand. We recruited 15 healthy, right-handed men (age 24.5 ± 6.4) and 15 healthy, right-handed women (age 21.3 ± 4.9). For the tasks, we used pictures of left and right arrows and 32 hand pictures (left and right, palm and back) placed in cons (each at 45° from 0° to 315°). Hand and arrow pictures alternated and were shown at random. Participants decided as quickly as possible whether each picture was left or right. To compare the time taken for the transformation of mental rotation of the hand, we subtracted the average arrow response time from that for the left and right hand pictures for each participant. Correct response rates did not differ significantly between men and women or left and right for either arrow or hand pictures. Regardless of gender, the response time was longer for the left arrow picture than right arrow picture. The response time for the hand picture was longest for both men and women for pictures at rotation angles that were most difficult to align with participants' hands. While there was no difference between men's responses for left and right hand pictures, the responses of women were longer for left than right hand pictures and also than those of men. These findings suggest that both men and women mainly perform the hand mental rotation task with implicit motor imagery. On the other hand, the gender difference in performance might be explained by the difference in balance with other strategies, such as visual imagery, and by cognitive, neurophysiological, and morphological differences.

Ability of electrical stimulation therapy to improve the effectiveness of robotic training for paretic upper limbs in patients with stroke.

We investigated whether untriggered neuromuscular electrical stimulation (NMES) can increase the effectiveness of shoulder and elbow robotic training in patients with hemiparesis. Thirty subacute stroke patients were randomly equally allocated to robot only (RO) and robot and electrical stimulation (RE) groups. During training, shoulder and elbow movements were trained by operating the robotic arm with the paretic arm, and the robotic device helped to move the arm. In the RE group, the anterior deltoid and triceps brachii muscles were electrically stimulated at sub-motor threshold intensity. Training was performed (approximately 1h/day, 5 days/week for 2 weeks) in addition to regular rehabilitation. Active range of motion (ROM) values of shoulder flexion and abduction, and Fugl-Meyer assessment (FMA) scores were measured before and after training. Active shoulder ROM was significantly better after than before training in the RE group; however, no such improvement was noted in the RO group. FMA scores were significantly better in both groups, and there was no significant difference between the groups. Untriggered NMES might increase the effectiveness of shoulder and elbow robotic training in patients with hemiparesis. Additionally, NMES at a sub-motor threshold during robotic training might facilitate activation of paretic muscles, resulting in paralysis improvement.

Neuroprotective effect of yokukansan against cytotoxicity induced by corticosterone on mouse hippocampal neurons.

Yokukansan, a traditional Japanese herbal medicine, has been used for the management of neurodegenerative disorders and for the treatment of neurosis, insomnia, and behavioral and psychological symptoms of dementia. Recently, several studies have shown that yokukansan has a neuroprotective effect. The aim of this study was to examine the neuroprotective effect of yokukansan on hippocampal neurons from embryonic mouse brain against the effects of corticosterone, which is considered to be a stress hormone and to be cytotoxic toward neurons. The cell survival rates were measured by the WST-8 assay and LDH assay. Twenty-four hours after treatment with corticosterone, cell numbers were significantly decreased compared with the control or treatment with vehicle in a dose-dependent manner. When cells were treated with 30 µM corticosterone, the decrease in the number of cells was significantly recovered by treatment with yokukansan (100-1,000 µg/ml) in a dose-dependent manner. However, yokukansan did not suppress the decrease in cell numbers that was induced by treatment with 100 µM corticosterone. In the LDH assay, treatment with yokukansan at a high concentration (500-1,000 µg/ml) suppressed the LDH concentration induced by treatment with both 30 µM and 100 µM corticosterone compared to treatment with corticosterone alone, respectively. These results suggest that yokukansan protects against the cytotoxic effect of a low concentration of corticosterone on hippocampal neurons.

Yokukansan, a traditional Japanese herbal medicine, alleviates the emotional abnormality induced by maladaptation to stress in mice.

The aim of the present study was to examine the effect of yokukansan, a traditional Japanese herbal medicine that is composed of Atractylodis lanceae Rhizoma, Poria, Cnidii Rhizoma, Uncariae Uncis cum Ramulus, Angelicae Radix, Bupleuri Radix and Glycyrrhizae Radix, on the emotional abnormality induced by maladaptation to stress in mice. Mice were exposed to repeated restraint stress for 60 or 240 min/day for 14 days. From the 3rd day of stress exposure, mice were given yokukansan orally (p.o.) or the 5-HT1A receptor agonist flesinoxan intraperitoneally (i.p.) immediately after the daily exposure to restraint stress. After the final exposure to restraint stress, the emotionality of mice was evaluated using an automatic hole-board apparatus. A single exposure to restraint stress for 60 min induced a decrease in head-dipping behavior in the hole-board test. This emotional stress response disappeared in mice that had been exposed to repeated restraint stress for 60 min/day for 14 days, which confirmed the development of stress adaptation. In contrast, mice that were exposed to restraint stress for 240 min/day for 14 days did not develop this stress adaptation, and still showed a decrease in head-dipping behavior. The decreased emotionality observed in stress-maladaptive mice was significantly recovered by chronic treatment with yokukansan (1000 mg/kg, p.o.) as well as flesinoxan (0.25 and 0.5 mg/kg, i.p.) immediately after daily exposure to stress. These findings suggest that yokukansan may have a beneficial effect on stress adaptation and alleviate the emotional abnormality under conditions of excessive stress.

Specifications of an electromyogram-driven neuromuscular stimulator for upper limb functional recovery.

An electromyogram (EMG)-driven neuromuscular stimulator for upper limb functional recovery (Muraoka et al., 1998) can stimulate target muscles in proportion to the amount of voluntary EMG of the identical target muscles. Furthermore, it can facilitate the contraction of paralyzed muscles by electrical stimulation at subthreshold intensity level. Although it has been suggested that to use the stimulator for as long a time as possible might be needed for more effective treatment, the utilization time was limited by the size of the stimulator, which involved a laptop personal computer. To use in daily life, the device was improved to be a smaller size of 95×65×40 mm (including batteries) which was equivalent to a mobile phone (in 2002). The stimulator was called the Integrated Volitional-control Electrical Stimulator (IVES). IVES has already been manufactured and its use has spread in Japan since 2008. Nowadays, therapy using IVES is an effective therapy to improve the motor function of the upper limb in post-stroke patients with hemiparesis. However, the signal processing and internal structure of IVES has not yet been reported. In this study the device specification of IVES is described, especially its electrical circuits and signal processing that detect voluntary EMG and stimulate from the same electrodes. IVES uses two DIACs for detecting voluntary EMG from stimulating electrodes. The DIACs switch passively between the stimulation circuit and the EMG amplifier circuit. Furthermore, the signal processing of the time-shifted difference of the 2-cycle EMG signal following identical stimulation pulses eliminates stimulation artifacts and evoked potentials, and extracts voluntary EMG.

A pilot study of sensory feedback by transcutaneous electrical nerve stimulation to improve manipulation deficit caused by severe sensory loss after stroke.

BACKGROUND: Sensory disturbance is common following stroke and can exacerbate functional deficits, even in patients with relatively good motor function. In particular, loss of appropriate sensory feedback in severe sensory loss impairs manipulation capability. We hypothesized that task-oriented training with sensory feedback assistance would improve manipulation capability even without sensory pathway recovery. METHODS: We developed a system that provides sensory feedback by transcutaneous electrical nerve stimulation (SENS) for patients with sensory loss, and investigated the feasibility of the system in a stroke patient with severe sensory impairment and mild motor deficit. The electrical current was modulated by the force exerted by the fingertips so as to allow the patient to identify the intensity. The patient had severe sensory loss due to a right thalamic hemorrhage suffered 27 months prior to participation in the study. The patient first practiced a cylindrical grasp task with SENS for 1 hour daily over 29 days. Pressure information from the affected thumb was fed back to the unaffected shoulder. The same patient practiced a tip pinch task with SENS for 1 hour daily over 4 days. Pressure information from the affected thumb and index finger was fed back to the unaffected and affected shoulders, respectively. We assessed the feasibility of SENS and examined the improvement of manipulation capability after training with SENS. RESULTS: The fluctuation in fingertip force during the cylindrical grasp task gradually decreased as the training progressed. The patient was able to maintain a stable grip force after training, even without SENS. Pressure exerted by the tip pinch of the affected hand was unstable before intervention with SENS compared with that of the unaffected hand. However, they were similar to each other immediately after SENS was initiated, suggesting that the somatosensory information improved tip pinch performance. The patient's manipulation capability assessed by the Box and Block Test score improved through SENS intervention and was partly maintained after SENS was removed, until at least 7 months after the intervention. The sensory test score, however, showed no recovery after intervention. CONCLUSIONS: We conclude that the proposed system would be useful in the rehabilitation of patients with sensory loss.

Event related desynchronization-modulated functional electrical stimulation system for stroke rehabilitation: a feasibility study.

BACKGROUND: We developed an electroencephalogram-based brain computer interface system to modulate functional electrical stimulation (FES) to the affected tibialis anterior muscle in a stroke patient. The intensity of FES current increased in a stepwise manner when the event-related desynchronization (ERD) reflecting motor intent was continuously detected from the primary cortical motor area. METHODS: We tested the feasibility of the ERD-modulated FES system in comparison with FES without ERD modulation. The stroke patient who presented with severe hemiparesis attempted to perform dorsiflexion of the paralyzed ankle during which FES was applied either with or without ERD modulation. RESULTS: After 20 minutes of training, the range of movement at the ankle joint and the electromyography amplitude of the affected tibialis anterior muscle were significantly increased following the ERD-modulated FES compared with the FES alone. CONCLUSIONS: The proposed rehabilitation technique using ERD-modulated FES for stroke patients was feasible. The system holds potentials to improve the limb function and to benefit stroke patients.

Analysis of extrinsic and intrinsic factors affecting event related desynchronization production.

Recently there has been an increase in the number of stroke patients with motor paralysis. Appropriate re-afferent sensory feedback synchronized with a voluntary motor intention would be effective for promoting neural plasticity in the stroke rehabilitation. Therefore, BCI technology is considered to be a promising approach in the neuro-rehabilitation. To estimate human motor intention, an event-related desynchronization (ERD), a feature of electroencephalogram (EEG) evoked by motor execution or motor imagery is usually used. However, there exists various factors that affect ERD production, and its neural mechanism is still an open question. As a preliminary stage, we evaluate mutual effects of intrinsic (voluntary motor imagery) and extrinsic (visual and somatosensory stimuli) factors on the ERD production. Experimental results indicate that these three factors are not always additively interacting with each other and affecting the ERD production.

Single session of transcranial direct current stimulation transiently increases knee extensor force in patients with hemiparetic stroke.

BACKGROUND: Transcranial direct current stimulation (tDCS) of the motor cortex can enhance the performance of a paretic upper extremity after stroke. Reported effects on lower limb (LL) function are sparse. OBJECTIVE: The authors examined whether tDCS can increase the force production of the paretic quadriceps. METHODS: In this double-blind, crossover, sham-controlled experimental design, 8 participants with chronic subcortical stroke performed knee extension using their hemiparetic leg before, during, and after anodal or sham tDCS of the LL motor cortex representation in the affected hemisphere. Affected hand-grip force was also recorded. RESULTS: The maximal knee-extension force increased by 21 N (13.2%, P < .01) during anodal tDCS compared with baseline and sham stimulation. The increase persisted less than 30 minutes. Maximal hand-grip force did not change. CONCLUSIONS: Anodal tDCS transiently enhanced knee extensor strength. The modest increase was specific to the LL. Thus, tDCS might augment the rehabilitation of stroke patients when combined with lower extremity strengthening or functional training.