Céline Crajé

Action planning in typically and atypically developing children (unilateral cerebral palsy)

In the present study, we investigated the development of action planning in children with unilateral Cerebral Palsy (CP, aged 3-6 years, n=24) and an age matched control group. To investigate action planning, participants performed a sequential movement task. They had to grasp an object (a wooden play sword) and place the sword in a hole in a wooden block. Our main dependent variable was the grip type that participants used, i.e., did they adapt their initial grip choice such that they would reach a comfortable posture at the end of the action? This end-state comfort effect has been abundantly shown in research on action planning, and is taken as evidence for anticipatory planning. The first aim of the study was to investigate the development of action planning in the unilateral CP group and the control group. Our hypothesis was that action planning improves with age in the control group, but not in the unilateral CP group. The results showed that planning was impaired in the unilateral CP group compared with the control group. Consistent with our hypothesis, we found an age effect in the control group, but not in the unilateral CP group. In the control group 5 and 6 years olds showed more anticipatory planning compared with the 3 and 4 years olds. The second aim of this study was to examine whether an intervention for children with unilateral CP (i.e., constrained induced movement therapy combined with bimanual training) affected action planning. The children with unilateral CP were therefore measured on the experimental task before and after an 8-week intervention period. The results showed that planning improved after the intervention. This finding suggests that action planning ability in young children with unilateral CP may be sensitive to improvement. These findings are discussed within the context of typical and atypical development of action planning and further guidelines for intervention in children with unilateral CP are given.

Motor imagery training in hemiplegic cerebral palsy: a potentially useful therapeutic tool for rehabilitation

Converging evidence indicates that motor deficits in cerebral palsy (CP) are related not only to problems with execution, but also to impaired motor planning. Current rehabilitation mainly focuses on alleviating compromised motor execution. Motor imagery is a promising method of training the more ‘cognitive’ aspects of motor behaviour, and may, therefore, be effective in facilitating motor planning in patients with CP. In this review first we present the specific motor planning problems in CP followed by a discussion of motor imagery and its use in clinical practice. Second, we present the steps to be taken before motor imagery can be used for rehabilitation of upper limb functioning in CP. Motor imagery training has been shown to be a useful addition to existing rehabilitation protocols for poststroke rehabilitation. No such study has been conducted in CP. The age at which children can reliably use motor imagery, as well as the specific way in which motor imagery training needs to be implemented, must be researched before motor imagery training can be employed in children with CP. Based on the positive results for poststroke rehabilitation, and in light of the motor problems in CP, motor imagery training may be a valuable additional tool for rehabilitation in CP.

Compromised motor planning and Motor Imagery in right Hemiparetic Cerebral Palsy

We investigated whether motor planning problems in people with Hemiparetic Cerebral Palsy (HCP) are paralleled by impaired ability to use Motor Imagery (MI). While some studies have shown that individuals with HCP can solve a mental rotation task, it was not clear if they used MI or Visual Imagery (VI). In the present study, motor planning and MI were examined in individuals with right HCP (n=10) and controls. Motor planning was measured using an object manipulation task, where participants had to anticipate the end of the motor action. MI was measured using a mental rotation paradigm, where participants judged laterality of hands presented from a back view and a palm view. To test if participants used MI or VI we compared reaction times of lateral versus medial rotations, under the assumption that MI is subject to biomechanical constraints of rotated hands, but VI is not. Individuals with HCP had a higher proportion of task failures due to inappropriate grip choice, exemplifying impaired planning. Second, individuals with HCP did not show a reaction time difference between lateral and medial rotations, indicating an impaired ability to use MI. These findings show that compromised motor planning in HCP is paralleled by an impairment in the ability to use MI. Training of MI may be a useful entry-point for rehabilitation of motor planning problems.

Anticipatory action planning increases from 3 to 10 years of age in typically developing children

The primary aim of this study was to assess the development of action planning in a group of typically developing children aged 3 to 10 years (N=351). The second aim was to assess reliability of the action planning task and to relate the results of the action planning task to results of validated upper limb motor performance tests. Participants performed an action planning task in which they needed to grasp an object (a wooden play sword) and place it into a tight-fitting hole. Our main dependent variable was the grip type that participants used; that is, we measured whether initial grip was adapted in such a way that children reached a comfortable posture at the end of the action (the end-state comfort effect). Older children planned their actions more often in line with the end-state comfort effect compared with younger children. Test-retest and interrater reliability of the action planning task were good, with intraclass correlation coefficients (ICCs) of .90 and .95, respectively. We compared the action planning task with manual dexterity tests in a subset of participants (n=197). We found a marginal relation with the manual dexterity tests, indicating that the action planning task measures different processes. In sum, our study showed that action planning increases from 3 to 10 years of age and that the experimental task we used is reliable in assessing anticipatory planning. Therefore, it may be used as a reliable additional test to investigate the degree to which motor behavior is affected at the cognitive level of anticipatory planning.

Neural evidence for impaired action selection in right hemiparetic cerebral palsy

Recent studies suggest that in addition to low-level motor impairments, individuals with hemiparetic cerebral palsy (HCP) are characterized by anticipatory action planning deficits as well. In the present EEG study we investigated the neural and temporal dynamics of action planning in participants with right-sided HCP (n=10) and in left-handed control subjects (n=10). An anticipatory planning task was used in which participants were required to grasp and rotate a hexagonal knob over different angles (60 degrees, 120 degrees or 180 degrees). At a behavioral level, participants with HCP were slower in their movements and often selected an inappropriate grip when grasping the object. At a neural level, individuals with HCP showed a strong reduction in the amplitude of the P2 component, likely reflecting an impaired process of action selection. In addition, a strong correlation was observed between the P2 amplitude and grasping and rotation times. The P2 component was localized to sources in the dorsal posterior cingulate cortex (dPCC), an area that is known to be involved in orienting visual body parts in space. Together these findings suggest that anticipatory planning deficits in cerebral palsy arise mainly due to an impaired process of action selection.

Neural Evidence for Compromised Motor Imagery in Right Hemiparetic Cerebral Palsy

In the present event-related potential (ERP) study we investigated the neural and temporal dynamics of motor imagery in participants with right-sided hemiparetic cerebral palsy (HCP; n = 10) and in left-handed control participants (n = 10). A mental rotation task was used in which participants were required to judge the laterality of hand pictures. At a behavioral level participants with HCP were slower in making hand laterality judgments compared to control subjects, especially when presented with pictures representing the affected hand. At a neural level, individuals with HCP were characterized by a reduced rotation-related negativity (RRN) over parietal areas, that was delayed in onset with respect to control participants. Interestingly, participants that were relatively mildly impaired showed a stronger RRN for the rotation of right-hand stimuli than participants that were more strongly impaired in their motor function, suggesting a direct relation between the motor imagery process and the biomechanical constraints of the participant. Together, the results provide new insights in the relation between motor imagery and motor capabilities and indicate that participants with HCP may be characterized by a compromised ability to use motor imagery.

Determining Specificity of Motor Imagery Training for Upper Limb Improvement in Chronic Stroke Patients: A Training Protocol and Pilot Results.

Motor imagery (MI) refers to the mental rehearsal of a movement without actual motor output. MI training has positive effects on upper limb recovery after stroke. However, until now it is unclear whether this effect is specific to the trained task or a more general motor skill improvement. This study was set up to advance our insights into the efficacy of MI training and the specificity of its effects. We investigated whether MI training affected the trained hand exclusively, or both hands. Four stroke participants received a 15-min MI training four times a week for 3 weeks. Hand function was measured before and after the training using three measurements of increasing complexity. Hand function improved after MI training, thus confirming the earlier studies. Second, we found specific effects of the MI training for two of the three measurements. These results suggest that MI specificity is dependent on the complexity of the hand function task.