Cortical oscillations that underlie working memory are altered in adults with cerebral palsy

Comparison of Executive Function Skills between Patients with Cerebral Palsy and Typically Developing Populations: A Systematic Review and Meta-Analysis

Background: Children with CP show deficits in executive function compared to their typically developing peers, based on the majority of the available evidence. However, the magnitude of these deficits, as well as the proportions of the shortfalls in the three main components, have not yet been examined. This is the first meta-analysis to synthesize evidence on the magnitude of differences between patients with cerebral palsy (CP) and typically developing populations in different components of executive function skills (working memory, inhibitory control and cognitive flexibility), and thus makes recommendations on which areas of executive functioning are in greatest need of intervention. Methods: We conducted a systematic literature search of four databases for studies that measured executive functions in these two groups until 31 August 2023. We calculated the standardized mean difference (Hedges' g), an average effect size overall, and for the three components of executive function skills separately, we used several moderator analyses, including methodological differences between the primary studies. Results: Fifteen articles were included in the meta-analysis. The average mean difference in executive functioning overall was large (g+ = -0.82). Furthermore, large significant differences were found in working memory (g+ = -0.92) and inhibitory control (g+ = -0.82) and a moderate difference was identified in cognitive flexibility (g+ = -0.57). In addition, results of moderator analyses reveal the importance of a rigorous matching of control group participants and CP patients. Conclusions: The results demonstrate a severe impairment in all executive functions among CP patients compared to typically developing peers, which do not decrease over time.

Cognitive Functioning and Assessment in Adults with Cerebral Palsy: A Scoping Review

In this scoping review, we summarize the current knowledge of cognitive functioning in adults with cerebral palsy (CP), and identify the neuropsychological tests typically used in this population. 39 studies from the period January 1990 - August 2023 were included in the review, and they differ widely in their aims and approach to studying cognition. Very few studies have cognitive assessment as their core aim and use a neuropsychological test battery. The included studies show great variability in reported intelligence and cognitive functioning in adults with CP, and cognitive deficits have been reported in all cognitive domains. Most of the studies suffer from methodological limitations, and there is ample room for improvement within the field. We conclude by suggesting a number of recommendations that may contribute to increasing our understanding of cognitive impairments in adults with CP.

Spinal cord H-reflex post-activation depression is linked with hand motor control in adults with cerebral palsy

OBJECTIVE

Cerebral palsy (CP) is associated with upper extremity motor impairments that are largely assumed to arise from alterations in the supraspinal networks. The objective of this study was to determine if post-activation depression of the spinal H-reflexes is altered in adults with CP and connected with altered upper extremity function.

METHODS

The post-activation depression of the flexor carpi radialis (FCR) H-reflex of adults with CP and healthy adults (HA) controls were assessed by 1) a 1 Hz continuous single-pulse stimulus train and 2) 0.11 Hz / 1 Hz paired-pulse stimuli. Secondarily, we measured the maximum key grip force and the box and blocks assessment of manual dexterity.

RESULTS

Our results revealed that adults with CP had reduced post-activation depression of the FCR H-reflex during the stimulus train and the paired pulse protocol. A greater reduction in H-reflex post-activation depression was connected to lower manual dexterity and weaker grip forces.

CONCLUSIONS

Our results indicate that the post-activation depression of the upper extremity spinal H-reflex pathways is altered in adults with CP and possibly linked with their uncharacteristic upper extremity motor performance. Alterations in the spinal networks may also play a significant role in the altered motor control of adults with CP.

SIGNIFICANCE

Our results identify spinal H-reflex modulation as a possible locus for hand motor control in CP.

Effects of working memory span training on top-down attentional asymmetry at both neural and behavioral levels

The leftward asymmetry of the visual field and posterior brain regions, a feature of the normal attention process, can be strengthened by brain stimulation, e.g. administering alpha frequency stimulation to the left posterior cortex. However, whether it can be strengthened by cognitive training, especially with nonlateralized tasks, is unknown. We used a dataset from a 2-month-long randomized controlled trial and compared the control group with 2 training groups trained with backward or forward memory span tasks. A lateralized change detection task with varied memory loads was administered as the pre-, mid-, and post-tests with simultaneous electroencephalographic recording. Intrasubject response variability (IRV) and the alpha modulation index (MI) were calculated. Analysis of IRV showed more enhanced leftward attentional bias in the backward group than in the other groups. Consistently, analysis of MI found that its enhancements in the left hemisphere (but not the right hemisphere) of the backward group were significantly higher than those of the other groups. Further analysis revealed that left MI changes predicted left IRV improvement. All of these results indicated that backward memory span training enhanced leftward attentional asymmetry at both the behavioral and neural levels.

Reduced wrist flexor H-reflex excitability is linked with increased wrist proprioceptive error in adults with cerebral palsy

Although most neurophysiological studies of persons with cerebral palsy (CP) have been focused on supraspinal networks, recent evidence points toward the spinal cord as a central contributor to their motor impairments. However, it is unclear if alterations in the spinal pathways are also linked to deficits in the sensory processing observed clinically. This investigation aimed to begin to address this knowledge gap by evaluating the flexor carpi radialis (FCR) H-reflex in adults with CP and neurotypical (NT) controls while at rest and during an isometric wrist flexion task. The maximal H-wave (Hmax) and M-wave (Mmax) at rest were calculated and utilized to compute Hmax/Mmax ratios (H:M ratios). Secondarily, the facilitation of the H-wave was measured while producing an isometric, voluntary wrist flexion contraction (i.e., active condition). Finally, a wrist position sense test was used to quantify the level of joint position sense. These results revealed that the adults with CP had a lower H:M ratio compared with the NT controls while at rest. The adults with CP were also unable to facilitate their H-reflexes with voluntary contraction and had greater position sense errors compared with the controls. Further, these results showed that the adults with CP that had greater wrist position sense errors tended to have a lower H:M ratio at rest. Overall, these findings highlight that aberration in the spinal cord pathways of adults with CP might play a role in the sensory processing deficiencies observed in adults with CP.

Altered spontaneous cortical activity predicts pain perception in individuals with cerebral palsy

Cerebral palsy is the most common paediatric neurological disorder and results in extensive impairment to the sensorimotor system. However, these individuals also experience increased pain perception, resulting in decreased quality of life. In the present study, we utilized magnetoencephalographic brain imaging to examine whether alterations in spontaneous neural activity predict the level of pain experienced in a cohort of 38 individuals with spastic diplegic cerebral palsy and 67 neurotypical controls. Participants completed 5 min of an eyes closed resting-state paradigm while undergoing a magnetoencephalography recording. The magnetoencephalographic data were then source imaged, and the power within the delta (2–4 Hz), theta (5–7 Hz), alpha (8–12 Hz), beta (15–29 Hz), low gamma (30–59 Hz) and high gamma (60–90 Hz) frequency bands were computed. The resulting power spectral density maps were analysed vertex-wise to identify differences in spontaneous activity between groups. Our findings indicated that spontaneous cortical activity was altered in the participants with cerebral palsy in the delta, alpha, beta, low gamma and high gamma bands across the occipital, frontal and secondary somatosensory cortical areas (all p_FWE < 0.05). Furthermore, we also found that the altered beta band spontaneous activity in the secondary somatosensory cortices predicted heightened pain perception in the individuals with cerebral palsy (P = 0.039). Overall, these results demonstrate that spontaneous cortical activity within individuals with cerebral palsy is altered in comparison to their neurotypical peers and may predict increased pain perception in this patient population. Potentially, changes in spontaneous resting-state activity may be utilized to measure the effectiveness of current treatment approaches that are directed at reducing the pain experienced by individuals with cerebral palsy.