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Prior research has shown that the sensorimotor cortical oscillations are uncharacteristic in persons with cerebral palsy (CP); however, it is unknown if these altered cortical oscillations have an impact on adaptive sensorimotor control. This investigation evaluated the cortical dynamics when the motor action needs to be changed "on-the-fly". Adults with CP and neurotypical controls completed a sensorimotor task that required either proactive or reactive control while undergoing magnetoencephalography (MEG). When compared with the controls, the adults with CP had a weaker beta (18–24 Hz) event-related desynchronization (ERD), post-movement beta rebound (PMBR, 16–20 Hz) and theta (4–6 Hz) event-related synchronization (ERS) in the sensorimotor cortices. In agreement with normative work, the controls exhibited differences in the strength of the sensorimotor gamma (66–84 Hz) ERS during proactive compared to reactive trials, but similar condition-wise changes were not seen in adults with CP. Lastly, the adults with CP who had a stronger theta ERS tended to have better hand dexterity, as indicated by the Box and Blocks Test and Purdue Pegboard Test. These results may suggest that alterations in the theta and gamma cortical oscillations play a role in the altered hand dexterity and uncharacteristic adaptive sensorimotor control noted in adults with CP. [ABSTRACT FROM AUTHOR]

Previous animal models have illustrated that reduced cortical activity in the developing brain has cascading activity-dependent effects on the microstructural organization of the spinal cord. A limited number of studies have attempted to translate these findings to humans with cerebral palsy (CP). Essentially, the aberrations in sensorimotor cortical activity in those with CP could have an adverse effect on the spinal cord microstructure. To investigate this knowledge gap, we utilized magnetoencephalographic (MEG) brain imaging to quantify motor-related oscillatory activity in fourteen adults with CP and sixteen neurotypical (NT) controls. A subset of these participants also underwent cervical-thoracic spinal cord MRI. Our results showed that the strength of the peri-movement beta desynchronization and the post-movement beta rebound were each weaker in the adults with CP relative to the controls, and these weakened responses were associated with poorer task performance. Additionally, our results showed that the strength of the peri-movement beta response was associated with the total cross-sectional area of the spinal cord and the white matter cross-sectional area. Altogether these results suggest that the altered sensorimotor cortical activity seen in CP may result in activity-dependent plastic changes within the spinal cord microstructure, which could ultimately contribute to the sensorimotor deficits seen in this population. [ABSTRACT FROM AUTHOR]

Adolescence is a critical period for the development and refinement of several higher-level cognitive functions, including visual selective attention. Clinically, it has been noted that adolescents with cerebral palsy (CP) may have deficits in selectively attending to objects within their visual field. This study aimed to evaluate the neural oscillatory activity in the ventral attention network while adolescents with CP performed a visual selective attention task. Adolescents with CP (N = 14; Age = 15.7 ± 4 years; MACS I–III; GMFCS I–IV) and neurotypical (NT) adolescents (N = 21; Age = 14.3 ± 2 years) performed the Eriksen flanker task while undergoing magnetoencephalographic (MEG) brain imaging. The participants reported the direction of a target arrow that was surrounded by congruent or incongruent flanking arrows. Compared with NT adolescents, adolescents with CP had slower responses and made more errors regarding the direction of the target arrow. The MEG results revealed that adolescents with CP had stronger alpha oscillations in the left insula when the flanking arrows were incongruent. Furthermore, participants that had more errors also tended to have stronger alpha oscillatory activity in this brain region. Altogether these results indicate that the aberrant activity seen in the left insula is associated with diminished visual selective attention function in adolescents with CP. [ABSTRACT FROM AUTHOR]

During active movement the somatosensory cortical responses are often attenuated. This attenuation is referred to as movement-related sensory gating. It is well known that patients with multiple sclerosis (MS) have sensory processing deficits, and recent work has also suggested that these patients display impaired motor control of the ankle musculature. The primary goal of the current study was to: (1) examine the movement-related somatosensory gating in patients with MS and demographically-matched controls, and (2) identify the relationship between the sensory gating and motor control of the ankle musculature. To this end, we used magnetoencephalography brain imaging to assess the neural responses to a tibial nerve electrical stimulation that was applied at rest (passive) and during an ankle plantarflexion motor task (active condition). All participants also completed an ankle isometric motor control task that was performed outside the scanner. Our results indicated that the controls, but not patients with MS, exhibited significantly reduced somatosensory responses during the active relative to passive conditions, and that patients with MS had stronger responses compared with controls during the active condition. Additionally, control of the ankle musculature was related to the extent of movement-related sensory attenuation, with poor motor control being associated with reduced gating. Overall, these results show that patients with MS do not attenuate the somatosensory cortical activity during motor actions, and that the inability to modulate somatosensory cortical activity is partially related to the poor ankle motor control seen in these patients. [ABSTRACT FROM AUTHOR]

Shortly after movement termination, there is a strong increase or resynchronization of the beta rhythm (15-30 Hz) across the sensorimotor network of humans, known as the post-movement beta rebound (PMBR). This response has been associated with active inhibition of the motor network following the completion of a movement, sensory afferentation of the sensorimotor cortices, and other functions. However, studies that have directly probed the role of the PMBR in movement execution have reported mixed results, possibly due to differences in the amount of total motor output and/or movement complexity. Herein, we used magnetoencephalography during an isometric-force control task to examine whether alterations in the timing of motor termination demands modulate the PMBR, independent of differences in the motor output itself. Briefly, we manipulated the amount of time between the cue to initiate the force and the cue to terminate the force, such that participants were either forced to terminate quickly or slowly. We also performed a control experiment to test for temporal predictability effects. Our results indicated that the PMBR was stronger immediately following movement termination in the prefrontal cortices, supplementary motor area, left postcentral gyrus, paracentral lobule, and parietal cortex when participants were forced to terminate more quickly. These results were not attributable to the temporal predictability of each condition. These findings support the notion that the PMBR response at least partially serves motor inhibition, independent of the parameters within the motor output itself, and that particular nodes of the motor network may be differentially modulated by motor termination. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to use relative phase dynamics to evaluate gait in individuals with a reconstructed anterior cruciate ligament (ACL) during walking and running. Relative phase dynamics can describe the coordination strategies between the interacting segments at the lower extremity. Ten subjects who had undergone ACL reconstruction using the central third of their patellar tendon and ten healthy controls walked and ran on a treadmill at a self-selected pace. Relative phase dynamics were calculated for the foot-shank and shank-thigh coordinative relationships. Statistical differences between the groups were noted for the foot-shank relationship (p < 0.05) during both walking and running and for the shank-thigh relationship (p < 0.05) during walking. Our results indicate that current ACL reconstructive techniques may result in altered relative phase dynamics. These changes in relative phase dynamics could be related to a loss of sensory information about joint position and velocity that is typically provided by the intact ACL. Additionally, relative phase adaptations could be a learned response from the early stages of postsurgical rehabilitation. Relative phase dynamics provide quantitative information about the dynamic status of the ACL-reconstructed knee that cannot be gained from the conventional time-series evaluation of gait analysis data. Relative phase dynamics measures should supplement the conventional gait analysis measures that are used today for the clinical evaluation of the functional dynamic stability of the reconstructed knee. The examination of relative phase dynamics could be clinically important for the quantification of new ACL surgical interventions and of patient performance at various stages of rehabilitation. Further research should incorporate relative phase dynamics to understand the influence of ACL reconstruction on coordination and functional patient outcomes. [ABSTRACT FROM AUTHOR]

There is currently a void in the scientific literature on the cortical beta oscillatory activity that is associated with the production of leg motor actions. In addition, we have limited data on how these cortical oscillations may progressively change as a function of development. This study began to fill this vast knowledge gap by using high-density magnetoencephalography to quantify the beta cortical oscillatory activity over a cross-section of typically developing children as they performed an isometric knee target matching task. Advanced beamforming methods were used to identify the spatiotemporal changes in beta oscillatory activity during the motor planning and motor action time frames. Our results showed that a widespread beta event-related desynchronization (ERD) was present across the pre/postcentral gyri, supplementary motor area, and the parietal cortices during the motor planning stage. The strength of this beta ERD sharply diminished across this fronto-parietal network as the children initiated the isometric force needed to match the target. Rank order correlations indicated that the older children were more likely to initiate their force production sooner, took less time to match the targets, and tended to have a weaker beta ERD during the motor planning stage. Lastly, we determined that there was a relationship between the child's age and the strength of the beta ERD within the parietal cortices during isometric force production. Altogether our results suggest that there are notable maturational changes during childhood and adolescence in beta cortical oscillatory activity that are associated with the planning and execution of leg motor actions. [ABSTRACT FROM AUTHOR]

Children with balance impairments have an increased amount of variability in the sway of the center of pressure (COP) during standing. Limited efforts have been made to quantify the nature of the variability. This exploratory investigation examined the deterministic and stochastic features that comprise the time-dependent postural sway variability during standing. We measured the COP in standing of a heterogeneous group of children with balance impairments and an age-matched cohort of typically developing children, both with and without vision. The standard deviation of the COP was used to quantify the amount of variability present in the postural sway. A Langevin equation methodology was additionally employed to reconstruct the deterministic and stochastic features that comprised the postural sway variability. Our experiment resulted in three key findings: (1) removal of visual information increased the stochastic features of the postural sway variability, (2) the stochastic features were greater for the children with balance impairments, (3) the change in the amount of variability was strongly correlated with change the stochastic features. These results imply that the inability to suppress the stochastic features present in the nervous system may play a prominent role in the balance problems of children. Moreover, our results imply that alterations in the stochastic features drive the postural system away from successful balance strategies. [ABSTRACT FROM AUTHOR]

The aim of the investigation was to explore the influence of levodopa therapy on the regularity of the structural variations present in the lower extremity joints of individuals with Parkinson’s disease (PD). Ten participants with PD walked on a treadmill during the states of “off” and “on” levodopa. Approximate entropy was used to quantify the regularity of the structural variations present in the joint kinematics. Additionally, a pseudo-periodic surrogation analysis was used to evaluate if changes in the regularity of the joint’s movement were associated with a noisy or deterministic motor process. This investigation provided two key findings. The first was that the structural variations present in ankle joint were more regular with levodopa therapy. The second was that changes in the structural variations were related to a deterministic motor process. This indicated that the variations present in the walking patterns of individuals with PD most likely arose from higher-order neural couplings rather than noise in the motor process. Monitoring the regularity of the structural variations present in gait may help improve the management of PD. [ABSTRACT FROM AUTHOR]

Chaos is a central feature of human locomotion and has been suggested to be a window to the control mechanisms of locomotion. In this investigation, we explored how the principles of chaos can be used to control locomotion with a passive dynamic bipedal walking model that has a chaotic gait pattern. Our control scheme was based on the scientific evidence that slight perturbations to the unstable manifolds of points in a chaotic system will promote the transition to new stable behaviors embedded in the rich chaotic attractor. Here we demonstrate that hip joint actuations during the swing phase can provide such perturbations for the control of bifurcations and chaos in a locomotive pattern. Our simulations indicated that systematic alterations of the hip joint actuations resulted in rapid transitions to any stable locomotive pattern available in the chaotic locomotive attractor. Based on these insights, we further explored the benefits of having a chaotic gait with a biologically inspired artificial neural network (ANN) that employed this chaotic control scheme. Remarkably, the ANN was quite robust and capable of selecting a hip joint actuation that rapidly transitioned the passive dynamic bipedal model to a stable gait embedded in the chaotic attractor. Additionally, the ANN was capable of using hip joint actuations to accommodate unstable environments and to overcome unforeseen perturbations. Our simulations provide insight on the advantage of having a chaotic locomotive system and provide evidence as to how chaos can be used as an advantageous control scheme for the nervous system. [ABSTRACT FROM AUTHOR]