Numerous studies of motor control have confirmed beta and gamma oscillations in the primary motor cortices during basic movements. These responses include a robust beta decrease that precedes and extends through movement onset, a transient gamma response that coincides with the movement, and a post-movement beta rebound (PMBR) response that occurs after movement offset. While the existence of these responses has been confirmed by many studies, very few studies have examined their developmental trajectory. In the current study, we utilized magnetoencephalography (MEG) to investigate age-related changes in sensorimotor cortical oscillations in a large cross-section of children and adolescents (n = 94; age range = 9 -15 years-old). All participants performed a stimulus detection task with their right finger and the resulting MEG data were examined using oscillatory analysis methods and imaged using a beamformer. Consistent with adult studies, these youth participants exhibited characteristic beta (16-24 Hz) decreases prior to and during movement, as well as PMBR responses following movement offset, and a transient gamma (74-84 Hz) response during movement execution. Our primary findings were that the strength of the PMBR increased with age, while the strength of the gamma synchronization decreased with chronological age. In addition, the strength of each motor-related oscillatory response was significantly correlated with the power of spontaneous activity in the same frequency range and same voxel. This was the case for all three oscillatory responses. In conclusion, we investigated motor-related oscillatory activity in the largest cohort of children and adolescents reported to date, and our results indicated that beta and gamma cortical oscillations continue to develop as children transition into adolescents, and that these responses may not be fully matured until young to middle adulthood.

ABBREVIATIONS CSACross-sectional area MTR Magnetization transfer ratio AIM To quantify the microstructural differences in the cervical-thoracic spinal cord of adults with cerebral palsy (CP).METHOD Magnetic resonance imaging of the proximal spinal cord (C6-T3) was conducted on a cohort of adults with CP (n=13; mean age=31y 11mo, standard deviation [SD] 8y 7mo; range=20y 8mo-47y 6mo; eight females, five males) and population norm adult controls (n=16; mean age=31y 4mo, SD 9y 9mo; range=19y 4mo-49y 5mo; seven females, nine males). The cross-sectional area (CSA) of the spinal cord, gray and white matter, magnetization transfer ratio (MTR), and fractional anisotropy of the cuneatus and corticospinal tracts were calculated. RESULTSThe total spinal cord CSA and proportion of the spinal cord gray matter CSA were significantly decreased in the adults with CP. The corticospinal tracts' MTR was lower in the adults with CP. Individuals that had reduced gray matter also tended to have reduced MTR in their corticospinal tracts (r=0.42, p=0.029) and worse hand dexterity clinical scores (r=0.53, p=0.004).INTERPRETATION These results show that there are changes in the spinal cord microstructure of adults with CP. Ultimately, these microstructural changes play a role in the extent of the hand sensorimotor deficits seen in adults with CP.

Adolescents demonstrate increasing mastery of motor actions with age. One prevailing hypothesis is that maturation of the somatosensory system during adolescence contributes to the improved motor control. However, limited efforts have been made to determine if somatosensory cortical processing is different in adolescents during movement. In this study, we used magnetoencephalographic brain imaging to begin addressing this knowledge gap by applying an electrical stimulation to the tibial nerve as adolescents (Age = 14.8 ± 2.5 yrs.) and adults (Age = 36.8 ± 5.0 yrs.) produced an isometric ankle plantarflexion force, or sat with no motor activity. Our results showed strong somatosensory cortical oscillations for both conditions in the alpha-beta (8–30 Hz) and gamma (38–80 Hz) ranges that occurred immediately after the stimulation (0–125 ms), and a beta (18–26 Hz) oscillatory response shortly thereafter (300–400 ms). Compared with the passive condition, all of these frequency specific cortical oscillations were attenuated while producing the ankle force. The attenuation of the alpha-beta response was greater in adolescents, while the adults had a greater attenuation of the beta response. These results imply that altered attenuation of the somatosensory cortical oscillations might be central to the under-developed somatosensory processing and motor performance characteristics in adolescents.

Key points Individuals with cerebral palsy (CP) have a reduced somatosensory cortical response Somatosensory cortical response strength decreases from adolescence to early adulthood Somatosensory cortical responses in youth with CP are similar to adult controls Individuals with CP may have aberrant maturation of the somatosensory system Abstract Numerous studies have documented tactile and proprioceptive deficits in children with cerebral palsy (CP) and linked these with weaker somatosensory cortical activity. However, whether such aberrations in somatosensory processing extend and/or progress into adulthood remains poorly understood. In the current study, we used magnetoencephalography (MEG) to investigate the primary somatosensory responses in a sample of individuals with CP (N = 42; age = 9–28 years) and a cohort of healthy controls (N = 23; age range = 11–23 years). Briefly, transient electrical stimulation was applied to the right tibial nerve, and standardized low‐resolution brain electromagnetic tomography (sLORETA) was used to image the dynamic somatosensory cortical response. We found that the strength of somatosensory cortical activity within the 112–252 ms time window was significantly reduced in the individuals with CP compared with the healthy controls (HC = 286.53 ± 30.51, 95% CI [226.74, 346.32]; CP = 208.30 ± 19.66,CI [169.77, 246.83], P = 0.0126). These results corroborate previous findings of aberrant somatosensory cortical activity in individuals with CP. Our results also suggest that the somatosensory cortical activity tends to become weaker with age, with a similar rate of neurophysiological change in individuals with CP and healthy controls (P = 0.8790). Visualization of regression models fitted to the data imply that youth with CP may have somatosensory cortical activity similar to adult controls. These findings suggest that some individuals with CP exhibit an aberrant developmental trajectory of their somatosensory system.

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Somatosensory cortical activity is altered in individuals with cerebral palsy (CP). However, previous studies have focused on the lower extremities in children with CP and have given less attention to structural changes that may contribute to these alterations. We used a multimodal neuroimaging approach to investigate the relationship between somatosensory cortical activity and cortical thickness in 17 adults with CP (age = 32.8 ± 9.3 years) and 18 healthy adult controls (age = 30.7 ± 9.8 years). Participants performed a median nerve paired-pulse stimulation paradigm while undergoing magnetoencephalography (MEG) to investigate somatosensory cortical activity and sensory gating. Participants also underwent magnetic resonance imaging to evaluate cortical thickness within the area of the somatosensory cortex that generated the MEG response. We found that the somatosensory responses were attenuated in the adults with CP (P = 0.004). The adults with CP also hypergated the second stimulation (P = 0.030) and had decreased cortical thickness in the somatosensory cortex (P = 0.015). Finally, the strength of the somatosensory response was significantly correlated with the cortical thickness (P = 0.023). These findings demonstrate that the aberrant somatosensory cortical activity in adults with CP extends to the upper extremities and appears to be related to cortical thickness.

Dynamically allocating neural resources to salient features or objects within our visual space is fundamental to making rapid and accurate decisions. Impairments in such visuospatial abilities have been consistently documented in the clinical literature on individuals with cerebral palsy (CP), although the underlying neural mechanisms are poorly understood. In this study, we used magnetoencephalography (MEG) and oscillatory analysis methods to examine visuospatial processing in children with CP and demographically matched typically developing (TD) children. Our results indicated robust oscillations in the theta (4–8 Hz), alpha (8–14 Hz), and gamma (64–80 Hz) frequency bands in the occipital cortex of both groups during visuospatial processing. Importantly, the group with CP exhibited weaker cortical oscillations in the theta and gamma frequency bands, as well as slower response times and worse accuracy during task performance compared to the TD children. Furthermore, we found that weaker theta and gamma oscillations were related to greater visuospatial performance deficits across both groups. We propose that the weaker occipital oscillations seen in children with CP may reflect poor bottom-up processing of incoming visual information, which subsequently affects the higher-order visual computations essential for accurate visual perception and integration for decision-making.

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.