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There are numerous clinical reports showing that persons with cerebral palsy (CP) have proprioceptive, stereognosis, and tactile discrimination deficits. The current consensus is that these altered perceptions are attributable to aberrant somatosensory cortical activity. It has been inferred from these data that persons with CP do not adequately process ongoing sensory feed back during motor actions, which accentuates the extent of their mobility impairments. However, this hypothesis has yet to be directly tested. We used magnetoencephalographic brain imaging to address this knowledge gap by quantifying the somatosensory dynamics evoked by applying electrical stimulation to the tibial nerve in 22 persons with CP and 25 neurotypical controls at rest and during an ankle plantarflexion isometric force motor task. We also quantified the spatiotemporal gait biomechanics of participants outside the scanner. Consistent with the literature, our results confirmed that the strength of somatosensory cortical activity was weaker in the persons with CP compared to the neurotypical controls. Our results also showed that the strength of the somatosensory cortical responses were significantly weaker during the isometric ankle force task than at rest. Most importantly, our results showed that the strength of somatosensory cortical activity during the ankle plantarflexion force production task mediated the relationship between somatosensory cortical activity at rest and both walking velocity and step length. These results suggest that youth with CP have aberrant somatosensory cortical activity during isometric force generation, which ultimately contributes to the extent of mobility impairments seen in this patient population. [ABSTRACT FROM AUTHOR]

Key points: Individuals with cerebral palsy (CP) have a reduced somatosensory cortical responseSomatosensory cortical response strength decreases from adolescence to early adulthoodSomatosensory cortical responses in youth with CP are similar to adult controlsIndividuals with CP may have aberrant maturation of the somatosensory system 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. Key points: Individuals with cerebral palsy (CP) have a reduced somatosensory cortical responseSomatosensory cortical response strength decreases from adolescence to early adulthoodSomatosensory cortical responses in youth with CP are similar to adult controlsIndividuals with CP may have aberrant maturation of the somatosensory system [ABSTRACT FROM AUTHOR]

Key points: Magnetoencephalography data were acquired during a leg force task in pre‐/post‐practice sessions in adolescents and adults.Strong peri‐movement alpha and beta oscillations were mapped to the cortex.Following practice, performance improved and beta oscillations were altered.Beta oscillations decreased in the sensorimotor cortex in adolescents after practice, but increased in adults.No pre‐/post‐practice differences were detected for alpha oscillations. There is considerable evidence that there are motor performance and practice differences between adolescents and adults. Behavioural studies have suggested that these motor performance differences are simply due to experience. However, the neurophysiological nexus for these motor performance differences remains unknown. The present study investigates the short‐term changes (e.g. fast motor learning) in the alpha and beta event‐related desynchronizations (ERDs) associated with practising an ankle plantarflexion motor action. To this end, we utilized magnetoencephalography to identify changes in the alpha and beta ERDs in healthy adolescents (n = 21; age = 14 ± 2.1 years) and middle‐aged adults (n = 22; age = 36.6 ± 5 years) after practising an isometric ankle plantarflexion target‐matching task. After practice, all of the participants matched more targets and matched the targets faster, and had improved accuracy, faster reaction times and faster force production. However, the motor performance of the adults exceeded what was seen in the adolescents regardless of practice. In conjunction with the behavioural results, the strength of the beta ERDs across the motor planning and execution stages was reduced after practice in the sensorimotor cortices of the adolescents, but was stronger in the adults. No pre‐/post‐practice changes were found in the alpha ERDs. These outcomes suggest that there are age‐dependent changes in the sensorimotor cortical oscillations after practising a motor task. We suspect that these noted differences might be related to familiarity with the motor task, GABA levels and/or maturational differences in the integrity of the white matter fibre tracts that comprise the respective cortical areas. Key points: Magnetoencephalography data were acquired during a leg force task in pre‐/post‐practice sessions in adolescents and adults.Strong peri‐movement alpha and beta oscillations were mapped to the cortex.Following practice, performance improved and beta oscillations were altered.Beta oscillations decreased in the sensorimotor cortex in adolescents after practice, but increased in adults.No pre‐/post‐practice differences were detected for alpha oscillations. [ABSTRACT FROM AUTHOR]

Key points: Several behavioural studies have shown the sensory perceptions are reduced during movement; yet the neurophysiological reason for this is not clear.Participants underwent stimulation of the median nerve when either sitting quietly (i.e. passive stimulation condition) or performing haptic exploration of a ball with the left hand.Magnetoencephalographic brain imaging and advanced beamforming methods were used to identify the differences in somatosensory cortical responses.We show that the neural populations active during the passive stimulation condition were strongly gated during the haptic exploration task.These results imply that the reduced haptic perceptions might be governed by gating of certain somatosensory neural populations. Several behavioural studies have shown that children have reduced sensory perceptions during movement; however, the neurophysiological nexus for these altered perceptions remains unknown. We used magnetoencephalographic brain imaging and advanced beamforming methods to address this knowledge gap. In our experiment, a cohort of children (aged 10–18 years) underwent stimulation of the median nerve when either sitting quietly (i.e. passive stimulation condition) or performing haptic exploration of a ball with the left hand. Our results revealed two novel observations. First, there was a relationship between the child's age and the strength of the beta (18–26 Hz) response seen within the somatosensory cortices during the passive stimulation condition. This suggests that there may be an age‐dependent change in the processing of peripheral feedback by the somatosensory cortices. Second, all of the cortical regions that were active during the passive stimulation condition were almost completely gated during the haptic task. Instead, the haptic task involved neural oscillations within Brodmann area 2, which is known to convey less spatially precise tactile information but is involved in the processing of more complex somatosensations across the respective digits. These results imply that the reduced somatosensory perceptions seen during movements in healthy children may be related to the gating of certain neural generators, as well as activation of haptic‐specific neural generators within the somatosensory cortices. The utilization of such haptic‐specific circuits during development may lead to the enhanced somatosensory processing during haptic exploration seen in healthy adults. Key points: Several behavioural studies have shown the sensory perceptions are reduced during movement; yet the neurophysiological reason for this is not clear.Participants underwent stimulation of the median nerve when either sitting quietly (i.e. passive stimulation condition) or performing haptic exploration of a ball with the left hand.Magnetoencephalographic brain imaging and advanced beamforming methods were used to identify the differences in somatosensory cortical responses.We show that the neural populations active during the passive stimulation condition were strongly gated during the haptic exploration task.These results imply that the reduced haptic perceptions might be governed by gating of certain somatosensory neural populations. [ABSTRACT FROM AUTHOR]

Key Points Sensory gating is important for preventing excessive environmental stimulation from overloading neural resources., Gating in the human somatosensory cortices is a critically understudied topic, particularly in the lower extremities., We utilize the unique capabilities of magnetoencephalographic neuroimaging to quantify the normative neural population responses and dynamic functional connectivity of somatosensory gating in the lower extremities of healthy human participants., We show that somatosensory processing is subserved by a robust gating effect in the oscillatory domain, as well as a dynamic effect on interhemispheric functional connectivity between primary sensory cortices., These results provide novel insight into the dynamic neural mechanisms that underlie the processing of somatosensory information in the human brain, and will be vital in better understanding the neural responses that are aberrant in gait-related neurological disorders (e.g. cerebral palsy)., Abstract Sensory gating (SG) is a phenomenon in which neuronal responses to subsequent similar stimuli are weaker, and is considered to be an important mechanism for preventing excessive environmental stimulation from overloading shared neural resources. Although gating has been demonstrated in multiple sensory systems, the neural dynamics and developmental trajectory underlying SG remain poorly understood. In the present study, we adopt a data-driven approach to map the spectrotemporal amplitude and functional connectivity (FC) dynamics that support gating in the somatosensory system (somato-SG) in healthy children and adolescents using magnetoencephalography (MEG). These data underwent time-frequency decomposition and the significant signal changes were imaged using a beamformer. Voxel time series were then extracted from the peak voxels and these signals were examined in the time and time-frequency domains, and then subjected to dynamic FC analysis. The results obtained indicate a significant decrease in the amplitude of the neural response following the second stimulation relative to the first in the primary somatosensory cortex (SI). A significant decrease in response latency was also found between stimulations, and each stimulation induced a sharp decrease in FC between somatosensory cortical areas. Furthermore, there were no significant correlations between somato-SG metrics and age. We conclude that somato-SG can be observed in SI in both the time and oscillatory domains, with rich dynamics and alterations in inter-hemispheric FC, and that this phenomenon has already matured by early childhood. A better understanding of these dynamics may provide insight to the numerous psychiatric and neurologic conditions that have been associated with aberrant SG across multiple modalities. [ABSTRACT FROM AUTHOR]