Developmental Trajectory of Beta Cortical Oscillatory Activity During a Knee Motor Task

Abstract

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.

Keywords: Children; Leg; Magnetoencephalography; Parietal; Sensorimotor.

Fig. 1

a Depiction of the custom-built pneumatic force transducer that is positioned just proximal to the lateral malleolus of the child. b The isometric knee extension force generated by the child animates the yellow box to ascend vertically to match the green target box (Color figure online)

Fig. 2

Statistical parametric maps (SPMs) showing the dynamics of beta oscillations (16–24 Hz) during the isometric knee extension motor task. The images have been thresholded at (p < 0.001, cluster-corrected) and are displayed following the radiological convention (R = L). As shown, there was a prominent beta ERD that was spread across the pre/postcentral gyri, SMA and parietal cortices during the motor planning stage (−0.3 to 0.0 s). The strength of the beta ERD diminished across all brain regions as children initiated the isometric knee extension force towards the displayed target (0.0–0.3 s), and this decline in beta ERD amplitude progressively continued throughout the isometric knee extension task (0.0–1.2 s)

Fig. 3

Rank order correlations between a the strength of the beta event-related desynchronization (ERD) within the parietal cortices during the 0.0–0.3 s time window and the child’s reaction time, b the strength of the beta ERD within the parietal cortices during the 0.3–0.6 s time window and the child’s reaction time, c the strength of the beta ERD within the parietal cortices during the 0.0–0.3 s time window and the time to match the target. Overall these correlations imply that a stronger beta ERD within the parietal cortices during the motor action time frame was related to a slower reaction time and longer time to match the target. All correlations were significant at (p < 0.05)

Fig. 4

Rank order correlations between a the child’s reaction time and age, b time to match the target and age, c the strength of the beta ERD within the parietal cortices during the motor planning period (−0.3 to 0.0 s) and the child’s age, and d the strength of the beta ERD within the parietal cortices during the isometric force performance period (0.3–0.6 s) and the child’s age. Overall these correlations imply that the older children had faster reaction times and took less time to match the target. In addition, the older children also tended to have a weaker ERD during the motor planning period and a stronger ERD during the performance period