NEURAL CORRELATES OF INFANT SELECTIVE MOTOR CONTROL EMERGENCE WITHIN 5 MONTHS OF LIFE: IMPLICATIONS FOR CEREBRAL PALSY
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Background
Selective motor control (SMC)—the ability to isolate joint movements—is a critical component of early motor development and a strong predictor of later motor outcomes in individuals with cerebral palsy (CP). While SMC is thought to emerge as descending control from the cortex increases, the neural mechanisms supporting this process in early infancy are not well defined. This study utilizes multimodal MRI to investigate the relationship between microstructural changes in the corticospinal tract (CST) and the development of SMC in preterm infants during the first five postnatal months.
Methods
Fifteen preterm infants (<32 weeks GA, <1500g) underwent MRI between 3– 21 weeks corrected age, including macromolecular proton fraction (MPF) mapping to quantify myelination, diffusion tensor imaging (DTI) to assess fractional anisotropy (FA), and g-ratio estimation. SMC was measured using BabyOSCAR, a clinical tool that captures an infant’s capacity to perform isolated joint movements. Regions of interest included the posterior limb of the internal capsule (PLIC; CST) and the corpus callosum. One infant with spastic CP was included for exploratory comparison.
Results
In infants with typical development, SMC scores increased with age and were strongly correlated with MPF in the PLIC (R² = 0.81), suggesting close alignment between CST myelination and emerging motor control. MPF in the CST increased rapidly (from 24% to 80% of adult values), outpacing both FA and corpus callosum. In the infant with CP, ipsilesional CST myelination and contralesional SMC scores were substantially lower than expected for their age. Elevated MPF values in the rubrospinal tract suggested compensatory reorganization. In contrast, the infant with early motor delay demonstrated typical MPF, FA, and SMC scores and achieved independent walking by age two, indicating a transient delay rather than evolving CP.
Conclusion
Rapid CST myelination during early infancy closely parallels the development of selective motor control. Measures of MPF provide a sensitive structural correlate of this emerging capacity and may help identify early disruptions in motor system development. These findings provide a neurobiological framework for the early detection of motor impairment and more precise timing of intervention in infants with or at an increased chance of CP.
