Altered Somatosensory Cortical Entrainment in Cerebral Palsy
Somatosensory dysfunction contributes substantially to mobility impairments in cerebral palsy (CP), yet their somatosensory cortical responses to rhythmic sustained input remains unstudied. This study examined somatosensory cortical entrainment in 28 ambulatory youth with CP (Gross Motor Function Classification System levels I-III; 21.9 {+/-} 6.3y; 14 unilateral CP) and 34 neurotypical controls (23.4 {+/-} 3.8y). Participants underwent magnetoencephalography while an 8 Hz cutaneous electrical stimulation was applied to the right posterior tibial nerve. Rhythmic neural responses were mapped to the contralateral somatosensory cortices using beamforming, and virtual sensor time series were extracted to quantify neural dynamics. The entrainment response declined more steeply over time in CP compared to controls, whereas the concurrent alpha response strengthened progressively in CP but changed minimally in controls (Group x Time interactions, ps<.001). Significant cross-spectral coupling of entrainment x concurrent alpha responses was observed only in CP (p<.001) and was most pronounced in those with bilateral CP. Weaker cross-spectral coupling was associated with better functional mobility in controls (p=.004) but brain-behavior links in CP were phenotype-specific. Finally, the second harmonic neural response in CP was weaker (p<.001) and demonstrated a blunted temporal modulation relative to controls (p=.003). These findings implicate disrupted somatosensory cortical entrainment responses as possible neurophysiological features of youth with CP.