Factors Affecting Tactile Modulation

Several factors may influence tactile processing and modulation in the children with spastic hemiplegia. Children with hemiplegia frequently have asymmetrical postures and weight-bearing, and may also present with neglect of the affected side6; resulting in atypical sensation and movement. Hemi-neglect manifests as avoidance of the affected side, which may be contributing to the higher sensitivity and avoiding patterns described above. These behaviours may negatively influence their tactile modulation. Furthermore, uneven weight-bearing through the limbs may alter their experience of somatosensory feedback, resulting in conflicting sensory messages in the cortex. Through crawling, typically developing children acquire intense proprioceptive and different tactile inputs through the upper limbs, which in turn has an integrating and organising effect. Children with hemiplegia frequently crawl in an asymmetrical pattern, bottom-shuffle to avoid using their hands, or avoid crawling altogether. Their experience of proprioceptive and tactile sensations is thereby diminished or atypical. Subsequently, they may be less able to integrate and modulate these inputs, especially in their hands. Recent research has found evidence that interhemispheric reorganisation occurs in the motor systems. In this way, other areas of the brain can take over the damaged areas functions, particularly when the lesion happens early on.