Despite much lay interest in "the out-of-sync child", the biological underpinnings of sensory processing dysfunction have been to characterize. Part of the dilemma is that "out-of-sync" children encompass a wide range of dysfunctions, due to wide variations in brain differences that occur with birth stress and injury, developmental delay, familial conditions, autism spectrum disorders, and children diagnosed with ADD.
This study used fMRI to examine how different networks had to be coordinated for time perception (visual and sound stimulus). The multifocal nature of these pathways underscores how easily it must be to get "out-of-sync." If either visual or auditory pathways are disrupted, visual-auditory synchrony would be disrupted. Add in problems in position sense and motor control, and you've got a lot of asynchrony on your hands.
Excerpt: "Consistent with the foregoing research, our results suggest that a network of areas comprising prefrontal, sensory and parietal cortices establishes the perception of asynchrony, whereas just the sense of the presence of timing association (without any specific relations, synchrony or asynchrony) activates only sensory and prefrontal areas."
Multisensory Integration for Timing Engages Different Brain Networks
Timing Problems in Cerebellar / Developmental Coordination Disorder
Sensory Integration: Current Concepts pdf
Eide Neurolearning Blog: Timing is Everything - Dyslexia, ADHD, Auditory Processing, Sensory Integration
Time Perception Deficits in ADHD