Functional hemispheric segregation of sensory-motor laterality

Functional laterality manifests across motor and sensory domains, yet analysis of their combined organization within individuals remains underexplored. Gerrits' 2024 (doi: 10.1007/s11065-022-09575-y) segregation bias model provides theoretical support that allows testing specific predictions for the lateralization of brain functions and their phenotype distributions in the population. We applied this approach to investigate sensory-motor laterality on the behavioral level (handedness, footedness, and eyedness) using a large sample (n = 900; 11-70 years).

Participants completed the Global Lateral Preference Inventory, and laterality indices were computed to categorize individuals into typical functional segregation (all preferences to the same side) or deviation patterns (either 1 or 2 deviations from the handedness side). We compared the observed distribution with Gerrits' (2024) predictions and analyzed associations with handedness, sex, and age.

Our findings partially supported the segregation bias model, as non-right-handers exhibited more atypical segregation patterns, confirming one of the model's primary predictions. However, exact percentages differed, likely due to methodological differences between behavioral inventories and neuroimaging, and differences in the lateralized functions being assessed. Contrary to expectations, no sex differences in segregation patterns emerged, suggesting the organizational principles for segregation bias in sensory-motor laterality may override sex-linked variability. Age effects were observed, with young adults displaying higher deviation rates, potentially reflecting continued neural and motor refinement during early adulthood.

These findings extend the segregation model framework to sensory-motor domains, highlighting its potential for neurodevelopmental, clinical, and research contexts, further emphasizing the importance of multidimensional assessments of laterality beyond handedness alone.