Age-related shifts in hemispheric dominance for syntactic processing

Genetic factors related to handedness, such as history of familial sinistrality, have been linked to neuroanatomical and neurophysiological differences in a variety of brain areas, including those associated with language. However, the functional implications of these differences remain unclear. Recent event-related potential (ERP) data from young adults have revealed that simple syntactic anomalies elicit a different pattern of lateralization depending upon the familial sinistrality of the participant. Whereas participants with left handed family members elicited a bilateral P600, a component that is typically seen in adult native speakers to syntactic processing difficulties, participants with no history of familial sinistrality showed a strongly lateralized response pattern, with P600 responses only following left hemisphere-biased presentations. Given that the aging literature has documented a tendency to change from asymmetry of function to a more bilateral pattern with advancing age, we tested the stability of this asymmetric response to syntactic violations by recording ERPs as 24 older adults (age 60+) with no history of familial sinistrality made grammaticality judgments on simple two-word phrases. Results showed that the asymmetric pattern observed in young adults indeed changes with age, such that P600 responses come to be elicited bilaterally even in individuals without familial sinistrality. These findings suggest that, as with many other cognitive functions, syntactic processing becomes more bilateral with age, possibly because of reduced interhemispheric inhibition