Development and plasticity of dorsal and ventral visual functions : insights from behavioral and FMRI investigations of bilateral spastic cerebral palsy

Bilateral spastic cerebral palsy (BSCP) is the most common form of cerebral palsy, and has risen in prevalence in recent years as advances in neonatal care improve survival rates for at-risk infants. In addition to the motor disability that defines the disorder, affected individuals often demonstrate pervasive visual cognitive deficits. Although the typical pattern of brain injury predicts greater compromise of dorsal than ventral stream visual functions, behavioral evidence is currently limited and no studies have evaluated this prediction using functional neuroimaging methods. To further characterize the nature and severity of visual cognitive deficits in BSCP, we probed dorsal and ventral stream functioning in typically developing 8-10 year-old children (n=15), adults (n=15), and children and adolescents with BSCP (n=6), using working memory tasks for locations and faces. In Study 1, behavioral and FMRI data were compared across child and adult control groups to chart the normal course of developmental change in dorsal and ventral stream functioning. Study 2 explored the relative compromise of dorsal and ventral stream functions in BSCP participants via a series of individual case studies. Results of Study 1 revealed continued refinement of dorsal and ventral stream functioning from mid-childhood through adulthood. Across both tasks, ongoing development was apparent at the behavioral level through improvements in speed and accuracy of performance, and at the neural level through increasing reliance on higher-order prefrontal and parietal brain regions. Overall, the data from Study 2 underscored a striking degree of resilience in the face of early brain injury. BSCP participants as a whole performed within normal limits on both tasks and demonstrated only slight departures from expected profiles of regional brain activation. Specifically, across individual cases, findings converged to suggest subtle inefficiencies with face processing and modest reduction in BOLD response in dorsolateral prefrontal regions. Results will be discussed with reference to theories of visual cognitive and prefrontal dysfunction in BSCP, the likely inadequacy of predictions based on adult structure-function correspondences in the study of early brain injury, protective socioeconomic factors potentially relevant to our sample, and implications for neuroplasticit