Neuroimaging Measures in the Study
of Specific Language Impairment
Paavo H. T. Leppänen
University of Jyväskylä, Finland
April A. Benasich
Specific language impairment (SLI) is a complex syndrome whose etiology remains elusive. Although several hypotheses exist to account for its development (see van Balkom & Verhoeven, chap. 12, this volume), there is some consensus that SLI is associated with subtle structural and functional cortical deviations that may be developmental in origin. Advances in modern brain research have increased interest in the search for potential neural substrates of this disorder, but as yet the number of neuroimaging studies with children with SLI is surprisingly small. In this chapter, we review neurobiological correlates of SLI at three different levels: neuroanatomical, hemodynamic, and electrocortical.
Neuroanatomical measures can reveal subtle structural changes of the brain that are associated with cognitive disorders. Studies showing anatomical differences in SLI populations have used magnetic resonance imaging (MRI)—a technique that has provided an unprecedented opportunity to visualize human brain structure with clarity comparable to autopsy evaluation. Differences in brain function have been studied with hemodynamic and event-related potential (ERP) techniques. Hemodynamic techniques (e.g., positron emission tomography [PET], related single photon emission computerized tomography [SPECT], and functional magnetic resonance imaging [fMRI]) rely on detecting small changes in blood flow and measure oxygen consumption in active brain areas. Hemodynamic techniques are well suited to imaging brain activation during relatively long periods of ongoing cognitive processing. The ERP tech-