TECHNOLOGY IN THE ASSESSMENT OF LEARNING-DISABILITY

Recent neuroradiologic and brain imaging technologies, along with meth ods for displaying electrophysiologic data, have promulgated active ex ploration in the assessment of learning disability with attempts to im prove diagnostic precision and elucidate the neurobiological substrate s of learning disorders. The following article reviews these technique s and explores the research that has been conducted in this area over the past two decades. Initial investigations attempted to elucidate ir regularities or abnormalities of brain morphology in individuals with learning disability utilizing computerized tomography (CT). The curren t standard for structural imaging of the brain is magnetic resonance ( MR) imaging, which has allowed for greater specificity in identifying brain abnormalities. More recently, functional magnetic resonance imag ing (fMRI) has been postulated as holding some promise in distinguishi ng anatomic/ function differences in LD. Electrophysiological (EEG) an d metabolic imaging techniques offer methods by which human brain acti vity can be studied during cognitive processes. Computerized EEG studi es including evoked potentials (EP) or event-related potentials (ERP), spectral EEG analysis, and topographic EEG brain mapping have also id entified a number of brain irregularities in individuals with learning disabilities, though no consistent exemplars have emerged. Studies wi th positron emission tomography (PET) and single photon emission compu terized tomography (SPECT) have also demonstrated a number of abnormal ities and inconsistencies in individuals with learning disabilities, b ut, again, no systematic research has demonstrated specific diagnostic abnormalities. Though inroads and some consistent patterns have begun to emerge in the assessment of learning disability with the preceding technologies, a number of challenges persist with neuroimaging and ne urophysiological and metabolic imaging techniques. To date, no diagnos tic conclusions have been drawn utilizing these methods in the assessm ent of the neurobiologic basis to LD.