Experiments were initiated to identify the neuroanatomical basis underlying different types of memory and perceptual dysfunctions exhibited by patients with neurological disorders. One theoretical line focused on using implicit and explicit memory tasks within the framework of data versus conceptually-driven; other investigations examined the relative contributions of the left and right brain to language by means of neuroimaging. Left TLE subjects consistently show deficits on conceptually driven memory tasks, but show normal patterns of transfer on data-driven tasks such as completing word fragments or stems, and generating words that are graphemically (but not semantically) similar to cue items. The finding of normal transfer patterns on both data-driven and conceptually driven tests for right TLE patients appears to hold only for verbal memory tasks. When memory for nonverbal visuospatial material is assessed, right TLEs show deficits in data-driven, but not conceptually driven transfer. Thus, lesions of the left temporal lobe appear to disrupt conceptual processing for all material types whereas lesions of the right temporal lobe impair data-driven processing of abstract visuospatial information. Data from PET-MRI studies shoved activation in visual cortex associated with visual word forms, and bilateral representation for picture recognition. Motor speech resulted in activation of sensory motor and supplementary motor cortex. Increased activation of Broca's area in passive viewing conditions (objects and words) suggest a complex interactions between traditional language zones and task demands. There appears to be substantial variability in the location of speech and language zones while regions associated with motor output (motor and sensory cortex) and with visual processing, were relatively consistent across subjects.
