Memory for a recent event can be expressed through intentional recollection (explicit memory) or inferred from facilitations of task performance, often referred to as priming effects, that need not involve intentional recollection of any previous experience (implicit memory). The goals of this project are to deepen and broaden our knowledge of implicit memory by examining conditions in which priming is spared or impaired by cortical lesions, and to evaluate empirically a theoretical account recently put forward by the principal investigator. This view holds that many priming effects reflect the activity of a perceptual representation system (PRS): a presemantic system composed of several subsystems that are dedicated to the representation of information about the form and structure, but not the meaning, of words and objects. These goals will be accomplished by studying the performance of five groups of patients with cortical lesions on a common set of priming paradigms. The patients to be studied will exhibit 1) reading deficits with sparing of the visual word form system ; 2) reading deficits with impairment of the word form system; 3) phonological processing deficits; 4) auditory comprehension deficits; and 5) object processing deficits. Seven paradigms will be used to examine priming in each group: 1) visual word identification; 2) visual stem completion; 3) auditory word identification; 4) auditory stem completion; 5) object decision; 6) object completion; and 7) category instance production. The performance of each patient group will be compared to that of matched controls and to the other patient groups. This latter feature of the design is important, because the PRS framework leads to predictions of various double dissociations among patient groups. Priming performance will be related to MRI lesion analyses. The proposed research should provide a more detailed empirical and theoretical picture of the functional organization and neural basis of systems underlying priming and implicit memory than is currently available. Because it focusses on spared functions, the research may also provide useful clues for cognitive rehabilitation.
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