ELECTROPHYSIOLOGICAL STUDIES OF PRIMING AND RECOLLECTION

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This proposal is aimed at expanding our knowledge of the psychological and physiological bases of memory primarily from scalp recordings of event-related potentials (ERPs) to verbal and pictorial stimuli in a variety of implicit and explicit memory tasks. Current evidence suggests that a late positive component between 300 and 800 msec may index conscious recollection while several earlier components may be related to perceptual priming. We plan to test these working hypotheses. The resulting data should further our knowledge as to the independence, interdependence, and relative timing of the processes underlying perceptual priming, conceptual priming, and performance on explicit tests of memory. The proposed studies continue our investigations of word priming (perceptual and conceptual) and recognition memory using manipulations that differentially affect measures of one but not the other. We will also extend these questions to pictures. Several experiments will also utilize patients with memory disorders as we think that such a combined approach is necessary to fully understand memory mechanisms and to validate the proposed links between memory-related processes and their brain substrates as indexed by ERP measures. By altering the modality of presentation from study (auditory) to test (visual), Expt. 1 will investigate the hypothesis that an early occipital negativity elicited by words in a lexical decision task is an index of perceptual priming. Expt. 2 will examine the specificity of this effect by replicating Expt. l employing an auditory lexical decision task. Expt 3 will examine the modality independence of the recollection template by examining the ERPs elicited during an auditory lexical decision with interleaved recognition judgements following a levels-of-processing study manipulation. Expt. 4 would isolate the ERP components associated with perceptual priming in the word stem completion task by altering both the font and typecase from study to test. Expt. 5 attempts to tease apart perceptual and conceptual priming effects by examining ERPs to visual word stems during completion and cued recall following study in either the same (visual) or a different (auditory) modality. Expts. 6 & 7 utilize the method of opposition in a word stem completion paradigm to separate facilitation due to priming from that due to intentional retrieval. To that end, Expt. 6 will vary the amount of attention directed at words during study while Expt. 7 will present words too briefly to allow identification (Expt. 7). Expts. 8 & 9 will examine perceptual (for same token as study) and conceptual (for token different from study) ERP priming effects on picture fragments prior to their identification. Expt. 10-Il use amnesic patients and elderly controls to further validate our ERP indices of priming and memory tested explicitly.