Intact priming for novel perceptual representations in amnesia

Recent studies have challenged the notion that priming for ostensibly novel stimuli such as pseudowords (REAB) reflects the creation of new representations. Priming for such stimuli could instead reflect the activation of familiar memory representations that are orthographically similar (READ) and/or the activation of subparts of stimuli (RE, EX, AR), which are familar because they occur commonly in English. We addressed this issue in three experiments that assessed perceptual identification priming and recognition memory for novel and familiar letter strings in amnesic patients and control subjects. Priming for words, pseudowords, and orthographically illegal nonwords was fully intact in the amnesic patients following a single exposure, whereas recognition memory was impaired for the same items. Thus, priming can occur for stimuli that are unlikely to have preexisting representations. Words and pseudowords exhibited twice as much priming as illegal nonwords, suggesting that activation may contribute to priming for words and wordlike stimuli. Additional results showed that priming for illegal nonwords resulted from the formation of new perceptual associations among the component letters of each nonword rather than the activation of individual letter representations. In summary, the results demonstrate that priming following a single exposure can depend on the creation of new perceptual representations and that such priming is independent of the brain structures essential for declarative memory.