IMPLICIT MEMORY IN AMNESIC PATIENTS: Evidence for Spared Auditory Priming

Previous observations of spared priming in amnesic patients have been based almost entirely on data from visual implicit memory tests. Our research examined perceptual priming in amnesic patients and control subjects on an auditory identification task in which previously spoken words and new words were presented in white noise. We manipulated type of encoding task (semantic vs. nonsemantic) and speaker's voice at study and test (same vs. different). Priming was little affected by either manipulation, and amnesic patients exhibited normal priming in all experimental conditions. On an explicit test of recognition memory, by contrast, amnesic patients exhibited severely impaired performance following the semantic study task; all subjects showed poor explicit memory following the nonsemantic study task. Results are consistent with the idea that auditory priming depends largely on a presemantic auditory perceptual representation system. The hallmark of the amnesic syndrome is a severe impairment in the ability to recollect recent experiences. Despite this pervasive deficit in explicit memory, amnesic patients exhibit robust and frequently normal implicit memory for various kinds of information on tests that do not require conscious recollection of specific experiences (for review, see Schacter, Chiu, & Ochsner, 1993; Squire, 1992). Perhaps the most extensively studied type of implicit memory in amnesic patients is repetition or direct priming: facilitated identification of words and objects as a consequence of recent exposure to them (Tulving & Schacter, 1990). Beginning with the seminal studies of Warrington and Weiskrantz (1974), a large and ever increasing number of experiments have revealed normal or near-normal priming effects on a variety of implicit memory tests in amnesic patients who exhibit significant impairments of explicit memory. These findings have important theoretical consequences for understanding the structure of both normal and abnormal memory (for review, see Bowers & Schacter, 1993; Shimamura,