Word priming with brief multiple presentation technique: preservation in amnesia

Many studies have shown relative preservation of word priming in subjects with mild amnesia, but some decrease in severe amnesia. This calls into question the degree of separation between implicit and explicit memory. Possible contamination of implicit memory tasks by impaired explicit memory strategies might be obscuring the actual dissociation between the two memory systems. We have developed a method of circumventing explicit memory contamination by using brief duration repeated primes below the awareness threshold of subjects. We have used this approach to evaluate the status of word priming in densely amnesic subjects. One group of amnesic subjects with alcoholic Korsakoff's syndrome and one group of normal elderly control subjects were tested for word priming on a speeded category membership decision task. Implicit or explicit encoding procedures were used in three different experiments. Results demonstrated that brief multiple presentation of words can offer a means of producing word priming in the absence of explicit recognition or recall of the primed words in both amnesic subjects and normal elderly control subjects. Moreover, there was no significant difference in the magnitude of the priming effect between these groups in the three experiments. These findings show that amnesic subjects can exhibit normal levels of word priming. They also suggest that amnesics retain the capacity to encode, store and retrieve information implicity, e.g. unintentionally.