Priming for novel between-word associations in patients with organic amnesia

Ten amnesic patients of various etiologies and 10 matched normal controls participated in this study. On 2 consecutive days, subjects studied 30 novel word-word associations 6 times. Using a cued recall task, we assessed episodic learning and delayed retention of the study material immediately after each study phase and again 24 hr after the final study phase. Further, we evaluated implicit memory for new between-word associations by means of an automatic relational priming paradigm immediately after the delayed cued recall trial. Amnesic patients performed poorly on the cued recall task. Moreover, in the overall group of amnesics the priming effect failed to reach statistical significance. When the overall group of amnesics was split according to mean performance on the cued recall task, those in the low performer subgroup - comprised of 6 patients with direct or indirect involvement of the hippocampi - were particularly poor at episodically remembering the associations and did not reveal any relational priming. These data support the hypothesis of similar impairment of new episodic and implicit learning in amnesic patients and suggest that the hippocampus is crucial for both kinds of new learning.