Effect of Unitization on Associative Recognition in Amnesia

We examined how associative recognition performance in amnesic patients is mediated by use of a unitized (i.e., holistic) encoding strategy, and the degree to which the unitization effect is related to sparing of familiarity-based recognition. Participants studied word pairs as either separate lexical units in sentences (i.e., nonunitized) or as compounds (unitized). Under standard recognition instructions, normal controls and patients with left-temporal lobe damage (previously determined to have impairments in both recollection and familiarity) showed no difference for unitized and nonunitized pairs, whereas hypoxics (previously determined to have impaired recollection but relatively preserved familiarity) showed an advantage of unitized over nonunitized pairs. This effect was reproduced in normal healthy participants under instructions to restrict responses to judgments of familiarity. The results indicate that unitization may mediate the degree of associative recognition impairment exhibited by some amnesic patients, and that the effect is related to preserved familiarity capacity. The relevance of the results to the debate over the importance of the hippocampus in memory for associations is discussed.