Effect of unitization on associative recognition in amnesia

Abstract

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.

Electrophysiological evidence for the effect of interactive imagery on episodic memory: Encouraging familiarity for non-unitized stimuli during associative recognition

“…Although familiarity is traditionally associated with item recognition, the present study reinforces the idea that familiarity can be used to support retrieval during an associative recognition task, consistent with recent behavioural evidence of face recognition (Yonelinas et al, 1997), behavioural evidence from amnesic patients (Quamme et al, 2007), electrophysiological evidence for pre-existing associations between words (Rhodes and Donaldson, 2007), and for pairs of faces (Jager et al, 2006). We interpret this finding as showing that the use of interactive imagery at encoding successfully encouraged unitization of these word-pairs in memory, and this in turn leads to familiarity becoming a viable retrieval route.…”

“…Evidence that unitization encourages familiarity can also be found in neuropsychological data, comparing hypoxic patients who have impaired recollection but preserved familiarity, with medial temporal lobe damage patients who have impairments in familiarity and recollection (Quamme et al, 2007). Hypoxic patients showed superior performance on an associative recognition task under encoding conditions that encouraged unitization in contrast to a 'nonunitization' condition.…”

“…According to the unitization account of associative recognition, familiarity can be engaged if to-be-remembered information is perceived as a single unit (cf. Mayes et al, 2007;Quamme et al, 2007;Rhodes and Donaldson, 2007;Yonelinas et al, 1999).…”

Recognition memory: opposite effects of hippocampal damage on recollection and familiarity

“…When the pairs are processed as separate stimulus elements, performance may depend largely on recollection of the acquired associations, as old and new pairs cannot be distinguished on the basis of differential familiarity for the individual elements 3 . Alternatively, when the elements of a pair are readily 'unitized' into a single configuration, such as when the elements are features of a face or parts of a compound word, familiarity can support memory for stimulus pairings just as it does for single stimuli 11 . Both kinds of processing can contribute to recognition, and here we asked whether selective experimental damage to the hippocampus would decrease the contribution of recollection, consistent with a diminished ability to associate the elements, and conversely increase the contribution of familiarity, consistent with an uncovering of the ability of other brain areas to unitize the stimuli.…”

Course of relational and non-relational recognition memory across the adult lifespan

“…This is unlikely for the present task, since Norman and O'Reilly (2003) argued that associating two features to one item, but not spatiotemporal relational associations, can be supported by a familiarity-type process, and selective hippocampal lesions spare the recognition for items and also associations between items of the same kind (e.g., word-word or face-face pairs) (Mayes et al 2004). Still, the current non-relational memory task clearly supported unitization to a lesser degree than, e.g., encoding of arbitrary word pairs in relational vs. non-relational conditions (Quamme et al 2007). In this study, the strategy to encode arbitrary word pairs as compounds appeared to be clearly related to familiarity memory.…”