Memory For New Associations Research Articles

Neural Reinstatement of Overlapping Memories in Young and Older Adults.

When we update our episodic memories with new information, mnemonic competition between old and new memories may result because of the presence of shared features. Behavioral studies suggest that this competition can lead to proactive interference, resulting in unsuccessful memory updating, particularly for older adults. It is difficult with behavioral data alone to measure the reactivation of old, overlapping memories during retrieval and its impact on memory for new memories. Here, we applied encoding-retrieval representational similarity (ERS) analysis to EEG data to estimate event-specific encoding-related neural reinstatement of old associations during the retrieval of new ones and its impact on memory for new associations in young and older adults. Our results showed that older adults' new associative memory performance was more negatively impacted by proactive interference from old memories than that of young adults. In both age groups, ERS for old associative memories was greater for trials for which new associative memories were forgotten than remembered. In contrast, ERS for new associative memories was greater when they were remembered than forgotten. In addition, older adults showed relatively attenuated target (i.e., new associates) and lure (i.e., old associates) ERS effects compared to younger adults. Collectively, these results suggest that the neural reinstatement of interfering memories during retrieval contributes to proactive interference across age, whereas overall attenuated ERS effect in older adults might reflect their reduced memory fidelity.

Interference From Previous Distraction Disrupts Older Adults' Memory

Previously relevant information can disrupt the ability of older adults to remember new information. Here, the researchers examined whether prior irrelevant information, or distraction, can also interfere with older adults' memory for new information. Younger and older adults first completed a 1-back task on pictures that were superimposed with distracting words. After a delay, participants learned picture-word paired associates and memory was tested using picture-cued recall. In 1 condition (high interference), some pairs included pictures from the 1-back task now paired with new words. In a low-interference condition, the transfer list used all new items. Older adults had substantially lower cued-recall performance in the high- compared with the low-interference condition. In contrast, younger adults' performance did not vary across conditions. These findings suggest that even never-relevant information from the past can disrupt older adults' memory for new associations.

Implicit memory for novel associations between pictures: effects of stimulus unitization and aging.

Studies of implicit memory for novel associations have focused primarily on verbal materials and have highlighted the contribution of conceptually unitized representations to such priming. Using pictorial stimuli in a perceptual identification task, we examined whether new association priming can occur at a purely perceptual level. By manipulating the spatial contiguity of stimuli, we also evaluated whether such priming requires the creation of perceptually unitized representations. Finally, we examined the status of such priming in aging. In Experiment 1, we found that spatial contiguity of stimuli is not necessary for novel pictorial association priming to emerge, although such contiguity does enhance the magnitude of associative priming. In Experiment 2, we found that new association priming is age invariant, regardless of spatial contiguity. In Experiment 3, we provide additional evidence that pictorial association priming is perceptually based. These findings expand the scope and delineate the conditions of novel association priming and inform theories about the nature of implicit memory for new associations.

Involvement of the medial temporal lobe in priming for new associations

This study was addressed to the question of whether the medial temporal lobe (MTL) plays a critical role in implicit memory for new associations. Priming for new associations was examined in two different tasks in 18 patients with focal lesions all involving the MTL. In Experiment 1, following a study phase for pairs of unrelated words, subjects performed a perceptual identification task on old, recombined, and new pairs of words presented at brief exposure durations. In contrast to control subjects, and despite a normal level of item priming, the patients failed to show superior identification of the old pairs relative to the recombined pairs, the measure of associative priming. In Experiment 2, subjects engaged in speeded naming of the print color for previously studied words presented in the original color or in a different old color, and for unstudied words. Again, in contrast to control subjects and despite a normal level of item facilitation on color naming reaction time (RT), the patients failed to show priming for recently experienced new associations between words and colors. Explicit recognition memory by the patients was abnormal in both experiments. This study records an absence of priming for new associations, in two different tasks in which the nature of the stimuli was considerably different, in a large group of patients with lesions in the MTL. Although some previous research has reported significant associative priming in other tasks for patients with MTL lesions, the present results suggest that this region is critical for forming new associations of the types assessed here.

Event-related potential studies of associative recognition and recall: electrophysiological evidence for context dependent retrieval processes

To investigate the neural correlates of episodic recollection the ERP correlates of memory for new associations (recently studied novel word pairs) were investigated using two tasks, associative recognition and associative recall. For the recognition task subjects discriminated old from new word pairs and, for pairs judged old, reported whether the pairs were intact or recombined (compared to at study). For the recall task, subjects discriminated old from new words and, for each word judged old, reported its study associate. ERPs were recorded at test from 25 scalp electrodes, with a 1944-ms recording epoch. In Experiment 1, the tasks were randomly interleaved. Consistent with previous findings, relative to the ERPs for correctly classified new items, the ERP correlates of successful associative recognition consisted of a sustained left parietal positivity, and two frontal positivities, one early and bilateral, the other occurring later and showing a right-sided maximum. In contrast to previous findings, successful associative recall elicited similar effects to those found for recognition. Topographic analyses revealed that the distribution of these retrieval-related ERP effects were similar across the two tasks, suggesting that the recognition and recall of associative information gives rise to activity in overlapping, if not the same, neural populations. In Experiment 2 the tasks were blocked. In contrast to the findings of Experiment 1, successful associative recall elicited left parietal and late onsetting right frontal positivities, in the absence of the early bilateral frontal positivity. This finding suggests that frontally-distributed memory-related ERP effects are both neurally and functionally dissociable. Specifically, we argue that the functional significance of the early frontally distributed ERP effect cannot be accounted for by the `post-retrieval processing' hypothesis that is taken to account for the late right frontal effect, suggesting that episodic recollection itself is neither neurally nor functionally homogenous.

Recognition memory for new associations: electrophysiological evidence for the role of recollection

The electrophysiological correlates of recognition memory for new associations were investigated in two experiments. In both experiments subjects first studied unrelated word pairs. At test, they were presented with old words in the same pairing as at study (same pairs), old words in a different pairing from study (rearranged pairs), and pairs of new words. In Experiment 1 the test requirement was to discriminate between old and new pairs and, for any pair judged old, to then judge whether the pair was the same or rearranged. In Experiment 2 the requirement was merely to discriminate between old and new pairs. Event-related potentials (ERPs) were recorded for correctly classified same, rearranged and new pairs. The ERPs elicited by same pairs exhibited a similar pattern of effects in both experiments. Relative to the ERPs to new pairs, these effects took the form of sustained positive shifts with two distinct scalp maxima, over the left temporo–parietal and right frontal scalp respectively. ERPs to rearranged pairs showed effects which were similar in scalp topography, but markedly smaller in magnitude. This pattern of ERP effects closely resembles that found previously for test items defined as recollected on the basis of their attracting a successful source judgement. The findings therefore suggest that associative recognition memory shares some of the recollective processes that are engaged by the requirement to retrieve contextual information about a study episode. The findings from Experiment 2 indicate that the processes associated with the recollection of associated pairs are engaged regardless of whether the retrieval of associative information is an explicit task requirement.

Preservation of Implicit Memory for New Associations in Global Amnesia

This study examined whether amnesic patients have preserved implicit memory for new associations between unrelated words, as measured by repetition priming, despite impaired explicit memory for such new associations Prior studies provide conflicting and ambiguous results Amnesic and control participants read aloud visually presented, unrelated word pairs and then attempted to identify old, recombined, and new word pairs shown at threshold durations Amnesic and control groups showed equivalent priming for new associations by identifying old pairs better than recombined pairs Amnesic patients were impaired on a matched explicit test of memory for new associations The preserved priming in amnesia indicates that implicit memory for new associations need not be supported by the mnemonic processes and brain structures that mediate explicit memory for new associations.

Explicit contamination in "implicit" memory for new associations.

In one view of implicit memory, priming arises from modification of preexisting representations; however, the role of such representations is currently in doubt following findings of implicit memory for newly formed associations. Closer consideration of studies reporting this effect, and of others that have failed to obtain it, suggests that such priming might results from the employment of explicit memory strategies. With measures designed to permit exclusion of such strategies, three experiments using lexical decision and stem-completion tasks found no evidence of truly implicit memory for unrelated pairs. Instead, priming was found only in those subjects (50% of the total in one experiment) who reported using explicit memory in stem completion. Contrary to previous conclusions, the results indicate a role for established representations in explaining implicit memory.

Sources of priming in text rereading: intact implicit memory for new associations in older adults and in patients with Alzheimer's disease.

The contributions of text meaning, new between-word associations, and single-word repetition to priming in text rereading in younger and older adults, and in patients with Alzheimer's disease. (AD), were assessed in Experiment 1. Explicit recognition memory for text was also assessed. Equivalent single-word and between-word priming was observed for all groups, even though patients with AD showed impaired explicit memory for individual words in the text. The contribution of generalized reading task skill to priming in meaningless text rereading in younger adults was assessed in Experiment 2. Generalized reading task skill was also found to contribute to priming. These results reveal 3 mechanisms of priming: new between-word associations for meaningful and meaningless text, individual word repetition for meaningless text, and general task or skill factors for meaningless text. All priming mechanisms appear to be intact in older adults and in patients with AD.

Sources of priming in text rereading: Intact implicit memory for new associations in older adults and in patients with Alzheimer's disease.

Sources of priming in text rereading: Intact implicit memory for new associations in older adults and in patients with Alzheimer's disease.

Implicit memory for new associations: The pictorial influence

A series of experiments was conducted in order to show that implicit memory for new associations is not always dependent on semantic integrative processing during study. The material used in these experiments differed from traditional studies that employed pairs of unrelated words. Instead, targets (words in Exps. 1 and 2 and pictures in Exps. 3 and 4) were encoded in the context of an unrelated picture. The implicit tests used were word-stem completion (Exps. 1, 2, and 3) and picture-fragment identification (Exp. 4). The explicit test was word-stem cued recall (Exps. 1, 2, and 3) and picture-fragment cued recall (Exp 4). For implicit tests, context effects were not obtained using words as targets with a non-integrative semantic-elaboration encoding task (Exp. 1). When an integrative semantic-elaboration encoding task was used, a standard context effect emerged (Exp. 2) for implicit memory. Importantly, with pictures as targets, context effects appeared without integrative semantic encoding (Exps. 3 and 4). However, context effects were obtained for all conditions of cued recall. Results are discussed with regard to the concept of unitization.

Separating consciously controlled and automatic influences in memory for new associations.

The process dissociation paradigm was applied to investigate the contributions of automatic and consciously controlled processes to the repetition priming effect for new associations, under elaborative encoding (Experiments 1 and 2) and copy instructions (Experiment 3). Semantically unrelated context-target word pairs were presented during study, and context words and stems were presented during test. Target word stems were paired with the same context words as at study (intact), paired with different context words from study (recombined), or were the stems of unstudied words (control), Participants had to complete stems with the first word that came to mind (indirect), with studied words (inclusion), or with new, unstudied words (exclusion). Results indicated that consciously controlled processes mediated the associative repetition effect under elaborative encoding, whereas automatic processes were implicated under copy instructions.

Separating consciously controlled and automatic influences in memory for new associations.

Separating consciously controlled and automatic influences in memory for new associations.

Implicit memory for new associations: An interactive process approach.

Implicit memory for new associations: An interactive process approach.

Aging and memory for new associations: Direct versus indirect measures.

Aging and memory for new associations: Direct versus indirect measures.

Aging and memory for new associations: Direct versus indirect measures.

Three experiments examined adult age differences in memory for new associations between unrelated words. On the indirect (word-stem completion) test, age differences appeared under the less-than-optimal study conditions of Experiments 1 and 3 but not under the self-paced study conditions of Experiment 2. In contrast, all experiments revealed significant age-related deficits on the direct tests, even those (word-stem cued recall) in which the cue was identical to those provided on the indirect test. The findings show that although age-related deficits in memory for new associations are particularly pronounced on tests requiring conscious recollection, age differences are not limited to such tests. Age deficits on both direct and indirect tests are related to the precision of elaborations produced during study. Similarities and differences between normal aging and amnesia are discussed, as are functional dissociations between direct and indirect measures.

Implicit memory for new associations: An interactive process approach.

The contributions of data-driven and conceptually driven processes to implicit memory for new associations were examined using a word stem completion task. Targets encoded in the context of an unrelated word were more likely to be produced on the completion task if tested in the presence of the original, rather than a different, cue word. This context effect was obtained using a semantic elaboration encoding task and a copying task that required no elaboration, but not when orthographically or semantically similar cue words were used at test. With homograph cue words the context effect depended on reinstating the appropriate interpretation of the cue word

Modality specificity of implicit memory for new associations.

In previous research we demonstrated that newly acquired associations between unrelated word pairs influence the magnitude of priming effects on word-completion tests. This phenomenon of implicit memory for new associations is observed only following semantic study elaboration. The present experiments reveal that implicit memory for new associations, though elaboration dependent, is also modality specific: Associative effects on a visual word-completion test were consistently reduced by study-test modality shifts. In contrast, explicit memory for new associations, as indexed by cued-recall performance, was uninfluenced by modality shifts. The modality effect on completion performance was eliminated when subjects were given brief visual preexposures to, or were required to construct visual images of, word pairs presented in auditory study conditions. The results pose a theoretical puzzle insofar as they indicate that within the domain of implicit memory, access to the products of elaborative processing depends on modality-specific, sensory-perceptual processing.

Unitization and grouping mediate dissociations in memory for new associations.

Unitization and grouping mediate dissociations in memory for new associations.

Unitization and grouping mediate dissociations in memory for new associations.

Quatre experiences visent a expliquer les aspects explicites et implicites de la memoire en terme de deux facteurs: l'unification (structuration en un tout coherent de plusieurs items separes) et le groupement (associations entre des representations separees). Elles mettent en œuvre les associations nouvelles par des mots et par leur utilisation dans des phrases et dans des histoires