Roni Tibon

Associative recognition processes are modulated by the semantic unitizability of memoranda

Although memory of episodic associations is generally considered to be recollective in nature, it has been suggested that when stimuli are experienced as a unit, familiarity processes might contribute to their subsequent associative recognition. To investigate the effect of semantic relatedness during episodic encoding on the processes of retrieval of associative information, we had participants interactively encode pairs of object pictures, vertically arranged so as to suggest a functional or configural relationship between them. Half the pairs were independently judged to be of related objects (e.g., a lamp over a table) and half of unrelated objects (e.g., a key-ring over an apple). At test, participants discriminated between intact, recombined, and new pairs while event related potentials (ERPs) were recorded. In an early ERP marker of retrieval success generally associated with familiarity processes, differences related to associative memory only emerged for related pairs, while differences associated with item memory emerged for both related and unrelated pairs. In contrast, in a later ERP effect associated with recollection, differences related to associative memory emerged for both related and unrelated pairs. These findings may indicate that retrieval of episodic associations formed between two semantically related visual stimuli can be supported by familiarity-related processes.

The time course of episodic associative retrieval: Electrophysiological correlates of cued recall of unimodal and crossmodal pair-associate learning

Little is known about the time course of processes supporting episodic cued recall. To examine these processes, we recorded event-related scalp electrical potentials during episodic cued recall following pair-associate learning of unimodal object-picture pairs and crossmodal object-picture and sound pairs. Successful cued recall of unimodal associates was characterized by markedly early scalp potential differences over frontal areas, while cued recall of both unimodal and crossmodal associates were reflected by subsequent differences recorded over frontal and parietal areas. Notably, unimodal cued recall success divergences over frontal areas were apparent in a time window generally assumed to reflect the operation of familiarity but not recollection processes, raising the possibility that retrieval success effects in that temporal window may reflect additional mnemonic processes beyond familiarity. Furthermore, parietal scalp potential recall success differences, which did not distinguish between crossmodal and unimodal tasks, seemingly support attentional or buffer accounts of posterior parietal mnemonic function but appear to constrain signal accumulation, expectation, or representational accounts.

Striking a balance: analyzing unbalanced event-related potential data

The cognitive events examined in many event-related potentials (ERPs) studies do not occur in aneuralvacuum,andseparatingthesignalsofinterestfromthebrain’sbackgroundelectricalactivitygenerally requires averaging multiple EEG segments of a condition of interest (Luck, 2005). Inaddition to within-subject averaging, the vast majority of ERP studies are based on across-subjectgrand average data, i.e., group waveforms representing the means of subjects’ averaged waveforms,with statistical significance examined by comparing variance between conditions of interest withvariance between participants. Using this approach may not always portray a valid picture.Consider, for example, the following experimental paradigm: in a study of episodic associativememory, participants encoded 120 pairs of stimuli (unrelated object picture pairs in the unimodaltask, and unrelated environmental sound-object picture pairs in the crossmodal task). At test, cuepictures were presented to probe recall of the associated picture (in the unimodal task) or sound(in the crossmodal task). ERPs were time-locked to the onset of the cue, and sorted post-hocinto recall-success and recall-failure trials (for details of the procedures, see Tibon and Levy,2014a). This experimental design poses several challenges to the conventional grand-averagingmethod. First, since the assignment of trials to experimental conditions is based on participants’responses, it is quite likely that the data will be unbalanced (that is, an unequal number of trialsin each condition). Therefore, signal-to-noise ratio and variance can vary significantly betweenexperimental conditions. Second, since experimental conditions are mutually dependent (i.e.,a participant who had 100 recall-success responses can only have 20 recall-failure responses),participants who were very successful (having a low number of recall-failure trials) or veryunsuccessful (having a low number of recall-success trials) in performing the task are likely tobe excluded due to an insufficient number of trials for addressing signal-to-noise ratio (SNR)challenges in one of the experimental conditions.

Associative recognition processes are modulated by modality relations

Although memory of episodic associations is generally considered to be recollective in nature, it has been suggested that when stimuli are experienced as a unit, familiarity-related processes might contribute to their subsequent associative recognition. Furthermore, intradomain associations are believed to be unitized more readily than interdomain associations. To assess these claims, we tested associative recognition following two types of pair associate learning. In the unimodal task, stimulus pairs were pictures of common objects, whereas in the cross-modal task, stimulus pairs consisted of an object picture and an unrelated environmental sound. At test, participants discriminated intact from recombined pairs while ERPs were recorded. In the unimodal task only, associative recognition was accompanied by a robust frontal deflection reminiscent of a component commonly interpreted as related to familiarity processes. In contrast, ERP correlates of associative recognition observed at more posterior sites, akin to a component that has been related to recollection, were apparent in both tasks. These findings indicate that retrieval of unimodal associations can be supported by familiarity-related processes that are dissociable from recollective processes required for the retrieval of cross-modal associations.

Temporal texture of associative encoding modulates recall processes

Binding aspects of an experience that are distributed over time is an important element of episodic memory. In the current study, we examined how the temporal complexity of an experience may govern the processes required for its retrieval. We recorded event-related potentials during episodic cued recall following pair associate learning of concurrently and sequentially presented object-picture pairs. Cued recall success effects over anterior and posterior areas were apparent in several time windows. In anterior locations, these recall success effects were similar for concurrently and sequentially encoded pairs. However, in posterior sites clustered over parietal scalp the effect was larger for the retrieval of sequentially encoded pairs. We suggest that anterior aspects of the mid-latency recall success effects may reflect working-with-memory operations or direct access recall processes, while more posterior aspects reflect recollective processes which are required for retrieval of episodes of greater temporal complexity.

Age effects on associative memory for novel picture pairings

Normal aging is usually accompanied by greater memory decline for associations than for single items. Though associative memory is generally supported by recollection, it has been suggested that familiarity can also contribute to associative memory when stimuli can be unitized and encoded as a single entity. Given that familiarity remains intact during healthy aging, this may be one route to reducing age-related associative deficits. The current study investigated age-related differences in associative memory under conditions that were expected to differentially promote unitization, in this case by manipulating the spatial arrangement of two semantically unrelated objects positioned relative to each other in either spatially implausible or plausible orientations. Event-related potential (ERP) correlates of item and associative memory were recorded whilst younger and older adults were required to discriminate between old, recombined and new pairs of objects. These ERP correlates of item and associative memory did not vary with plausibility, whereas behavioral measures revealed that both associative and item memory were greater for spatially plausible than implausible pair arrangements. Contrary to predictions, older adults were less able to take advantage of this memory benefit than younger participants. Potential reasons for this are considered, and these are informed by those lines of evidence which indicate older participants were less sensitive to the bottom-up spatial manipulation employed here. It is recommended that future strategies for redressing age-related associative deficits should take account of the aging brains increasing reliance on pre-existing semantic associations.

Episodic temporal structure modulates associative recognition processes: an MEG study.

The formation of mnemonic associations can occur between items processed in temporal proximity. It has been proposed that such intertemporal associations are not unitizable, and may therefore be retrieved only via recollective processes. To examine this claim, we conducted a magnetoencephalograph study of recognition memory for items encoded and retrieved sequentially. Participants studied successively presented pairs of object pictures, and subsequently made old-new item judgments under several retrieval conditions, differing in degree of reinstatement of associative information. Correct recognition was accompanied by an early event-related field (ERF) component, seemingly corresponding to the FN400 event-related potential component asserted to reflect familiarity; this retrieval success effect was not modulated by degree of associative binding. A later ERF component, corresponding to the late positive component asserted to reflect recollection, was modulated by degree of associative reinstatement. These results suggest that memory of intertemporal associations, which are not amenable to unitization, is accessed via recollection.

Title TBA: Revising the Abstract Submission Process

Academic conferences are among the most prolific scientific activities, yet the current abstract submission and review process has serious limitations. We propose a revised process that would address these limitations, achieve some of the aims of Open Science, and stimulate discussion throughout the entire lifecycle of the scientific work.

Behavioral reconsolidation interference with episodic memory within-subjects is elusive.

HIGHLIGHTSWe assessed behavioral reconsolidation interference in episodic memory.Employed within‐subjects paradigm measuring direct memory strength.Three experiments found no effects of reminder‐potentiated interference.Null effects were substantiated by Bayesian analyses.Highlights boundary conditions for behavioral reconsolidation interference effects. ABSTRACT In studies of behavioral reconsolidation interference, reactivation of a consolidated memory using some form of reminder is followed by the presentation of new information that can cause interference with that memory. Under these conditions, the interference not only impairs retrieval by indirect processes such as cue interference, but supposedly disrupts the original memory trace directly. Almost all studies of behavioral reconsolidation interference in episodic memory in humans have employed between‐subjects paradigms, and deduced reminder effects from intrusion errors. Such studies might introduce confounds arising, for example, from differences in retrieval strategies engendered by the pre‐test treatments. We therefore set out to examine whether behavioral reconsolidation interference in episodic memory might be demonstrated within‐subjects and by direct memory strength rather than intrusion errors. In three separate experiments, we attempted to disrupt reconsolidation of episodic object‐picture memory using a reminder+retroactive interference manipulation. We applied the manipulation over three consecutive days, using a forced‐choice recognition test without intrusions from interfering learning, keeping all other study and test parameters constant. No effects of reminder‐potentiated interference were observed for measures of accuracy, response times, subjective expressions of recollection, or levels of confidence, as substantiated by Bayesian analyses. These results highlight the difficulty of observing clear behavioral reconsolidation interference effects within‐subjects in human episodic memory, and provide some indications of what might be boundary conditions for its demonstration.

The missing link? Testing a schema account of unitization

Unitization refers to the creation of a new unit from previously distinct items. The concept of unitization has been used to explain how novel pairings between items can be remembered without requiring recollection, by virtue of new, item-like representations that enable familiarity-based retrieval. We tested an alternative account of unitization – a schema account – which suggests that associations between items can be rapidly assimilated into a schema. We used a common operationalization of “unitization” as the difference between two unrelated words being linked by a definition, relative to two words being linked by a sentence, during an initial study phase. During the following relearning phase, a studied word was re-paired with a new word, either related or unrelated to the original associate from study. In a final test phase, memory for the relearned associations was tested. We hypothesized that, if unitized representations act like schemas, then we would observe some generalization to related words, such that memory would be better in the definition than sentence condition for related words, but not for unrelated words. Contrary to the schema hypothesis, evidence favored the null hypothesis of no difference between definition and sentence conditions for related words (Experiment 1), even when each cue was associated with multiple associates, indicating that the associations can be generalized (Experiment 2), or when the schematic information was explicitly re-activated during Relearning (Experiment 3). These results suggest that unitized associations do not generalize to accommodate new information, and therefore provide evidence against the schema account.