Overlap between hippocampal pre-encoding and encoding patterns supports episodic memory.

It is well-established that whether the information will be remembered or not depends on the extent to which the learning context is reinstated during post-encoding rest and/or at retrieval. It has yet to be determined, however, if the fundamental importance of contextual reinstatement to memory extends to periods of spontaneous neurocognitive activity prior to learning. We thus asked whether memory performance can be predicted by the extent to which spontaneous pre-encoding neural patterns resemble patterns elicited during encoding. Individuals studied and retrieved lists of words while undergoing fMRI-scanning. Multivoxel hippocampal patterns during resting periods prior to encoding resembled hippocampal patterns at encoding most strongly for items that were subsequently remembered. Furthermore, across subjects, the magnitude of similarity correlated with a behavioral measure of episodic recall. The results indicate that the neural context before learning is an important determinant of memory.

Working Memory Has Better Fidelity Than Long-Term Memory: The Fidelity Constraint Is Not a General Property of Memory After All.

How detailed are long-term-memory representations compared with working memory representations? Recent research has found an equal fidelity bound for both memory systems, suggesting a novel general constraint on memory. Here, we assessed the replicability of this discovery. Participants (total N = 72) were presented with colored real-life objects and were asked to recall the colors using a continuous color wheel. Deviations from study colors were modeled to generate two estimates of color memory: the variability of remembered colors-fidelity-and the probability of forgetting the color. Estimating model parameters using both maximum-likelihood estimation and Bayesian hierarchical modeling, we found that working memory had better fidelity than long-term memory (Experiments 1 and 2). Furthermore, within each system, fidelity worsened as a function of time-correlated mechanisms (Experiments 2 and 3). We conclude that fidelity is subject to decline across and within memory systems. Thus, the justification for a general fidelity constraint in memory does not seem to be valid.

The Electrophysiological Signature of Remember-Know Is Confounded with Memory Strength and Cannot Be Interpreted as Evidence for Dual-process Theory of Recognition.

The quantity and nature of the processes underlying recognition memory remains an open question. A majority of behavioral, neuropsychological, and brain studies have suggested that recognition memory is supported by two dissociable processes: recollection and familiarity. It has been conversely argued, however, that recollection and familiarity map onto a single continuum of mnemonic strength and hence that recognition memory is mediated by a single process. Previous electrophysiological studies found marked dissociations between recollection and familiarity, which have been widely held as corroborating the dual-process account. However, it remains unknown whether a strength interpretation can likewise apply for these findings. Here we describe an ERP study, using a modified remember-know (RK) procedure, which allowed us to control for mnemonic strength. We find that ERPs of high and low mnemonic strength mimicked the electrophysiological distinction between R and K responses, in a lateral positive component (LPC), 500-1000 msec poststimulus onset. Critically, when contrasting strength with RK experience, by comparing weak R to strong K responses, the electrophysiological signal mapped onto strength, not onto subjective RK experience. Invoking the LPC as support for dual-process accounts may, therefore, be amiss.

Old processes, new perspectives: Familiarity is correlated with (not independent of) recollection and is more (not equally) variable for targets than for lures.

According to dual-process models of memory, recognition is subserved by two processes: recollection and familiarity. Many variants of these models assume that recollection and familiarity make stochastically independent contributions to performance in recognition tasks and that the variance of the familiarity signal is equal for targets and for lures. Here, we challenge these 'common-currency' assumptions. Using a model-comparison approach, featuring the Continuous Dual Process (CDP; Wixted & Mickes, 2010) model as the protagonist, we show that when these assumptions are relaxed, the model's fits to individual participants' data improve. Furthermore, our analyses reveal that across items, recollection and familiarity show a positive correlation. Interestingly, this across-items correlation was dissociated from an across-participants correlation between the sensitivities of these processes. We also find that the familiarity signal is significantly more variable for targets than for lures. One striking theoretical implication of these findings is that familiarity-rather than recollection, as most models assume-may be the main contributor responsible for one of the most influential findings of recognition memory, that of subunit zROC slopes. Additionally, we show that erroneously adopting the common-currency assumptions, introduces severe biases to estimates of recollection and familiarity.

Putting Humpty together and pulling him apart: accessing and unbinding the hippocampal item-context engram.

A remarkable act of memory entails binding different forms of information. We focus on the timeless question of how the bound engram is accessed such that its component features-item and context-are extracted. To shed light on this question, we investigate the dynamics between brain structures that together mediate the binding and extraction of item and context. Converging evidence has implicated the Parahippocampal cortex (PHc) in contextual processing, the Perirhinal cortex (PRc) in item processing, and the hippocampus in item-context binding. Effective connectivity analysis was conducted on fMRI data gathered during retrieval on tests that differ with regard to the to-be-extracted information. Results revealed that recall is initiated by context-related PHc activity, followed by hippocampal item-context engram activation, and completed with retrieval of the study-item by the PRc. The reverse path was found for recognition. We thus provide novel evidence for dissociative patterns of item-context unbinding during retrieval.

Not all faces are processed equally: evidence for featural rather than holistic processing of one's own face in a face-imaging task.

The present work considers the mental imaging of faces, with a focus in own-face imaging. Experiments 1 and 3 demonstrated an own-face disadvantage, with slower generation of mental images of one's own face than of other familiar faces. In contrast, Experiment 2 demonstrated that mental images of facial parts are generated more quickly for one's own face. Finally, Experiment 4 established that a bias toward local processing is advantageous for one's own face, whereas a global-processing bias produces an enhanced own-face disadvantage. The results suggest that own-face imaging is more synchronized with retrieval of face features and less attuned to a face's holistic pattern than is imaging of other people's faces. The authors propose that the salient information for own and other face identification reflects, in part, differences in the purpose and experiences (expertise) generally associated with processing of own and other faces. Consistent with work examining the range of face processing, including other-race faces, our results suggest that not all faces receive the same holistic emphasis.

Short-term memory after all: comment on Sederberg, Howard, and Kahana (2008).

P. B. Sederberg, M. W. Howard, and M. J. Kahana have proposed an updated version of the temporal-context model (TCM-A). In doing so, they accepted the challenge of developing a single-store model to account for the dissociations between short- and long-term recency effects that were reviewed by E. J. Davelaar, Y. Goshen-Gottstein, A. Ashkenazi, H. J. Haarmann, and M. Usher (2005). In this commentary, the authors argue that the success of TCM-A in addressing the dissociations is dependent not only on an episodic encoding matrix but--critically--also on its implicit use of a short-term memory store--albeit exponential rather than buffer-like. The authors also highlight some difficulties of TCM-A in accounting for these dissociations, and they argue that TCM-A fails to account for critical data--the presentation-rate effect--that dissociates exponential and buffer-like models.

A Remember/Know Examination of Free-recall Reveals Dissociative Roles of Item- and Context-Information over Time.

It is well-established that the ability to freely recall information is driven by the extent to which the context at encoding is reinstated at retrieval. Still, when asked to judge the subjective quality of one's memories giving Remember/Know (R/K) judgments, people tend to classify a substantial proportion of recalls as being devoid of context. We suggest that R- and K-recalls differ with regard to their reliance on context- and item-information, with R-recalls driven primarily by contextual-information (e.g., associations evoked by the study-items) and K-recalls driven primarily by information pertaining to the items (e.g., semantic information). Memory was tested both immediately after study and in a final free-recall test conducted ~20 minutes after encoding-a timescale which is akin to real-life events. In line with our predictions, as compared to K-recalls, R-recalls show stronger contextual effects, but similarly strong item-related effects over these timescales. Furthermore, drawing on theories regarding the forgetting of item- and contextual information, we hypothesized and found that R- and K-recalls are differentially affected by the passage of time. Our findings provide several converging pieces of evidence for differential roles of item and contextual information in driving recall and thus highlight the need to extend longstanding theories of free-recall to account for cases in which recall relies less on context.

The unitary zROC slope in amnesics does not reflect the absence of recollection: critical simulations in healthy participants of the zROC slope.

The functional deficit underlying amnesia has been argued to be in recollective processing. This idea is based on the DPSD model, wherein recognition comprises a mixture of recollection and familiarity signals, with familiarity conforming to an equal-variance signal-detection mechanism while recollection is binary. This model interprets the greater variance for targets than for lures revealed in sub-unit zROC slopes, to be a consequence of the mixture of two signals. Importantly, equal variance between targets and lures is found in amnesic, and is consequently interpreted by DPSD to reflect impairment to recollection alongside the sparing of familiarity. Here, we pointed to a logical fallacy in this interpretation. We then asked participants, in two experiments, to make remember-know (RK) and confidence judgments. Simulating equal variance in healthy participants, we either excluded from the analysis 'remember' responses, reflecting recollection, or the most accurate memories, reflecting strength. We found that only the exclusion of the strongest responses led to equal-variance distributions. In addition, we found that accuracy was associated with an interlaced ordering of RK response groups nested under confidence, a pattern hard to reconcile with classic recognition models (DPSD, UVSD). This pattern can, however, be accommodated by the Continuous Dual Process (CDP) model (Wixted and Mickes, 2010), wherein both familiarity and recollection are continuous signals. Amnesia may thus be characterized as the inability to form strong memories, recollection as well as familiarity.

The involvement of the "fusiform face area" in processing facial expression.

We conducted an fMRI investigation to test the widely accepted notion that the fusiform face area (FFA) mediates the processing of facial identity but not expression. Participants attended either to the identity or to the expression of the same set of faces. If the processing of identity is neuroanatomically dissociable from that of expression, then one might expect the FFA to show higher activation when processing identity as opposed to expression. Contrary to this prediction, the FFA showed higher activation for judgments of expression. Furthermore, the FFA was sensitive to variations in expression even when attention was directed to identity. Finally, an independent observation showed higher activation in the FFA for passive viewing of faces when expression was varied as compared to when it remained constant. These findings suggest an interactive network for the processing of expression and identity, in which information about expression is computed from the unique structure of individual faces.

The demise of short-term memory revisited: empirical and computational investigations of recency effects.

In the single-store model of memory, the enhanced recall for the last items in a free-recall task (i.e., the recency effect) is understood to reflect a general property of memory rather than a separate short-term store. This interpretation is supported by the finding of a long-term recency effect under conditions that eliminate the contribution from the short-term store. In this article, evidence is reviewed showing that recency effects in the short and long terms have different properties, and it is suggested that 2 memory components are needed to account for the recency effects: an episodic contextual system with changing context and an activation-based short-term memory buffer that drives the encoding of item-context associations. A neurocomputational model based on these 2 components is shown to account for previously observed dissociations and to make novel predictions, which are confirmed in a set of experiments.

Interactions between the processing of gaze direction and facial expression.

In this article, we explored the relationship between the processing of facial expression and the processing of gaze direction. In Experiment 1, participants were unable to ignore gaze while classifying expression-or to ignore expression while classifying gaze. This suggests that the processing of expression and the processing of gaze are interdependent. In Experiment 2, the faces were inverted to isolate configural from part-based contributions to this interdependence. Inversion had a striking effect on expression judgments, which could now be processed independently of gaze, but not on gaze judgments, which were still influenced by expression, even when photos that contained only the eye region of faces were presented (Experiment 4). In Experiment 3 the processing of expression was found to be sensitive to even small variations in the direction of gaze. These results suggest that the processing underlying judgments of expression is configural and entails an obligatory computation of gaze direction. Judgments of gaze direction, however, are carried out in a part-based manner using local features around the eyes and are insensitive to the configural aspects of facial processing.

Recollection-Based Retrieval Is Influenced by Contextual Variation at Encoding but Not at Retrieval.

In this article, we investigated the effects of variations at encoding and retrieval on recollection. We argue that recollection is more likely to be affected by the processing that information undergoes at encoding than at retrieval. To date, manipulations shown to affect recollection were typically carried out at encoding. Therefore, an open question is whether these same manipulations would also affect recollection when carried out at retrieval, or whether there is an inherent connection between their effects on recollection and the encoding stage. We therefore manipulated, at either encoding or retrieval, fluency of processing (Experiment 1)-typically found not to affect recollection-and the amount of attentional resources available for processing (Experiments 2 and 3)-typically reported to affect recollection. We found that regardless of the type of manipulation, recollection was affected more by manipulations carried out at encoding and was essentially unaffected when these manipulations were carried out at retrieval. These findings suggest an inherent dependency between recollection-based retrieval and the encoding stage. It seems that because recollection is a contextual-based retrieval process, it is determined by the processing information undergoes at encoding-at the time when context is bound with the items-but not at retrieval-when context is only recovered.

When items 'pop into mind': variability in temporal-context reinstatement in free-recall.

It is well established that performance in free-recall is mediated by an individual's ability to reinstate the study-context during retrieval. This notion is supported by an abundance of evidence and is reflected in prominent models of memory. Introspectively, however, we often feel that a memory just 'pops into mind' and its recall is not accompanied by contextual detail. Here we ask whether this introspection is honored by the cognitive system. Namely, do items one recalls vary in the extent to which their contexts are reinstated? Previous research has provided evidence that indeed recall of some items relies on only little, if any, contextual reinstatement. This evidence pertains to one aspect of context: the concurrent, static encoding context of items, as tapped by the source-memory paradigm. However, because real-life events are strongly embedded in time, it is crucial to also investigate the dynamic, temporal aspects of context. To do so, we capitalized on one of the seminal findings linking recall with temporal-context: the temporal-contiguity effect, whereby the closer two items at study, the higher the probability that they will be retrieved one after the other during test. Using the Remember/Know paradigm, we show that in free-recall, 'Remember' retrievals, which are supposedly accompanied by contextual reinstatement, produce a larger temporal-contiguity effect as compared to 'Know' retrievals. Furthermore, 'Know' retrievals are more likely to be followed by retrieval errors (e.g., intrusions) than 'Remember' retrievals. These findings provide evidence that recalled items vary in the degree to which their temporal-context is reinstated.

Delineating the effect of semantic congruency on episodic memory: the role of integration and relatedness.

A fundamental challenge in the study of learning and memory is to understand the role of existing knowledge in the encoding and retrieval of new episodic information. The importance of prior knowledge in memory is demonstrated in the congruency effect-the robust finding wherein participants display better memory for items that are compatible, rather than incompatible, with their pre-existing semantic knowledge. Despite its robustness, the mechanism underlying this effect is not well understood. In four studies, we provide evidence that demonstrates the privileged explanatory power of the elaboration-integration account over alternative hypotheses. Furthermore, we question the implicit assumption that the congruency effect pertains to the truthfulness/sensibility of a subject-predicate proposition, and show that congruency is a function of semantic relatedness between item and context words.

Perceptual integrality of sex and identity of faces: further evidence for the single-route hypothesis.

According to current face-recognition models, sex (gender) and identity of faces are processed in independent routes. Using Garner's speeded-classification task, the authors provide evidence that sex and identity are processed within a single route. In 4 experiments, participants judged the sex or the familiarity of faces while the other dimension remained constant or varied randomly. The results of Experiments 1, 2, and 4 showed that participants could not selectively attend to either sex or familiarity without being influenced by the other, irrelevant dimension. Thus, identity and sex are integral dimensions. Experiment 3 provided evidence that when sex judgments are based on hairstyle heuristics, false separability can emerge. The findings support the claim that identity and sex are processed within a single route.

Effects of familiarity on the perceptual integrality of the identity and expression of faces: the parallel-route hypothesis revisited.

The effects of familiarity on selective attention for the identity and expression of faces were tested using Garner's speeded-classification task. In 2 experiments, participants classified expression (or identity) of familiar and unfamiliar faces while the irrelevant dimension of identity (or expression) was either held constant (baseline condition) or varied randomly (filtering condition). Selective attention was measured by the difference in performance between these 2 conditions. Failure of selective attention was larger for familiar than for unfamiliar faces. In addition, failure of selective attention was found both for identity and for expression judgments. These findings show that familiarity increases (he perceptual integrality between identity and expression, and they question previous studies arguing that identity judgments are always resistant to irrelevant variations in expression. The authors suggest that the systems processing identity and expression are interconnected in that facial identity serves as a reference from which expressions can be more easily derived.

The conditional-recency dissociation is confounded with nominal recency: should unitary models of memory still be devaluated?

The conditional-recency dissociation between immediate and delayed free recall FR; Farrell (Journal of Experimental Psychology: Learning, Memory, and Cognition, 36, 324-347, 2010) has critical implications regarding the prolonged debate between unitary and dual-store models of memory. In immediate FR, when the availability of items is controlled for, the recency of the final list item increases across the first few output positions. No such increase is found in delayed FR, with a trend in the opposite direction. This dissociation challenges temporal context TCM; Howard & Kahana (Journal of Mathematical Psychology, 46, 269-299, 2002) and distinctiveness SIMPLE; Brown, Neath, & Chater (Psychological Review, 114, 539-576, 2007) unitary models of memory and suggests the involvement of a short-term buffer in immediate FR. We show that this dissociation is confounded with the different magnitudes of nominal recency (i.e., the prevalence of the final list item) found in immediate as compared to delayed FR. By reshuffling output orders and comparing the empirical results to those of a null hypothesis of no output-order effect, we controlled for the greater prevalence of the final list item that has been observed in immediate FR. Under this control, we found no evidence for a dissociation in the tendency to recall the final list item across output positions. This finding suggests that the conditional-recency dissociation imposes no new constraint on unitary models of memory. More generally, we demonstrate how biases that influence measures of output-order tendencies (e.g., conditional recency) can be controlled for, thus yielding "purer" measures of these variables.