Implicit Retrieval Research Articles

Incidentally encoded temporal associations produce priming in implicit memory.

A key assumption of some leading memory theories is that information about the relative order of events is automatically encoded whenever memories are formed and automatically retrieved whenever events are remembered. This information is often used to guide memory search: Remembering one event tends to trigger the retrieval of other events previously experienced nearby in time (temporal contiguity effect). The retrieved context framework attributes this temporal contiguity effect to automatic encoding and retrieval processes, predicting temporal contiguity even in incidental encoding and implicit retrieval. There is strong evidence of temporal contiguity following incidental encoding, but does the prediction hold for implicit retrieval? In this experiment, we tested the framework's predictions for recall and repetition priming. Across 30 trials, undergraduates ( ) read a series of words aloud as they appeared onscreen. In each trial, two words were repeated (cue and target), initially separated by |lag 1, 2, or 5. On their second presentation, the cue word was presented first, immediately followed by the target word. We found a strong temporal contiguity effect in a surprise free recall test, replicating previous work with explicit retrieval. For implicit retrieval, we compared repetition priming (how quickly subjects began reading a word on its first versus second presentation) for cue and target words. Repeating a cue word enhanced repetition priming for its associated target word, and this effect varied with the initial lag between the cue and target. These results support theories that assume temporal information is encoded and retrieved automatically.

Neural correlates of sleep-induced benefits on traumatic memory processing.

Recent findings indicate that sleep after trauma compared to sleep loss inhibits intrusive memory development, possibly by promoting adequate memory consolidation and integration. However, the underlying neural mechanisms are still unknown. Here, we examined the neural correlates underlying the effects of sleep on traumatic memory development in 110 healthy participants using a trauma film paradigm and an implicit memory task with fMRI recordings in a between-subjects design. To further facilitate memory integration, we used targeted memory reactivation (TMR) to reactivate traumatic memories during sleep. We found that sleep (i.e., nap) compared to wakefulness reduced the number of intrusive traumatic memories for the experimental trauma groups. TMR during sleep only descriptively reduced the intrusions further. On the level of brain activity, increased activity in the anterior and posterior cingulate cortex, retrosplenial cortex and precuneus was found in the experimental trauma group compared to the control group after wakefulness. After sleep, on the other hand, these findings could not be found in the experimental trauma groups compared to the control group. Sleep compared to wakefulness increased activity in the cerebellum, fusiform gyrus, inferior temporal lobe, hippocampus, and amygdala during implicit retrieval of trauma memories in the experimental trauma groups. Activity in the hippocampus and the amygdala predicted subsequent intrusions. Results demonstrate the beneficial behavioral and neural effects of sleep after experimental trauma and provide indications for early neural predictor factors. This study has implications for understanding the important role of sleep for personalized treatment and prevention in posttraumatic stress disorder.

Bayesian approach to the tomographic problem with constraints from geodynamic modeling: Application to a synthetic subduction zone

Geodynamic tomography, an imaging technique that incorporates constraints from geodynamics and mineral physics to restrict the potential number of candidate seismic models down to a subset consistent with geodynamic predictions, is applied to a thermal subduction model. The goal is to test the ability of geodynamic tomography to recover structures harbouring complex deformation patterns. The subduction zone is parameterised in terms of four unknown parameters namely the slab length L, thickness R, temperature Tc, and dip angle θ that define its thermal structure. A temperature-dependent viscosity is then prescribed with an activation coefficient E controlling the sensitivity. Using the full forward approach to geodynamic tomography, we generate anisotropic surface wave dispersion measurements as synthetic data. We then attempt to retrieve the five unknown parameters by inverting the synthetics corrupted with random uncorrelated noise. The final output is an ensemble of models of L, R, θ, Tc and E cast in terms of a posterior probability distribution and their uncertainty limits. Results show that the parameters are tightly constrained with the apparent existence of a single misfit minima in each of them, which implies the implicit retrieval of the complete patterns of upper mantle deformation, and correspondingly, the 21-independent coefficients defining elastic anisotropy. Each model realisation however fails to swarm around its true value. Such results are attributed to the inability of the surrogate model to accurately replicate the correct forward model for computing anisotropy due to the inherent complexity of the deformation patterns considered. Nevertheless, this proof of concept shows a self-consistent method that incorporates mantle flow modeling in a seismic inversion scheme.

Fast Electromagnetic Validations of Large-Scale Digital Coding Metasurfaces Accelerated by Recurrence Rebuild and Retrieval Method

The recurrence rebuild and retrieval method (R3M) is proposed in this paper to accelerate the electromagnetic (EM) validations of large-scale digital coding metasurfaces (DCMs). R3M aims to accelerate the EM validations of DCMs with varied codebooks, which involves the analysis of a group of similar but not identical structures. The method transforms general DCMs to rigorously periodic arrays by replacing each coding unit with the macro unit, which comprises all possible coding states. The system matrix corresponding to the rigorously periodic array is globally shared for DCMs with arbitrary codebooks via implicit retrieval. The discrepancy of the interactions for edge and corner units are precluded by the basis extension of periodic boundaries. Moreover, the hierarchical pattern exploitation (HPE) algorithm is leveraged to efficiently assemble the system matrix for further acceleration. Due to the fully utilization of the rigid periodicity, the computational complexity of R3M-HPE is theoretically lower than that of $\mathcal{H}$-matrix within the same paradigm. Numerical results for two types of DCMs indicate that R3M-HPE is accurate in comparison with commercial software. Besides, R3M-HPE is also compatible with the preconditioning for efficient iterative solutions. The efficiency of R3M-HPE for DCMs outperforms the conventional fast algorithms in both the storage and CPU time cost.

Event-Related Potential Evidence for Involuntary Consciousness During Implicit Memory Retrieval.

Classical notion claims that a memory is implicit if has nothing to do with consciousness during the information retrieval from storage, or is otherwise explicit. Here, we demonstrate event-related potential evidence for involuntary consciousness during implicit memory retrieval. We designed a passive oddball paradigm for retrieval of implicit memory in which an auditory stream of Shepard tones with musical pitch interval contrasts were delivered to the subjects. These contrasts evoked a mismatch negativity response, which is an event-related potential and a neural marker of implicit memory, in the subjects with long-term musical training, but not in the subjects without. Notably, this response was followed by a salient P3 component which implies involvement of involuntary consciousness in the implicit memory retrieval. Finally, source analysis of the P3 revealed moving dipoles from the frontal lobe to the insula, a brain region closely related to conscious attention. Our study presents a case of involvement of involuntary consciousness in the implicit memory retrieval and suggests a potential challenge to the classical definition of implicit memory.

The warning stimulus as retrieval cue: The role of associative memory in temporal preparation

In a warned reaction time task, the warning stimulus (S1) initiates a process of temporal preparation, which promotes a speeded response to the impending target stimulus (S2). According to the multiple trace theory of temporal preparation (MTP), participants learn the timing of S2 by storing a memory trace on each trial, which contains a temporal profile of the events on that trial. On each new trial, S1 serves as a retrieval cue that implicitly and associatively activates memory traces created on earlier trials, which jointly drive temporal preparation for S2. The idea that S1 assumes this role as a retrieval cue was tested across eight experiments, in which two different S1s were associated with two different distributions of S1-S2 intervals: one with predominantly short and one with predominantly long intervals. Experiments differed regarding the S1 features that made up a pair, ranging from highly distinct (e.g., tone and flash) to more similar (e.g., red and green flash) and verbal (i.e., “short” vs “long”). Exclusively for pairs of highly distinct S1s, the results showed that the S1 cue modified temporal preparation, even in participants who showed no awareness of the contingency. This cueing effect persisted in a subsequent transfer phase, in which the contingency between S1 and the timing of S2 was broken – a fact participants were informed of in advance. Together, these findings support the role of S1 as an implicit retrieval cue, consistent with MTP.

Functional dissociation of hippocampal subregions corresponding to memory types and stages

BackgroundThe hippocampus reportedly plays a crucial role in memory. However, examining individual human hippocampal-subfield function remains challenging because of their small sizes and convoluted structures. Here, we identified hippocampal subregions involved in memory types (implicit and explicit memory) and stages (encoding and retrieval).MethodsWe modified the serial reaction time task to examine four memory types, i.e. implicit encoding, explicit encoding, implicit retrieval, and explicit retrieval. During this task, 7-T functional magnetic resonance imaging was used to compare brain activity evoked by these memory types.ResultsWe found hippocampal activation according to all memory types and stages and identified that the hippocampus subserves both implicit and explicit memory processing. Moreover, we confirmed that cornu ammonis (CA) regions 1–3 were implicated in both memory encoding and retrieval, whereas the subiculum was implicated only in memory retrieval. We also found that CA 1–3 was activated more for explicit than implicit memory.ConclusionsThese results elucidate human hippocampal-subfield functioning underlying memory and may support future investigations into hippocampal-subfield functioning in health and neurodegenerative disease.

Conditional automaticity: interference effects on the implicit memory retrieval process

Many studies have indicated that executing a secondary task during encoding has little influence on implicit memory (priming effect). However, relatively few studies have discussed the effect of interference on implicit memory during retrieval. Our previous studies found asymmetry between implicit encoding and retrieval processes, with the priming effect disrupted by retrieval interference. Therefore, the present study investigated why and how the priming effect is affected by interference at retrieval. We adopted a dual-task paradigm, with a lexical decision task as the memory task and an odd-even decision task as the interference task. The effect of interference during retrieval was assessed by comparing the performance in the interference condition with that in the full-attention condition. In Experiment 1, we observed that the priming effect was absent in the synchronous retrieval interference condition. In Experiment 2, asynchronous interference was also found to block the priming effect. To verify the assumption that the priming effect is sensitive to attentional resource competition during retrieval, we used two different manipulations (an extended stimulus interval in the dual-task paradigm, Experiment 3, and an interference inhibition manipulation, Experiment 4) known to reduce attentional distraction. In these experiments, the priming effect was protected from interference effects. We suggest that implicit memory retrieval could be regarded as a conditional automatic process that depends on a configuration of the cognitive system by attention and task sets. If the limited resources are occupied by another task, the implicit retrieval process can be impacted.

Subjectively-defined optimal/non-optimal time of day modulates controlled but not automatic retrieval processes in verbal memory.

Performance for controlled, resource-demanding retrieval in episodic memory has been consistently found to be better at an optimal compared with non-optimal time of the day, evidencing a synchrony effect. However, performance in memory tasks in which retrieval is mostly based on automatic processes was inconclusively found either to be better at a non-optimal time of day or independent of synchrony effects. A caveat in most prior studies is that optimal/non-optimal time of day is based on morningness-eveningness composite scores derived from chronotype questionnaires, which might not efficiently predict subjectively-defined cognitive efficiency periods. An additional caveat is that separate tasks are used to assess explicit and implicit retrieval in verbal memory. Indeed, no task is process-pure, and both controlled and automatic retrieval processes may potentially contribute to retrieval scores in different types of memory tasks. In the present study, we investigated the impact of individually defined subjective optimal/non-optimal time of day on verbal memory retrieval, using an adaptation of the Process-Dissociation Procedure that allows estimating the respective contributions of automatic and controlled memory retrieval processes within the same memory task. Our results disclose a higher involvement of controlled processes at subjectively optimal compared with non-optimal time of day, but no differences for automatic processes. Synchrony effects and subjectively-defined peaks and troughs of performance for controlled components of memory retrieval should be considered in the evaluation of episodic memory.

An Eye-Movement Study of relational Memory in Adults with Autism Spectrum Disorder

Persons with Autism Spectrum Disorder (ASD) demonstrate good memory for single items but difficulties remembering contextual information related to these items. Recently, we found compromised explicit but intact implicit retrieval of object-location information in ASD (Ring et al. Autism Res 8(5):609–619, 2015). Eye-movement data collected from a sub-sample of the participants are the focus of the current paper. At encoding, trial-by-trial viewing durations predicted subsequent retrieval success only in typically developing (TD) participants. During retrieval, TD compared to ASD participants looked significantly longer at previously studied object-locations compared to alternative locations. These findings extend similar observations recently reported by Cooper et al. (Cognition 159:127–138, 2017a) and demonstrate that eye-movement data can shed important light on the source and nature of relational memory difficulties in ASD.

Neural correlates of experimental trauma memory retrieval.

Traumatic memories such as intrusions and flashbacks play a major role in the development and maintenance of post-traumatic stress disorder (PTSD). A thorough understanding of the neural mechanisms underlying traumatic memories is indispensable for precise diagnosis, for personalized treatment and prevention. In particular, the identification of early neural predictor variables for intrusion development shortly after trauma exposure requires detailed investigation. Here, we examined the neural correlates of early experimental trauma memory retrieval in a traumatic film paradigm in 42 young healthy females, using both implicit and explicit retrieval tasks. We show that implicit experimental trauma retrieval specifically involved the retrosplenial cortex and the anterior cingulate cortex (ACC), while both retrieval tasks resulted in trauma-related activity in the posterior cingulate cortex (PCC) and the precuneus. Importantly, neural activity early after experimental trauma exposure predicted later intrusion development, with independent contributions from activity in the retrosplenial cortex (implicit retrieval) and the PCC (explicit retrieval). Additional analyses revealed a stronger connectivity between the bilateral amygdala and the supplementary motor area, precentral and paracentral lobule for the control group compared to the experimental trauma group. Our study gives new insights in the neural correlates of experimental trauma memory retrieval and their predictive value for subsequent symptom development. Our results could provide the basis for personalized early treatment and prevention of PTSD. Hum Brain Mapp, 2017. © 2017 Wiley Periodicals, Inc. Hum Brain Mapp 38:3592-3602, 2017. © 2017 Wiley Periodicals, Inc.

Comparative functional neuroanatomy between implicit and explicit memory tasks under negative emotional condition in schizophrenia

PurposeTo evaluate the brain activation patterns in response to negative emotion during implicit and explicit memory in patients with schizophrenia. Material and methodsFourteen patients with schizophrenia and 14 healthy controls were included in this study. The 3.0T fMRI was obtained while the subjects performed the implicit and explicit retrievals with unpleasant words. ResultsThe different predominant brain activation areas were observed during the implicit retrieval and explicit with unpleasant words. ConclusionThe differential neural mechanisms between implicit and explicit memory tasks associated with negative emotional processing in schizophrenia.

AFFECT: Altered-Fidelity Framework for Enhancing Cognition and Training

In this paper, we present a new framework for analyzing and designing virtual reality (VR) techniques. This framework is based on two concepts—system fidelity (i.e., the degree with which real-world experiences are reproduced by a system) and memory (i.e., the formation and activation of perceptual, cognitive, and motor networks of neurons). The premise of the framework is to manipulate an aspect of system fidelity in order to assist a stage of memory. We call it the Altered-Fidelity Framework for Enhancing Cognition and Training (AFFECT). AFFECT provides nine categories of approaches to altering system fidelity to positively affect learning or training. These categories are based on the intersections of three aspects of system fidelity (interaction fidelity, scenario fidelity, and display fidelity) and three stages of memory (encoding, implicit retrieval, and explicit retrieval). In addition to discussing the details of our new framework, we show how AFFECT can be used as a tool for analyzing and categorizing VR techniques designed to facilitate learning or training. We also demonstrate how AFFECT can be used as a design space for creating new VR techniques intended for educational and training systems.

Timing Matters? Learning of Complex Spatiotemporal Sequences in Left-hemisphere Stroke Patients.

During rehabilitation after stroke motor sequence learning is of particular importance because considerable effort is devoted to (re)acquiring lost motor skills. Previous studies suggest that implicit motor sequence learning is preserved in stroke patients but were restricted to the spatial dimension, although the timing of single action components is as important as their spatial order. As the left parietal cortex is known to play a critical role in implicit timing and spatiotemporal integration, in this study we applied an adapted version of the SRT task designed to assess both spatial (different stimulus locations) and temporal (different response-stimulus intervals) aspects of motor learning to 24 right-handed patients with a single left-hemisphere (LH) stroke and 24 age-matched healthy controls. Implicit retrieval of sequence knowledge was tested both at Day 1 and after 24 hr (Day 2). Additionally, voxel-based lesion symptom mapping was used to investigate the neurobiological substrates of the behavioral effects. Although LH stroke patients showed a combined spatiotemporal learning effect that was comparable to that observed in controls, LH stroke patients did not show learning effects for the learning probes in which only one type of sequence information was maintained whereas the other one was randomized. Particularly on Day 2, patients showed significantly smaller learning scores for these two learning probes than controls. Voxel-based lesion symptom mapping analyses revealed for all learning probes that diminished learning scores on Day 2 were associated with lesions of the striatum. This might be attributed to its role in motor chunking and offline consolidation as group differences occurred on Day 2 only. The current results suggest that LH stroke patients rely on multimodal information (here: temporal and spatial information) when retrieving motor sequence knowledge and are very sensitive to any disruption of the learnt sequence information as they seem to build very rigid chunks preventing them from forming independent spatial and temporal sequence representations.

Neuroanatomical assessment of the impact of negative emotion on implicit memory in patients with obsessive compulsive disorder.

We performed functional magnetic resonance imaging (fMRI) to discriminate the differential brain activation patterns in patients with obsessive compulsive disorder (OCD) and healthy controls during implicit retrieval tasks with emotionally neutral and unpleasant words. Sixteen patients with OCD (mean age: 31.4±10.1 years) and 16 healthy controls (mean age: 32.6±5.8 years) with no history of neurological or psychiatric illness underwent 3-T fMRI. The stimulation paradigm consisted of the following cycle: rest, encoding of a string of two-syllable words, rest, and retrieval of the previously encoded words with the first consonant omitted. During the implicit retrieval task with emotionally neutral words, no distinct brain activity was observed in either the patients with OCD or healthy controls. On the other hand, during the retrieval task with unpleasant words, the patients with OCD showed predominant activity in the superior/middle temporal pole, medial superior frontal gyrus, and orbitofrontal cortex (uncorrected p<0.001, extent threshold: 30 voxels), whereas the healthy controls did not show any distinct regions of activation. This study revealed the differential brain activation patterns between patients with OCD and healthy controls during implicit memory tasks with unpleasant words. Our results suggest that the impact of negative emotion on implicit memory task may be associated with the symptomatology of OCD. This finding may be helpful for understanding the neural mechanisms that underlie implicit memory retrieval, particularly the interaction between emotion and cognition, in patients with OCD.

Long-term priming of visual search prevails against the passage of time and counteracting instructions.

Studies on intertrial priming have shown that in visual search experiments, the preceding trial automatically affects search performance: facilitating it when the target features repeat and giving rise to switch costs when they change-so-called (short-term) intertrial priming. These effects also occur at longer time scales: When 1 of 2 possible target colors is more frequent during an experiment block, this results in a prolonged and persistent facilitation for the color that was biased, long after the frequency bias is gone-so-called long-term priming. In this study, we explore the robustness of such long-term priming. In Experiment 1, participants were fully informed of the bias and instructed to prioritize the other unbiased color. Despite these instructions, long-term priming of the biased color persisted in this block, suggesting that guidance by long-term priming is an implicit effect. In Experiment 2, long-term priming was built up in 1 experimental session and was then assessed in a second session a week later. Long-term priming persisted across this week, emphasizing that long-term priming is truly a phenomenon of long-term memory. The results support the view that priming results from the automatic and implicit retrieval of memory traces of past trials. (PsycINFO Database Record

L1 and L2 Spoken Word Processing: Evidence from Divided Attention Paradigm.

The present study aims to reveal some facts concerning first language (L1) and second language (L2) spoken-word processing in unbalanced proficient bilinguals using behavioral measures. The intention here is to examine the effects of auditory repetition word priming and semantic priming in first and second languages of these bilinguals. The other goal is to explore the effects of attention manipulation on implicit retrieval of perceptual and conceptual properties of spoken L1 and L2 words. In so doing, the participants performed auditory word priming and semantic priming as memory tests in their L1 and L2. In a half of the trials of each experiment, they carried out the memory test while simultaneously performing a secondary task in visual modality. The results revealed that effects of auditory word priming and semantic priming were present when participants processed L1 and L2 words in full attention condition. Attention manipulation could reduce priming magnitude in both experiments in L2. Moreover, L2 word retrieval increases the reaction times and reduces accuracy on the simultaneous secondary task to protect its own accuracy and speed.

Inefficient stimulus processing at encoding affects formation of high-order general representation: A study on cross-modal word-stem completion task

Priming is an implicit memory effect in which previous exposure to one stimulus influences the response to another stimulus. The main characteristic of priming is that it occurs without awareness. Priming takes place also when the physical attributes of previously studied and test stimuli do not match; in fact, it greatly refers to a general stimulus representation activated at encoding independently of the sensory modality engaged. Our aim was to evaluate whether, in a cross-modal word-stem completion task, negative priming scores could depend on inefficient word processing at study and therefore on an altered stimulus representation. Words were presented in the auditory modality, and word-stems to be completed in the visual modality. At study, we recorded auditory ERPs, and compared the P300 (attention/memory) and N400 (meaning processing) of individuals with positive and negative priming. Besides classical averaging-based ERPs analysis, we used an ICA-based method (ErpICASSO) to separate the potentials related to different processes contributing to ERPs. Classical analysis yielded significant difference between the two waves across the whole scalp. ErpICASSO allowed separating the novelty-related P3a and the top-down control-related P3b sub-components of P300. Specifically, in the component C3, the positive deflection identifiable as P3b, was significantly greater in the positive than in the negative priming group, while the late negative deflection corresponding to the parietal N400, was reduced in the positive priming group. In conclusion, inadequacy of specific processes at encoding, such as attention and/or meaning retrieval, could generate weak semantic representations, making words less accessible in subsequent implicit retrieval.

Intelligent Science of Knowledge Retrieval System Model Based on Ontology

Compared with the traditional information retrieval, knowledge retrieval based on ontology has higher retrieval efficiency. In order to adequate arena for the effectiveness of knowledge,and intelligence to meet the users on the implicit and explicit knowledge retrieval demand, the author designed a system model of intelligent science based on ontology. Detailed analysis and elaboration of the three aspects: subject knowledge ontology construction, ontology knowledge retrieval, service based on intelligent. Provide methodological guidance and technical support to enrich the research contents in the field of knowledge retrieval.

Effects of Auditory Translation Priming under Divided Attention in Unbalanced Persian-English Bilinguals

In bilingual studies, repetition priming across languages or translation priming can be used to examine themental representations of bilingual lexicon and language in memory. Motivated to demonstrate the effects ofdividing attention during implicit retrieval of L2 spoken words, we investigated the nature of the processesinvolved in translation priming. In so doing, we used behavioral measures (i.e. reaction time and accuracy) tostudy 60 Persian-English unbalanced proficient bilinguals performing translation priming in two languagedirections under two attention conditions. The present study compared a divided attention (DA) condition, inwhich participants carried out the priming task in auditory modality while simultaneously performing asecondary task in visual modality, and a full attention (FA) condition, in which participants performed only thepriming task. We also examined secondary tasks costs produced by memory tests. Despite significant primingeffects and symmetrical pattern of translation priming in the FA condition, translation priming effects in L2-to-L1direction were absent in the DA condition. The secondary task was disrupted by memory test in this direction aswell. The paper ends with discussion on the role of attention in L2 spoken word processing and languagedirection in translation priming in light of models of bilingual memory.