The Mechanisms Underlying Interference and Inhibition: A Review of Current Behavioral and Neuroimaging Research

The dynamic reconfiguration of the functional network during episodic memory task predicts the memory performance

Episodic memory is essential for forming and retaining personal experiences, representing a fundamental aspect of human cognition. Traditional studies of episodic memory have typically used static analysis methods, viewing the brain as an unchanging entity and overlooking its dynamic properties over time. In this study, we utilized dynamic functional connectivity analysis on fMRI data from healthy adults performing an episodic memory task. We quantified integration and recruitment metrics and examined their correlation with memory performance using Pearson correlation. During encoding, integration across the entire brain, especially within the frontoparietal subnetwork, was significantly correlated with memory performance. During retrieval, recruitment becomes significantly associated with memory performance in visual subnetwork, somatomotor subnetwork, and ventral attention subnetwork. At the nodal level, a significant negative correlation was observed between memory scores and integration of the anterior cingulate gyrus, precentral gyrus, and inferior frontal gyrus within the frontoparietal network during encoding task. During retrieval task, a significant negative correlation was found between memory scores and recruitment in the left progranular cortex and right transverse gyral ventral, whereas positive correlations were seen in the right posterior inferior temporal, left middle temporal, right frontal operculum, and left operculum nodes. Moreover, the dynamic reconfiguration of the functional network was predictive of predict memory performance, as demonstrated by a significant correlation between actual and predicted memory scores. These findings advance our understanding network mechanisms underlying memory processes and developing intervention approaches for memory-related disorders as they shed light on critical factors involved in cognitive processes and provide a deeper understanding of the underlying mechanisms driving cognitive function.

Survival processing and directed forgetting: enhanced memory for both to-be-remembered and to-be-forgotten information

In a recently published study, (Parker, A., Parkin, A., & Dagnall, N. (2021). Effects of survival processing on list method directed forgetting. Memory (Hove, England), 29(5), 645-661) examined directed forgetting in a survival processing context using the list-method directed forgetting procedure. (Parker, A., Parkin, A., & Dagnall, N. (2021). Effects of survival processing on list method directed forgetting. Memory (Hove, England), 29(5), 645-661) found that the costs of directed forgetting were greater when engaging in survival processing than when making moving relevance or pleasantness ratings. However, according to most current accounts of directed forgetting, engaging in survival processing should not have enhanced the directed forgetting effect but rather should not have impacted the directed forgetting effect. In the present study, we further investigated how survival processing impacts directed forgetting using both the list (Experiment 1) and item method of directed forgetting (Experiment 2). In Experiment 1, we did not replicate the findings of (Parker, A., Parkin, A., & Dagnall, N. (2021). Effects of survival processing on list method directed forgetting. Memory (Hove, England), 29(5), 645-661) - that the directed forgetting effect is enhanced when engaging in survival processing. Rather, we demonstrated that making survival ratings and moving ratings yielded a similar cost of directed forgetting for List 1 items. In Experiment 2, survival processing provided an overall memory benefit (but not when recalling to-be-remembered and to-be-forgotten items in separate recall tests) but did not differentially impact to-be-remembered and to-be-forgotten words. Thus, we did not find evidence that survival processing influences directed forgetting.

The pretesting effect thrives in the presence of competing information

Taking a pretest (e.g., blanket - ?) before some target material (blanket - sheet) is studied can promote recall of that material on a subsequent final test compared to material which was initially only studied. Here, we examine whether such pretesting can shield the tested material from interference-induced forgetting, which often occurs when before final testing, related material is encountered. We applied a typical pretesting task but asked subjects, between acquisition and final testing of the target list (list 1), to study two additional lists of items with either completely new and unique pairs (e.g., atom - cell) or overlapping - and thus potentially interfering - pairs (e.g., blanket - sleep). Target-list recall on the final test showed a typical pretesting effect for unique pairs, but the size of the effect even increased for overlapping pairs, as recall of study-only pairs was impaired, whereas recall of pretest pairs was left largely unaffected. This held regardless of whether a low (Experiment 1) or high (Experiment 2) degree of learning was induced for the interfering material, suggesting that pretesting can indeed protect the tested material from interference. These findings indicate that pretesting could play a significant role in educational settings where information often needs to be retained in the presence of competing information.

Enhanced Learning and Forgetting Behavior for Contextual Knowledge Tracing

Knowledge tracing (KT) is based on modeling students’ behavior sequences to obtain students’ knowledge state and predict students’ future performance. The KT task aims to model students’ knowledge state in real-time according to their historical learning behavior, so as to predict their future learning performance. Online education has become more critical in recent years due to the impact of COVID-19, and KT has also attracted much attention due to its importance in the education field. However, previous KT models generally have the following three problems. Firstly, students’ learning and forgetting behaviors affect their knowledge state, and past KT models have yet to exploit this fully. Secondly, the input of traditional KT models is mainly limited to students’ exercise sequence and answers. In the learning process, students’ answering performance can reflect their knowledge level. Finally, the context of students’ learning sequence also affects their judgment of the knowledge state. In this paper, we combined educational psychology theories to propose enhanced learning and forgetting behavior for contextual knowledge tracing (LFEKT). LFEKT enriches the features of exercises by introducing difficulty information and considers the influence of students’ answering behavior on the knowledge state. In order to model students’ learning and forgetting behavior, LFEKT integrates multiple influencing factors to build a knowledge acquisition module and a knowledge retention module. Furthermore, LFEKT introduces a long short-term memory (LSTM) network to capture the contextual relations of learned sequences. From the experimental results, it can be seen that LFEKT had better prediction performance than existing models on four public datasets, which indicates that LFEKT can better trace students’ knowledge state and has better prediction performance.

Episodic memory formation in unrestricted viewing

The brain systems of episodic memory and oculomotor control are tightly linked, suggesting a crucial role of eye movements in memory. But little is known about the neural mechanisms of memory formation across eye movements in unrestricted viewing behavior. Here, we leverage simultaneous eye tracking and EEG recording to examine episodic memory formation in free viewing. Participants memorized multi-element events while their EEG and eye movements were concurrently recorded. Each event comprised elements from three categories (face, object, place), with two exemplars from each category, in different locations on the screen. A subsequent associative memory test assessed participants' memory for the between-category associations that specified each event. We used a deconvolution approach to overcome the problem of overlapping EEG responses to sequential saccades in free viewing. Brain activity was time-locked to the fixation onsets, and we examined EEG power in the theta and alpha frequency bands, the putative oscillatory correlates of episodic encoding mechanisms. Three modulations of fixation-related EEG predicted high subsequent memory performance: (1) theta increase at fixations after between-category gaze transitions, (2) theta and alpha increase at fixations after within-element gaze transitions, (3) alpha decrease at fixations after between-exemplar gaze transitions. Thus, event encoding with unrestricted viewing behavior was characterized by three neural mechanisms, manifested in fixation-locked theta and alpha EEG activity that rapidly turned on and off during the unfolding eye movement sequences. These three distinct neural mechanisms may be the essential building blocks that subserve the buildup of coherent episodic memories during unrestricted viewing behavior.

The unidirectional prosaccade switch-cost: no evidence for the passive dissipation of an oculomotor task-set inertia

Cognitive flexibility is a core component of executive function and supports the ability to ‘switch’ between different tasks. Our group has examined the cost associated with switching between a prosaccade (i.e., a standard task requiring a saccade to veridical target location) and an antisaccade (i.e., a non-standard task requiring a saccade mirror-symmetrical to veridical target) in predictable (i.e., AABB) and unpredictable (e.g., AABAB…) switching paradigms. Results have shown that reaction times (RTs) for a prosaccade preceded by an antisaccade (i.e., task-switch trial) are longer than when preceded by its same task-type (i.e., task-repeat trial), whereas RTs for antisaccade task-switch and task-repeat trials do not differ. The asymmetrical switch-cost has been attributed to an antisaccade task-set inertia that proactively delays a subsequent prosaccade (i.e., the unidirectional prosaccade switch-cost). A salient question arising from previous work is whether the antisaccade task-set inertia passively dissipates or persistently influences prosaccade RTs. Accordingly, participants completed separate AABB (i.e., A = prosaccade, B = antisaccade) task-switching conditions wherein the preparation interval for each trial was ‘short’ (1000–2000 ms; i.e., the timeframe used in previous work), ‘medium’ (3000–4000 ms) and ‘long’ (5000–6000 ms). Results demonstrated a reliable prosaccade switch-cost for each condition (ps < 0.02) and two one-sided test statistics indicated that switch cost magnitudes were within an equivalence boundary (ps < 0.05). Hence, null and equivalence tests demonstrate that an antisaccade task-set inertia does not passively dissipate and represents a temporally persistent feature of oculomotor control.

Hippocampal Estrogen Signaling Mediates Sex Differences in Retroactive Interference

Despite being a crucial physiological function of the brain, the mechanisms underlying forgetting are still poorly understood. Estrogens play a critical role in different brain functions, including memory. However, the effects of sex hormones on forgetting vulnerabilitymediated by retroactive interference (RI), a phenomenon in which newly acquired information interferes with the retrieval of already stored information, are still poorly understood. The aim of our study was to characterize the sex differences in interference-mediated forgetting and identify the underlying molecular mechanisms. We found that adult male C57bl/6 mice showed a higher susceptibility to RI-dependent memory loss than females. The preference index (PI) in the NOR paradigm was 52.7 ± 5.9% in males and 62.3 ± 13.0% in females. The resistance to RI in female mice was mediated by estrogen signaling involving estrogen receptor α activation in the dorsal hippocampus. Accordingly, following RI, females showed higher phosphorylation levels (+30%) of extracellular signal-regulated kinase1/2 (ERK1/2) in the hippocampus. Pharmacological inhibition of ERK1/2 made female mice prone to RI. The PI was 70.6 ± 11.0% in vehicle-injected mice and 47.4 ± 10.8% following PD98059 administration. Collectively, our data suggest that hippocampal estrogen α receptor-ERK1/2 signaling is critically involved in a pattern separation mechanism that inhibits object-related RI in female mice.