The resolution of proactive interference in a novel visual working memory task: A behavioral and pupillometric study.

Proactive interference (PI) occurs when previously learned information impairs memory for more recently learned information. Most PI studies have employed verbal stimuli, while the role of PI in visual working memory (VWM) has had relatively little attention. In the verbal domain, Johansson and colleagues (2018) found that pupil diameter - a real-time neurophysiological index of cognitive effort - reflects the accumulation and resolution of PI. Here we use a novel, naturalistic paradigm to test the behavioral and pupillary correlates of PI resolution for what-was-where item-location bindings in VWM. Importantly, in our paradigm, trials (PI vs. no-PI condition) are mixed in a block, and participants are naïve to the condition until they are tested. This design sidesteps concerns about differences in encoding strategies or generalized effort differences between conditions. Across three experiments (N = 122 total) we assessed PI's effect on VWM and whether PI resolution during memory retrieval is associated with greater cognitive effort (as indexed by the phasic, task-evoked pupil response). We found strong support for PI's detrimental effect on VWM (even with our spatially distributed stimuli), but no consistent link between interference resolution and effort during memory retrieval (this, even though the pupil was a reliable indicator that higher-performing individuals tried harder during memory encoding). We speculate that when explicit strategies are minimized, and PI resolution relies primarily on implicit processing, the effect may not be sufficient to trigger a robust pupillometric response.

When Load is Low, Working Memory is Shielded From Long-Term Memory's Influence.

Previous studies found that episodic long-term memory (eLTM) enhances working memory (WM) performance when both novel and previously learnt word pairs must be retained on a short-term basis. However, there is uncertainty regarding how and when WM draws on eLTM. Three possibilities are (a) that people draw on eLTM only if WM capacity is exceeded; (b) that there is always a contribution of eLTM to WM performance, irrespective of whether prior knowledge is helpful or not; or (c) benefits of prior knowledge are specific to comparisons between conditions which are similarly ambiguous concerning whether LTM may be useful. We built on the assumption that under conditions of a contribution from LTM, these LTM traces of memoranda could benefit or hamper performance in WM tasks depending on the match between the traces stored in LTM and the ones to-be stored in WM in the current trial, yielding proactive facilitation (PF) and proactive interference (PI), respectively. Across four experiments, we familiarized participants with some items before they completed a separate WM task. In accordance with possibility (a) we show that there are indeed conditions in which only WM contributes to performance. Performance deteriorated with the addition of stimuli from eLTM when WM load was low, but not when it was high; and an exchange of information between LTM and WM occurred only when WM capacity was exceeded, with PI and PF effects affecting immediate memory performance in verbal and visual tasks only at higher set sizes.

Buildup and release from proactive interference: The forward testing effect in children's spatial memory.

Previous work has indicated that testing can enhance memory for subsequently studied new information by reducing proactive interference from previously studied information. Here, we examined this forward testing effect in children's spatial memory. Kindergartners (5-6 years) and younger (7-8 years) and older (9-10 years) elementary school children studied four successively presented 3 × 3 arrays, each composed of the same 9 objects. The children were asked to memorize the locations of the objects that differed across the four arrays. Following presentation of each of the first three arrays, memory for the object locations of the respective array was tested (testing condition) or the array was re-presented for additional study (restudy condition). Results revealed that testing Arrays 1 to 3 enhanced children's object location memory for Array 4 relative to restudying. Moreover, children in the testing condition were less likely to confuse Array 4 locations with previous locations, suggesting that testing reduces the buildup of proactive interference. Both effects were found regardless of age. Thus, the current findings indicate that testing is an effective means to resolve proactive interference and, in this way, to enhance children's learning and remembering of spatial information even before the time of school entry.

Patterns of proactive interference in CVLT-II: evidence of a low-organized, disorganized, and highly organized learning style.

OBJECTIVE: Previous studies have interpreted proactive interference (PI) either as indicating executive dysfunction or a normal process indicating deep level encoding. We investigated these competing models of PI in a large clinical sample using cluster analyses. We expected to find clusters defined by high PI but otherwise characterized by either EF impairment or of good memory performance. METHOD: File records of 731 patients with neurological or psychiatric disorders were analyzed. PI-scores, false positive recognition errors, and semantic organization scores on the California Verbal Learning Test-II (CVLT-II) were subjected to cluster analyses. Clusters were compared regarding buildup and release from PI, memory performance and strategy measures, measures of intelligence, EF, and processing speed. RESULTS: The analyses revealed six analyzable clusters. Two clusters showed no buildup of PI and normal release from PI. Discriminability was impaired both in List A and B. Learning acquisition and speeded measures of EF were reduced. One cluster showed both buildup of PI and problems with releasing from PI, and particularly impaired discriminability of List B. Semantic organization was low. Learning consolidation and EF speeded measures were impaired. Two other clusters showed buildup of PI, but no problem with release. Learning was highly organized, and they showed good memory and normal neuropsychological performance. CONCLUSIONS: Results shows differentiation between a low organized EF dysfunction pattern with no PI, a disorganized PI pattern also indicating EF dysfunction and a highly organized pattern where PI seems to be the price to pay for high effort put into the learning process.

When Does Episodic Memory Contribute to Performance in Tests of Working Memory?

Both the experimental and the psychometric investigation of the WM capacity limit depend critically on the assumption that performance in our tests of WM reflects that capacity limit to a good approximation. Most tasks to measure WM rely on testing memory after a short time during which participants are asked to maintain information in WM. In these tests, episodic long-term memory is likely to also lay down a trace of the memory set. Therefore, participants can draw on two sources of information when memory is tested, making it difficult to separate the contributions of WM and episodic LTM to the performance on immediate-memory tests. Here we use proactive interference to distinguish between these two sources of remembered information, building on the fact that episodic memory is vulnerable to proactive interference, whereas WM is protected against it. We use a release-from-PI paradigm to determine the extent to which commonly used WM tasks reflect contributions from episodic LTM. We focus on memory for serial order of verbal lists, but also include visual and spatial WM tasks. The results of five experiments demonstrate that although some tasks used to investigate WM are heavily contaminated by episodic LTM, other popular paradigms such as serial and probed recall, and the standard version of the continuous color-reproduction task, are not. Measuring proactive interference can help researchers determine the extent to which WM and episodic LTM contribute to performance in immediate-memory tasks.

Domain-Specific Cognitive Impairment Reflects Prefrontal Dysfunction in Aged Common Marmosets.

Age-related cognitive impairment is not expressed uniformly across cognitive domains. Cognitive functions that rely on brain areas that undergo substantial neuroanatomical changes with age often show age-related impairment, whereas those that rely on brain areas with minimal age-related change typically do not. The common marmoset has grown in popularity as a model for neuroscience research, but robust cognitive phenotyping, particularly as a function of age and across multiple cognitive domains, is lacking. This presents a major limitation for the development and evaluation of the marmoset as a model of cognitive aging and leaves open the question of whether they exhibit age-related cognitive impairment that is restricted to some cognitive domains, as in humans. In this study, we characterized stimulus-reward association learning and cognitive flexibility in young adults to geriatric marmosets using a Simple Discrimination task and a Serial Reversal task, respectively. We found that aged marmosets show transient impairment in learning-to-learn but have conserved ability to form stimulus-reward associations. Furthermore, aged marmosets have impaired cognitive flexibility driven by susceptibility to proactive interference. As these impairments are in domains critically dependent on the prefrontal cortex, our findings support prefrontal cortical dysfunction as a prominent feature of neurocognitive aging. This work positions the marmoset as a key model for understanding the neural underpinnings of cognitive aging.

Searching in the sand: Protracted video deficit in U.S. preschoolers' spatial recall using a continuous search space.

Young children exhibit a video deficit for spatial recall, learning less from on-screen than in-person demonstrations. Some theoretical accounts emphasize memory constraints (e.g., insufficient retrieval cues, competition between memory representations). Such accounts imply memory representations are graded, yet video deficit studies measuring spatial recall operationalize memory retrieval as dichotomous (success or failure). The current study tested a graded-representation account using a spatial recall task with a continuous search space (i.e., sandbox) rather than discrete locations. With this more sensitive task, a protracted video deficit for spatial recall was found in children 4-5 years old (n = 51). This may be due to weaker memory representations in the screen condition, evidenced by higher variability and greater perseverative bias. In general, perseverative bias decreased with repeated trials. The discussion considers how the results support a graded-representation account, potentially explaining why children might exhibit a video deficit in some tasks but not others. RESEARCH HIGHLIGHTS: The task used a continuous search space (sandbox), making it more difficult and sensitive than spatial recall tasks used in prior video deficit research. Spatial recall among 4- and 5-year-old children was more variable after watching hiding events on screen via live video feed than through a window. Children's spatial recall from screens was more susceptible to proactive interference, evidenced by more perseverative bias in an A-not-B design. The results demonstrate memory representations blend experiences that accumulate over time and explain why the video deficit may be protracted for more difficult tasks.

Genetic dissection of mutual interference between two consecutive learning tasks in Drosophila.

Animals can continuously learn different tasks to adapt to changing environments and, therefore, have strategies to effectively cope with inter-task interference, including both proactive interference (Pro-I) and retroactive interference (Retro-I). Many biological mechanisms are known to contribute to learning, memory, and forgetting for a single task, however, mechanisms involved only when learning sequential different tasks are relatively poorly understood. Here, we dissect the respective molecular mechanisms of Pro-I and Retro-I between two consecutive associative learning tasks in Drosophila. Pro-I is more sensitive to an inter-task interval (ITI) than Retro-I. They occur together at short ITI (<20 min), while only Retro-I remains significant at ITI beyond 20 min. Acutely overexpressing Corkscrew (CSW), an evolutionarily conserved protein tyrosine phosphatase SHP2, in mushroom body (MB) neurons reduces Pro-I, whereas acute knockdown of CSW exacerbates Pro-I. Such function of CSW is further found to rely on the γ subset of MB neurons and the downstream Raf/MAPK pathway. In contrast, manipulating CSW does not affect Retro-I as well as a single learning task. Interestingly, manipulation of Rac1, a molecule that regulates Retro-I, does not affect Pro-I. Thus, our findings suggest that learning different tasks consecutively triggers distinct molecular mechanisms to tune proactive and retroactive interference.

Effects of proactive interference on olfactory memory in dogs.

Proactive interference (PI) occurs when memories of past events or stimuli intrude in the present moment, causing working memory (WM) errors. These errors are often measured through WM tests such as matching-to-sample (MTS). When the repetition of individual stimuli increases, there is a greater chance of these intrusions, and thus there can be a decrease in accuracy in such tasks. In two experiments, we explored the nature of PI on dog working memory. First, we manipulated the size of the set of odors (2, 6, trial-unique) used to construct each session to maximize (2-odor set) and minimize (trial-unique) within-session proactive interference during an olfactory MTS task. Matching-to-sample accuracy decreased with greater PI. Second, we adapted procedures originally designed for pigeons and rhesus macaques to determine the locus of PI in dogs. To test for proactive interference, probe trials were inserted into MTS sessions where sample odors from earlier trials reappeared as incorrect comparisons. Incorrect responses on these probe trials indicated proactive interference. These probe tests were conducted with a 0-s or 20-s retention interval in separate sessions. We found that dogs performed worse on the matching task when the source of interference (odor stimulus) was from the immediately preceding trial compared with when they were from trials further back in the session but only for the 0-s retention interval. These results are compared with previous work examining the effects of proactive interference on working memory in other species.

Elementary math in elementary school: the effect of interference on learning the multiplication table.

Memorizing the multiplication table is a major challenge for elementary school students: there are many facts to memorize, and they are often similar to each other, which creates interference in memory. Here, we examined whether learning would improve if the degree of interference is reduced, and which memory processes are responsible for this improvement. In a series of 16 short training sessions over 4 weeks, first-grade children learned 16 multiplication facts-4 facts per week. In 2 weeks the facts were dissimilar from each other (low interference), and in 2 control weeks the facts were similar (high interference). Learning in the low-similarity, low-interference weeks was better than in the high-similarity weeks. Critically, this similarity effect originated in the specific learning context, i.e., the grouping of facts to weeks, and could not be explained as an intrinsic advantage of certain facts over others. Moreover, the interference arose from the similarity between facts in a given week, not from the similarity to previously learned facts. Similarity affected long-term memory-its effect persisted 7 weeks after training has ended; and it operated on long-term memory directly, not via the mediation of working memory. Pedagogically, the effectiveness of the low-interference training method, which is dramatically different from currently used pedagogical methods, may pave the way to enhancing how we teach the multiplication table in school.

Phase separation of competing memories along the human hippocampal theta rhythm.

Competition between overlapping memories is considered one of the major causes of forgetting, and it is still unknown how the human brain resolves such mnemonic conflict. In the present magnetoencephalography (MEG) study, we empirically tested a computational model that leverages an oscillating inhibition algorithm to minimise overlap between memories. We used a proactive interference task, where a reminder word could be associated with either a single image (non-competitive condition) or two competing images, and participants were asked to always recall the most recently learned word-image association. Time-resolved pattern classifiers were trained to detect the reactivated content of target and competitor memories from MEG sensor patterns, and the timing of these neural reactivations was analysed relative to the phase of the dominant hippocampal 3 Hz theta oscillation. In line with our pre-registered hypotheses, target and competitor reactivations locked to different phases of the hippocampal theta rhythm after several repeated recalls. Participants who behaviourally experienced lower levels of interference also showed larger phase separation between the two overlapping memories. The findings provide evidence that the temporal segregation of memories, orchestrated by slow oscillations, plays a functional role in resolving mnemonic competition by separating and prioritising relevant memories under conditions of high interference.

Meaningful stimuli inflate the role of proactive interference in visual working memory.

The use of meaningful daily objects in visual working memory (VWM) tasks revealed two uncharacteristic findings: enlarged memory capacity, and strong proactive interference (PI), which was previously believed to play only a modest role in VWM. To disassociate the roles of meaning and visual complexity in these effects, a set of stimuli composed of meaningful daily objects was compared to visually similar meaningless sets. These sets were included in a Repeated (PI-prone) condition in which stimuli were repeatedly drawn from a limited set of items, and in a Unique (PI-free) condition in which each stimulus appeared only once. In line with past findings, the results consistently showed superior memory for meaningful stimuli. Importantly, they also showed a stronger PI-effect for meaningful stimuli as the difference between the Repeated and Unique conditions was greatly reduced (Experiment 1) or eliminated (Experiment 2) for meaningless stimuli. Together, these results strongly imply that meaning, and not visual complexity, plays a key role not only in boosting memory capacity but also in inflating the role of PI in VWM.

Tracking Proactive Interference in Visual Memory.

The current contents of visual working memory can be disrupted by previously formed memories. This phenomenon is known as proactive interference, and it can be used to index the availability of old memories. However, there is uncertainty about the robustness and lifetime of proactive interference, which raises important questions about the role of temporal factors in forgetting. The present study assessed different factors that were expected to influence the persistence of proactive interference over an inter-trial interval in the visual recent probes task. In three experiments, participants encoded arrays of targets and then determined whether a single probe matched one of those targets. On some trials, the probe matched an item from the previous trial (a "recent negative"), whereas on other trials the probe matched a more distant item (a "non-recent negative"). Prior studies have found that recent negative probes can increase errors and slow response times in comparison to non-recent negative probes, and this offered a behavioral measure of proactive interference. In Experiment 1, factors of array size (the number of targets to be encoded) and inter-trial interval (300 ms vs. 8 s) were manipulated in the recent probes task. There was a reduction in proactive interference when a longer delay separated trials on one measure, but only when participants encoded two targets. When working memory capacity was strained by increasing the array size to four targets, proactive interference became stronger after the long delay. In Experiment 2, the inter-trial interval length was again manipulated, along with stimulus novelty (the number of stimuli used in the experiment). Proactive interference was modestly stronger when a smaller number of stimuli were used throughout the experiment, but proactive interference was minimally affected by the inter-trial interval. These findings are problematic for temporal models of forgetting, but Experiment 3 showed that proactive interference also resisted disruption produced by a secondary task presented within the inter-trial interval. Proactive interference was constantly present and generally resilient to the different manipulations. The combined data suggest a relatively durable, passive representation that can disrupt current working memory under a variety of different circumstances.

Is Splitting Related to Resistance to Proactive Interference? A Process-Oriented Study of Kernberg's Conceptualization of Splitting.

INTRODUCTION: Splitting, as a defense mechanism in Kernberg's theory, plays a significant role in the development and maintenance of polarized and oscillating representations of self/other characteristics of borderline personality disorder (BPD). Although the notion of splitting can be considered from a structural and a functional point of view, almost all empirical studies to date have focused on the former elements to the detriment of related cognitive processes. METHODS: To further investigate the cognitive processes related to splitting, 60 participants were administered the Splitting Index and indexes of resistance to proactive interference (PI) using the interpersonal recent negative task with words that reflect negative or positive interactions compared to neutral words. RESULTS: The use of splitting was uniquely and significantly predicted by a higher capacity to resist PI and a lower capacity to consistently maintain this resistance when presented with negative words, above and beyond BPD traits, primitive defenses, and the presentation of neutral words. Results showed no evidence of a relationship between splitting and resistance to PI with positive words. CONCLUSION: Results appear compatible with Kernberg's conceptualization of splitting as an active defense process that relates to an unstable capacity to inhibit negative representations of the object from entering working memory.

The association between control of interference and white-matter integrity: A cross-sectional and longitudinal investigation.

Proactive interference (PI) occurs when old information interferes with newly acquired information and has been suggested as a major cause of forgetting in working memory. In this study, we investigate cross-sectional (N = 267) and longitudinal (N = 148) associations between PI and white-matter integrity (WMI) using diffusion-weighted imaging in an adult life-span sample (25-80 years; Mage = 60.15; 138 female). Older age was related to higher PI and lower WMI. Cross-sectional analyses showed associations between PI and WMI spanning several white-matter tracts as well as globally, suggesting that the age-related decline in PI may be driven primarily by global changes in WMI. Furthermore, longitudinal changes in PI were shown to be negatively correlated with concurrent changes in WMI in the fornix. Mediation analyses showed that WMI mediated the relationship between age and PI only in older adults, indicating that WMI becomes increasingly connected to cognitive functioning with increasing age. This is the first demonstration of WMI decline contributing to the age-related decline in PI.

Automatic and effortful control of interference in working memory can be distinguished by unique behavioral and functional brain representations.

Goal-irrelevant information in working memory (WM) may enter the focus of attention (FOA) during a task and cause proactive interference (PI). In the current study we used fMRI to test several hypotheses concerning the boundary conditions of PI in WM using a modified verbal 2-back task. Temporal distance between item and lure presentation was manipulated to evaluate potential differences among hypothesized states of FOA, short-term memory and long-term memory. PI was present for the most proximal 3-back lures but dissipated with lure distance along with increased activation in brain regions critical for memory recollection, such as right prefrontal cortex, parietal cortex, and hippocampus. Reduced PI and less IFG activation were also observed after repeated item presentation, supporting the notion that a rehearsed encoding of item-context information reduces the need for interference control. Moreover, a trial-by-trial approach revealed activity in ACC, insula, IFG, and parietal cortex with increasing lure trial interference regardless of distance. The current results are first evidence for an observable transition of cognitive control, to include MTL regions involved in recalling task-relevant information from outside the FOA when resolving PI in WM.

Does testing enhance new learning because it insulates against proactive interference?

Taking a test on previously learned material can enhance new learning. One explanation for this forward testing effect is that retrieval inoculates learners from proactive interference (PI). Although this release-from-PI account has received considerable empirical support, most extant evidence is correlational rather than causal. We tested this account by manipulating the level of PI that participants experience as they studied several lists while receiving interpolated tests or not. In Experiments 1 and 2, we found that testing benefited new learning similarly regardless of PI level. These results contradict those from Nunes and Weinstein (Memory, 20(2), 138-154, 2012), who found no forward testing effect when encoding conditions minimized PI. In Experiments 3 and 4, we failed to replicate their results. Together, our data indicate that reduced PI might be a byproduct, rather than a causal factor, of the forward testing effect.

Magnitude and sources of proactive interference in visual memory.

Proactive interference - the disruptive effect of old memories on new learning - is a long-established forgetting mechanism, yet there are doubts about its impact on visual working memory and uncertainty about the kinds of information that cause proactive interference. The present study aimed to assess these issues in three experiments using a modified recent probes task. Participants encoded four target images on each trial and determined whether a probe matched one of those targets. In Experiment 1, probes matching targets from trial N-1 or N-3 damaged responding in relation to a novel probe. Proactive interference was also produced by probes differing in state to a previously experienced target. This was further assessed in Experiments 2 and 3. Here, probes differing in colour to a previous target, or matching the general target category only, produced little proactive interference. Conversely, probes directly matching a prior target, or differing in state information, hindered task performance. This study found robust proactive interference in visual working memory that could endure over multiple trials, but it was also produced by stimuli closely resembling an old target. This challenges the notion that proactive interference is produced by an exact representation of a previously encoded image.

Memory and Proactive Interference for spatially distributed items.

Our ability to briefly retain information is often limited. Proactive Interference (PI) might contribute to these limitations (e.g., when items in recognition tests are difficult to reject after having appeared recently). In visual Working Memory (WM), spatial information might protect WM against PI, especially if encoding items together with their spatial locations makes item-location combinations less confusable than simple items without a spatial component. Here, I ask (1) if PI is observed for spatially distributed items, (2) if it arises among simple items or among item-location combinations, and (3) if spatial information affects PI at all. I show that, contrary to views that spatial information protects against PI, PI is reliably observed for spatially distributed items except when it is weak. PI mostly reflects items that appear recently or frequently as memory items, while occurrences as test items play a smaller role, presumably because their temporal context is easier to encode. Through mathematical modeling, I then show that interference occurs among simple items rather than item-location combinations. Finally, to understand the effects of spatial information, I separate the effects of (a) the presence and (b) the predictiveness of spatial information on memory and its susceptibility to PI. Memory is impaired when items are spatially distributed, but, depending on the analysis, unaffected by the predictiveness of spatial information. In contrast, the susceptibility to PI is unaffected by either manipulation. Visual memory is thus impaired by PI for spatially distributed items due to interference from recent memory items (rather than test items or item-location combinations).