Differential Recruitment of Inhibitory Control Processes by Directed Forgetting and Thought Substitution.

Humans have the ability to intentionally forget information via different strategies, included suppression of encoding (directed forgetting) and mental replacement of the item to encode (thought substitution). These strategies may rely on different neural mechanisms; namely, encoding suppression may induce prefrontally mediated inhibition, whereas thought substitution is potentially accomplished through modulating contextual representations. Yet, few studies have directly related inhibitory processing to encoding suppression, or tested its involvement in thought substitution. Here, we directly tested whether encoding suppression recruits inhibitory mechanisms with a cross-task design, relating the behavioral and neural data from male and female participants in a Stop Signal task (a task specifically testing inhibitory processing) to a directed forgetting task with both encoding suppression (Forget) and thought substitution (Imagine) cues. Behaviorally, Stop Signal task performance (stop signal reaction times) was related to the magnitude of encoding suppression, but not thought substitution. Two complementary neural analyses corroborated the behavioral result. Namely, brain-behavior analysis demonstrated that the magnitude of right-frontal beta activity following stop signals was related to stop signal reaction times and successful encoding suppression, but not thought substitution; and classifiers trained to discriminate successful and unsuccessful stopping in the Stop Signal task could also classify successful and unsuccessful forgetting following Forget cues, but not Imagine cues. Importantly, inhibitory neural mechanisms were engaged following Forget cues at a later time than motor stopping. These findings not only support an inhibitory account of directed forgetting, and that thought substitution engages separate mechanisms, but also potentially identify a specific time in which inhibition occurs when suppressing encoding.SIGNIFICANCE STATEMENT Forgetting often seems like an unintended experience, but forgetting can be intentional, and can be accomplished with multiple strategies. These strategies, including encoding suppression and thought substitution, may rely on different neural mechanisms. Here, we test the hypothesis that encoding suppression engages domain-general prefrontally driven inhibitory control mechanisms, while thought substitution does not. Using cross-task analyses, we provide evidence that encoding suppression engages the same inhibitory mechanisms used for stopping motor actions, but these mechanisms are not engaged by thought substitution. These findings not only support the notion that mnemonic encoding processes can be directly inhibited, but also have broad relevance, as certain populations with disrupted inhibitory processing may be more successful accomplishing intentional forgetting through thought substitution strategies.

The role of prior familiarisation and meaningfulness of verbal and visual stimuli on directed forgetting.

ABSTRACTIntentional forgetting of unwanted information is a crucial cognitive function that is often studied with directed forgetting (DF) procedure, whereby cuing some study materials with Forget (F) instruction impairs their memory compared to cuing with Remember (R) instruction. This study investigates how the nature of information (verbal or pictorial), its semantic significance (meaningful or meaningless), and the degree of prior episodic familiarity influence DF. Before the DF phase, stimuli were familiarised by pre-exposing them 0, 2, or 6 times in a prior preview phase. Finally, memory for all items was assessed with old/new recognition test. Experiment 1 employed words, Experiment 2 utilised fractal images, Experiment 3 featured both meaningful and meaningless object images, and Experiment 4 used words and nonwords. Our results indicate that materials that produced better memory performance are not always harder to intentionally forget. Previewed items showed reduced DF compared to non-previewed items regardless of the nature of information, and meaningless stimuli are challenging to intentionally forget regardless of their degrees of familiarisation unless they are meaningless verbal materials. Collectively, the results highlight the importance of joint consideration of the stimulus format, its meaningfulness, and its episodic familiarity in understanding conditions that interact with intentional forgetting.

Mnemonic discrimination deficits in multidimensional schizotypy.

Current developmental psychopathology models indicate that schizophrenia can be understood as the most extreme expression of a multidimensional continuum of symptoms and impairment referred to as schizotypy. In nondisordered adults, schizotypy predicts risk for developing schizophrenia-spectrum psychopathology. Schizophrenia is associated with disruptions in detecting subtle differences between objects, which is linked to hippocampal dysfunction. These disruptions have been shown in the Mnemonic Similarity Task (MST) when patients are less likely to reject lures that are similar but not identical to studied objects, and instead mistake them for studied items. This pattern of errors may be a behavioral manifestation of impaired pattern separation, a key episodic memory ability associated with hippocampal integrity and overreliance on pattern completion. We examined whether multidimensional schizotypy is associated with such deficits in nondisordered young adults. Participants (n = 230) were assessed for positive, negative, and disorganized schizotypy and completed the MST and a perceptual discrimination task. MST performance showed that a combination of elevated negative and disorganized schizotypy was associated with decreased rejections of similar lures because they were mistakenly identified as studied items. These deficits were not observed in traditional recognition measures within the same task, nor in perceptual discrimination, suggesting that mnemonic discrimination deficits assessed by MST were selective and did not reflect generalized deficits. These findings extend the results obtained in schizophrenia patients and support a multidimensional model of schizophrenia-spectrum psychopathology.

Separation of item and context in item-method directed forgetting.

Contextual information plays a critical role in directed forgetting (DF) of lists of items, whereas DF of individual items has been primarily associated with item-level processing. This study was designed to investigate whether context processing also contributes to the forgetting of individual items. Participants first viewed a series of words, with task-irrelevant scene images (used as "context tags") interspersed between them. Later, these words reappeared without the scenes and were followed by an instruction to remember or forget that word. Multivariate pattern analyses of fMRI data revealed that the reactivation of context information associated with the studied words (i.e., scene-related activity) was greater whereas the item-related information diminished after a forget instruction compared to a remember instruction. Critically, we found the magnitude of the separation between item information and context information predicted successful forgetting. These results suggest that the unbinding of an item from its context may support the intention to forget, and more generally they establish that contextual processing indeed contributes to item-method DF.

List-strength effects in older adults in recognition and free recall.

The present investigation provides a novel extension of the retrieving effectively from memory (REM) model to examine free-recall and recognition memory in older adults to inform our understanding of age-related cognitive decline. When some items on a list are strengthened through distributed repetitions, memory for the nonstrengthened items on that list may become impaired depending on how memory is tested-a phenomenon known as the list-strength effect (LSE; e.g., Tulving & Hastie, Journal of Experimental Psychology, 92, 297-304, 1972). When the strengthening operation involves distributed repetitions, LSE is robust in free recall, but it is reliably absent in recognition (Malmberg & Shiffrin, Journal of Experimental Psychology, 31, 322-336, 2005; Ratcliff, Clark, & Shiffrin, Journal of Experimental Psychology, 16, 163-178, 1990). Two experiments investigated LSE in recall and recognition in older adults and young adults who encoded items with full or divided attention. Despite showing impaired recall and recognition, older adults showed patterns of LSEs across both experiments that were similar to young adults with full attention rather than young adults with divided attention. In recognition, there was a null LSE in older and young adults, but a positive LSE was observed under divided attention. In contrast, in free recall, there was a positive LSE in older and young adults, but a null LSE under divided attention. Collectively, the results suggest that older adults do not have impaired encoding of context information (evidenced by intact LSE in recall), and they do not have impaired differentiation of item representations (evidenced by the null LSE in recognition). Age-related impairment in both memory tasks can be accounted for by sparse encoding of item-based information.

Repeated failures to obtain selective directed forgetting in lab and online samples and variations in stimuli.

Previous research has produced mixed findings as to whether it is possible to selectively forget a subset of items while maintaining access to the remaining items from the same episode, using a modified version of the list-method directed forgetting (LMDF) paradigm. The present study includes six attempts to obtain the selective directed forgetting (SDF) effect with the aim of exploring its underlying mechanisms. However, despite variations in the stimuli and samples, which included both lab and online participants, we failed to obtain SDF across five experiments. In one of the experiments, we observed what appeared to be an SDF effect; however, the unexpected baseline differences across the conditions make the interpretation of this result equivocal. In contrast, standard directed forgetting effect was obtained when an LMDF condition was included in the design. An evaluation of the previous literature in combination with the present study raises questions about the reliability of the SDF phenomenon.

Trial-level fluctuations in pupil dilation at encoding reflect strength of relational binding.

Eye-tracking methodologies have revealed that eye movements and pupil dilations are influenced by our previous experiences. Dynamic fluctuations in pupil size during learning reflect in part the formation of memories for learned information, while viewing behavior during memory testing is influenced by memory retrieval and drawn to previously learned associations. However, no study to date has linked fluctuations in pupil dilation at encoding to the magnitude of viewing behavior at test. The current investigation involved monitoring eye movements both in single item recognition and relational recognition tasks. In the item task, all faces were presented with the same background scene and memory for faces was subsequently tested, whereas in the relational task each face was presented with its own unique background scene and memory for the face-scene association was subsequently tested. Pupil size changes during encoding predicted the magnitude of preferential viewing during test, as well as future recognition accuracy. These effects emerged only in the relational task, but not in the item task, and were replicated in an additional experiment in which stimulus luminance was more tightly controlled. A follow-up experiment and additional analyses ruled out differences in orienting instructions or number of fixations to the encoding display as explanations of the observed effects. The results shed light on the links between pupil dilation, memory encoding, and eye movement patterns during recognition and suggest that trial-level fluctuations in pupil dilation during encoding reflect relational binding of items to their context rather than general memory formation or strength. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Trait schizotypy and the psychosis prodrome: Current standard assessment of extended psychosis spectrum phenotypes.

Schizotypy has become an increasingly important construct for elaborating psychotic disorders that vary along the schizophrenic spectrum. However, different schizotypy inventories vary in conceptual approach and measurement. In addition, commonly used schizotypy scales have been seen as qualitatively different from screening instruments for prodromal schizophrenia like the Prodromal Questionnaire-16 (PQ-16). Our study investigated the psychometric properties of three schizotypy questionnaires (the Schizotypal Personality Questionnaire-Brief, Oxford-Liverpool Inventory of Feelings and Experiences, and the Multidimensional Schizotypy Scale) as well as the PQ-16 in a cohort of 383 non-clinical subjects. We initially evaluated their factor structure using Principal Component Analysis (PCA) and used Confirmatory Factor Analysis (CFA) to test a newly proposed composition of factors. PCA results support a three-factor structure of schizotypy that accounts for 71 % of the total variance, but also shows cross-loadings of some schizotypy subscales. CFA of the newly composed schizotypy factors (together with an added neuroticism factor) shows good fit. Analyses including the PQ-16 indicate considerable overlap with measures of trait schizotypy, suggesting that the PQ-16 might not be quantitatively or qualitatively different from schizotypy measurements. Taken together, results indicate that there is good support for a three-factor structure of schizotypy but also that different schizotypy measurements grasp facets of schizotypy differently. This points towards the need for an integrative approach for assessing the construct of schizotypy.

Context change and retrieval difficulty in the list-before-last paradigm.

Using the "list-before-last" paradigm (Jang & Huber, Journal of Experimental Psychology: Learning, Memory, and Cognition, 34, 112-127, 2008; Shiffrin, Science, 168, 1601-1603, 1970), we examined whether the difficulty involved in retrieving a previously studied list affects the recall of the current list. Participants studied three lists (L1, L2, and L3), and between L2 and L3 study they either engaged in retrieval of L1 or solved math problems for the same duration of time. After L3 encoding, all participants recalled L2. We examined accurate recall of L2, intrusions from L3, and also the first-response function from L2 across all four experiments. In Experiments 1 and 2, retrieval difficulty was manipulated by presenting participants with variable numbers of letter cues for the L1 words, with some participants receiving more cues than others. In Experiment 1, L1 and L2 words shared the first two letters in common to create potential item interference, whereas in Experiment 2, they did not share common cues. In Experiments 3 and 4, we manipulated retrieval difficulty using a delay manipulation-L1 was encoded 1, 24, or 72 h prior to the session during which L2 and L3 were encoded. In Experiment 3, L1 retrieval involved a cued recall test, whereas in Experiment 4, it involved a free recall test. The results of all of these experiments showed that, as compared to solving math problems, retrieving L1 led to forgetting of L2, reduced intrusions from L3, and reduced first-response functions from L2. However, all of the dependent measures were invariant across the various manipulations of retrieval difficulty. We discuss the results in terms of the context-change interpretation of prior-list retrieval.

Can intentional forgetting reduce the cross-race effect in memory?

Across three studies, we utilized an item-method directed forgetting (DF) procedure with faces of different races to investigate the magnitude of intentional forgetting of own-race versus other-race faces. All three experiments shared the same procedure but differed in the number of faces presented. Participants were presented with own-race and other-race faces, each followed by a remember or forget memory instruction, and subsequently received a recognition test for all studied faces. We obtained a robust cross-race effect (CRE) but did not find a DF effect in Experiment 1. Experiments 2 and 3 used shorter study and test lists and obtained a significant DF effect along with significant CRE, but no interaction between face type and memory instruction. The results suggest that own-race and other-race faces are equally susceptible to DF. The results are discussed in terms of the theoretical explanations for CRE and their implications for DF.

Directed forgetting in associative memory: Dissociating item and associative impairment.

We report three item-method directed forgetting (DF) studies to evaluate whether DF impairs primarily item memory, or whether it also impairs associative memory. The current studies used a modified associative recognition paradigm that allowed disentangling item impairment from associative impairment in DF. Participants studied scene-object pairings, followed by DF cues (item-method), and at test were presented with a previously studied scene along with three objects, one of which was studied with that scene (target), whereas the remaining two objects were studied with different scenes (lures). Experiment 1 used an associative encoding orienting task, and DF impairment was observed only when the forget targets were paired with forget lures within the test display; however, DF was eliminated when the forget targets were paired with remember lures, possibly due to a recall-to-reject strategy. Experiment 2 used an object-focused orienting task that downplayed the encoding of associative information. The results revealed the opposite of Experiment 1, with significant DF when the forget targets were paired with remember lures, and no DF when the lures and the target came from the same memory instruction. Experiment 3 used the same orienting task as Experiment 1, but testing used a sequential procedure, where item recognition was assessed first, followed by associative recognition test. Conditionalizing associative recognition on item recognition outcomes confirmed that DF impairment of associative memory can be obtained despite retained memory for forget-cued objects. Overall, the results provide strong support for the impairment of associative memory by DF. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

The role of forget-cue salience in list-method directed forgetting.

Research suggests that manipulating the wording of the forget cue in list-method directed forgetting affects the magnitude of directed forgetting both in younger children (Aslan, Staudigl, Samenieh, & Bauml, in press) and in older adults (Sahakyan, Delaney, & Goodmon, 2008). This occurs when the forget cue overemphasises the importance of forgetting in the current context. The present experiment investigated whether de-emphasising forgetting affected the magnitude of list-method directed forgetting in college adults. Some participants received overt forget cues that explicitly instructed them to forget earlier studied items, whereas others received covert forget cues that implied forgetting by emphasising selective remembering (e.g., "you will only need to remember some of the items"). Results indicated equivalent directed forgetting for both types of cues. However, regardless of the type of cue received, participants who reported using specific forgetting strategies in response to the forget cue showed directed forgetting, whereas those that reported doing nothing did not show any effects. The results underscore that successful directed forgetting requires engagement of controlled processes.

Separable neural mechanisms support intentional forgetting and thought substitution.

Psychological and neuroscientific experiments have established that people can intentionally forget information via different strategies: direct suppression and thought substitution. However, few studies have directly compared the effectiveness of these strategies in forgetting specific items, and it remains an open question if the neural mechanisms supporting these strategies differ. Here, we developed a novel item-method directed forgetting paradigm with Remember, Forget, and Imagine cues, and recorded EEG to directly compare these strategies. Behaviorally, Forget and Imagine cues produced similar forgetting compared to Remember cues, but through separable neural processes; Forget cues elicited frontal oscillatory power changes that were predictive of future forgetting, whereas item-cue representational similarity was predictive of later accuracy for Imagine cues. These results suggest that both strategies can lead to intentional forgetting, but directed forgetting may rely on frontally-mediated suppression, while thought substitution may lead to contextual shifting, impairing successful retrieval.

Anterior vs Posterior Hippocampal Subfields in an Extended Psychosis Phenotype of Multidimensional Schizotypy in a Nonclinical Sample.

Numerous studies have implicated involvement of the hippocampus in the etiology and expression of schizophrenia-spectrum psychopathology, and reduced hippocampal volume is one of the most robust brain abnormalities reported in schizophrenia. Recent studies indicate that early stages of schizophrenia are specifically characterized by reductions in anterior hippocampal volume; however, studies have not examined hippocampal volume reductions in subclinical schizotypy. The present study was the first to examine the associations of positive, negative, and disorganized schizotypy dimensions with hippocampal subfield volumes in a large sample (n = 195) of nonclinically ascertained young adults, phenotyped using the Multidimensional Schizotypy Scale (MSS). Hippocampal subfields were analyzed from high-resolution 3 Tesla structural magnetic resonance imaging scans testing anatomical models, including anterior vs posterior regions and the cornu ammonis (CA), dentate gyrus (DG), and subiculum subfields separately for the left and right hemispheres. We demonstrate differential spatial effects across anterior vs posterior hippocampus segments across different dimensions of the schizotypy risk phenotype. The interaction of negative and disorganized schizotypy robustly predicted left hemisphere volumetric reductions for the anterior and total hippocampus, and anterior CA and DG, and the largest reductions were seen in participants high in negative and disorganized schizotypy. These findings extend previous early psychosis studies and together with behavioral studies of hippocampal-related memory impairments provide the basis for a dimensional neurobiological hippocampal model of schizophrenia risk. Subtle hippocampal subfield volume reductions may be prevalent prior to the onset of detectable prodromal clinical symptoms of psychosis and play a role in the etiology and development of such conditions.

Remembering to forget: the amnesic effect of daydreaming.

Daydreaming mentally transports people to another place or time. Many daydreams are similar in content to the thoughts that people generate when they intentionally try to forget. Thus, thoughts like those generated during daydreaming can cause forgetting of previously encoded events. We conducted two experiments to test the hypothesis that daydreams that are more different from the current moment (e.g., in distance, time, or circumstance) will result in more forgetting than daydreams that are less different from the current moment, because they result in a greater contextual shift. Daydreaming was simulated in the laboratory via instructions to engage in a diversionary thought. Participants learned a list of words, were asked to think about autobiographical memories, and then learned a second list of words. They tended to forget more words from the first list when they thought about their parents' home than when they thought about their current home (Experiment 1). They also tended to forget more when they thought about an international vacation than when they thought about a domestic vacation (Experiment 2). These results support a context-change account of the amnesic effects of daydreaming.

Differential impairment of positive and negative schizotypy in list-method and item-method directed forgetting.

Schizophrenia is characterized by cognitive impairment and this impairment is expected to occur, albeit to a lesser degree, in people putatively at risk for schizophrenia. Two experiments assessed the relationship between directed forgetting (DF) and schizotypy, which is a multidimensional construct that reflects the expression of the underlying vulnerability for schizophrenia. Experiment 1 involved item-method DF and Experiment 2 involves list-method DF study. The schizotypy dimensions exhibited differential patterns of impairment across the 2 methods that suggest different underlying processes. Positive schizotypy showed impairment in item-method DF that was driven by reduced ability to forget forget-cued items, whereas performance on remember-cued items was unaffected in positive schizotypy. Despite the deficit in item-method DF, positive schizotypy participants showed preserved performance in list-method DF. The opposite pattern was found in negative schizotypy participants, who showed impairment in list-method DF, despite preserved performance in item-method DF. Negative schizotypy was previously associated with deficits in context processing and, consistent with context-change account of list-method DF, showed deficits in list-method DF task. Positive schizotypy is characterized by deficits in inhibitory control and, consistent with inhibitory account of item-method DF, showed deficits in item-method DF task. Collectively, these results (a) suggest that different DF methods involve different underlying mechanisms, (b) support the context-account of list-method DF and an inhibitory account of item-method DF, and (c) support the multidimensional model of schizotypy by showing differential impairment in positive and negative schizotypy across the 2 DF tasks. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Eye movement analyses of strong and weak memories and goal-driven forgetting.

Research indicates that eye movements can reveal expressions of memory for previously studied relationships. Specifically, eye movements are disproportionately drawn to test items that were originally studied with the test scene, compared to other equally familiar items in the test display - an effect known as preferential viewing (e.g., Hannula, Ryan, Tranel, & Cohen, 2007). Across four studies we assessed how strength-based differences in memory are reflected in preferential viewing. Participants studied objects superimposed on background scenes and were tested with three-object displays superimposed on the scenes viewed previously. Eye movements were monitored at test. In Experiment 1 we employed an item-method directed forgetting (DF) procedure to manipulate memory strength. In Experiment 2, viewing patterns were examined across differences in memory strength assessed through subjective confidence ratings. In Experiment 3, we used spaced repetitions to objectively strengthen items, and Experiment 4 involved a list-method DF manipulation. Across all experiments, eye movements consistently differentiated the effect of DF from other strength-based differences in memory, producing different viewing patterns. They also differentiated between incidental and successful intentional forgetting. Finally, despite a null effect in recognition accuracy in list-method DF, viewing patterns revealed both common as well as critical differences between list-method DF and item-method DF. We discuss the eye movement findings from the perspective of theoretical accounts of DF and other strength-based differences in memory.

Hits and false alarms in recognition memory show differential impairment in positive and negative schizotypy.

The present study examined the extent to which positive and negative schizotypy are associated with impairment in recognition memory in 3 large samples of nonclinically ascertained adults (total n = 826). Schizophrenia is associated with a wide array of cognitive deficits, but the study of cognitive impairment in schizophrenia is confounded by generalized performance deficits related to symptoms and consequences of the disorder, and by failure to separately examine positive and negative symptom dimensions. Schizotypy provides a promising framework for examining these deficits relatively unconfounded by symptoms and sequelae of the disorder. The present study obtained recognition memory deficits in positive and negative schizotypy across verbal and figural stimuli in three different samples. Importantly, although discrimination accuracy is impaired across higher scores on both schizotypy dimensions, the mechanism of impairment differs across positive and negative schizotypy. Negative, but not positive, schizotypy was associated with impaired hit rates, whereas the false alarm rates remained unaffected. In contrast, positive, but not negative, schizotypy was associated with increased false alarm rates despite stable hit rates. The results are discussed from the perspective of a signal-detection theoretic model that accounts for negative schizotypy results through reduced signal mechanism, and accounts for positive schizotypy results through increased noise mechanism. These findings further support the utility of multidimensional schizotypy for assessing and understanding episodic memory impairment in the schizophrenia spectrum. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Examination of relational memory in multidimensional schizotypy.

We report the first study to examine the association of positive, negative, and disorganized schizotypy with relational memory. Relational memory refers to memory for relations among multiple elements of an experience, and this form of episodic memory is different from memory for individual elements themselves. Using a cornerstone task from the neurocognitive literature that is designed specifically to assess relational memory, we found that negative schizotypy, but not positive or disorganized schizotypy, is associated with impaired relational memory performance. The deficit was observed both in poorer accuracy and slower response time. The results demonstrate the importance of examining schizotypy as a multidimensional construct, and indicate that using a total schizotypy score both obscures the nature of the association with various dimensions of schizotypy and also explains only half of the variance accounted for by taking into consideration the multidimensionality of schizotypy. These results add to previous findings that negative schizotypy is associated with a wide array of episodic memory deficits linked to impairment in retrieval and processing of contextual information.

Oh, honey, I already forgot that: strategic control of directed forgetting in older and younger adults.

Two experiments investigated list-method directed forgetting with older and younger adults. Using standard directed forgetting instructions, significant forgetting was obtained with younger but not older adults. However, in Experiment 1 older adults showed forgetting with an experimenter-provided strategy that induced a mental context change--specifically, engaging in diversionary thought. Experiment 2 showed that age-related differences in directed forgetting occurred because older adults were less likely than younger adults to initiate a strategy to attempt to forget. When the instructions were revised to downplay their concerns about memory, older adults engaged in effective forgetting strategies and showed significant directed forgetting comparable in magnitude to younger adults. The results highlight the importance of strategic processes in directed forgetting.