Directed forgetting in schizophrenia: prefrontal memory and inhibition deficits

Developmental trajectories and brain correlates of directed forgetting in 22q11.2 deletion syndrome

22q11.2 deletion syndrome (22q11DS), also known as velo-cardio-facial syndrome (VCFS) is the most common copy number variant (CNV) in humans caused by a microdeletion on chromosome 22q11.2. The phenotype encompasses heart anomalies, cleft palate and cognitive difficulties. Alongside brain differences in VCFS, such as reduced hippocampal volume, different cognitive developmental trajectories can be observed. The aim of this study was to explore the developmental trajectories of cognitive inhibition in memory using longitudinal data acquired in a large cohort of individuals with 22q11DS and the brain correlates to those developmental changes. 51 participants with 22q11DS (mean age: 13.75 ± 4.26, mean IQ score: 70.50 ± 10.75) and 43 typically developing individuals matched for age (M = 13.50 ± 4.91) and gender were recruited. To explore inhibition in memory, the Directed Forgetting paradigm was used. 30 words were presented, half were 'To be remembered items'(TBR) and the other half 'To be forgotten items' (TBF). To measure source memory, participants were asked during the recognition stage to say if the world was a TBR or a TBF item. Participants were tested during two consecutive visits, with a mean interval of 3 years. T1-weighted images were acquired using a 1.5 T Philips or a 3 T Siemens scanner at both visits. Both groups recognized more TBR than TBF items (Directed forgetting effect), however, participants with 22q11DS recognized fewer TBR items and did not show an increased recognition of TBR items with age. Furthermore, in participants with VCFS increased source memory errors with age was associated with a decline in hippocampal volume.

Effects of prepulse format and lead interval on the assessment of automatic and attention-modulated prepulse inhibition

Prepulse inhibition (PPI) of the acoustic startle response can index automatic and attention-modulated aspects of sensorimotor gating. Automatic sensorimotor gating is typically assessed by a no-task PPI protocol in which participants are presented with discrete white noise prepulse and startle stimuli over continuous background broadband noise at brief short-lead intervals (e.g., 60-120 ms). In contrast, attention-modulated sensorimotor gating is typically assessed through a task-based PPI protocol using continuous format pure tone prepulses and white noise startle stimuli presented over an ambient background at a lead interval of 120 ms. The present study sought to test the extent that the assessment of attention-modulated PPI is dependent on prepulse type and lead interval across two experiments. Experiment 1 assessed attention effects on PPI produced by discrete prepulses at lead intervals of 60 and 120 ms. Experiment 2 examined attention effects on PPI with matched stimulus conditions apart from continuous prepulses. Results indicated that the use of discrete prepulses failed to elicit attentional-modulation of PPI and that assessment therein was dependent on the use of continuous prepulses at a lead interval of 120 ms. These results highlight additional methods to concurrently assess automatic and attention-modulated PPI in a single testing session using a task-based tone counting task.

Forgetting Unwanted Memories: Active Forgetting and Implications for the Development of Psychological Disorders

Intrusive memories are a common feature of many psychopathologies, and suppression-induced forgetting of unwanted memories appears as a critical ability to preserve mental health. In recent years, biological and cognitive studies converged in revealing that forgetting is due to active processes. Recent neurobiological studies provide evidence on the active role of main neurotransmitter systems in forgetting, suggesting that the brain actively works to suppress retrieval of unwanted memories. On the cognitive side, there is evidence that voluntary and involuntary processes (here termed "intentional" and "incidental" forgetting, respectively) contribute to active forgetting. In intentional forgetting, an inhibitory control mechanism suppresses awareness of unwanted memories at encoding or retrieval. In incidental forgetting, retrieval practice of some memories involuntarily suppresses the retrieval of other related memories. In this review we describe recent findings on deficits in active forgetting observed in psychopathologies, like post-traumatic stress disorder, depression, schizophrenia, and obsessive-compulsive disorder. Moreover, we report studies in which the role of neurotransmitter systems, known to be involved in the pathogenesis of mental disorders, has been investigated in active forgetting paradigms. The possibility that biological and cognitive mechanisms of active forgetting could be considered as hallmarks of the early onset of psychopathologies is also discussed.

What can directed forgetting tell us about clinical populations?

This paper reviews and critically assesses the implications of directed forgetting (DF) research on clinical populations. We begin by reviewing the typical methods and results of the item method and list method directed forgetting procedures and provide best practice recommendations for future studies using clinical populations. Next, we note that DF was often interpreted as being due to inhibition, and when clinical populations showed impaired directed forgetting, it was treated as evidence in inhibitory control difficulties. However, inhibition may not be the cause of DF effects, based on current understanding of these cognitive tasks. We instead suggest that item method DF is tied to attentional control, which might include inhibitory mechanisms (or might not). In contrast, list method DF is tied to two forms of memory control: control of mental context (indicated by effective forgetting of List 1), and changes in the strategies used to remember (indicated by better learning of List 2). We review the current state of the clinical DF literature, assess its strength based on our best practice recommendations, and call for more research when warranted.

Memory and cognition in schizophrenia

Episodic memory deficits are consistently documented as a core aspect of cognitive dysfunction in schizophrenia patients, present from the onset of the illness and strongly associated with functional disability. Over the past decade, research using approaches from experimental cognitive neuroscience revealed disproportionate episodic memory impairments in schizophrenia (Sz) under high cognitive demand relational encoding conditions and relatively unimpaired performance under item-specific encoding conditions. These specific deficits in component processes of episodic memory reflect impaired activation and connectivity within specific elements of frontal-medial temporal lobe circuits, with a central role for the dorsolateral prefrontal cortex (DLPFC), relatively intact function of ventrolateral prefrontal cortex and variable results in the hippocampus. We propose that memory deficits can be understood within the broader context of cognitive deficits in Sz, where impaired DLPFC-related cognitive control has a broad impact across multiple cognitive domains. The therapeutic implications of these findings are discussed.

Many ways to forget - Neurophysiology of directed forgetting mechanisms in schizophrenia

Numerous studies have shown dysfunctional mechanism of interaction between bottom-up emotional and top-down cognitive processes in persons with schizophrenia (SCZ). During the emotional directed forgetting (DF) paradigm participants have to apply volitional mechanisms to resist automatic emotional enhancement of the memory. Here we sought to compare mechanisms underlying emotional DF in SCZ and in healthy persons (HC). Eighteen SCZ and eighteen HC completed a DF paradigm with neutral and negative pictures. EEG was recorded during study and test phase of the task. We analyzed both the behavioral outcomes and event-related potential components, indicating emotional enhancement of memory (Late Positive Potential elicited by pictures) and DF strategies (N2/P3 elicited by forget/remember cues during study-phase; "old/new" and "reversed old/new" effects during test-phase of the task). Directed forgetting effects and emotional enhancement of memory were observed in both groups, even despite overall lower recognition rates in SCZ. Furthermore, cue presentation elicited similar pattern of N2/P3s in SCZ and in HC. However, "reversed old/new" effect was observed only in HC for negative stimuli. Patients may show similar reaction to affective stimuli as healthy controls during the emotional DF task. However, further investigation is needed to elicit the specific mechanisms underlying the DF strategies in SCZ.

The effect of positive and negative memory bias on anxiety and depression symptoms among adolescents

OBJECTIVE

To examine the interaction effect of anxiety and depression on the intentional forgetting of positive and negative valence words.

METHODS

One hundred fifty-five grade 7 to grade 10 students participated in the study. The item-method directed forgetting paradigm was used to examine the intentional forgetting of positive-valence, negative-valence, and neutral-valence words.

RESULTS

Negative-valence words were recognized better than either positive-valence or neutral-valence words. The results revealed an anxiety main effect (p = .01, LLCI = -.09, and ULCI = -.01) and a depression main effect (p = .04, LLCI = .00, and ULCI = .24). The anxiety score was negative, whereas the depression score was positively related to the directed forgetting of negative-valence words. Regression-based moderation analysis revealed a significant anxiety × depression interaction effect on the directed forgetting of positive-valence words (p = .02, LLCI = .00, and ULCI = .01). Greater anxiety was associated with more directed forgetting of positive-valance words only among participants with high depression scores. With negative-valence words, the anxiety × depression interaction effect was not significant (p = .15, LLCI = - .00, and ULCI = .01).

CONCLUSION

Therapeutic strategies to increase positive memory bias may reduce anxiety symptoms only among those with high depression scores. Interventions to reduce negative memory bias may reduce anxiety symptoms irrespective of levels of depression.

Cognitive Control of Episodic Memory in Schizophrenia: Differential Role of Dorsolateral and Ventrolateral Prefrontal Cortex

Background: Dorsal (DLPFC) and ventral (VLPFC) subregions in lateral prefrontal cortex play distinct roles in episodic memory, and both are implicated in schizophrenia. We test the hypothesis that schizophrenia differentially impairs DLPFC versus VLPFC control of episodic encoding.

Methods: Cognitive control was manipulated by requiring participants to encode targets and avoid encoding non-targets based upon stimulus properties of test stimuli. The more automatic encoding response (target versus non-target) was predicted to engage VLPFC in both groups. Conversely, having to overcome the prepotent encoding response (non-targets versus targets) was predicted to produce greater DLPFC activation in controls than in patients. Encoding occurred during event-related fMRI in a sample of 21 individuals with schizophrenia and 30 healthy participants. Scanning was followed by recognition testing outside the scanner.

Results: Patients were less successful differentially remembering target versus non-target stimuli, and retrieval difficulties correlated with more severe disorganized symptoms. As predicted, the target versus non-target contrast activated the VLPFC and correlated with retrieval success in both groups. Conversely, the non-target versus target contrast produced greater DLPFC activation in controls than in patients, and DLPFC activation correlated with performance only in controls.

Conclusion: Individuals with schizophrenia can successfully engage the VLPFC to provide control over semantic encoding of individual items, but are specifically impaired at engaging the DLPFC to main context for task-appropriate encoding and thereby generate improved memory for target versus non-target items. This extends previous cognitive control models based on response selection tasks to the memory domain.

The inhibition of proactive interference among adults with Internet gaming disorder

INTRODUCTION

Cognitive control plays a pivotal role in the mechanism of addictive behavior. The aim of the study was to evaluate the deficit in inhibition of proactive interference of Internet gaming disorder (IGD) using a directed forgetting task among young adults.

METHODS

A total of 64 participants with IGD and 69 controls were recruited on a university campus. They completed the directed forgetting task for online gaming words and neutral words.

RESULTS

The results demonstrated that the IGD group had a poorer performance on the directed forgetting task, and this represented a deficit in inhibition of proactive interference. They also had a higher tendency to remember online gaming words rather than neutral words in comparison with the control group. This demonstrated memory bias toward online gaming words.

DISCUSSION

These results suggested that more attention should be paid to deficits in inhibition of proactive interference and memory bias toward gaming content when treating subjects with IGD. Furthermore, it is essential and practical to prevent exposure to online gaming-related cues when endeavoring to control online gaming behavior.

Neurophysiological correlates of emotional directed-forgetting in persons with Schizophrenia: An event-related brain potential study

BACKGROUND

Recent research has shown that patients with schizophrenia (SCZ) exhibit reduced directed forgetting (DF) for negative words, suggesting impaired ability to instantiate goal-directed inhibition in order to suppress a competing, emotion-driven responses (i.e., emotional memory enhancement). However, disrupted inhibition is not the only possible mechanism by which patients could manifest reduced emotional DF. Therefore, the primary objective of the current study was to use event-related brain potential (ERP) recordings to investigate alternative hypotheses.

METHODS

ERPs were recorded while patients and controls completed an item-method DF paradigm using negative and neutral words. The N2 indexed goal-directed inhibition of to-be-forgotten items. The late positive potential (LPP) indexed emotional memory enhancement for negative study items. The P300 indexed selective rehearsal of to-be-remembered items.

RESULTS

The SCZ group exhibited a reduced DF effect overall, but this was not modulated by emotion. N2 amplitude at anterior sites was larger for forget versus remember cues in the control group only, but this effect was not modulated by emotion. LPP amplitude was greater for negative versus neutral words in both groups, independent of region. P300 amplitude at posterior sites was greater for remember versus forget cues in the control group only.

DISCUSSION

These data suggest that reduced DF in SCZ may be due, in part, to both diminished goal-directed inhibition of to-be-forgotten items and reduced selective rehearsal of to-be-remembered items. However, these data do not support the hypothesis that goal-directed, inhibitory processes are disrupted by competing, emotion-driven processes in SCZ. Patients' ERP data also suggested that they did not exhibit disproportionately heightened encoding of emotional stimuli, nor did they have deficient selective rehearsal of to-be-remembered emotional items.

Reduced directed forgetting for negative words suggests schizophrenia-related disinhibition of emotional cues

BACKGROUND

Several psychological and neurobiological models imply that patients with schizophrenia (SCZ) are more inclined to utilize emotional cues as response determinants to the detriment of more task-appropriate cognitive or contextual cues. However, there is a lack of behavioural data from human clinical studies to support this assertion. Therefore, it is important to evaluate the performance of persons with SCZ using tasks designed to index the resolution between competing emotional and cognitive determinants of goal-directed behaviour.

METHOD

The current study employed a list-method, emotional directed-forgetting (DF) paradigm designed to invoke inhibitory mechanisms necessary to override emotional memory enhancement for successful task completion. Four psycholinguistically matched lists were constructed that were comprised of five negative, five positive, and five neutral words.

RESULTS

Compared with healthy controls, individuals with SCZ showed a reduced DF effect overall. When broken down according to valence, this effect was only observed for negative words, which, in turn, resulted from reduced forgetting of list 1 words following the forget cue.

CONCLUSIONS

These results indicate that individuals with SCZ were less able to engage strategic inhibitory mechanisms for the purpose of overriding recall of negative stimuli when tasks demand call for such action. Thus, our data support the theoretical assertion that SCZ patients have difficulty utilizing cognitive or contextual cues as determinants of goal-directed behaviour in the face of countermanding emotional cues.

Memory blocking in schizophrenia reflects deficient retrieval control mechanisms

Retrieval interference and orthographic processing were evaluated in schizophrenia, schizotypal personality disorder, and non-psychiatric control participants using a word fragment completion paradigm. Participants studied solutions and later completed corresponding fragments preceded by solutions, orthographically similar blocking words, or ampersands. Although schizophrenia patients completed fewest fragments, they showed equivalent repetition priming and blocking magnitude, supporting intact orthographic processing. Schizophrenia patients were more likely to commit intrusions in the blocking condition, whereas control participants displayed better mental control because they were more likely to withhold the response. These results suggest schizophrenia patients show abnormal functioning of control mechanisms responsible for selection and inhibition of competitors.

Absence of a positive bias in social anxiety: the application of a directed forgetting paradigm

The present study used a directed forgetting paradigm to investigate whether socially anxious individuals show a memory bias for social information. Socially anxious and non-anxious participants viewed three types of words: socially negative, socially positive, and neutral. Each word was presented on a computer screen and was followed by a cue instructing participants to either remember or forget the word. A free recall test and a recognition test were then administered by asking participants to recall and recognize both "to-be-remembered" and "to-be-forgotten" words. When compared to non-anxious participants, socially anxious participants showed a greater directed forgetting effect for socially positive words in the free recall test, indicating that socially anxious individuals more easily forget socially positive words than do non-anxious individuals. This result suggests that socially anxious individuals lack the positive bias (i.e., difficulty in forgetting socially positive information) displayed by non-anxious individuals.

Considerations for analysis of source monitoring data when investigating hallucinations in schizophrenia research

Self/other (i.e., internal/external) source monitoring is one of the leading paradigms for the study of hallucinations in schizophrenia. The cognitive processes that underlie hallucinations are theorized to transform self-generated (internal) cognitive events into other-generated (external) cognitive events. These proposed cognitive operations also appear to play a role in producing analogous types of errors in self/other source monitoring, namely a memory bias whereby recalled material that was self-generated is misremembered as other-generated, referred to as an externalization bias. Externalization biases are more frequent in groups of hallucinating schizophrenia patients than in other groups. One source of measurement error that is inherent in the study of the externalization bias is that, even for never-previously viewed items, there is a tendency to guess an external source under conditions of uncertainty. If such guessing takes place in response to self-generated but forgotten items, these guesses will be summed along with true externalization biases in the frequency count of externalizations, producing measurement error. Multinomial modeling is a statistical technique that has been used to estimate the influence of external-source guessing in order to separate it from true externalization bias estimates. However, a number of challenges related to model choice and model validation are involved, and these challenges may render multinomial modeling impractical. We instead recommend analysis of covariance (ANCOVA), or difference score methodology, as an appropriate method for partialling external-source guessing rates (external-source false positives) out of externalization bias rates.

Disrupted memory inhibition in schizophrenia

A feature of schizophrenia is disrupted executive function leading to learning difficulties and memory problems. In two experiments we measured the ability of patients with schizophrenia to suppress irrelevant parts of acquired information by intentional (executive) and autonomic (non-executive) strategies. In the first experiment using directed forgetting by lists patients were found to be unable to intentionally suppress recently acquired episodic memories. In a second experiment using a procedure that induces inhibition automatically schizophrenic patients showed levels of inhibition comparable to those of normal controls. These findings indicate that in schizophrenia memory is most impaired in tasks that load heavily on control or executive processes.

Inhibition of inappropriate responses is preserved in the Think-No-Think and impaired in the random number generation tasks in schizophrenia

We examined the ability of 23 schizophrenia patients and 24 healthy controls to exert intentional inhibition of prepotent responses in the Think-No-Think (TNT) paired-associate learning paradigm (Anderson & Green, 2001). TNT manipulates the frequency (1, 8, 16 times) of intentional attempts to suppress (inhibit) some target words and to respond to most cue words. Following a TNT practice-phase, recall of suppressed words was tested in two ways, using the same cue words initially learned, and the category name plus letter-stem of the target words. Inhibition of prepotent responses was also examined in a random number generation (RNG) task. In TNT, speed results showed longer reaction times after 16 suppress attempts in patients, not in controls, reflecting increased difficulty with retrieving the memory traces of the overridden items. In accuracy, no between-groups differences were evidenced, and overall patterns replicated those of Anderson & Green. In RNG, patients produced more stereotyped responses and ascending and descending counting than controls, pointing to on-line failures to inhibit prepotent responses. These findings suggest that schizophrenia patients' difficulties to inhibit prepotent responses appear specific, not widespread, the intentional inhibition addressed in TNT being preserved, and on-line inhibition in RNG being impaired.

Cognitive functioning in the early course of first-episode schizophrenia spectrum disorders: timing and patterns

OBJECTIVE

The aim of this study was to examine possible cognitive changes throughout the early course of schizophrenia spectrum disorders.

METHOD

Forty-two patients, aged 15-50 years, admitted to a first episode psychosis program (PAFIP) serving to the community of Cantabria (Spain) and 43 healthy volunteers completed a brief battery of five neurocognitive tests at four time-points over 3 months. The cognitive testing comprise five domains: attention, visuomotor speed, declarative memory, working memory and executive function. Baseline assessment occurred within 72 hour after the initiation of standard pharmacological treatment, and after then parallel forms of the tests were applied at week-2, week-6, and month-3.

RESULTS

Patient scores showed a significant impairment compared to healthy volunteers in the five cognitive domains at baseline and week-2 assessments. After the first 3 months of antipsychotic treatment, the patient group performance reached healthy volunteers level on executive function (Stroop interference) and immediate verbal memory tests. In contrast, performance on working memory, sustained attention, visuomotor speed, and verbal memory delayed recall domains still remained below healthy volunteers, although visuomotor processing speed showed a significant improvement.

CONCLUSION

Schizophrenia spectrum patients show heterogeneous patterns and degrees of cognitive changes that contribute to stress the importance of when, what, and how neurocognitive functioning in the early phases of the illness is evaluated.

Cognitive predictors of skill acquisition on social problem solving in patients with schizophrenia

The aim of the study was to evaluate the relationship between social problem solving ability, clinical features and cognitive functions, and determine the predictors of benefit from social problem solving training in 63 patients with schizophrenia. We administered Brief Psychiatric Rating Scale (BPRS), Wisconsin Card Sorting Test (WCST), Digit Span Test, Continuous Performance Test (CPT) and the Assessment of Interpersonal Problem Solving Skills (AIPSS). Only BPRS-positive symptoms subscale was negatively related to AIPSS on linear regression analysis. After the completion of the pretest, the patients were randomized to either problem solving training (n = 32) or control groups (n = 31). Patients in training group received 6 weeks problem solving training in-group modality, and those in control group were treated as usual. We readministered AIPSS at the end of 6 weeks. There were significant changes from pretest to posttest on AIPSS-total, AIPSS-receiving skills, and AIPSS-processing skills score in training group but not in control group. The number of correct answers in WCST and CPT hit rate were the predictors of post-training AIPSS scores in training group. Our findings suggest that skill acquisition on social problem solving is related with cognitive flexibility and sustained attention.