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.     

Directed forgetting in frontal patients' episodic recall

The aim of this study was to examine the performance of a group of patients with lesions of the prefrontal cortex in directed forgetting in episodic memory, i.e. the capacity to actively forget irrelevant information. Four lists of 24 intermixed to-be-remembered (TBR) and to-be-forgotten (TBF) words were presented for retention. Restricted (TBR only) and unrestricted (TBR and TBF) recall were tested. The results showed that prefrontal patients presented with a general reduction in episodic memory but a normal ability to selectively recall the TBR items during restricted and unrestricted recall. These results are consistent with previous reports of intact directed forgetting in frontal patients and are discussed in terms of their implications for the current debate on the neural substrate of executive functions.     

Avoidant encoding in acute stress disorder: a prospective study

This study investigated the relationship between ongoing posttraumatic adjustment and encoding style. Eleven acute stress disorder (ASD) participants and 14 non-traumatized controls completed the item method of directed forgetting and were retested 1 year later. Trauma-related, positive and neutral words were followed by a "remember" or "forget" instruction. At Time 1, ASD participants demonstrated directed forgetting for trauma and neutral words; controls showed directed forgetting for all word types. At Time 2, directed forgetting was replicated in controls for each word type, but only for neutral words in the ASD group. Directed forgetting effects were absent for positive words in the ASD group. The findings raise the possibility that individuals who develop ASD possess an encoding style for positive material that reflects a trait-like manner of information processing.     

Directed forgetting in PTSD: a comparative study versus normal controls

The most characteristic feature of Post-Traumatic Stress Disorder (PTSD) is the reexperiencing syndrome. The patient's memory seems to be fixed on the traumatic event, which may be due to disturbance of the autobiographic memory. To retrieve memories, others have to be inhibited. These inhibition mechanisms have been studied using the Directed Forgetting Paradigm, which measures the capacity to forget recently processed information and to retain the relevant information. Our hypothesis is that during PTSD, the memory is saturated with traumatic memories, so that the patients are no longer able to use the inhibitory processes. Therefore, during a Directed Forgetting Task (DFT) in which words "to remember" and words "to forget" are given, PTSD patients cannot inhibit the words "to forget", and so recall more words than the controls. We studied 30 patients with PTSD and compared them with 30 healthy controls, using DFT. The results show that the patients remembered significantly fewer words overall, and fewer of the words "to remember" than the controls, both for immediate and final recall. Our results are in favor of a reduction in directed forgetting in patients suffering from PTSD, resulting in difficulty in inhibiting irrelevant information from the overall information. There seems to be a deficit in the inhibitory processes in the memory in PTSD.     

Episodic memory in patients with focal frontal lobe lesions

Episodic memory was evaluated in patients with unilateral, frontal lobe damage and matched controls using a list- method directed forgetting paradigm. Directed forgetting instructions (forget vs. remember the word), encoding instructions (learn vs. judge the word) and test format (recall vs. recognition) were manipulated in order to explore how variations in encoding and retrieval affect verbal memory. Controls demonstrated a normal directed forgetting effect in recall and less directed forgetting in recognition. Patients with left frontal (LF) damage did not show directed forgetting in either recall or recognition and patients with right frontal (RF) damage showed directed forgetting in recall, but not in recognition. Furthermore, the LF group recalled significantly more of the judge than learn words, suggesting that this group's performance improves by providing them with an encoding strategy. Conversely, the RF group's performance did not depend on encoding instructions and their recognition memory was impaired relative to the other two groups when they were instructed to judge the words. Our results suggest that (a) patients with LF damage show deficits in the rehearsal of to-be-remembered information, (b) whereas patients with RF damage show impairments in recognition memory. Furthermore, both patient groups show a lack of directed forgetting when familiarity-based processes guide performance.     

An electrophysiological test of directed forgetting: the role of retrieval inhibition

A central issue in the research of directed forgetting is whether the differential memory performance for to-be-remembered (TBR) and to-be-forgotten (TBF) items is solely due to differential encoding or whether retrieval inhibition of TBF items plays an additional role. In this study, recognition-related event-related brain potentials (ERPs) were used to examine this issue. The spatio-temporal distributions of the old/new ERP effects obtained in Experiment 1 that employed a directed forgetting paradigm were compared with those recorded in Experiment 2 in which the level of processing was manipulated. In Experiment 1, participants were instructed to remember or to forget words by means of a cue presented after each word. ERPs recorded in the recognition test revealed early phasic frontal and parietal old/new effects for TBR items, whereas TBF items elicited only a frontal old/new effect. Moreover, a late right-frontal positive slow wave was more pronounced for TBF items, suggesting that those items were associated with a larger amount of post-retrieval processing. In Experiment 2, the same cueing method and the same stimulus materials were used, and memory encoding was manipulated by cueing participants to process the words either deeply or shallowly. Both deeply and shallowly encoded items elicited phasic frontal and parietal old/new effects followed by a late right-frontal positive slow wave. However, in contrast to TBR and TBF items, these effects differed only quantitatively. The results suggest that differential encoding alone cannot account for the effects of directed forgetting. They are more consistent with the view that items followed by an instruction to forget become inhibited and less accessible, and, therefore, more difficult to retrieve.     

Memory suppression in Alzheimer’s disease

An important challenge for memory is the competition between appropriate and inappropriate information during retrieval. This competition is normally reduced thanks to controlled inhibitory processes that suppress irrelevant memories. In Alzheimer’s disease (AD), compromise of suppression ability may result in strong competition between relevant and irrelevant memories during retrieval. The present review highlights this issue by examining studies using the directed forgetting method in AD. This method in which participants are typically instructed to forget no longer relevant information is argued to reflect suppression in memory. Studies using the directed forgetting method suggest that AD participants experience difficulties when they are asked to suppress no longer relevant information in working, autobiographical, source and destination memory. Difficulties in suppressing irrelevant information, as may be observed in AD, may hamper memory retrieval by activating irrelevant memories at the expense of relevant ones.     

Predictive validity of event-related potentials (ERPs) in relation to the directed forgetting effects.

OBJECTIVE: A directed forgetting paradigm (word method) was used to assess the relationships between the event-related potentials (ERPs) recorded during the study phase and the subsequent forgetting effects. METHODS: In the study phase 100 words were presented each followed by either an instruction to remember (R) or to forget (F). Then these 100 words, together with another 100 new words, were presented and subjects had to perform an old/new decision task. The forgetting effect was considered as the difference between the rate of R- and F-words correctly recognised. Based on this difference, the whole sample was divided into two 10-subject groups with high and low forgetting effect. RESULTS: From 300 to 600 msec post-instruction differences in ERPs between R and F instructions were similar in both groups. In contrast, in the 100-300 msec epoch, ERP differences only appeared in the high-effect group and consisted of an enhanced positive activity elicited by F instruction at frontal and prefrontal areas and a larger positivity associated to R instruction at parietal area. CONCLUSIONS: The findings suggest that the processing of the word is kept on stand-by until the instruction is provided. Instruction to remember would reactivate this processing, which would mainly involve the parietal area, whereas instruction to forget appears to trigger frontal and prefrontal mechanisms trying to inhibit such processing.     

ERP dynamics underlying successful directed forgetting of neutral but not negative pictures

Subjective experience suggests that negatively arousing memories are harder to control than neutral ones. Here, we investigate this issue in an item-cued directed forgetting experiment. Electroencephalogram event-related potentials (ERPs) were recorded as participants viewed un-arousing neutral and highly arousing negative photographs, each followed by a cue to remember or forget it. Directed forgetting, that is reduced recognition of ‘to-be-forgotten’ items, occurred for neutral but not negative pictures. ERPs revealed three underlying effects: first, during picture viewing a late parietal positive potential (LPP) was more pronounced for negative than for neutral pictures. Second, ‘remember’ cues were associated with larger LPPs than ‘forget’ cues. Third, an enhanced frontal positivity appeared for ‘forget’ cues. This frontal positivity was generated in right dorso-lateral prefrontal regions following neutral pictures and in medial frontal cortex following negative pictures. LPP magnitude when viewing negative pictures was correlated with reduced directed forgetting, whereas both the enhanced frontal positivity for forget cues and the larger parietal positivity for remember cues predicted more directed forgetting. This study indicates that both processes of selective rehearsal (parietal positivities) and frontally controlled inhibition contribute to successful directed forgetting. However, due to their deeper incidental processing, highly arousing negative pictures are exempt from directed forgetting.     

Failure to replicate a memory bias in panic disorder

Nineteen panic disorder and twenty nonclinical subjects participated in a word association task followed by direct and indirect tests of memory. Subjects were presented with three types of words in random order (physical threat, social threat, and matched neutral words), and were asked to state the first word that came to mind. They were then, unexpectedly, asked to perform a free recall task (direct) or word completion task (indirect). Panic disorder subjects reported a greater number of threat associates to all types of words. However, they did not show a memory bias toward physical threat on either the direct on indirect task.