Remember Cues Research Articles

Impaired directed forgetting in abstinent heroin addicts

Drug-related memories persist long into abstinence and are potent elicitors of drug craving and relapse. We report two experiments examining whether heroin-dependent individuals are impaired in intentionally suppressing drug-related memories. Experiment 1 adopted the Item paradigm where addicts and healthy controls were presented with a list of words each followed by a remember or forget cue. Experiment 2 adopted the List paradigm where they studied one list of items and were then split into a remember group and a forget group. Both groups studied a second list, except that the forget group was told to forget the first list. Compared with controls, addicts showed a reduced directed forgetting effect in the Item method and a total absence of one measure of directed forgetting in the List method (List 2 benefits). Results indicate that heroin addicts are impaired in directed forgetting and that the deficits are likely associated with memory encoding as opposed to retrieval. Possible problems include reduced ability in actively suppressing/stopping encoding of irrelevant information into memory or inability in changing/resetting encoding strategies. In neither experiment did the addicts show any differential directed forgetting effects between drug-related words and neutral words, indicating the generic nature of their intentional forgetting deficits.

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.

Dissociation between phase‐locked and nonphase‐locked alpha oscillations in a working memory task

The functions of human alpha oscillations ( approximately 10 Hz) were related to cognitive processes such as memory and top-down control. Recent models suggest that alpha phase serves as a mechanism especially relevant for the timing of neural activity, whereas alpha amplitude is important for the inhibition of task-irrelevant brain areas. This study investigates directly the influence of top-down modulation on phase-locked and nonphase-locked alpha rhythms. We conducted an EEG experiment where subjects performed a working memory task. In the encoding phase of the task subjects had to learn presented pictures of nonliving objects that could later be asked to be retrieved. We varied the top-down modulation by including cues indicating either to remember or to forget (not to remember) the next following item. Spectral analyses showed that nonremember cues elicited pronounced alpha amplitude increase compared to remember cues. Furthermore, phase-locking in low frequencies, especially in the alpha range (7-12 Hz), was stronger for remember as opposed to not-to-remember items. In conclusion, we propose that alpha amplitude reflects top-down modulated inhibition and that alpha phase is important for the exact timing of neural activity and can be related to binding processes.

An event-related potential investigation of the processing of Remember/Forget cues and item encoding in item-method directed forgetting

This study examined the electrophysiological correlates of the processing of the Remember/Forget cues and the successful encoding of study items in item-method directed forgetting. Subjects engaged in an old/new recognition test and an item-method directed forgetting task. Event-related potentials (ERPs) time-locked to study items and Remember/Forget cues were compared according to the subsequent recognition performance. A reliable subsequent memory effect was elicited by the study items in the old/new recognition test. In contrast, the study items in the directed forgetting task did not yield reliable subsequent memory effects. Importantly, the Remember/Forget cues gave rise to ERPs that were predictive of the subsequent recognition performance to the study items preceding the cues. The subsequent memory effect elicited by the Remember cues was more sustained than that elicited by the Forget cues and showed distinct scalp distribution during the extended period. These results suggest that study items in the directed forgetting task are maintained in short-term memory with minimal further processing until the presentation of the Remember/Forget cues. In addition, the encoding mechanisms engaged by Remember cues and Forget cues are not entirely equivalent.

Neural correlates of directed forgetting in the avian prefrontal cortex.

The authors trained 2 homing pigeons (Columba livia) on a directed forgetting task with 3 cues: a remember cue that was followed by a memory test and the opportunity to obtain a reward, a forget cue that was not followed by a memory test or a reward, and a free-reward cue that was not followed by a memory test but was followed by a free reward. The authors examined the activity of single neurons in the avian nidopallium caudolaterale, an area equivalent to the primate prefrontal cortex. Following the remember cue there was sustained neural activity during the delay period, whereas following the forget cue the neural activity in the delay period was significantly reduced. The activity following the free-reward cue mirrored that following the remember cue. The authors discuss the extent to which the findings are in line with the view that the sustained activity reflects memory for the sample stimulus or memory for reward.

The crucial role of postcue encoding in directed forgetting and context-dependent forgetting.

People can intentionally forget previously studied material if, after study, a forget cue is provided and new material is learned. It has recently been suggested that such list-method directed forgetting arises because the forget cue induces a change in internal context and causes context-dependent forgetting of the studied material (L. Sahakyan & C. M. Kelley, 2002). The authors compared directed forgetting and context-dependent forgetting by examining whether, like a forget cue, a change in internal context needs subsequent learning of new material to be effective. Participants studied an item list and, after study, received a remember cue or a forget cue or their internal context was changed through an imagination task. In each condition, half the participants learned a second list, and the other half fulfilled an unrelated distractor task. Both the forget cue and the change in internal context induced forgetting of the first list only when learning of the second list was interpolated. These results suggest that postcue encoding of new material is crucial for both directed forgetting and (some forms of) context-dependent forgetting.

The recall of stereotypes: the effects of incidentally activated directed forgetting instructions.

Based on the automotive model (J. A. Bargh, 1990) and the directed forgetting paradigm, the present study investigated whether incidentally activated forget and remember cues can lead to similar effects as explicitly given instructions. To this end, the present paper attempted to replicate the findings of Macrae, Bodenhausen, Milne, and Ford (1997) employing their category primes (child abuser, neutral), study lists (List 1, List 2), and procedure. Using explicit directed forgetting instructions, Experiment 1 showed that the recall of the stereotypically relevant words (List 1) was higher when participants were given a remember than a forget instruction. This effect was found regardless of the prime conditions. Similarly, Experiment 2 showed that participants in the child abuser and neutral prime conditions recalled more stereotypically relevant words (List 1) when they were implicitly cued to remember than to forget these words. Experiment 3 showed that cognitively busy participants in the child-abuser, but not in the neutral prime condition, recalled more to-be-forgotten stereotypical words than nonbusy participants. These results are consistent with Macrae et al. s findings, and show that the effects of directed forgetting instructions are similar regardless of whether they were given explicitly or were activated incidentally. Results are discussed in relation to stereotype maintenance.

Item-Cued Directed Forgetting of Related Words and Pictures in Children and Adults: Selective Rehearsal Versus Cognitive Inhibition

The main purpose of this study was to compare the relative importance of selective rehearsal and cognitive inhibition in accounting for developmental changes in the directed-forgetting paradigm developed by R. A. Bjork (1972). In two experiments, children in Grades 2 and 5 and college students were asked to remember some words or pictures and to forget others when items were categorically related. Their memory for both items and the associated remember or forget cues was then tested with recall and recognition. Fifth graders recognized more of the forget-cued words than college students did. The pattern of results suggested that age differences in rehearsal and source monitoring (i.e., remembering whether a word had been cued remember or forget) were better explanatory mechanisms for children's forgetting inefficiencies than retrieval inhibition was. The results are discussed in terms of a multiple process view of inhibition.

Directed Forgetting: Short-term Memory or Conditioned Response?

Previous researchers have interpreted the phenomenon of directed forgetting in terms of animal short-term memory and rehearsal. An alternative explanation-that directed forgetting is attributable to the response or nonresponse to a sequence of stimuli-is proposed and tested with rats. Rats were tested for directed forgetting using a variation of the standard directed forgetting task, in which the sample was followed by either a remember cue or a forget cue, and in which there was a second cue immediately before the presentation of the comparison stimuli. Results appear to support the memory and rehearsal explanation of directed forgetting.

Is there hypermnesia and reminiscence for information intentionally forgotten?

Memory performance was examined across consecutive tests in three directed-forgetting experiments. Following word-method or list-method cueing to forget, significant directed forgetting was observed for all tests: Free recall for remember cue words always exceeded free recall for forget cue words. Moreover, following either cueing method, similar magnitudes of hypermnesia (improved free recall across tests) and reminiscence (recovery of words across tests) were observed for both word types. Regardless of cueing method, after an initial free recall test, the level of recovery for both word types did not differ significantly. That is, directed forgetting was not observed for the reminiscence data. Taken together, the pattern of results suggest that cues to forget impair the encoding of information but, after an initial memory test, they do not interrupt the accessing of that information. These findings are consistent with the selective rehearsal account but not the retrieval inhibition account of directed forgetting.

To Forget or Not to Forget: The Effect of Probability of Test on Directed Forgetting

Two experiments investigated how individuals use explicit memory cues that designate different probabilities of test. As in typical directed forgetting studies, subjects received words explicitly cued as having either a 0% or a 100% chance of being on a subsequent memory test (i.e. forget and remember cues, respectively). In addition, some words were explicitly cued as having the potential to be either forgotten or remembered (i.e. a 50% cue). Recall of 50% words was between that of 0% and 100% words. In addition, the presence of 50% words lowered recall of the 100% words compared to that of a control group that did not receive 50% words, but received the same number of 100% words. A think-aloud task indicated that these results were due to 50% words being treated like either 100% of 0% words at encoding. The results are discussed in terms of the effect of different probabilities of test on the strategic processing and representation of information.

MOST DIRECTED FORGETTING IN PIGEONS CAN BE ATTRIBUTED TO THE ABSENCE OF REINFORCEMENT ON FORGET TRIALS DURING TRAINING OR TO OTHER PROCEDURAL ARTIFACTS

In research on directed forgetting in pigeons using delayed matching procedures, remember cues, presented in the delay interval between sample and comparisons, have been followed by comparisons (i.e., a memory test), whereas forget cues have been followed by one of a number of different sample-independent events. The source of directed forgetting in delayed matching to sample in pigeons was examined in a 2 x 2 design by independently manipulating whether or not forget-cue trials in training ended with reinforcement and whether or not forget-cue trials in training included a simultaneous discrimination (involving stimuli other than those used in the matching task). Results were consistent with the hypothesis that reinforced responding following forget cues is sufficient to eliminate performance deficits on forget-cue probe trials. Only when reinforcement was omitted on forget-cue trials in training (whether a discrimination was required or not) was there a decrement in accuracy on forget-cue probe trials. When reinforcement is present, however, the pattern of responding established during and following a forget cue in training may also play a role in the directed forgetting effect. These findings support the view that much of the evidence for directed forgetting using matching procedures may result from motivational and behavioral artifacts rather than the loss of memory.

The effects of scopolamine and cues to forget on pigeons' memory for time

Pigeons were trained with a 0-s delayed symbolic matching-to-sample procedure to indicate whether a houselight sample stimulus was short (2 s) or long (8 s) by pecking a red or a green comparison stimulus. In Experiment 1, the pigeons received injections of scopolamine hydrobromide (0.015 mg/kg), or saline, and the delay interval was manipulated (0, 1, 3, and 9 s). Memory for time was significantly poorer following scopolamine injections than following saline injections. A significant choose-short bias was observed under scopolamine at delays as brief as 3 s, but not under saline. In Experiment 2, a brief postsample cue (a vertical or horizontal line) signaled whether the comparison stimuli would be presented or omitted on each trial. During training, comparison stimuli were always presented following the remember (R) cue, but never following the forget (F) cue. During testing, memory for time was significantly poorer on F-cue trials than on R-cue trials. A significant choose-short bias was observed on F-cue trials at the 5- and 10-s delays, but not on R-cue trials. The results suggest that anticholinergic blockade accelerates the rate at which memory for temporal events is foreshortened in working memory. This effect is similar to that produced by an explicit cue to forget the temporal sample.

Differential outcome expectancies and directed forgetting effects in pigeons

Pigeons were trained in a two-choice delayed matching-to-sample task with red and green hues. A brief postsample cue (a vertical or horizontal line) signaled whether the comparison stimuli would be presented or omitted on each trial. Comparison stimuli were always presented following the remember (R) cue, but never following the forget (F) cue or no-cue trials. One group of birds, the differential outcome (DO) group, received reinforcement with a probability of 1.0 for correct responses following one sample stimulus and a probability of 0.2 for correct responses following the other sample stimulus. The nondifferential outcome (NDO) group received reinforcement with a probability of 0.6 for correct responses to either stimulus. The effect of postsample cues was greater for the DO group than for the NDO group. Relative to the NDO group, the DO group displayed higher accuracy on R-cue trials and lower accuracy on F- and no-cue trials. Both tendencies contributed to the enhanced cue effectiveness obtained in the DO group. The results indicate that outcome expectancies are subject to maintenance rehearsal, which comes under the control of postsample R and F cues. They also suggest that maintenance rehearsal may be easier to sustain under DO conditions than under NDO conditions when a memory test is anticipated, but that it may be easier to terminate maintenance rehearsal under DO conditions when a memory test is not anticipated. The results are inconsistent with the assumption that the rehearsal of outcome expectancies is automatic.

Effects of level of processing and rehearsal on frequency judgments.

The effects of attention during encoding and rehearsal after initial encoding on frequency estimates were investigated in three experiments. Varying the level of processing affected the linear increase in frequency estimates as a function of actual frequency, but varying processing after encoding with remember or forget cues had the greatest effects on the intercept of the function relating judged to actual frequency. Deeper levels of processing improved performance in a frequency discrimination task, whereas remember and forget cues had only very small effects on performance. Materials that are easy to rehearse were compared with materials that are difficult to rehearse in Experiment 2. The results were interpreted as evidence against a covert rehearsal explanation of slope effects in frequency estimation tasks because materials that are difficult to rehearse tended to produce larger interactions between remember versus forget cues and frequency than materials that are easier to rehearse. In Experiment 3, an arithmetic task that was performed during word encoding affected the slope of the function relating judged to actual frequency, but the same task performed immediately after word presentation had no effect on frequency estimates. It was concluded that frequency is not stored automatically because attention during the initial stages of encoding affects it; however, attention devoted to processing after initial encoding does not affect the rate with which subjective frequency increases with repetitions.

Directed forgetting effects in pigeons: Remember cues initiate rehearsal

Pigeons were trained in a two-choice delayed matching-to-sample task with red and green hues. A brief postsample cue (a vertical or horizontal line) signaled whether the comparison stimuli would be presented or omitted on each trial. Comparison stimuli were always presented following the remember-cue (R-cue) trial, but never following the forget-cue (F-cue) and no-cue trials. In Experiment 1, matching accuracy on F-cue and no-cue trials was equivalent and was considerably inferior to accuracy on R-cue trials. In Experiment 2, the placement of the postsample cue was manipulated. Matching accuracy decreased as the R cue was delayed in the retention interval, but performance in the F-cue condition was not affected. These data indicate that the no-cue condition can function as an implicit F cue and that the R cue can function to initiate and maintain rehearsal.

Directed forgetting in monkeys

Based on several recent demonstrations of a directed forgetting effect in pigeons, three experiments were carried out in an attempt to demonstrate directed forgetting in three squirrel monkeys. During initial training with a delayed matching-to-sample procedure, retention tests were always given for sample stimuli followed by remember cues (R-cues) and were always omitted for sample stimuli followed by forget cues (F-cues). Retention of F-cued items was tested on probe trials after initial training. The first two experiments examined the effects of R- and F-cues on memory for slide-projected pictures, with different pictures used on each trial of a session. In Experiment 1, a complex design was used in which one or two sample pictures were presented on each trial; when two pictures were presented, both could be R-cued or F-cued, or one could be R-cued and the other F-cued. A simpler design was used in Experiment 2, with only single pictures presented as sample stimuli and half the trials within a session R-cued and the other half F-cued. In both of these experiments, no differential retention of R- and F-cued stimuli was found, even at a retention interval as long as 16 sec. In Experiment 3, a series of studies was performed to test for directed forgetting when only two sample stimuli were used repeatedly throughout training and testing. With two pictures as sample stimuli, clear evidence of directed forgetting was found in Experiment 3b. It is suggested that the directed forgetting effect may arise only when a small set of sample stimuli is used.

Time dependent effects of double cuing in directed forgetting

Previous research in directed forgetting in pigeons has focused on the effect of single forget cues (F-cues) interpolated within the retention interval in delayed matching-to-sample (DMTS). The present series of experiments focuses on the ability of a remember cue (R-cue) to cancel the effects of a previously presented forget cue both when the forget cue occurs within the retention interval and when the forget cue precedes sample presentation. In the first experiment, an R-cue decreased the effect of an F-cue within the same retention interval in successive DMTS if the R-cue immediately followed the F-cue, but not if the second cue was delayed until the end of the retention interval. In Experiment 2, the double-cue effect was extended to choice DMTS. In addition, when a novel stimulus replaced the R-cue in the double-cue probe trials, matching performance was not restored, indicating that through its conditioning history the R-cue had gained control over memory processes in a direction opposite to that of the F-cue. Experiment 3 presents evidence that presample R- and F-cues can also effectively gain control over matching performance. Matching to R-cued samples was superior to matching to F-cued samples. When F-cued samples were followed immediately by R-cues, matching performance was not restored to R-cue levels, suggesting differential encoding of the R-cued and F-cued samples.

Stimulus control of information processing in pigeon short-term memory

Six pigeons were trained initially on a delayed successive matching-to-sample task using red and green fields as sample and test stimuli. Following acquisition, each sample was followed either by a vertical line (“remember” cue), which indicated that sample memory would be tested, or by a horizontal line (“forget” cue), which indicated that sample memory would not be tested. During the experiments, sample memory on forget trials was tested occasionally. A series of five experiments revealed: (a) better retention on remember trials than on forget trials, (b) increased effectiveness of a forget cue when it followed closely sample offset, (c) more rapid forgetting over a retention interval ranging from 3 to 6 sec on forget trials than on remember trials, (d) a “cancellation” effect in which a remember cue which followed immediately the offset of a forget cue attenuated markedly the effectiveness of the forget cue, and (e) an “insulation” effect in which the effectiveness of a forget cue was reduced considerably when presented after a remember cue. It was concluded that pigeons actively process or rehearse the sample memory during the retention interval.