Effects of Level of Processing on Implicit and Explicit Memory in Depressed Mood

The present study investigated (a) whether the pattern of performance on implicit and explicit memory of patients with type 2 diabetes mellitus (DM2) is more similar to those of patients with Alzheimer's disease (AD) or to cognitively normal older adults and (b) whether glycosylated hemoglobin levels (a measure of glucose regulation) are related to performance on the two memory tasks, implicit word-stem completion and "old-new" recognition. The procedures of both memory tasks included encoding and memory test phases separated by a short delay. Three groups of participants (healthy older adults, DM2 patients and AD patients) completed medical and psychological assessments and performed both memory tasks on a computer. The results of the word-stem completion task showed similar implicit memory in the three groups. By contrast, explicit recognition of the three groups differed. Implicit memory was not affected by either normal or pathological aging, but explicit memory deteriorated in the two groups of patients, especially in AD patients, showing a severe impairment compared to the cognitively healthy older adults. Importantly, glycosylated hemoglobin levels were not related to performance on either implicit or explicit memory tasks. These findings revealed a clear dissociation between explicit and implicit memory tasks in normal and pathological aging. Neuropsychologists and clinicians working with TM2 patients should be aware that the decline of voluntary, long-term explicit memory could have a negative impact on their treatment management. By contrast, the intact implicit memory of the two clinical groups could be used in rehabilitation.

Explicit and implicit memory bias in panic disorder with agoraphobia

Two experiments were carried out to investigate a possible mood-congruent memory bias in explicit memory (free-recall test) and implicit memory (word-stem completion task) for positive and negative words in depressed and non depressed college students. A comparison of implicit and explicit mood-congruent memory bias should help to reveal cognitive processes involved in this effect. The results of both studies indicated that depressed subjects showed a memory bias not only on the traditional explicit memory task, but on the implicit memory task as well. The theoretical implications of these results are discussed.

Transfer‐appropriate processing theory (Roediger, Weldon, & Challis, 1989) proposes that dissociations between performance on explicit and implicit memory tests arise because these tests often rely on different types of information processing (e.g., perceptual processing vs conceptual processing). This perspective predicts that implicit and explicit memory tasks that rely primarily on conceptual processing should show comparable results, not dissociations. Numerous studies have demonstrated such similarities. It is, however, possible that these results arise from explicit memory contamination of performance on implicit memory tasks. To address this issue, an experiment was conducted in which participants were administered the sedative midazolam prior to study. Midazolam is known to create a temporary, but dense, period of anterograde amnesia. The effects of blocking stimulus materials by semantic category at study and generation at study were investigated on category exemplar production and category‐cued recall. The results of this study demonstrated a dissociation of the effects of midazolam on category exemplar production and category‐cued recall. Specifically, midazolam reduced the effect of blocking stimulus materials in category‐cued recall, but not in category exemplar production. The differential effect of midazolam on explicit and implicit memory is at odds with transfer‐appropriate processing theory and suggests that theories of memory must distinguish the roles of different types of conceptual processing on implicit and explicit memory tests.

ObjectiveTo investigate not only differential patterns of functional connectivity of core brain regions between implicit and explicit verbal memory tasks underlying negatively evoked emotional condition, but also correlations of functional connectivity (FC) strength with clinical symptom severity in patients with generalized anxiety disorder (GAD).MethodsThirteen patients with GAD and 13 healthy controls underwent functional magnetic resonance imaging for memory tasks with negative emotion words.ResultsClinical symptom and its severities of GAD were potentially associated with abnormalities of task-based FC with core brain regions and distinct FC patterns between implicit vs. explicit memory processing in GAD were potentially well discriminated. Outstanding FC in implicit memory task includes positive connections of precentral gyus (PrG) to inferior frontal gyrus and inferior parietal gyrus (IPG), respectively, in encoding period; a positive connection of amygdala (Amg) to globus pallidus as well as a negative connection of Amg to cerebellum in retrieval period. Meanwhile, distinct FC in explicit memory included a positive connection of PrG to inferior temporal gyrus (ITG) in encoding period; a positive connection of the anterior cingulate gyrus to superior frontal gyrus in retrieval period. Especially, there were positive correlation between GAD-7 scores and FC of PrG-IPG (r2 = 0.324, p = 0.042) in implicit memory encoding, and FC of PrG-ITG (r2 = 0.378, p = 0.025) in explicit memory encoding.ConclusionThis study clarified differential patterns of brain activation and relevant FC between implicit and explicit verbal memory tasks underlying negative emotional feelings in GAD. These findings will be helpful for an understanding of distinct brain functional mechanisms associated with clinical symptom severities in GAD.

Intact and impaired conceptual memory processes in amnesia.

The present research was designed to provide a direct test of the transfer-appropriate processing framework as it applies to performance on two implicit memory tasks and also to identify the component processes that are engaged on these memory tasks. The general strategy involved employing study tasks that mimicked (more so than a standard Read condition) the processing that appears to occur during the memory task. Performance on a stem-- completion task was not consistently enhanced by a study task in which participants selected potential word endings for the three-letter stems. However, inducing participants to engage in a letter-substitution task during encoding enhanced priming on a fragment-completion test, relative to the standard Read condition. Consistent with the transfer-- appropriate processing framework, the letter-substitution task showed evidence of optimizing priming effects, as additional manipulations of similarity had no further effect on performance on the implicit test. The data suggest that the Read condition does not induce maximum processing, as has been suggested previously, whereas a letter-by-letter substitution strategy mimics the processes used to complete word fragments on an implicit test. However, participants may not normally solve word stems by generating possible word endings and then selecting among these alternatives. Implicit memory tasks are operationally defined as memory tests for which the participant is given no instructions to consciously retrieve information from a prior study list, even though performance on the test may be affected by exposure to the prior study list. By contrast, explicit memory tests are defined as those for which the participant is given instructions at test to retrieve previously studied information (e.g., Richardson-Klavehn & Bjork, 1988). Although everyday uses of memory likely establish a predominant role for implicit memory (see also Masson & Graf, 1993), the extensive theoretical and empirical interest in implicit test performance over the last several years appears to have been motivated by two findings in particular. First, it is now well-established that individuals suffering from amnesia show performance on implicit memory tests that often does not differ from that of people with normal memory function (Morris & Kopelman, 1986; Richardson-- Klavehn & Bjork, 1988; Schacter, 1987; Shimamura, 1986, 1993). Although there are a few exceptions to this pattern (e.g., Hamann & Squire, 1996; Hodges, Salmon, & Butters, 1992), the generalization holds across a large number of etiological bases for the amnesia, including most forms of temporary and permanent amnesia. The second reason for interest in implicit memory is the finding that many independent variables have different effects on implicit and explicit memory performance. This research has been summarized in several places (e.g., Roediger & McDermott, 1993). Of primary relevance to the present work is the finding that performance on most tests of implicit memory is driven primarily by processing of the stimulus whereas performance on most tests of explicit memory is driven primarily by conceptual processing. Several aspects of processing have been shown to affect performance on these implicit memory tests, including typographic format (e.g., Clarke & Morton, 1983; Graf & Ryan, 1990; Jacoby & Hayman, 1987) and modality (e.g., Graf, Shimamura, & Squire, 1985; Jacoby & Dallas, 1981; Roediger & Blaxton, 1987). In contrast, conceptual processing yields much larger effects on explicit memory tasks than on implicit memory tasks (e.g., Gellatly, Parker, Blurton, & Woods, 1994). One of the most widely cited examples of this is the manipulation of depth of processing at study: Whereas depth effects are well-established on explicit tasks (e.g., Craik & Tulving, 1975), they are generally much smaller or even nonexistent on standard perceptual implicit tasks (for reviews, see Brown & Mitchell, 1994; Challis & Brodbeck, 1992; see also Hamann & Squire, 1996; Thapar & Greene, 1994). …

How our memory is affected as we age has been given considerable attention over recent decades as we strive to understand the cognitive processes involved. Memory types have been identified as either explicit (declarative - related to episodes or semantics) or implicit (non-declarative – related to procedures, habits, or earlier priming). Studies have identified likely age-related decline in explicit but not implicit memory though there are opposing results suggested from other studies. It is thought cognitive reserve capacities might explain any non-decline as aging individuals use alternative or additional pathways to ‘remember’. This theory might be supported indirectly if older members remember material accurately but take longer to supply answers. In our current study we re-examined whether age-related differences in accuracy and speed of access in memory are present in both implicit and explicit memory processes and we increased the number of experimental age groups (from 2 to 3) - most previous studies have compared just two groups (young, and old). With three groups (young, middle-old, and older aged groups) we can identify trends across the age range towards deterioration or preservation of memory. We examined sixty-six participants (49 females; 17 males) aged 18 to 86 years (M = 50.27, SD = 21.06) from South-Eastern Queensland and divided these into younger (18 to 46 years of age), middle old (50 to 64) and older aged (65+) cohorts. Participants were administered tasks assessing implicit and explicit memory using computer presentations. Consistent with most prior research, no age differences were identified on accuracy in the implicit memory tasks (verbal and non-verbal, including priming), suggesting that memory for implicit material remains preserved. However, on the explicit memory tasks, older adults performed less accurately than the younger adults, indicative of decline in explicit memory as we age. The finding of a decline in explicit memory but no significant decline in implicit memory confirms most earlier research and is consistent with a view of modular decline rather than overall decline in memory with increasing age. In addition, differences found in speed of response in otherwise accurate implicit memory with older respondents significantly slower, suggests possible support for the cognitive reserve hypothesis.

Purpose – Prescription drug advertisements are commonly seen in magazines and on television. Many drug ads are targeted toward older adults, who tend to use more medications and suffer from more chronic conditions. Nonetheless, the effectiveness of such advertising remains uncertain. The aim of this paper is to compare implicit and explicit memory for drug ads in older and younger adults. Design/methodology/approach – Older adults typically perform more poorly than young adults on explicit memory tasks, but not on implicit memory tasks. The current study measured implicit memory with an incidental ratings exercise and an indirect test of preference; explicit memory was also measured with intentional studying and a direct test of recognition. The study was a 2 x 2 mixed experimental design with one between-participants variable and one within-participants variable. The between-participants variable was age group (older vs younger adults) and the within-participants variable was implicit and explicit memory. The memory test measures were the outcome variables of the study. Findings – The results showed no age difference for implicit memory for drug ads, but an age difference was found for explicit memory for the ads. The implicit memory manipulation succeeded in demonstrating that drug ads are persuasive, suggesting that a complete assessment of advertising effectiveness should include a test of implicit memory. Research limitations/implications – The fact that age differences were not found for implicit memory, but were found for explicit memory, is not surprising. Practical implications – The study is of theoretical significance because it contributes to cognitive aging research and examines memory within an everyday context. The study is of practical significance because pharmaceutical companies spend vast amounts of money on prescription drug advertisements that may or may not be effective with older adults. The component of this study that may be most important is that the results expanded everyday memory research to another applied context using an implicit memory measure, and the indirect test of memory demonstrated that the prescription drug advertising was effective. Originality/value – Although the findings were consistent with previous research, the study focuses on the real-world context of direct-to-consumer advertising for prescription drugs. Given that older adults have poorer explicit memory than younger adults, but not poorer implicit memory, it is particularly important for advertisers to use implicit memory measures when assessing advertisements aimed at older adult consumers. Marketers of pharmaceutical drug companies must remain aware that the memory abilities of their potential customers are extremely variable, and in some cases, limited.

The aim of this study was to investigate the effect of emotional load of words (positive, negative and neutral) on explicit and implicit memory performances of participants with low and high alexithymia levels. The sample of the study consisted of 381 participants who were undergraduate students studying at Aydın Adnan Menderes University (M = 20.48, S = 1.73), with the age range between 18 and 26, and the second stage was consisted of 95 participants (M = 21,07, S = 2.21) with the age range between 18 and 26. Demographic Information Form and Toronto Alexithymia Scale were applied to the participants at the first stage. Participants who obtained one standard deviation below and above from Toronto Alexithymia Scale were invited to the second stage. Then the word completion task (implicit memory task) and free recall task (explicit task) were applied. The experimental design was 2 (Alexithymia Lev-el: low and high) x 3 (Emotional Use of Words: positive, negative, neutral) mixed ANOVA. The results showed significant difference between low and high alexithymia on explicit memory task. Participants with high levels of alexithymia remembered fewer words than those with low levels. There was no significant difference in neutral words on the main effect of emotional load according to alexithymia level. However, the group with high alexithymia remembered positive and negative words less than neutral words as compared to low alexithymia group. There was no significant difference in implicit memory performance according to interaction effect of alexithymia level and emotional load. Findings showed that high alexithymia level caused a deterioration on explicit memory but did not cause an impairment on implicit memory. The effect of alexithymia level on performance of remembering emotional words in explicit memory and implicit memory tasks was discussed in the light of emotional memory enhancement effect and related literature.

Background: Previous research has indicated that persecutory delusions and depression may share similar cognitive biases at implicit levels of processing, but differentiate at explicit levels, supporting the theory that paranoia may have a protective function against underlying negative schemata. The study aimed to investigate attentional bias and both implicit and explicit memory biases for personally salient and standardised emotional stimuli in persecutory delusions and depression. Sampling: 36 participants, with 12 in each group, were interviewed in order to generate personally salient stimuli to be employed within the cognitive tests. Standardised emotional stimuli were additionally employed as a control. Participants completed two probe detection tasks, one including personally salient stimuli and one including standard emotional stimuli. Memory for the stimuli presented in this task was assessed by a free recall task (explicit memory) followed by a word completion task (implicit memory). Results: On an implicit memory task, both the deluded and depressed groups displayed comparable retrieval of positive and negative words. However, on the explicit memory task, the depressed group demonstrated a bias for negative stimuli, whereas the deluded group demonstrated a bias for positive stimuli. The groups did not demonstrate an attentional bias for personally salient information. However, an attentional bias for standardised emotional stimuli was found in the depressed group, although this was not specific to either negative or positive stimuli. Conclusion: The results indicate that depression and persecutory delusions may share similar patterns of processing at an implicit level but differentiate at the explicit level, which may be indicative of cognitive avoidance of threatening stimuli in psychosis. However, this does not seem to be a feature of automatic attentional processes in people with persecutory delusions. Implications for further research are discussed.

The influence of response bias on tests of implicit and explicit memory was assessed by using word-stem completion and recognition. During acquisition, subjects were presented either with a list of words unrelated to the task in the retrieval phase or with a list of words whose stems could be completed in only two ways (e.g. “appeal,” “appear”). In the word-stem-completion retrieval phase, the subjects, who were given either explicit or implicit memory instructions, were asked to complete these stems. Retrieval of items in implicit and explicit memory tasks was highly correlated (r =.593 and.625, respectively) when the acquisition list had contained the words completing the stems and similarly correlated (r =.667) when the acquisition list had contained no words completing the stems. There was no correlation between recognition and explicit stem completion. In contrast to stem completion, there was no overall correlation between “recognition” in the condition in which the acquisition list contained words to be recognized later and the guessing condition, in which the acquisition list had contained no words presented during the retrieval phase. However, when the items were divided into two groups differing in memorability, a negative correlation appeared between recognition and guessing probability with the more memorable items, and a positive correlation appeared with the less memorable items. This suggests that response bias, rather than the memory the tasks are designed to test, is responsible for the normally reported lack of correlation between recognition and word completion.

We tested the idea that real-world situations, such as the highly strenuous exercise involved in marathon running, that impose extreme physical demands on an individual may result in neurohormonal changes that alter the functioning of memory. Marathon runners were given implicit and explicit memory tasks before or immediately after they completed a marathon. Runners tested immediately upon completing the marathon showed impairment in the explicit memory task but enhancement in the implicit memory task. This postmarathon impairment in explicit memory is similar to that seen with amnesic patients with organic brain damage. However, no previous studies have shown a simultaneous enhancement in the implicit memory task, as shown by the marathon runners in the present study. This study indicates that human memory functioning can be dynamically altered by such activities as marathon running, in which hundreds of thousands of healthy normal individuals routinely partake.

Role of columns in data processing by linking patterns for memory compression and especially for formation of hierarchical knowledge structure

Biais mnésique associé à l’humeur dépressive : quelques réflexions critiques