Automatic influences of memory in Alzheimer's disease

Explicit and implicit memory for music in healthy older adults and patients with mild Alzheimer's disease

Introduction: Previous studies have found that music paired with lyrics at encoding may improve the memory performance of patients with mild Alzheimer's disease (AD). To further explore memory for different types of musical stimuli, the current study examined both implicit and explicit memory for music with and without lyrics compared to spoken lyrics. Method: In this mixed design, patients with probable mild AD (n = 15) and healthy older adults (n = 13) listened to auditory clips (song, instrumental, or spoken lyrics varied across three sessions) and then had their memory tested. Implicit memory was measured by the mere exposure effect. Explicit recognition memory was measured using a confidence-judgment receiver operating characteristic (ROC) paradigm, which allowed examination of the separate contributions made by familiarity and recollection. Results: A significant implicit memory mere exposure effect was found for both groups in the instrumental and song but not the spoken condition. Both groups had the best explicit memory performance in the spoken condition, followed by song, and then instrumental conditions. Healthy older adults demonstrated more recollection than patients with AD in the song and spoken conditions, but both groups performed similarly in the instrumental condition. Patients with AD demonstrated more familiarity in the instrumental and song conditions than in the spoken condition. Conclusions: The results have implications for memory interventions for patients with mild AD. The implicit memory findings suggest that patients with AD may still show a preference for information familiar to them. The explicit memory results support prior findings that patients with AD rely heavily on familiarity, but also suggest that there may be limitations on the benefits that music can provide to recognition memory performance.

Response bias and response monitoring: Evidence from healthy older adults and patients with mild Alzheimer's disease

Patients with Alzheimer's disease (AD) often exhibit an abnormally liberal response bias in recognition memory tests, responding "old" more frequently than "new." Investigations have shown patients can to shift to a more conservative response bias when given instructions. We examined if patients with mild AD could alter their response patterns when the ratio of old items is manipulated without explicit instruction. Healthy older adults and AD patients studied lists of words and then were tested in three old/new ratio conditions (30%, 50%, or 70% old items). A subset of participants provided estimates of how many old and new items they saw in the memory test. We demonstrated that both groups were able to change their response patterns without the aid of explicit instructions. Importantly, AD patients were more likely to estimate seeing greater numbers of old than new items, whereas the reverse was observed for older adults. Elevated estimates of old items in AD patients suggest their liberal response bias may be attributed to their reliance on familiarity. We conclude that the liberal response bias observed in AD patients is attributable to their believing that more of the test items are old and not due to impaired meta-memorial monitoring abilities.

Changes in response bias with different study-test delays: evidence from young adults, older adults, and patients with Alzheimer's disease

OBJECTIVE

Along with impaired discrimination, patients with Alzheimer's disease (AD) often show an abnormally liberal response bias (greater tendency to respond "old"). Previously we matched discrimination by varying study-test list length and found that participants' usual bias is maintained, such that patients with AD were more liberal than healthy controls. However, this pattern could be a result of the way in which discrimination was matched. In this experiment, we examined whether matching discrimination with the use of a delay would lead to a liberal response bias in healthy younger and older adults as it might lead to the use of more similar memorial processing to the patients with AD.

METHOD

Younger adults, older adults, and patients with AD were run in 2 study-test sessions, with study and recognition test separated by either a 1-min or 1-day delay.

RESULTS

With the 1-min delay, both younger adults and healthy older adults showed a conservative response bias, while patients with AD showed a liberal response bias. When discrimination was matched between patients with AD and controls by the use of a delay, response bias was also matched, with all participants showing a more liberal response bias.

CONCLUSIONS

The current study suggests that how discrimination is matched between patients with AD and controls matters greatly. Potentially, this liberal bias is a result of healthy younger and older adults relying primarily on familiarity at the longer delay, thus using more similar memorial processes to patients with AD who are dependent on familiarity at any delay.

Gist-based conceptual processing of pictures remains intact in patients with amnestic mild cognitive impairment

OBJECTIVE

The picture superiority effect, better memory for pictures compared to words, has been found in young adults, healthy older adults, and, most recently, in patients with Alzheimer's disease and mild cognitive impairment. Although the picture superiority effect is widely found, there is still debate over what drives this effect. One main question is whether it is enhanced perceptual or conceptual information that leads to the advantage for pictures over words. In this experiment, we examined the picture superiority effect in healthy older adults and patients with amnestic mild cognitive impairment (MCI) to better understand the role of gist-based conceptual processing.

METHOD

We had participants study three exemplars of categories as either words or pictures. In the test phase, participants were again shown pictures or words and were asked to determine whether the item was in the same category as something they had studied earlier or whether it was from a new category.

RESULTS

We found that all participants demonstrated a robust picture superiority effect, better performance for pictures than for words.

CONCLUSIONS

These results suggest that the gist-based conceptual processing of pictures is preserved in patients with MCI. While in healthy older adults preserved recollection for pictures could lead to the picture superiority effect, in patients with MCI it is most likely that the picture superiority effect is a result of spared conceptually based familiarity for pictures, perhaps combined with their intact ability to extract and use gist information.

Using stimulus form change to understand memorial familiarity for pictures and words in patients with mild cognitive impairment and Alzheimer's disease

Although it is generally accepted that patients with amnestic mild cognitive impairment (aMCI) and patients with Alzheimer's disease (AD) have significantly impaired recollection, recent evidence has been mixed as to whether these patients demonstrate impaired memorial familiarity. Recent work suggests that familiarity may remain intact for pictures, but not for words. Further, a recent event-related potential (ERP) study suggests that enhanced conceptual processing of pictures may underlie this intact familiarity. However, to date there has been no direct comparison of perceptual and conceptual-based familiarity for pictures and words in patients with aMCI and AD. To investigate this issue, patients with aMCI, patients with AD, and healthy older adults underwent four study-test conditions of word-word, picture-picture, word-picture, and picture-word. When stimuli undergo form change, it has been suggested that only conceptual processing can help support recognition in the absence of recollection. Our results showed that patients successfully relied on perceptual and conceptual-based familiarity to improve recognition for the within format conditions over the across format conditions. Further, results suggested that patients with aMCI and AD are able to use enhanced conceptual processing of pictures compared to words to allow them to overcome the deleterious effects of form change in a similar manner as controls. These results help us begin to understand which aspects of memory are impaired and which remain relatively intact in patients with aMCI and AD. This understanding can then in turn help us to assess, conceptualize, and build behavioral interventions to help treat these patients.

The utility of placing recollection in opposition to familiarity in early discrimination of healthy aging and very mild dementia of the Alzheimer's type

This study explored the ability to control familiarity-based information in a memory exclusion paradigm in healthy young, older adults, and early stage DAT individuals. We compared the predictive power of memory exclusion performance to standard psychometric performance in discriminating between aging and the earliest stage of DAT and between APOe4-present and APOe4-absent genotype in healthy control individuals. Participants responded "yes" to words that were previously semantically encoded, and "no" to words that were previously read aloud and to new words. The number of targets and distractors on the read "distractor" list was manipulated to investigate the degree to which aging and DAT influence the ability to recollect in the face of distractor familiarity due to repetition. Memory exclusion performance was better for healthy older adults than very mild DAT individuals and better for healthy control individuals with APOe4 allele than those without APOe4 allele even after controlling for standard psychometric performance. Discussion focuses on the importance of attentional control systems in memory retrieval and the utility of the opposition paradigm for discriminating healthy versus pathological aging.

Preserved frontal memorial processing for pictures in patients with mild cognitive impairment

Amnestic mild cognitive impairment (aMCI) has been conceptualized as a transitional stage between healthy aging and Alzheimer's disease (AD). Therefore, understanding which aspects of memory are impaired and which remain relatively intact in these patients can be useful in determining who will ultimately go on to develop AD, and subsequently designing interventions to help patients live more engaged and independent lives. The dual-process model posits that recognition memory decisions can rely on either familiarity or recollection. Whereas research is fairly consistent in showing impaired recollection in patients with aMCI, the results have been mixed regarding familiarity. A noted difference between these studies investigating familiarity has been stimulus type. The goal of the current investigation was to use high-density event-related potentials (ERPs) to help elucidate the neural correlates of recognition decisions in patients with aMCI for words and pictures. We also hoped to help answer the question of whether patients can rely on familiarity to support successful recognition. Patients and controls participated in separate recognition memory tests of words and pictures while ERPs were recorded during retrieval. Results showed that ERP components typically associated with familiarity and retrieval monitoring were similar between groups for pictures. However, these components were diminished in the patient group for words. Based on recent work, the authors discuss the possibility that implicit conceptual priming could have contributed to the enhanced ERP correlate of familiarity. Further, the authors address the possibility that enhanced retrieval monitoring may be needed to modulate increased familiarity engendered by pictures.

An evaluation of recollection and familiarity in Alzheimer's disease and mild cognitive impairment using receiver operating characteristics

There is a need to investigate exactly how memory breaks down in the course of Alzheimer's disease (AD). Examining what aspects of memorial processing remain relatively intact early in the disease process will allow us to develop behavioral interventions and possible drug therapies focused on these intact processes. Several recent studies have worked to understand the processes of recollection and familiarity in patients with mild cognitive impairment (MCI) and very mild AD. Although there is general agreement that these patient groups are relatively unable to use recollection to support veridical recognition decisions, there has been some question as to how well these patients can use familiarity. The current study used receiver operating characteristic (ROC) curves and a depth of processing manipulation to understand the effect of MCI and AD on the estimates of recollection and familiarity. Results showed that patients with MCI and AD were impaired in both recollection and familiarity, regardless of the depth of encoding. These results are discussed in relation to disease pathology and in the context of recent conflicting evidence as to whether familiarity remains intact in patients with MCI. The authors highlight differences in stimuli type and task difficulty as possibly modulating the ability of these patients to successfully use familiarity in support of memorial decisions.

Effects of distinctive encoding on source-based false recognition: further examination of recall-to-reject processes in aging and Alzheimer disease

OBJECTIVE

To examine the use of distinctive materials at encoding on recall-to-reject monitoring processes in aging and Alzheimer disease (AD).

BACKGROUND

AD patients, and to a lesser extent older adults, have shown an impaired ability to use recollection-based monitoring processes (eg, recall-to-reject) to avoid various types of false memories, such as source-based false recognition.

METHOD

Younger adults, healthy older adults, and AD patients engaged in an incidental learning task, in which critical category exemplars were either accompanied by a distinctive picture or were presented as only words. Later, participants studied a series of categorized lists in which several typical exemplars were omitted and were then given a source memory test.

RESULTS

Both older and younger adults made more accurate source attributions after picture encoding compared with word-only encoding, whereas AD patients did not exhibit this distinctiveness effect.

CONCLUSIONS

These results extend those of previous studies showing that monitoring in older adults can be enhanced with distinctive encoding, and suggest that such monitoring processes in AD patients many be insensitive to distinctiveness.

Automatic memory processes in normal ageing and Alzheimer's disease

This study examined the contribution of automatic and controlled uses of memory to stem completion in young, middle-aged and older adults, and compared these data with a study involving patients with Alzheimer's disease (AD) who performed the same task (Hudson and Robertson, 2007). In an inclusion task participants aimed to complete three-letter word stems with a previously studied word, in an exclusion task the aim was to avoid using studied words to complete stems. Performances under inclusion and exclusion conditions were contrasted to obtain estimates of controlled and automatic memory processes using process-dissociation calculations (Jacoby, 1991). An age-related decline, evident from middle age was observed for the estimate of controlled processing, whereas the estimate of automatic processing remained invariant across the age groups. This pattern stands in contrast to what is observed in AD, where both controlled and automatic processes have been shown to be impaired. Therefore, the impairment in memory processing on stem completion that is found in AD is qualitatively different from that observed in normal ageing.

Autonoetic consciousness in Alzheimer's disease: Neuropsychological and PET findings using an episodic learning and recognition task

OBJECTIVE

This study aims to map in patients with mild Alzheimer's disease (AD) the correlations between resting-state brain glucose utilization measured by FDG-PET and scores reflecting autonoetic consciousness in an episodic learning and recognition task.

METHODS

Autonoetic consciousness, that gives a subject the conscious feeling to mentally travelling back in time to relive an event, was assessed using the Remember/Know (R/K) paradigm.

RESULTS

AD patients provided less R responses (reflecting autonoetic consciousness) and more K ones (indicating the involvement of noetic consciousness) than healthy controls. Correct recognitions associated with a R response correlated with the metabolism of frontal areas bilaterally whereas those associated with a K response mainly correlated with the metabolism of left parahippocampal gyrus and lateral temporal cortex.

CONCLUSIONS

These data show that recollection is impaired in AD and recognition is more based on a feeling of familiarity than in controls. In addition, the findings of our correlative approach indicate that the impairment of episodic memory is mainly subserved by the dysfunction of frontal areas and of the hippocampal region.

Conceptual fluency at test shifts recognition response bias in Alzheimer's disease: implications for increased false recognition

The presence or absence of conceptual information in pictorial stimuli may explain the mixed findings of previous studies of false recognition in patients with mild Alzheimer's disease (AD). To test this hypothesis, 48 patients with AD were compared to 48 healthy older adults on a recognition task first described by Koutstaal et al. [Koutstaal, W., Reddy, C., Jackson, E. M., Prince, S., Cendan, D. L., & Schacter D. L. (2003). False recognition of abstract versus common objects in older and younger adults: Testing the semantic categorization account. Journal of Experimental Psychology: Learning, Memory, and Cognition, 29, 499-510]. Participants studied and were tested on their memory for categorized ambiguous pictures of common objects. The presence of conceptual information at study and/or test was manipulated by providing or withholding disambiguating semantic labels. Analyses focused on testing two competing theories. The semantic encoding hypothesis, which posits that the inter-item perceptual details are not encoded by AD patients when conceptual information is present in the stimuli, was not supported by the findings. In contrast, the conceptual fluency hypothesis was supported. Enhanced conceptual fluency at test dramatically shifted AD patients to a more liberal response bias, raising their false recognition. These results suggest that patients with AD rely on the fluency of test items in making recognition memory decisions. We speculate that AD patients' over reliance upon fluency may be attributable to (1) dysfunction of the hippocampus, disrupting recollection, and/or (2) dysfunction of prefrontal cortex, disrupting post-retrieval processes.

Automatic and Controlled Uses of Memory in Alzheimer's Disease

This study used the process-dissociation procedure (Jacoby, 1991) to examine the contribution of automatic and controlled uses of memory to a stem completion task in 16 patients with Alzheimer's disease (AD) and a matched group of healthy elderly subjects (EC). In an inclusion task subjects attempted to use a studied word to complete three-letter word stems, in an exclusion task they were instructed to complete stems with unstudied words. Relative to patients with AD, EC subjects produced more target word completions under inclusion conditions, and less target word completions under exclusion conditions. The probability of the AD group using studied words to complete stems was invariant across inclusion and exclusion conditions. Estimates derived from the process-dissociation calculations, showed that the performance of the AD patients was mediated entirely by automatic uses of memory, whereas for EC subjects controlled and automatic processes codetermined task performance. Both estimates of controlled and to a lesser extent automatic uses of memory were greater for the EC than the AD subjects, indicating that the stem completion impairment in AD may not be entirely attributable to a deficiency in controlled memory processes but also due to reduced automatic processing.

Episodic memory in Alzheimer's disease: separating response bias from discrimination

Most studies examining episodic memory in Alzheimer's disease (AD) have focused on patients' impaired ability to remember information, leading to poor discrimination between studied and unstudied items at test. Poor discrimination, however, can also be attributable to an abnormally high rate of false alarms. One cause of a high false alarm rate is an abnormally liberal response bias; that is, responding "old" too liberally to the test items. In the present study, discrimination and response bias were evaluated when participants were given a series of progressively longer study-test lists of unrelated words. As expected, patients with AD showed overall worse discrimination and a more liberal response bias compared with older adult controls. Critically, patients with AD also showed a more liberal response bias than older adults when discrimination was matched between the groups after performance was equated by giving the older adult controls a more difficult test than the patients with AD. This result confirms that the patients' abnormally liberal response bias is not simply attributable to their poor discrimination. Correlation analyses suggest that the patients' liberal response bias is related to the degree of their episodic memory deficit, which may in turn be related to the severity of their disease. Thus, our research suggests that as AD progresses two distinct abnormalities of episodic memory develop: worse discrimination and a more liberal response bias. Possible explanations of this liberal response bias in patients with AD are discussed.

When memory does not fail: Familiarity-based recognition in mild cognitive impairment and Alzheimer's disease

Recognition can be guided by familiarity, a restricted form of retrieval devoid of contextual recall, or by recollection, which occurs when retrieval is sufficient to support the full experience of remembering an episode. Recollection and familiarity were disentangled by testing recognition memory using silhouette object drawings, high target-foil resemblance, and both yes-no and forced-choice procedures. Theoretically, forced-choice recognition could be mediated by familiarity alone. Alzheimer's disease and its preclinical stage, mild cognitive impairment (MCI), were associated with memory impairments that were greater on the yes-no test. Remarkably, forced-choice recognition was unequivocally normal in patients with MCI compared with age-matched controls. Neuropathology in hippocampus and entorhinal cortex, known to be present in MCI, presumably disrupted recollection while leaving familiarity-based recognition intact.

Controlled and automatic uses of memory in depressed patients: effect of retention interval lengths

The present study examines controlled and automatic uses of memory in clinically depressed patients by applying the Process Dissociation Procedure developed by Jacoby (1991) to a stem completion memory task with short and long retention intervals. The results show that the contribution of controlled processes is lower in depressed patients than in controls, especially for the longest retention interval, whereas the contribution of automatic processes is equivalent in both groups and unaffected by the length of the retention interval. These findings are discussed in a cognitive control framework.

Metacognition and False Recognition in Alzheimer's Disease: Further Exploration of the Distinctiveness Heuristic

The distinctiveness heuristic is a response mode in which participants expect to remember vivid details of an experience and make recognition decisions on the basis of this metacognitive expectation. The authors examined whether the distinctiveness heuristic could be engaged to reduce false recognition in a repetition-lag paradigm in patients with Alzheimer's disease (AD). Patients with AD were able to use the distinctiveness heuristic--though not selectively--and thus they showed reduction of both true and false recognition. The authors suggest that patients with AD can engage in decision strategies on the basis of the metacognitive expectation associated with use of the distinctiveness heuristic, but the patients' episodic memory impairment limits both the scope and effectiveness of such strategies.

Further Exploration of Controlled and Automatic Memory Processes in Early Alzheimer's Disease

The authors' aim in this study was to explore automatic and controlled processes in Alzheimer's disease (AD) by using a variant of the word-stem completion task that applies the process-dissociation procedure. Several methodological precautions were taken in order to limit problems observed in previous studies (e.g., poor task sensitivity, ceiling and/or floor effects, no control over comprehension of instructions). Our results (a) confirmed the marked deterioration in controlled processes and (b) showed that when psychometric constraints were limited, automatic memory processes were preserved in AD. These data are in line with those from more global studies in suggesting that AD is characterized by an early deterioration in controlled processes and an initial preservation of automatic processes.

Patients with mild Alzheimer's disease attribute conceptual fluency to prior experience

Patients with Alzheimer's disease (AD) have been found to be relatively dependent on familiarity in their recognition memory judgments. Conceptual fluency has been argued to be an important basis of familiarity. This study investigated the extent to which patients with mild AD use conceptual fluency cues in their recognition decisions. While no evidence of recognition memory was found in the patients with AD, enhanced conceptual fluency was associated with a higher rate of "Old" responses (items endorsed as having been studied) compared to when fluency was not enhanced. The magnitude of this effect was similar for patients with AD and healthy control participants. Additionally, ERP recordings time-locked to test item presentation revealed preserved modulations thought critical to the effect of conceptual fluency on test performance (N400 and late frontal components) in the patients with AD, consistent with the behavioral results. These findings suggest that patients with mild AD are able to use conceptual fluency in their recognition judgments and the neural mechanisms supporting such processing is maintained.

Two aspects of impaired consciousness in Alzheimer's disease

Alzheimer's disease (AD) is a degenerative dementia characterized by different aspects of impaired consciousness. For example, there is a deficit of controlled processes that require conscious processing of information. Such an impairment is indexed by decreased performances at controlled cognitive tasks, and it is related to reduced brain metabolic activity in a network of frontal, posterior associative, and limbic regions. Another aspect of impaired consciousness is that AD patients show variable levels of anosognosia concerning their cognitive deficits. A discrepancy score between patient's and caregiver's assessment of cognitive functions is one of the most frequently used measures of anosognosia. A high discrepancy score has been related to impaired activity in the superior frontal sulcus and the parietal cortex in AD. Anosognosia for cognitive deficits in AD could be partly explained by impaired metabolism in parts of networks subserving self-referential processes (e.g., the superior frontal sulcus) and perspective-taking (e.g., the temporoparietal junction). We hypothesize that these patients are impaired in the ability to see themselves with a third-person perspective (i.e., being able to see themselves as other people see them).

Associative recognition in Alzheimer's disease: evidence for impaired recall-to-reject

Patients with mild Alzheimer's disease (AD) were compared with age-matched control subjects on an associative recognition task. Subjects studied pairs of unrelated words and were later asked to distinguish between these same studied pairs (intact) and new pairs that contained either rearranged studied words (rearranged) or non-studied words (non-studied). Studied pairs were presented either once or 3 times. Repetition increased hits to intact pairs in both groups, but repetition increased false alarms to rearranged pairs only in patients. This latter pattern indicates that repetition increased familiarity of the rearranged pairs, but only the control subjects were able to counter this familiarity by recalling the originally studied pairs (a recall-to-reject process). AD impaired this recall-to-reject process, leading to more familiarity based false alarms. These data support the idea that recollection-based monitoring processes are impaired in mild AD.

Effects of Alzheimer's disease on the recognition of novel versus familiar words: neuropsychological and clinico-metabolic data

This study explored recognition memory performance for novel versus familiar words in Alzheimer's disease (AD) patients and normal controls (NCs), using an adaptation of E. Tulving and N. Kroll's (1995) procedure. Results showed that both groups exhibited more hits and more false alarms for familiar than for novel words. The groups did not differ in the recognition of familiar words, reflecting preserved familiarity processes in AD. However, AD patients made more false alarms than NCs in the recognition of novel words, reflecting impairment of recollection processes in AD. A positron emission tomography analysis of clinico-metabolic correlations in AD patients showed a correlation between recognition of novel words and right hippocampal activity, whereas recognition of familiar words was more related to metabolic activity in the left posterior orbitofrontal cortex.

Brain correlates of performance in a free/cued recall task with semantic encoding in Alzheimer disease

The goal of this study was to explore in patients with Alzheimer's disease (AD) the brain correlates of free and cued recall performance using an adaptation of the procedure developed by Grober and Buschke (1987). This procedure, which ensures semantic processing and coordinates encoding and retrieval, has been shown to be very sensitive to an early diagnosis of AD. Statistical parametric mapping (SPM 99) was used to establish clinicometabolic correlations between performance at free and cued verbal recall and resting brain metabolism in 31 patients with AD. Results showed that patient's score on free recall correlated with metabolic activity in right frontal regions (BA 10 and BA 45), suggesting that performance reflected a strategic retrieval attempt. Poor retrieval performance was tentatively attributed to a loss of functional correlation between frontal and medial temporal regions in patients with AD compared with elderly controls. Performance on cued recall was correlated to residual metabolic activity in bilateral parahippocampal regions (BA 36), suggesting that performance reflected retrieval of semantic associations, without recollection in AD. In conclusion, this study demonstrates that the diagnostic sensitivity for Alzheimer's disease of the cued recall performance in the Grober and Buschke procedure (1987) depends on the activity of parahippocampal regions, one of the earliest targets of the disease. Moreover, the results suggest that the poor performance of patients with AD during free and cued recall is related to a decreased connectivity between parahippocampal regions and frontal areas.

Conscious and unconscious uses of memory in multiple sclerosis

Conscious and unconscious uses of memory and priming were studied in 30 patients with multiple sclerosis (MS) and 15 normal control (NC) subjects. MS patients were classified into two subgroups according to their cognitive status; 15 of them were cognitively deteriorated (the MS-D group) and 15 cognitively preserved (the MS-P group). A process dissociation procedure [J. Mem. Lang. 30 (1991) 513] was used to separate conscious and unconscious memory performance in a word stem completion task. The results showed that the MS-D group had deficient conscious memory performance, but had intact unconscious memory as well as priming. The MS-P group showed normal conscious and unconscious uses of memory and priming. Thus, in MS-related cognitive decline, conscious memory seems to be vulnerable, whereas unconscious memory remains intact. The results provide neuropsychological support for the distinction between conscious and unconscious memory processes. Moreover, the results show the importance of studying cognitively homogenous MS groups as opposed to heterogenous ones, in order to find the underlying mechanisms of memory deficits in MS. Interestingly, the neural systems needed for the unconscious use of memory do not seem to deteriorate even in MS patients with deficient overall cognitive capacity. This finding encourages the development of future rehabilitation programs, suggesting that unconscious remembering might help MS patients with deficient conscious memory to cope with their daily activities.

Memory processing in Alzheimer's disease

The aim of the present research was to examine automatic and controlled influences on memory processing in patients with Alzheimer's disease using the process-dissociation procedure. In Experiment 1, a source recognition procedure was used, and the patients were found to have significantly reduced estimates of automatic processing and capacity to recognise words seen during the study phase of the procedure. In Experiment 2, a detection of repetition procedure was used to determine whether automatic influences on memory decline as a dementia progressed. The patients showed the expected inability to detect repetition in their responding, but there was no evidence that estimates of automatic processing were predicted by mental status scores or by ratings of the severity of dementia. In the third study, a novel method for estimating parameters in the process-dissociation model, developed from the task used in Experiment 2, was tested in a student sample. In this procedure, participants first produce semantic associates with either high or low relatedness to a list of cue words. These responses are subsequently used in a paired associate learning paradigm to determine independent estimates of recollection and automatic processing. Evidence for the validity of this procedure was found in Experiment 3 and the procedure used to examine memory processing in a sample of persons with dementia (Experiment 4). The patient group was found to have a substantial deficit in controlled recollection and a reduced capacity for automatic memory processing.

The effects of repetition on allocation of study time and judgements of learning in Alzheimer's disease

Greene et al. [12] suggest that Alzheimer's disease (AD) patients approach repeated trials in a learning test as if they are single unrelated trials. Previous research [7] indicates that AD patients do not have explicit memory for item repetition when asked at test how many times a word was presented, but they do show benefits of repeated presentation in implicit tasks. In this experiment we examine metacognitive judgements made during study for repeated items. It was hypothesised that a lack of awareness of repetition may exacerbate the episodic memory impairment found in AD. To explore this, two measures of metamemory were taken for items presented once, twice or three times in a list: judgements of learning (JOLs), which are a declaration of how well an item has been learned, and recall readiness, which is the study time allocated by participants to ensure proficient learning of an item. With repetition, age matched controls made recall readiness judgements more quickly and reported higher JOLs. The AD patients showed faster recall readiness, but did not alter their JOLs. This suggests a dissociation in the AD group between judgements of learning and the allocation of study time. We discuss the implications for theories of the learning deficit in AD, and the use of metamemory measurements in clinical populations.