Memory processing in Alzheimer's disease

Urocanic acid facilitates acquisition of object recognition memory in mice

Trans-urocanic acid (UCA), an isomer of cis-UCA that is located in the skin, has recently been reported to have a role in short-term working memory and in the consolidation, reconsolidation and retrieval of long-term memory. However, its effect on memory acquisition remains unclear. In the present study, the effect of UCA on short-term and long-term memory acquisition in mice was investigated using novel object recognition (NOR) and object location recognition (OLR) protocols that each involved three stages: habituation, sampling and testing. UCA was intraperitoneally injected 0.5 h pre-sampling, and the discrimination index during subsequent testing was determined in NOR and OLR tasks. The results showed that 10 mg/kg UCA significantly facilitated short-term and long-term memory acquisition in both types of tasks. Furthermore, 30 mg/kg UCA significantly facilitated long-term memory acquisition in the NOR task and tended to facilitate long-term memory acquisition in the OLR tasks but did not facilitate short-term memory acquisition in either task. Additionally, the enhancing role of UCA on memory acquisition was not dependent on changes of nonspecific responses, e.g. exploratory behavior and locomotor activity. The current study suggests that UCA facilitates short-term and long-term recognition memory acquisition, which further extends the functional role of UCA in the brain function.

Short-Term Efficacy of Transcranial Focused Ultrasound to the Hippocampus in Alzheimer’s Disease: A Preliminary Study

Preclinical studies have suggested that low-intensity transcranial focused ultrasound (tFUS) may have therapeutic potential for Alzheimer’s disease (AD) by opening the blood–brain barrier (BBB), reducing amyloid pathology, and improving cognition. This study investigated the effects of tFUS on BBB opening, regional cerebral metabolic rate of glucose (rCMRglu), and cognitive function in AD patients. Eight patients with AD received image-guided tFUS to the right hippocampus immediately after intravenous injection of microbubble ultrasound contrast agents. Patients completed magnetic resonance imaging (MRI), ¹⁸F-fluoro-2-deoxyglucose positron emission tomography (PET), and cognitive assessments before and after the sonication. No evidence of transient BBB opening was found on T1 dynamic contrast-enhanced MRI. However, immediate recall (p = 0.03) and recognition memory (p = 0.02) were significantly improved on the verbal learning test. PET image analysis demonstrated increased rCMRglu in the right hippocampus (p = 0.001). In addition, increases of hippocampal rCMRglu were correlated with improvement in recognition memory (Spearman’s ρ = 0.77, p = 0.02). No adverse event was observed. Our results suggest that tFUS to the hippocampus of AD patients may improve rCMRglu of the target area and memory in the short term, even without BBB opening. Further larger sham-controlled trials with loger follow-up are warranted to evaluate the efficacy and safety of tFUS in patients with AD.

A systematic literature review of automatic Alzheimer's disease detection from speech and language

OBJECTIVE

In recent years numerous studies have achieved promising results in Alzheimer's Disease (AD) detection using automatic language processing. We systematically review these articles to understand the effectiveness of this approach, identify any issues and report the main findings that can guide further research.

MATERIALS AND METHODS

We searched PubMed, Ovid, and Web of Science for articles published in English between 2013 and 2019. We performed a systematic literature review to answer 5 key questions: (1) What were the characteristics of participant groups? (2) What language data were collected? (3) What features of speech and language were the most informative? (4) What methods were used to classify between groups? (5) What classification performance was achieved?

RESULTS AND DISCUSSION

We identified 33 eligible studies and 5 main findings: participants' demographic variables (especially age ) were often unbalanced between AD and control group; spontaneous speech data were collected most often; informative language features were related to word retrieval and semantic, syntactic, and acoustic impairment; neural nets, support vector machines, and decision trees performed well in AD detection, and support vector machines and decision trees performed well in decline detection; and average classification accuracy was 89% in AD and 82% in mild cognitive impairment detection versus healthy control groups.

CONCLUSION

The systematic literature review supported the argument that language and speech could successfully be used to detect dementia automatically. Future studies should aim for larger and more balanced datasets, combine data collection methods and the type of information analyzed, focus on the early stages of the disease, and report performance using standardized metrics.

Subjectively-defined optimal/non-optimal time of day modulates controlled but not automatic retrieval processes in verbal memory

Performance for controlled, resource-demanding retrieval in episodic memory has been consistently found to be better at an optimal compared with non-optimal time of the day, evidencing a synchrony effect. However, performance in memory tasks in which retrieval is mostly based on automatic processes was inconclusively found either to be better at a non-optimal time of day or independent of synchrony effects. A caveat in most prior studies is that optimal/non-optimal time of day is based on morningness-eveningness composite scores derived from chronotype questionnaires, which might not efficiently predict subjectively-defined cognitive efficiency periods. An additional caveat is that separate tasks are used to assess explicit and implicit retrieval in verbal memory. Indeed, no task is process-pure, and both controlled and automatic retrieval processes may potentially contribute to retrieval scores in different types of memory tasks. In the present study, we investigated the impact of individually defined subjective optimal/non-optimal time of day on verbal memory retrieval, using an adaptation of the Process-Dissociation Procedure that allows estimating the respective contributions of automatic and controlled memory retrieval processes within the same memory task. Our results disclose a higher involvement of controlled processes at subjectively optimal compared with non-optimal time of day, but no differences for automatic processes. Synchrony effects and subjectively-defined peaks and troughs of performance for controlled components of memory retrieval should be considered in the evaluation of episodic memory.

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.

Recollection and familiarity in aging individuals: Gaining insight into relationships with medial temporal lobe structural integrity

Dual-process theories posit that two separate processes are involved in recognition, namely recollection and familiarity. Studies investigating the neuroanatomical substrates of these two processes have frequently revealed that, while recollection is functionally linked with the hippocampus, familiarity appears to be associated with perirhinal and/or entorhinal cortices integrity. Interestingly these regions are known to be sensitive to normal and neuropathological aging processes. The objective of this study was to examine the effects of aging on recollection and familiarity performance, as well as to investigate associations with the rate of false alarms. In older individuals, we further aimed to explore relationships between these recognition variables and structural integrity of the hippocampus and the entorhinal and perirhinal cortices. Younger (N = 56) and older (N = 59) adults were tested on a computerized recollection and familiarity task. In a separate session, older adults (N = 56) underwent a structural MRI. Hippocampal, entorhinal and perihinal cortices volumes were automatically segmented and then manually corrected to ensure validity of the volumetric assessment. Regional volumes were normalized for total intracranial volume. While the overall recognition performance did not significantly differ across groups, our results reveal a decrease in recollection, together with an increase in familiarity in older adults. The increase reliance on familiarity was significantly and positively associated with the rate of false alarms. In the older adult sample, significant positive associations were found between recollection estimates and normalized hippocampal volumes. The normalized total hippocampal volume accounted for 25% of the variance in recollection performance. No correlation was found between any recognition variables and perirhinal or entorhinal cortices volumes. Overall, our results suggest that the age-related impairment in recollection is linked with reduced hippocampal structural integrity.

The imagination inflation effect in healthy older adults and patients with mild Alzheimer's disease

OBJECTIVE

The imagination inflation effect is a type of memory distortion defined as an increased tendency to falsely remember that an item has been seen, or an action has been performed, when it has only been imagined. For patients with very mild Alzheimer's disease (AD), susceptibility to the imagination inflation effect could have significant functional consequences in daily life.

METHOD

We assessed whether patients with very mild AD were more or less susceptible to the imagination inflation effect when compared with healthy older adults. In the first session, participants were read an action statement such as "fill the pillbox" and engaged in 1 of 3 activities: listened to the statement being read, performed the action, or imagined performing the action. During the second session, participants imagined action statements from the first session, as well as new action statements. During the recognition test, participants were asked to determine whether action statements were or were not performed during the first session.

RESULTS

We found that imagining performing actions increased the tendency of patients with very mild AD to falsely recall the action as having been performed to an extent similar to that of healthy older adults.

CONCLUSION

We concluded that, similar to healthy older adults, patients with very mild AD were susceptible to the imagination inflation effect, which we attributed to difficulties with source monitoring and reliance on familiarity.

Early onset of cognitive impairment is associated with altered synaptic plasticity and enhanced hippocampal GluA1 expression in a mouse model of depression

Memory deficit is a common manifestation of age-related cognitive impairment, of which depression is a frequently occurring comorbidity. Previously, we developed a submissive (Sub) mouse line, validated as a model of depressive-like behavior. Using learning paradigms testing hippocampus-dependent spatial and nonspatial memory, we demonstrate here that Sub mice developed cognitive impairments at earlier age (3 months), compared with wild-type mice. Furthermore, acute hippocampal slices from Sub animals failed to display paired-pulse facilitation, whereas primed burst stimulation elicited significantly enhanced long-term potentiation in region CA1, relative to control mice. Changes in synaptic plasticity were accompanied by markedly reduced hippocampal messenger RNA expression of insulin-like growth factor and brain-derived neurotrophic factor. Finally, we identified markedly elevated protein levels of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit GluA1 in the hippocampi of Sub mice, which was exacerbated with age. Taken together, the results point to a linkage between depressive-like behavior and the susceptibility to develop age-related cognitive impairment, potentially by hippocampal α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor-mediated glutamatergic signaling.

The effects of healthy aging, amnestic mild cognitive impairment, and Alzheimer's disease on recollection and familiarity: a meta-analytic review

It is well established that healthy aging, amnestic Mild Cognitive Impairment (aMCI), and Alzheimer's Disease (AD) are associated with substantial declines in episodic memory. However, there is still debate as to how two forms of episodic memory - recollection and familiarity - are affected by healthy and pathological aging. To address this issue we conducted a meta-analytic review of the effect sizes reported in studies using remember/know (RK), receiver operating characteristic (ROC) and process dissociation (PD) methods to examine recollection and familiarity in healthy aging (25 published reports), aMCI (9 published reports), and AD (5 published reports). The results from the meta-analysis revealed that healthy aging is associated with moderate-to-large recollection impairments. Familiarity was not impaired in studies using ROC or PD methods but was impaired in studies that used the RK procedure. aMCI was associated with large decreases in recollection whereas familiarity only tended to show a decrease in studies with a patient sample comprised of both single-domain and multiple-domain aMCI patients. Lastly, AD was associated with large decreases in both recollection and familiarity. The results are consistent with neuroimaging evidence suggesting that the hippocampus is critical for recollection whereas familiarity is dependent on the integrity of the surrounding perirhinal cortex. Moreover, the results highlight the relevance of method selection when examining aging, and suggest that familiarity deficits might be a useful behavioral marker for identifying individuals that will develop dementia.

Memory impairment among people who are homeless: a systematic review

Cognitive impairment may interfere with an individual's ability to function independently in the community and may increase the risk of becoming and remaining homeless. The purpose of this study was to systematically review the literature on memory deficits among people who are homeless in order to gain a better understanding of its nature, causes and prevalence. Studies that measured memory functioning as an outcome among a sample of homeless persons were included. Data on sampling, outcome measures, facet of memory explored and prevalence of memory impairment were extracted from all selected research studies. Included studies were evaluated using a critical appraisal process targetted for reviewing prevalence studies. Eleven studies were included in the review. Verbal memory was the most commonly studied facet of memory. Potential contributing factors to memory deficits among persons who are homeless were explored in seven studies. Memory deficits were common among the samples of homeless persons studied. However, there was a great deal of variation in the methodology and quality of the included studies. Conceptualisations of "homelessness" also differed across studies. There is a need for more controlled research using validated neuropsychological tools to evaluate memory impairment among people who are homeless.

Repetition-lag training to improve recollection memory in older people with amnestic mild cognitive impairment. A randomized controlled trial

The results of a randomized controlled trial of repetition-lag training in older adults with amnestic mild cognitive impairment (aMCI) are reported. A modified repetition-lag training procedure with extended encoding time and strategy choice was used. The training required discriminating studied words from non-studied lures that were repeated at varying intervals during the test phase. Participants were assessed pre/post using untrained measures of cognition and self-report questionnaires. Primary outcome measures were recall of unrelated word pairs both immediately following presentation and following a delay. Secondary outcomes were a measure of attention, cognitive flexibility, and visual working memory. Participants were also asked to report on the frequency of cognitive failures and mood before and after training. Participants (N = 31) were randomized into either the treatment or a no-contact control group and attended the clinic twice per week over a four week period. Twenty-four participants completed the study (twelve in each group). Results indicated that the training group improved at recalling unrelated word pairs after a delay. There were no significant effects of training on other outcomes, self-reported cognitive failures or mood. The results are discussed along with suggestions for future research.

Distinct medial temporal contributions to different forms of recognition in amnestic mild cognitive impairment and Alzheimer's disease

The simplest expression of episodic memory is the experience of familiarity, the isolated recognition that something has been encountered previously. Brain structures of the medial temporal lobe (MTL) make essential contributions to episodic memory, but the distinct contributions from each MTL structure to familiarity are debatable. Here we used specialized tests to assess recognition impairments and their relationship to MTL integrity in people with amnestic mild cognitive impairment (aMCI, n=19), people with probable Alzheimer's disease (AD; n=10), and age-matched individuals without any neurological disorder (n=20). Recognition of previously presented silhouette objects was tested in two formats-forced-choice recognition with four concurrent choices (one target and three foils) and yes/no recognition with individually presented targets and foils. Every foil was extremely similar to a corresponding target, such that forced-choice recognition could be based on differential familiarity among the choices, whereas yes/no recognition necessitated additional memory and decision factors. Only yes/no recognition was impaired in the aMCI group, whereas both forced-choice and yes/no recognition were impaired in the AD group. Magnetic resonance imaging showed differential brain atrophy, as MTL volume was reduced in the AD group but not in the aMCI group. Pulsed arterial spin-labeled scans demonstrated that MTL blood flow was abnormally increased in aMCI, which could indicate physiological dysfunction prior to the emergence of significant atrophy. Regression analyses with data from all patients revealed that regional patterns of MTL integrity were differentially related to forced-choice and yes/no recognition. Smaller perirhinal cortex volume was associated with lower forced-choice recognition accuracy, but not with lower yes/no recognition accuracy. Instead, smaller hippocampal volumes were associated with lower yes/no recognition accuracy. In sum, familiarity memory can be specifically assessed using the forced-choice recognition test, it declines later than other MTL-dependent memory functions as AD progresses, and it has distinct anatomical substrates.

Cognitive and neuroimaging evidence of impaired interaction between self and memory in Alzheimer's disease

In human cognition, self and memory processes strongly interact, as evidenced by the memory advantage for self-referential materials [Self-Reference Effect (SRE) and Self-Reference Recollection Effect (SRRE)]. The current study examined this interaction at the behavioural level and its neural correlates in patients with Alzheimer's disease (AD). Healthy older controls (HC) and AD patients performed trait-adjectives judgements either for self-relevance or for other-relevance (encoding phase). In a first experiment, the encoding and subsequent yes-no recognition phases were administrated in a Magnetic Resonance Imaging (MRI) scanner. Brain activation as measured by functional MRI (fMRI) was examined during self-relevance judgements and anatomical images were used to search for correlation between the memory advantage for self-related items and grey matter density (GMD). In a second experiment, participants described the retrieval experience that had driven their recognition decisions (familiarity vs recollective experience). The behavioural results revealed that the SRE and SRRE were impaired in AD patients compared to HC participants. Furthermore, verbal reports revealed that the retrieval of self-related information was preferentially associated with the retrieval of contextual details, such as source memory in the HC participants, but less so in the AD patients. Our imaging findings revealed that both groups activated the medial prefrontal cortex (MPFC) at encoding during self-relevance judgements. However, the variable and limited memory advantage for self-related information was associated with GMD in the lateral prefrontal cortex in the AD patients, a region supporting high-order processes linking self and memory. These findings suggest that even if AD patients engage MPFC during self-referential judgements, the retrieval of self-related memories is qualitatively and quantitatively impaired in relation with altered high-order processes in the lateral PFC.

Examining the impact of familiarity on faucet usability for older adults with dementia

BACKGROUND

Changes in cognition caused by dementia can significantly alter how a person perceives familiarity, impacting the recognition and usability of everyday products. A person who is unable to use products cannot autonomously complete associated activities, resulting in increased dependence on a caregiver and potential move to assisted living facilities. The research presented in this paper hypothesised that products that are more familiar will result in better usability for older adults with dementia. Better product usability could, in turn, potentially support independence and autonomy.

METHODS

This research investigated the impact of familiarity on the use of five faucet designs during 1309 handwashing trials by 27 older adults, who ranged from cognitively intact to the advanced (severe) stages of dementia. Human factors methods were used to collect empirical and self-reported data to gauge faucets' usability. Participants' data were grouped according to cognition (i.e., no/mild, moderate, or severe dementia). Logistic regression, ranking by odds, and Wald tests of odds ratios were used to compare performance of the three groups on the different faucets. Qualitative data were used in the interpretation of quantitative results.

RESULTS

Results indicated that more familiar faucets correlated with lower levels of assistance from a caregiver, fewer operational errors, and greater levels of operator satisfaction. Aspects such as the ability to control water temperature and flow as well as pleasing aesthetics appeared to positively impact participants' acceptance of a faucet. The dual lever design achieved the best overall usability.

CONCLUSIONS

While work must be done to expand these findings to other products and tasks, this research provides evidence that familiarity plays a substantial role in product usability for older adults that appears to become more influential as dementia progresses. The methods used in this research could be adapted to analyse usability for other products by older adults with dementia.

Item familiarity and controlled associative retrieval in Alzheimer's disease: an fMRI study

Typical Alzheimer's disease (AD) is characterized by an impaired form of associative memory, recollection, that includes the controlled retrieval of associations. In contrast, familiarity-based memory for individual items may sometimes be preserved in the early stages of the disease. This is the first study that directly examines whole-brain regional activity during one core aspect of the recollection function: associative controlled episodic retrieval (CER), contrasted to item familiarity in AD patients. Cerebral activity related to associative CER and item familiarity in AD patients and healthy controls (HCs) was measured with functional magnetic resonance imaging during a word-pair recognition task to which the process dissociation procedure was applied. Some patients had null CER estimates (AD-), whereas others did show some CER abilities (AD+), although significantly less than HC. In contrast, familiarity estimates were equivalent in the three groups. In AD+, as in controls, associative CER activated the inferior precuneus/posterior cingulate cortex (PCC). When performing group comparisons, no region was found to be significantly more activated during CER in HC than AD+ and vice versa. However, during associative CER, functional connectivity between this region and the hippocampus, the inferior parietal and dorsolateral prefrontal cortex (DLPFC) was significantly higher in HC than in AD+. In all three groups, item familiarity was related to activation along the intraparietal sulcus (IPS). In conclusion, whereas the preserved automatic detection of an old item (without retrieval of accurate word association) is related to parietal activation centred on the IPS, the inferior precuneus/PCC supports associative CER ability in AD patients, as in HC. However, AD patients have deficient functional connectivity during associative CER, suggesting that the residual recollection function in these patients might be impoverished by the lack of some recollection-related aspects such as autonoetic quality, episodic details and verification.

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.

Relationships between hippocampal shape and cognitive performances in drug-naïve patients with Alzheimer's disease

Previous studies provided hippocampal shape analysis of Alzheimer's disease (AD) patients using automated segmentation techniques. However, the relationships between the hippocampal deformations and various cognitive impairments were not clear. The aim of this study was to investigate hippocampal shape changes and their relationship to cognitive impairments. Fifty-one drug-naïve patients with AD and 50 group-matched healthy control subjects underwent 3T MRI scanning, and the hippocampal volumes and deformations were compared between the groups. Additionally, we explored the correlation pattern between the hippocampal deformations and the cognitive dysfunctions in AD using the Korean version of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD-K). AD subjects exhibited significant hippocampal deformations in the cornu ammnonis (CA1) and subiculum areas compared to those in healthy subjects (p<0.05, false discovery rate (FDR) corrected). Significant correlations were observed between hippocampal deformations in CA1 and subiculum areas and verbal immediate recall, verbal delayed recall, verbal recognition memory, and constructional recall scores (p<0.05, FDR corrected). This study was the first to explore the relationships between hippocampal deformations and various cognitive impairments of drug-naïve patients with AD. These structural changes in hippocampal CA1 and subiculum areas might be the core of the underlying neurobiological mechanisms of hippocampal dysfunction and their relevance to the various cognitive dysfunctions in AD.

Reliable change indices for the ruff 2 and 7 selective attention test in older adults

The assessment of suspected dementia often involves the analysis of change scores from neuropsychological tests administered on two occasions. Frequently, no information is available to allow the significance of a change to be evaluated. Our aim was to prepare data useful for estimating the statistical significance of retest changes for persons older than the age of 65 on the Ruff 2 and 7 Selective Attention Test, one of the few paper-and-pencil tests of attention available to the clinician. The sample tested was composed of 234 healthy adults taking part in a randomized double-blind trial of the effect on cognitive performance of lowering homocysteine using dietary supplements, during which no treatment effects were detected. The test was found to be sensitive to the effects of aging and was well tolerated by our sample of older adults. Retest reliability for the speed of visual search for digit targets (2 and 7) under both the same category (other digits) and different category (letter) distracter conditions was high, and the practice effects during a 12-month period were substantial. Test-retest data with a 1-year interval were used to estimate reliability coefficients and to calculate Reliable Change indices useful for evaluating persons with suspected dementia. The rate of decline in search speed as a function of age was the same for both distraction conditions, suggesting that older persons used a controlled serial search process for targets in both conditions of this test.

False item recognition in patients with Alzheimer's disease

Recent evidence suggests that patients with Alzheimer's disease (AD), as compared with normal individuals, exhibit increased false recognition by stimulus repetition in the Deese-Roediger-McDermott (DRM) task or associative recognition memory tasks, probably due to impaired recollection-based monitoring. However, because of possible alternative explanations for the findings of these previous studies, the evidence for impaired recollection-based monitoring in AD patients remains inconclusive. In this study, we employed stimulus repetition in old/new recognition judgments of single-item picture memory without a factor of association between the stimuli and examined whether AD patients showed increased false item recognition as compared with healthy controls. AD patients and healthy controls studied single-item pictures presented either once or three times. They were later asked to make an old/new recognition judgment in response to (a) Same pictures, pictures identical to those seen at encoding, (b) Similar lures, novel pictures similar to but not identical to those seen at encoding, and (c) Dissimilar lures, novel pictures not similar to those seen at encoding. For Same pictures, repeated presentation of stimuli increased the proportion of "old" responses in both groups. For Similar lures, repeated presentation of stimuli increased the rate of "old" responses in AD patients but not in control subjects. The results of the present study clearly demonstrated elevated false recognition by stimulus repetition in single-item recognition in AD patients. The present findings strongly support the view that AD patients are impaired in their ability to use item-specific recollection in order to avoid false recognition.

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.

Memory loss in Alzheimer's disease: implications for development of therapeutics

Alzheimer's disease (AD) is a progressive neurodegenerative disease marked by a constellation of cognitive disturbances, the earliest and most prominent being impaired episodic memory. Episodic memory refers to the memory system that allows an individual to consciously retrieve a previously experienced item or episode of life. Many recent studies have focused on characterizing how AD pathology impacts particular aspects of episodic memory and underlying mental and neural processes. This review summarizes the findings of those studies and discusses the effects of current and promising treatments for AD on episodic memory. The goal of this review is to raise awareness of the strides that cognitive neuroscientists have made in understanding intact and dysfunctional memory. Knowledge of the specific memorial processes that are impaired in AD may be of great value to basic scientists developing novel therapies and to clinical researchers assessing the efficacy of those therapies.

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.

Recollection and familiarity in amnestic mild cognitive impairment: a global decline in recognition memory

Despite memory failures being a central feature of amnestic mild cognitive impairment (a-MCI), there is limited research into the nature of the memory impairment associated with this condition. A further understanding could lead to refinement of criteria needed to qualify for this designation and aid in prediction of who will progress to development of clinical Alzheimer's disease. Dual process models posit that recognition memory is supported by the dissociable processes of recollection and familiarity. The present study sought to evaluate recognition memory in a-MCI in the framework of the dual process model. Patients with a-MCI and age- and education-matched controls were tested on three memory paradigms. Two paradigms were modifications of the process-dissociation procedure in which recollection required either memory of word-pair associations (associative) or the font color of words at study (featural). A final paradigm utilized the task-dissociation methodology comparing performance for item and visual spatial source memory. All three tasks revealed that familiarity was impaired to at least the same extent as recollection. As familiarity is thought to be spared in normal aging, its measurement may provide a relatively specific marker for the early pathological changes of Alzheimer's disease.

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.

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.

Controlled processes account for age-related decrease in episodic memory

A decrease in controlled processes has been proposed to be responsible for age-related episodic memory decline. We used the Process Dissociation Procedure, a method that attempts to estimate the contribution of controlled and automatic processes to cognitive performance, and entered both estimates in regression analyses. Results indicate that only controlled processes explained a great part of the age-related variance in a word recall task, especially when little environmental support was offered.

Memory for choices in Alzheimer's disease

Despite their cognitive impairment, patients with mild Alzheimer's disease (AD) often make important life choices. When making choices, people frequently attempt to directly compare the features of different options, rather than evaluating each option separately. Not every feature has an analogous (or alignable) feature in the other option, however. In 2005, Mather's group found that both younger and older adults filled in such gaps when remembering, creating features in the other option to contrast with existing features. In the present study, such effects of alignability on recognition memory were not found in patients with mild AD. This finding suggests that patients with mild AD are less likely to engage in feature-by-feature comparison processes across choice options, a change that may lead them to make qualitatively different choices than healthy older adults.

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.

Memory Impairment and Awareness of Memory Deficits inEarly-Stage Alzheimer's Disease

Recognition memory of auditory verbal learning tests and awareness of memory deficits were examined in 24 individuals with early-stage Alzheimer's disease (AD) using a performance prediction-postdiction paradigm. Individuals with AD displayed impaired recognition memory, and recognition performance correlated positively with regional cerebral blood flow at rest in bilateral prefrontal areas and the left medial temporal area. In addition, underawareness of memory deficits was also marked even at this early stage. Individuals with AD retrospectively overestimated memory performance after actual performance, but appeared to benefit from feedback, and displayed intact online awareness of memory dysfunction, leading to normal prediction of the second session. However, individuals with AD failed to retrospectively incorporate incidents of memory failure into generalized self-belief systems. Brain/ behavior correlational analyses suggest that the prefrontal cortex and posterior dorsomedial regions including the precuneus may be involved in self-awareness.

Comparing source-based and gist-based false recognition in aging and Alzheimer's disease

This study examined 2 factors contributing to false recognition of semantic associates: errors based on confusion of source and errors based on general similarity information or gist. The authors investigated these errors in patients with Alzheimer's disease (AD), age-matched control participants, and younger adults, focusing on each group's ability to use recollection of source information to suppress false recognition. The authors used a paradigm consisting of both deep and shallow incidental encoding tasks, followed by study of a series of categorized lists in which several typical exemplars were omitted. Results showed that healthy older adults were able to use recollection from the deep processing task to some extent but less than that used by younger adults. In contrast, false recognition in AD patients actually increased following the deep processing task, suggesting that they were unable to use recollection to oppose familiarity arising from incidental presentation.

Electrophysiological Dissociation of Picture Versus Word Encoding: The Distinctiveness Heuristic as a Retrieval Orientation

Event-related potentials (ERPs) were used to investigate the neural processes underlying the distinctiveness heuristic— a response mode in which participants expect to remember vivid details of an experience and make recognition decisions based on this metacognitive expectation. One group of participants studied pictures and auditory words; another group studied visual and auditory words. Studied and novel items were presented at test as words only, with all novel items repeating after varying lags. ERP differences were seen between the word and picture groups for both studied and novel items. For the novel items, ERP differences were largest in frontal and central midline electrodes. In separate analyses, the picture group showed the greatest ERP differences between item types in a parietally based component from 550 to 1000 msec, whereas the word group showed the greatest differences in a frontally based component from 1000 to 2000 msec. The authors suggest that the distinctiveness heuristic is a retrieval orientation that facilitates reliance upon recollection to differentiate between item types. Although the picture group can use this heuristic and its retrieval orientation on the basis of recollection, the word group must engage additional postretrieval processes to distinguish between item types, reflecting the use of a different retrieval orientation.

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.

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.

Context-specific memory and apolipoprotein E (ApoE) epsilon 4: cognitive evidence from the NIMH prospective study of risk for Alzheimer's disease

The aim of the study was to determine whether the epsilon 4 allele of the apolipoprotein E (ApoE) gene was associated primarily with context-specific memory among individuals at genetic risk for developing Alzheimer's disease. The effect of ApoE status on comprehensive neuropsychological results was examined in 176 healthy adults during baseline cognitive testing in the NIMH Prospective Study of Biomarkers for Older Controls at Risk for Alzheimer's Disease (NIMH Prospective BIOCARD Study). The presence of the epsilon 4 allele was associated with significantly lower total scores on the Logical Memory II subtest of the Wechsler Memory Scale-Revised and percent of information retained after delay. Further analysis indicated the prose recall and retention effect was partially explained by a small subgroup of epsilon 4 homozygotes, suggesting a gradually progressive process that may be presaged with specific cognitive measures. The current results may represent an epsilon 4-associated breakdown between gist-related information and context-bound veridical recall. This relative disconnection may be understood in light of putative epsilon 4-related preclinical accumulation of Alzheimer pathology (tangles and plaques) in the entorhinal cortex (EC) and among frontal networks, as well as the possibility of less-efficient compensatory strategies.

Prozessdissoziationsprozedur: Quo Vadis?

Zusammenfassung. Die Prozessdissoziationsprozedur (PDP) ist ein häufig benutztes Instrument zur Erfassung kontrollierter (“bewusster“) und automatischer (“unbewusster“) Gedächtnisprozesse. Die Forschung der letzten zehn Jahre hat jedoch eine Reihe von Problemen im von L. L. Jacoby (1991) vorgeschlagenen Zwei-Prozess-Messmodell aufgezeigt. Dies hat zur Entwicklung von alternativen Modellen geführt, die in dieser Arbeit vorgestellt, systematisiert und bewertet werden. Die Modelle unterscheiden sich auf drei Dimensionen: 1) Modelle mit diskreten vs. kontinuierlichen Prozessvariablen, 2) Modelle mit prüfbaren vs. unprüfbaren Annahmen über die Beziehungen zwischen den Prozessen und 3) Zwei-Prozess-Modelle versus Quellengedächtnismodelle. Für die Zukunft der PDP besonders bedeutsam dürfte sein, dass einige Befunde, die mit Zwei-Prozess-Modellen nur schwer vereinbar sind, plausibel erscheinen, wenn man dieselben Daten im Rahmen von Quellengedächtnismodellen analysiert.