Alzheimer's disease and feeling-of-knowing in episodic memory

Episodic memory feeling-of-knowing (FOK) was examined in 16 patients with Alzheimer’s disease (AD), 16 elderly participants, and 16 younger adults. Participants were given cued recall and recognition tests of 20 critical cue-target words. Subsequently, they judged their FOK for non-recalled words in terms of how likely they thought they would be to recognize the keywords on a subsequent recognition test. The results indicated dementia-related deficits on both the recall and recognition tests. Compared to older adults, AD patients exhibited impaired FOK accuracy. This pattern of outcome indicates that early AD is associated with a deficit in episodic memory and a deficit in memory monitoring for newly learned information. Furthermore, our observation revealed that in AD, episodic memory may be a more important factor than executive function in explaining the FOK inaccuracy.     

A role for right medial prefontal cortex in accurate feeling-of-knowing judgements: evidence from patients with lesions to frontal cortex

The hypothesis that prefrontal cortex plays a critical role in accurate predictions of episodic memory performance was tested using the feeling-of-knowing (FOK) paradigm. Fourteen patients with a broad spectrum of damage to the frontal cortex and matched controls read sentences and later were tested for recall memory, confidence judgments, and FOK accuracy using as cues the sentences with the final word missing. While frontal patients were impaired at recall and recognition memory, they were able to make accurate confidence judgments about their recall attempts. By contrast, as a group, the patients were markedly impaired in the accuracy of their prospective FOK judgments. Lesion analysis of frontal patients with clear FOK impairment revealed an overlapping region of damage in right medial prefrontal cortex. These findings provide functional and anatomical evidence for a dissociation between recall confidence and prospective memory monitoring and are discussed in terms of familiarity and access theories of FOK predictions.     

Early detection of cognitive disturbances in mild cognitive impairment: a systematic review of observational studies

Mild cognitive impairment (MCI) is an intermediate state between normal cognition and early dementia and is not considered as a typical outcome of brain aging. It has been estimated that 10% to 20% of individuals above 65 years of age will be diagnosed as having MCI. The increased rate of dementia and the importance of early detection of its forerunners have encouraged researchers to focus on detecting MCI and modifiable risk factors with the hope of developing better ways of managing dementia and its consequences. The main aim of this study was to systematically review the related literature concerning the cognitive changes in the spectrum of cognitive aging to cognitive impairment. Articles included in this review were identified through searching the databases of PubMed, Psych Info, Embase, ProQuest, and Scopus. Many domains like verbal memory, language, executive function, visual memory, attentional skills, and working memory showed acceptable predictive power. Testing subdomains such as executive function, speed of processing, working memory and semantic language are critical and others may indicate some suggestions for further clinical deteriorations in normal individuals. Although various cognitive instruments have been used for evaluation of impaired cognitive domains, it remains challenging to select the most appropriate ones having high‐level accuracy and their related cognitive subdomains. It also revealed that none of the identified cognitive domains solely fulfilled the criteria for MCI screening; in clinical settings, multiple neuropsychological batteries may be used for one single cognitive domain, while longitudinal studies prefer the use of at least two cognitive measures for each domain to improve accuracy and research settings might focus on only a single neuropsychological test. However, along with episodic memory, testing for amnestic MCI, executive function could increase the chance of early detection of MCI. Executive control has been found to deteriorate the earliest in MCI patients.     

帕金森病患者记忆监测与情景记忆的相关研究

目的 研究帕金森病患者( Parkinson's disease,PD)对情景记忆监测情况,并进一步探讨PD患者情景记忆障碍的可能机制.方法 建立情景记忆知晓感(feeling of knowing-episodic memory,FOK-EM)判断的试验范式,对25例PD患者和25名年龄及教育程度相匹配的健康对照(HC)者进行研究.结果 与HC组的FOK-EM的回忆率(39.67％±6.11％)、再认率(58.42％±7.50％)以及FOK判断准确率(0.61 ±0.22)比较,PD患者组FOK-EM的回忆率(19.33％±5.10％)、再认率(45.93％±7.82％)以及FOK判断准确率(-0.18±0.46)显著降低,差异均有统计学意义(t=-4.833,P＜0.01;t=-2.497,P＜0.05;t=-5.986,P＜0.01);FOK-EM的肯定判断/正确再认成绩(20.47％±10.78％)以及肯定判断/错误再认成绩(即高估,29.53％±5.62％)与HC组的肯定判断/正确再认成绩(39.47％±9.47％)以及肯定判断/错误再认成绩(即高估,13.90％±5.50％)之间差异有统计学意义(t =3.564,P＜0.05;t=2.306,P＜0.05),且Stroop效应与FOK-EM的肯定判断/错误再认成绩呈正相关(r =0.640,P＜0.01).结论 PD患者的情景记忆监测受损,表现为对自身再认能力的高估.这种记忆监测受损与执行功能的损害相关,提示此机制可能是导致PD患者情景记忆障碍的重要因素.     

The association between depressive and cognitive symptoms in amnestic mild cognitive impairment

BACKGROUND: Depressive symptoms are frequently observed in older adults with mild cognitive impairment (MCI). However, little is known regarding the cognitive characteristics of this important subgroup. METHODS: We examined executive functions (controlled inhibition) and verbal episodic memory in 33 healthy older adults (control group), 18 older adults with amnestic MCI plus subclinical depressive symptoms (a-MCI/D+ group), and 26 older adults with amnestic MCI but no depressive symptoms (a-MCI group). RESULTS: Compared to the a-MCI and control groups, patients with a-MCI/D+ showed poor controlled inhibition. Moreover, in verbal episodic memory these patients recalled fewer words than control participants on immediate free, delayed free, and delayed total (free plus cued) recall. Performance on immediate recall suggested a self-retrieval deficit, but delayed performance also revealed the existence of an encoding impairment. In the a-MCI group, participants exhibited normal performance on the executive task, but pervasive memory impairment; the memory deficit concerned free and total recall on both immediate and delayed tasks, suggesting the existence of encoding and self-retrieval disturbances. CONCLUSIONS: This study reveals differences between the pattern of cognitive impairment for a-MCI/D+ and a-MCI subgroups particularly at the level of executive capacities. In terms of memory functioning, the differences between the subgroups were more subtle; more studies are needed in order to better characterize the memory impairment of a-MCI/D+ and a-MCI patients.     

Factors mediating cognitive deficits and psychopathology among siblings of individuals with schizophrenia

Schizotypal traits and cognitive disturbances are known to be present in first-degree relatives of people with schizophrenia. However, there is little understanding of how these endophenotypes are related to each other. We explored the nature of this relationship in individuals with schizophrenia, their full siblings, community controls, and their siblings. All participants were assessed in the domains of working memory, attention, episodic memory, and executive function, as well as in their level of positive, negative, and disorganization symptoms. Schizophrenia probands were significantly impaired on all cognitive domains, as compared with the other 3 groups, and displayed the highest levels of positive, negative, and disorganization symptoms. Proband siblings performed significantly worse than controls on tasks of working memory, episodic memory, and executive function, and they displayed significantly more positive and negative symptoms as compared with controls. Poorer task performance across all 4 cognitive domains was most strongly correlated with increased negative symptoms. Mediation analyses revealed that working memory, episodic memory, and executive function deficits partially mediated increases in negative symptoms among proband siblings. Negative symptoms fully mediated deficits in working memory and episodic memory but only partially mediated deficits in executive function. Results suggest that there is a complex relationship between cognitive and clinical factors in this high-risk population.     

Prospective and retrospective episodic metamemory in posttraumatic stress disorder

Objectives: Posttraumatic stress disorder (PTSD) has been consistently associated with episodic memory deficits. To some extent, these deficits could be related to an impairment of metamemory in individuals with PTSD. This research consequently aims at investigating prospective (feeling-of-knowing, FOK) and retrospective (confidence) metamemory judgments for episodic information in PTSD.

Method: Twenty participants with PTSD and without depression were compared to 30 healthy comparison participants on metamemory judgments during an episodic memory task. The concordance between metamemory judgments and recognition performance was then assessed by gamma correlations.

Results: The results confirmed that PTSD is associated with episodic memory impairment. Regarding metamemory, gamma correlations indicated that participants with PTSD failed to accurately predict their future memory performance as compared to the comparison group (mean FOK gamma correlations: .23 vs. .42, respectively). Furthermore, participants with PTSD made less accurate confidence judgments than comparison participants (mean confidence gamma correlations: .62 vs. .74, respectively).

Conclusion: Our results demonstrate an alteration of both prospective and retrospective metamemory processes in PTSD, which could be of particular relevance to future therapeutic interventions focusing on metacognitive strategies.     

Different mechanisms of episodic memory failure in mild cognitive impairment

Mild cognitive impairment (MCI), defined as episodic memory impairment beyond what is expected in normal aging, is often associated with hippocampal atrophy (HA) and may represent incipient Alzheimer's disease. However, recent studies suggest that MCI is very heterogeneous and multiple etiologies likely exist. One possibility is small vessel cerebrovascular disease (CVD). Specifically, we hypothesized that white matter hyperintensities (WMH), an MRI marker for CVD, would lead to impairments in executive control processes critical for working memory that may, in turn, result in episodic memory impairment. To test this hypothesis, we examined a group of subjects clinically diagnosed with MCI and used MRI to further subcategorize individuals as either MCI with severe white matter hyperintensities (MCI-WMH) or MCI with severe hippocampal atrophy (MCI-HA). MCI-WMH, MCI-HA, and matched control subjects each performed a battery of working memory and episodic memory tasks. Results showed that MCI-HA and MCI-WMH were equally impaired on the episodic memory task relative to controls, but MCI-WMH were additionally impaired on tests tapping verbal and spatial working memory abilities and attentional control processes. These results suggest that CVD and hippocampal dysfunction are associated with distinct neuropsychological profiles. Although both syndromes are associated with episodic memory deficits, CVD is additionally associated with working memory and executive control deficits.     

Improvement of episodic memory in persons with mild cognitive impairment and healthy older adults: evidence from a cognitive intervention program

The efficacy of cognitive training was assessed in persons with mild cognitive impairment (MCI) and persons with normal cognitive aging. Forty-seven participants were included in this study: 28 with MCI and 17 controls. Twenty-one participants received intervention (20 MCI and 9 controls) and 16 participants (8 MCI and 8 controls) received no intervention (waiting-list group). The intervention focused on teaching episodic memory strategies. Three tasks of episodic memory (list recall, face-name association, text memory) were used as primary outcome measures. Results were analyzed using analyses of variance. The intervention effect (pre- and post-intervention difference) was significant on two of the primary outcome measures (delayed list recall and face-name association). A significant pre-post-effect was also found on measures of subjective memory and well-being. There was no improvement in the performance of groups of individuals with MCI and normal elderly persons who did not receive the intervention. These results suggest that persons with MCI can improve their performance on episodic memory when provided with cognitive training.     

Are all judgments created equal? An fMRI study of semantic and episodic metamemory predictions

Metamemory refers to the ability of individuals to monitor and control their own memory performance. Although little theoretical consideration of the possible differences between the monitoring of episodic and of semantic knowledge has been published, results from patient and drug studies that used the “feeling of knowing” (FOK) paradigm show a selective impairment in the accuracy of episodic monitoring but not in its semantic counterpart. Similarly, neuroimaging studies provide indirect evidence for separate patterns of activation during episodic or semantic FOKs. However, the semantic-episodic distinction hypothesis has not been directly addressed. In the current event-related fMRI study, we used a within-subject, within-experiment comparison of the monitoring of semantic and episodic content. Whereas the common neural correlates of episodic and semantic FOKs observed in this study generally replicate the previous neuroimaging findings, several regions were found to be differentially associated with each task. Activity of the right inferior frontal gyrus was modulated by the semantic-episodic factor only during the negative predictions of retrieval, suggesting that negative predictions are based on partially distinct mechanisms during each task. A posterior midline network, known to be activated during episodic retrieval, was activated during episodic and not semantic monitoring, suggesting that episodic FOKs rely, to some extent, on common episodic retrieval processes. These findings suggest that theoretical accounts of the etiology and function of FOKs may benefit from incorporating the prediction directionality (positive/negative) and the memory domain (semantic/episodic) distinctions.     

Metamemory for faces following frontal lobe damage.

Previous research has provided evidence of metamemory impairments in patients with frontal lobe damage on verbal episodic memory tasks. In the present study, we employed metamemory paradigms to investigate whether patients with frontal lesions show monitoring deficits on semantic memory tasks involving facial stimuli. Patients with frontal lobe damage and healthy control subjects made memory decisions to famous faces in a retrospective confidence judgment task and in a prospective feeling-of-knowing (FOK) task. Results indicated that frontal patients performed worse than controls on the retrospective confidence task, but there were no differences between the groups on the FOK task. These findings suggest that metamemory deficits in frontal patients are not confined to specific stimulus domains (words vs. faces) or memory systems (episodic vs. semantic). In addition, the dissociation between retrospective confidence judgments and FOK accuracy documented in this study and also in a recent report by Schnyer et al. suggesting that metamemory should not be considered a unitary function with a single neuroanatomic substrate.     

轻度认知障碍老年人情节记忆功能的磁共振成像研究

目的 运用核磁共振(MRI)技术探讨轻度认知障碍(MCI)老人与健康老人脑结构和功能的异同.方法 对14例MCI老人(MCI组)和15名健康老人(正常对照组)进行神经心理学检查,并应用基于体素的形态测量方法 ,测定两组的灰质体积,并用事件相关功能MRI技术,测定两组在执行情节记忆提取任务时相关脑区的功能变化.结果 (1)神经心理学:MCI组听觉词语记忆测试[(2.1±1.7)分]和画钟试验[(7.8±1.2)分]成绩差于正常对照组[分别为(9.2±1.3)分和(9.2±0.8)分;P＜0.05].(2)结构影像:MCI组的灰质体积小于正常对照组,主要位于情节记忆相关脑区(P＜0.001).(3)功能影像:MCI组与正常对照组任务正确率和反应时间的差别无统计学意义;MCI组激活降低的脑区主要是海马旁回,而增强激活的脑区主要是前额叶前侧、背外侧、右侧颞上回、右侧颞下回、枕叶皮层(P＜0.005).结论 MCI组内侧颞叶记忆系统结构萎缩、功能下降,在任务难度适当的情节记忆提取任务中,MCI组动员额外脑区激活,以代偿颞叶内侧记忆系统的损害.     

Multiple cognitive deficits in amnestic mild cognitive impairment

OBJECTIVE: To determine if more widespread cognitive deficits are present in a narrowly defined group of patients with the amnestic form of mild cognitive impairment (MCI). METHODS: From a larger sample of patients clinically diagnosed as meeting the criteria of Petersen et al. for amnestic MCI, we selected 22 subjects who had Clinical Dementia Rating scores of zero on all domains besides memory and orientation. These MCI subjects with presumably isolated memory impairments were compared to 35 age-matched normal controls and 33 very mild Alzheimer's disease (AD) patients on a battery of neuropsychological tests. RESULT: In addition to the expected deficits in episodic memory, the amnestic MCI group performed less well than the controls but better than the AD group on design fluency, category fluency, a set shifting task and the Stroop interference condition. Over half the amnestic MCI group (vs. none of the normal controls) scored at least 1 standard deviation below control means on 4 or more of the nonmemory cognitive tasks. CONCLUSIONS: Isolated memory impairment may be fairly uncommon in clinically diagnosed amnestic MCI patients, even when the criteria for amnestic MCI are fairly narrow. Additional cognitive impairments are likely to include fluency and executive functioning. These more diffuse deficits argue for comprehensive cognitive assessments, even when the patient and family are reporting only memory decline, and are consistent with the increase in attention paid to the heterogeneity of MCI.     

Memory, metamemory and their dissociation in temporal lobe epilepsy

Patients with temporal-lobe epilepsy (TLE) present with memory difficulties. The aim of the current study was to determine to what extent these difficulties could be related to a metamemory impairment. Fifteen patients with TLE and 15 matched healthy controls carried out a paired-associates learning task. Memory recall was measured at intervals of 30 min and 4 weeks. We employed a combined Judgement-of-Learning (JOL) and Feeling-of-Knowing (FOK) task to investigate whether participants could monitor their memory successfully at both the item-by-item level and the global level. The results revealed a clear deficit of episodic memory in patients with epilepsy compared with controls, but metamemory in TLE patients was intact. Patients were able to monitor their memory successfully at the item-by-item level, and tended to be even more accurate than controls when making global judgements.     

Metamemory monitoring and Parkinson's disease

Feeling-of-knowing (FOK) and global prediction in episodic memory were examined in 16 patients with Parkinson's disease (PD) and 16 elderly control subjects. Subjects were given cued recall and recognition tests of 20 critical cue-target words. Prior to the study phase, participants were asked to predict the number of words they could recall. During the recall phase, they judged their FOK for non-recalled words in terms of how likely they thought they would be able to recognize the key words on a subsequent recognition test. No difference was found in the two groups for global prediction accuracy. However in comparison to the older adults, PD patients exhibit impaired FOK accuracy, suggesting that in some circumstances metamemory may be altered in Parkinson's disease.     

Association between tea consumption and cognitive function in cognitively healthy older adults and older adults with mild cognitive impairment

BackgroundProspective studies suggest that tea consumption may decrease the risk for cognitive impairment in late life. However, little research has examined the association between tea consumption and cognitive performance across multiple domains. In addition, no research has examined the benefit of tea consumption on cognitive performance among older adults with existing impairment.AimsThe current study examined the association between tea consumption and performance on tasks of global cognitive function, episodic memory and executive function in cognitively healthy (CH) older adults and older adults with mild cognitive impairment (MCI).MethodsThe analytical sample included 1849 community-dwelling older adults from the Shanghai Brain Aging Study (65.6% female, mean age of 69.50 (8.02) years). Following ascertainment of cognitive function, 816 were categorised as MCI. In addition to completion of a demographics questionnaire, participants reported their tea consumption and completed a battery of tests to measure global cognitive function, episodic memory and working memory.ResultsIndependent analyses of covariance revealed a significant association between tea consumption and measures of episodic memory; however, these associations were restricted to CH older adults but not older adults with MCI. Tea consumption was not associated with working memory performance.ConclusionsThe current study suggests that the benefit of tea consumption is restricted to cognitively healthy older adults and does not extend to older adults with MCI.     

Assessment of planning abilities in individuals with mild cognitive impairment using an open-ended problem-solving task

Introduction: There is currently limited research evaluating planning abilities, a core subcomponent of executive functioning, in individuals with mild cognitive impairment (MCI). In the present study, we utilized the “Amap Task,” an open-ended problem-solving task, to separately evaluate the formulation and execution components of planning ability in individuals with MCI. Method: Thirty-seven cognitively healthy older adults and 37 individuals with MCI used a map layout of a university apartment to develop and write out a strategy (formulation stage) to successfully complete a list of tasks (e.g., retrieve and fill a water pitcher before placing it in the refrigerator). Subsequently, participants carried out the tasks in the apartment with the aid of their formulated plan (execution stage). Results: MCI participants performed more poorly than older adult (OA) controls during both the formulation and execution stages on measures of task accuracy and task efficiency. However, both groups were able to adjust and improve task accuracy and efficiency from formulation to task execution. Finally, MCI participants took significantly longer to complete the task and adhered less to their formulated plans during task completion. Conclusions: Using an open-ended problem-solving task, the findings revealed that individuals with MCI experienced difficulties with both the formulation and execution components of planning. Like controls, participants with MCI were able to successfully modify their plan online, improving their performance from task formulation to task execution.     

The profile of executive functioning in amnestic mild cognitive impairment: disproportionate deficits in inhibitory control

Amnestic mild cognitive impairment (aMCI) represents a group of individuals who are highly likely to develop Alzheimer's disease (AD). Although aMCI is typically conceptualized as involving predominantly deficits in episodic memory, recent studies have demonstrated that deficits in executive functioning may also be present, and thorough categorization of cognitive functioning in MCI may improve early diagnosis and treatment of AD. We first provide an extensive review of neuropsychology studies that examined executive functioning in MCI. We then present data on executive functioning across multiple sub-domains (divided attention, working memory, inhibitory control, verbal fluency, and planning) in 40 aMCI patients (single or multiple domain) and 32 normal elderly controls (NECs). MCI patients performed significantly worse than NECs in all 5 sub-domains, and there was impairment (>1.0 SD below the mean of NECs) in all sub-domains. Impairment on each test was frequent, with 100% of MCI patients exhibiting a deficit in at least one sub-domain of executive functioning. Inhibitory control was the most frequently and severely impaired. These results indicate that executive dysfunction in multiple sub-domains is common in aMCI and highlights the importance of a comprehensive neuropsychological evaluation for fully characterizing the nature and extent of cognitive deficits in MCI.     

Frontal and posterior cingulate metabolic impairment in the behavioral variant of frontotemporal dementia with impaired autonoetic consciousness

Although memory dysfunction is not a prominent feature of the behavioral variant of frontotemporal dementia (bv-FTD), there is evidence of specific deficits of episodic memory in these patients. They also have problems monitoring their memory performance. The objective of the present study was to explore the ability to consciously retrieve own encoding of the context of events (autonoetic consciousness) and the ability to monitor memory performance using feeling-of-knowing (FOK) in bv-FTD. Analyses of the patients' cerebral metabolism (FDG-PET) allowed an examination of whether impaired episodic memory in bv-FTD is associated with the frontal dysfunction characteristic of the pathology or a dysfunction of memory-specific regions pertaining to Papez's circuit. Data were obtained from eight bv-FTD patients and 26 healthy controls. Autonoetic consciousness was evaluated by Remember responses during the recognition memory phase of the FOK experiment. As a group, bv-FTD patients demonstrated a decline in autonoetic consciousness and FOK accuracy at the chance level. While memory monitoring was impaired in most (seven) patients, four bv-FTD participants had individual impairment of autonoetic consciousness. They specifically showed reduced metabolism in the anterior medial prefrontal cortex, the left dorsolateral prefrontal cortex (near the superior frontal sulcus), parietal regions, and the posterior cingulate cortex. These findings were tentatively interpreted by considering the role of the metabolically impaired brain regions in self-referential processes, suggesting that the bv-FTD patients' problem consciously retrieving episodic memories may stem at least partly from deficient access to and maintenance/use of information about the self. Frontal and posterior cingulate metabolic impairment in the behavioral variant of frontotemporal dementia with impaired autonoetic consciousness     

Semantic knowledge of famous people in mild cognitive impairment and progression to Alzheimer's disease

Patients with dementia of Alzheimer's type (DAT) show severe impairment in recognizing famous people. The aim of the current study was to investigate if this well-known memory impairment of famous faces is already present in the preclinical phase of DAT and if the famous faces test can help to differentiate patients with mild cognitive impairment (MCI) who progress to dementia and those who do not. We compared baseline performance in a task of famous face identification in a sample of 116 patients with subjective memory complaints classified in three groups: 17 participants with no evidence of cognitive impairment; 26 patients with MCI who had not developed dementia, and 27 patients with MCI who had developed probable DAT 2 years later. The remaining patients were excluded because they abandoned or did not meet the applied restrictive criteria for DAT, MCI or control. MCI patients who were diagnosed 2 years later with DAT performed significantly worse in the preclinical phase than MCI and control participants (p < 0.004). Patients with MCI but not DAT obtained intermediate results between control subjects and MCI patients who develop Alzheimer's disease. A neuropsychological task of semantic knowledge of famous people may be useful in the early diagnosis of Alzheimer's disease.