Semantic and episodic memory performances of patients with Alzheimer’s disease and minor neurocognitive disorder

The aim of this study is to provide a test that allows for evaluation of both semantic memory (SM) and episodic memory (EM). The study sought to examine psychometric characteristics of the Modified Dead–Alive Test (M-DAT) in patients with neurocognitive disorders and the healthy elderly (HE). The M-DAT consists of 45 names of celebrities who have died in the remote past (15), died in the last five years (15), and are still alive (15), and participants are asked whether they are alive or dead. The M-DAT performances of patients with Diagnostic and Statistical Manual of Mental Disorders-5 (DSM-5) major neurocognitive disorder due to Alzheimer’s Disease (MND-AD) (n = 69) and patients with minor neurocognitive disorder (MiND) (n = 27) who were admitted to a geriatric psychiatry clinic and healthy controls (HC) (n = 29) were compared. Age and level of education were taken as covariates, and an analysis of covariance (ANCOVA) was performed since the MND-AD group was older and less educated. The MND-AD group had lower performance in EM and SM scores of the M-DAT. M-DAT failed to differentiate between MiND and HE. Both subscale scores of the M-DAT were associated with other neuropsychological test performances as well as the level of education. The results suggest that M-DAT is a valid and reliable tool that examines both EM and SM performances. M-DAT is an alternative for the assessment of SM evaluated by verbal fluency or naming tests. Evaluating EM and SM together is an important advantage; however, M-DAT is influenced by education, and the items require updating.

Distinct neuroanatomical bases of episodic and semantic memory performance in Alzheimer’s disease

Nature of personal semantic memory: evidence from Alzheimer’s disease

Structural stability and change in semantic and episodic memory performance as well as interindividual differences in 5-year changes in these constructs are examined within a sample of older adults (age rangeT1 = 60-80; n = 361). Interindividual differences in change were limited but significant. Stability coefficients were higher for semantic memory (.95) than for episodic memory (.87). Changes in episodic and semantic memory performance were strongly associated (r =.68). Across time, variances and covariances increased, and a tendency toward dedifferentiation in terms of increasing correlations was found. Chronological age was related to both level and change, but gender and education were only related to level of memory performance. Collectively, these results depict relatively high degrees of structural stability and stability of interindividual differences in declarative memory in old age.

Episodic and semantic memory in children with mesial temporal sclerosis

Semantic, episodic, and autobiographical memory in a postmeningitic amnesic patient

As part of a unifying theory of autism, Ben Shalom (2009) proposed that while procedural, perceptual and semantic memory functions are intact in Autism Spectrum Disorder (ASD), the more integrative level of episodic memory is impaired. According to Ben Shalom, this reduced integration may be due to the reduced function of the medial prefrontal cortex (mPFC), which may also explain the reduced integration found in motor, sensory-perceptual and emotional processes in ASD. The present review examines this hypothesis, by focusing on evidence regarding autobiographical memory (AM) episodes in ASD—arguably the highest form of memory integration processes. Most research on memory in ASD thus far has focused on memory for experimentally-presented stimuli (Lind, 2010; Boucher et al., 2012). The present paper builds on this literature to examine the rich evidence that has recently accumulated from in-depth, systematic studies of AM in ASD—memories of personally-related events that are naturalistically accumulated over a person's lifetime. Of note, research on AM is limited in its focus on memories that cannot be as readily verified (but see Bruck et al., 2007), and in its reliance on high-functioning verbal individuals. Nonetheless, studies of AM provide us with an unparalleled perspective on the naturalistic process of memory integration in ASD. Specifically, this review aims to determine how well memory episodes are integrated in ASD; which elements become integrated and which do not; whether the ability to form integrated, episodic memories relates to other cognitive and emotional capacities; and how this pattern of integration changes over time. Semantic and episodic autobiographical memory (AM) The declarative memory system comprises semantic and episodic components. Semantic memories are memories of timeless, de-contextualized facts. Episodic memory refers to personal events recollected in the context of a particular time and place, with some reference to oneself as a participant in the episode (Tulving, 2002). Thus, episodic memories involve two functions: the ability to bind different perceptual elements; and, in humans, the ability to perceive of oneself within this context. On a neurobiological level, episodic memory storage and retrieval are thought to involve the interaction of cortical association areas, in which basic sensory information regarding what occurred and where is stored; the hippocampus, which binds these elements into cohesive memories of individual events; and the mPFC, which further contextualizes these events into schemas, such as the self (Preston and Eichenbaum, 2013). AM refers to memory for information pertaining to the self; and while it is often viewed as overlapping with episodic memory, the two are not synonymous (Gilboa, 2004). Episodic memory is a memory system, while AM is a type of content (Gardiner, 2008). Thus, episodic memory functions can encompass both AM and simple phenomena that do not necessarily represent self-relevant information (e.g., source memory). At the same time, AM in fact comprises of both semantic and episodic knowledge (e.g., semantic knowledge of one's date of birth, alongside an episodic memory of one's last birthday). In children with ASD, both semantic and episodic AM is reduced (Bruck et al., 2007; Bon et al., 2012; Goddard et al., 2014), though by adulthood, adults with ASD show a spared memory for semantic AM, alongside reduced episodic AM (Klein et al., 1999; Crane and Goddard, 2008). These studies suggest that as semantic AM may grow in ASD, episodic AM impairments are pervasive. These results fit with the general memory profile in ASD, viz., spared semantic memory alongside difficulties with episodic memory, which is found across experimental studies (Boucher and Bowler, 2008). The present review concerns itself primarily with episodic AM in ASD, though semantic memory will be discussed as it relates to the content of autobiographical narratives.

Individuals with mild cognitive impairment (MCI) can often progress into Alzheimer’s Disease (AD). Research suggests that decline in episodic memory and semantic memory, as well as functional abilities, can be sensitive in predicting disease progression. This study aimed to (a) investigate episodic and semantic memory performance differences between AD and MCI, (b) determine if memory performance predicts observation-based activities of daily living (ADLs), and (c) explore whether semantic memory mediates the relationship between episodic memory and ADLs. Fifty-eight AD, 53 MCI, and 72 healthy control participants were administered the Rey-O, California Verbal Learning Test, Animal Fluency Test, Boston Naming Test, and Direct Assessment of Functional Status (DAFS). The results revealed, first, that AD participants performed significantly lower than the MCI participants across semantic memory and episodic memory tasks, with the exception of the Boston Naming Test. Second, hierarchical-stepwise regression analyses found that semantic memory significantly predicted DAFS orientation, communication, and financial skills in AD, but episodic memory predicted shopping skills. Furthermore, semantic memory significantly predicted DAFS transportation skills in AD and MCI. Third, within the overall sample, semantic memory mediated the relationship between episodic memory and ADLs. Taken together, the findings suggest decline in semantic memory (as measured by confrontational naming and category fluency) and episodic memory (as measured by list and complex visual design learning and recall) may lead to decline in different and specific aspects of functional abilities in AD and MCI.

Pathological tau is suggested to play a role in cognitive deterioration in the preclinical phase of Alzheimer’s disease. We investigated cross-sectional associations of tau burden with episodic and semantic memory performance in older adults without dementia. A systematic search in MEDLINE (via PubMed), PsychINFO, and Embase resulted in 24 eligible studies for meta-analysis. Tau burden was assessed using CSF, PET, or histopathological measures. All studies evaluated associations of tau with episodic memory: weighted effect sizes were -0.46 (95 % CI [-0.73; -0.20], p < .001) for episodic composite scores, -0.19 ([-0.36; -0.03], p = .024) for delayed word list recall, and -0.05 ([-0.14; 0.04], p = .257) for logical memory. Fourteen studies evaluated associations of tau with semantic memory: weighted effect sizes were -0.28 ([-0.52; -0.04], p = .023) for semantic composite scores, -0.06 ([-0.16; 0.03], p = .194) for semantic fluency, and 0.06 ([-0.06; 0.18], p = .319) for picture naming. Our findings indicate that tau burden related to both episodic and semantic memory impairment in older individuals without a diagnosis of mild cognitive impairment or manifest dementia, with episodic composite scores showing the strongest association with tau burden. Future potential lies in developing more sensitive scores to detect this subtle cognitive impairment, which could contribute to early identification of individuals in the preclinical phase of Alzheimer’s disease, thereby improving early diagnosis and timely intervention.

BackgroundSchizophrenia is associated with deficits in both episodic and semantic memory however, our understanding of how the deficits in each system independently contribute to overall memory performance is poorly understood.The Hopkins Verbal Learning Task (HVLT) is a memory task using a single word list. To perform the task successfully, participants need to use both episodic and semantic abilities. Both episodic and semantic clustering scores can be calculated which provide nuanced information about the memory encoding and retrieval techniques used by those performing the task.MethodsSixty schizophrenia patients and sixty healthy controls were compared in their performance on the HVLT. In addition to analysing immediate recall, learning slope, delayed recall and recognition, semantic and episodic clustering were also compared. Further, given the link between thought disorder and semantic function, this symptom was correlated with memory performance measures.ResultsThe schizophrenia group demonstrated worse performance across learning trials, delayed recall, and recognition indicating a generalised memory problem. Clustering scores were used to probe into semantic and episodic function specifically. The schizophrenia group demonstrated normal episodic clustering in the face of significantly impaired semantic clustering. Further, semantic clustering performance positively correlated with all general memory measures whilst episodic clustering did not. Finally, thought disorder did not correlate with any HVLT performance measure apart from semantic clustering.DiscussionIt is difficult to tease apart the contributions of semantic and episodic memory impairments to poor overall memory function in schizophrenia. In this study, we have first demonstrated intact episodic clustering in the face of impaired semantic clustering. Then, by correlating semantic and episodic clustering scores with general memory performance measures, we were able to demonstrate that semantic memory performance is more significantly related to overall memory performance than episodic performance. Finally, this result supports the specificity of the relationship between thought disorder and semantic memory impairment.

BackgroundDepression impacts 50% of the elderly population and is a risk factor for dementia but its prevalence and role in cognitive decline in Non‐Whites and the oldest‐old is unclear.MethodLifeAfter90 is a racially/ethnically diverse cohort of individuals aged 90+ that launched in 2018 with the aim of characterizing cognitive and brain aging after the 9th decade of life. Participants are members of an integrated healthcare delivery system without a dementia diagnosis in their medical record at recruitment. Depression at baseline was evaluated with the Global Depression Scale (GDS) and defined as GDS&gt;4. Cognitive testing every 6 months uses the Spanish and English Neuropsychological Assessment Scales (SENAS), to assess cognitive domains of episodic memory, semantic memory, and executive function. Linear mixed models with random intercepts, evaluated the baseline and longitudinal association of depression with each SENAS domain. The models used years since baseline as the time variable, and adjusted for baseline age, sex, race/ethnicity, education, and practice effects. An interaction term (depression*time) tested for differences in decline in cognitive domains by baseline depression status.ResultOf 655 participants 32% are White, 22% Asian, 22% Black, 15% Latino, and 8% Other/Multiracial. 35% had &lt;high school education, 38% were male, and mean age was 93 years. At baseline, 32% were classified as having depression with the highest prevalence among Latinos and those with &lt;high school education (Table 1). The average follow‐up was 0.9 years (range: 0‐1.9). Depression was associated with poorer semantic memory (ß=‐0.17) and executive function (ß=‐0.18) but not with episodic memory (Table 2). Semantic memory (ß=‐0.28) and executive function (ß=‐0.11) decreased over time, however episodic memory did not. The semantic memory and executive function decline did not differ by depression (Figure 1 &amp; Table 2).ConclusionDepression impacts one third of this ethnically diverse cohort of oldest‐old individuals and ais more prevalent in Latino participants. While depression is associated with poorer baseline semantic memory and executive function; it is not associated with episodic memory, nor is it associated with greater cognitive decline. These results suggest that while depression may impact cognitive performance it may not impact cognitive change in those aged 90+.

Semantic cognition is supported by two interactive components: semantic representations and mechanisms that regulate retrieval (cf. ‘semantic control’). Neuropsychological studies have revealed a clear dissociation between semantic and episodic memory. This study explores if the same dissociation holds for control processes that act on episodic and semantic memory, or whether both types of long-term memory are supported by the same executive mechanisms. We addressed this question in a case-series of semantic aphasic patients who had difficulty retrieving both verbal and non-verbal conceptual information in an appropriate fashion following infarcts to left inferior frontal gyrus (LIFG). We observed parallel deficits in semantic and episodic memory: (i) the patients' difficulties extended beyond verbal materials to include picture tasks in both domains; (ii) both types of retrieval benefitted from cues designed to reduce the need for internal constraint; (iii) there was little impairment of both semantic and episodic tasks when control demands were minimised; (iv) there were similar effects of distractors across tasks. Episodic retrieval was highly susceptible to false memories elicited by semantically-related distractors, and confidence was inappropriately high in these circumstances. Semantic judgements were also prone to contamination from recent events. These findings demonstrate that patients with deregulated semantic cognition have comparable deficits in episodic retrieval. The results are consistent with a role for LIFG in resolving competition within both episodic and semantic memory, and also in biasing cognition towards task-relevant memory stores when episodic and semantic representations do not promote the same response.

Structural equation modeling was used to investigate whether age-related episodic and semantic memory impairments are better explained by decline in processing speed or executive functioning (or both), rather than directly in terms of memory components. The models tested were based on an extensive review of the literature on cognitive decline in normal aging, up to very old age. A computerized test battery, measuring episodic memory (free and cued recall; recognition), semantic memory (fluency; naming accuracy and latencies), processing speed and executive functioning, was administered to 234 elderly persons ranging from young-old to very old age (55–96 years). To avoid large variance in response times due to physical instead of cognitive limitations, no motor responses were required from participants. Age-related decline in episodic and semantic memory performance was found to be the consequence of declines in processing speed and executive functioning. Processing speed mainly mediated decline of...

BackgroundSubjective memory concerns are relatively easy to assess and are useful if they can identify people with cognitive deficits or can predict cognitive decline. In a multiethnic cohort of oldest‐old individuals, we studied whether baseline cognitive performance and cognitive decline differ between individuals who report memory concerns and those who do not.Method LifeAfter90 participants are long‐time members of the Kaiser Permanente Northern California Health Care System without a dementia diagnosis in their medical record at recruitment. Evaluations are every six months and include the Spanish and English Neuropsychological Assessment Scales (SENAS), which assesses episodic memory, semantic memory, and executive function domains. At baseline, participants answered the question ‘Are you concerned that you have a memory or other thinking problem?’ Using linear mixed models with random intercepts, we estimated the baseline and longitudinal association of memory concerns with each SENAS domain. The models used years since baseline as the time variable, and adjusted for baseline age, sex, race/ethnicity, education, and practice effects. Potential differences in cognitive decline by presence or absence of memory concerns were assessed with an interaction term (memory concerns*time).ResultAt baseline, the 665 participants were on average 92.8 years of age, 62% were women, 34% were college graduates, 69% were racial/ethnic minorities, and 40% reported memory concerns (Table 1). The average follow‐up was 0.9 years (range: 0‐1.9). Memory concerns were associated with worse baseline performance in episodic memory (ß=‐0.21) and executive function (ß=‐0.12) but not semantic memory (ß=‐0.01) (Figure &amp; Table 2). Although cognitive scores decreased over time for semantic memory (ß=‐0.31) and executive function (ß=‐0.10), the decline did not differ between people with and without memory concerns (Figure &amp; Table 2).ConclusionIn this multi‐ethnic oldest‐old cohort, individuals with memory concerns have worse baseline cognitive performance in executive function and episodic memory, but their rate of decline is similar to individuals without memory concerns. Although memory concerns appear to identify individuals with objective cognitive impairment, it does not identify those who may decline faster. With additional follow‐up, we will continue to explore the utility of memory concerns in predicting future cognitive performance.

The ERP correlates of self-knowledge: Are assessments of one’s past, present, and future traits closer to semantic or episodic memory?