Semantic Memory Tasks Research Articles

Episodic and Semantic Memory for Melodies in Alzheimer's Disease

the present study addressed episodic and semantic memory for melodies in three groups of participants: 35 younger adults, 40 older adults, and 10 individuals with mild to moderate Alzheimer's disease (AD). To assess episodic memory, a study list of eight novel target melodies was presented three times, followed by a test trial in which target melodies were mixed with foil (previously unheard) melodies. Both explicit and implicit measures were obtained. Explicit memory was assessed by the accuracy of discrimination of the target melodies from the foils. Younger adults were significantly more accurate than older adults, who in turn had significantly higher scores than AD adults. Implicit memory was assessed by examining the difference in pleasantness ratings between target and foil melodies. Younger adults showed significantly greater differences in pleasantness ratings than older adults and AD adults; scores for the two latter groups did not differ. To assess semantic memory, participants were asked to identify traditional melodies within a series of traditional and novel melodies. In contrast to the episodic memory results, all three groups showed very high scores on the semantic memory task with no significant differences among groups. The results support the notion that, though other forms of musical memory may be compromised, semantic memory for melody may be preserved in normal aging and in AD.

The metamemory approach to confidence: A test using semantic memory

The metamemory approach to memory confidence was extended and elaborated to deal with semantic memory tasks. The metamemory approach assumes that memory confidence is based on the products and processes of a completed memory task, as well as metamemory beliefs that individuals have about how their memory products and processes relate to memory accuracy. In two experiments participants were asked deceptive and nondeceptive questions involving geographical information. In both experiments, as predicted by the metamemory approach to memory confidence, there was a positive confidence/accuracy relationship for nondeceptive items and a negative relationship for deceptive items. Experiment 2 used items that constrained the memory strategies (e.g., hierarchical reasoning about spatial location) used by the participants. The results supported the hypothesis that the participants were aware of the levels of memory accuracy associated with the different strategies and used that information to generate their memory confidence judgments.

Influence of Aging on the Neural Correlates of Autobiographical, Episodic, and Semantic Memory Retrieval

We used fMRI to assess the neural correlates of autobiographical, semantic, and episodic memory retrieval in healthy young and older adults. Participants were tested with an event-related paradigm in which retrieval demand was the only factor varying between trials. A spatio-temporal partial least square analysis was conducted to identify the main patterns of activity characterizing the groups across conditions. We identified brain regions activated by all three memory conditions relative to a control condition. This pattern was expressed equally in both age groups and replicated previous findings obtained in a separate group of younger adults. We also identified regions whose activity differentiated among the different memory conditions. These patterns of differentiation were expressed less strongly in the older adults than in the young adults, a finding that was further confirmed by a barycentric discriminant analysis. This analysis showed an age-related dedifferentiation in autobiographical and episodic memory tasks but not in the semantic memory task or the control condition. These findings suggest that the activation of a common memory retrieval network is maintained with age, whereas the specific aspects of brain activity that differ with memory content are more vulnerable and less selectively engaged in older adults. Our results provide a potential neural mechanism for the well-known age differences in episodic/autobiographical memory, and preserved semantic memory, observed when older adults are compared with younger adults.

The nature and time‐course of medial temporal lobe contributions to semantic retrieval: An fMRI study on verbal fluency

Recent investigations have shown that the medial temporal lobe (MTL), a region thought to be exclusive to episodic memory, can also influence performance on tests of semantic memory. The present study examined further the nature of MTL contributions to semantic memory tasks by tracking MTL activation as participants performed category fluency, a traditional test of semantic retrieval. For categories that were inherently autobiographical (e.g. names of friends), the MTLs were activated throughout the time period in which items were generated, consistent with the MTLs role in retrieving autobiographical memories. For categories that could not benefit from autobiographical or spatial/context information (e.g. governmental offices), the MTL was not implicated at any time point. For categories for which both prototypical and episodically-related information exists (e.g. kitchen utensils), there was more robust MTL activity for the open-ended, late generation periods compared with the more well-defined, early item generation time periods. We interpret these results as suggesting that early in the generation phase, responses are based on well-rehearsed prototypical knowledge whereas later performance relies more on open-ended strategies, such as deriving exemplars from personally relevant contextual information (e.g. imagining one's own kitchen). These findings and interpretation were consistent with the results of an initial, separate behavioral study (Expt 1), that used the distinctiveness of responses as a measure of open-endedness across the generation phase: Response distinctiveness corresponded to the predicted open-endedness of the various tasks at early and late phases. Overall, this is consistent with the view that as generation of semantic information becomes open-ended, it recruits processes from other domains, such as episodic memory, to support performance.

The effects of marital status on episodic and semantic memory in healthy middle‐aged and old individuals

The present study examined the influences of marital status on different episodic and semantic memory tasks. A total of 1882 adult men and women participated in a longitudinal project (Betula) on memory, health and aging. The participants were grouped into two age cohorts, 35-60 and 65-85, and studied over a period of 5 years. Episodic memory tasks concerned recognition and recall, whereas semantic memory tasks concerned knowledge and fluency. The results showed, after controlling for education, some diseases, chronological age and leisure activity as covariates, that there were significant differences between married and single individuals in episodic memory, but not in semantic memory. Married people showed significantly better memory performances than singles in both subsystems of episodic memory, that is, recall and recognition. Also, the rate of decline in episodic memory was significantly larger for singles and widowed than other groups over the 5-year time period in both age groups. The findings demonstrate that the positive relation found between marriage and health can be extended to the relation between marriage and cognitive performance. This effect might be explained by the role played by cognitive stimulation in memory and cognition.

Misdiagnosis of depression in patients with selective cognitive deficits: A case study

Detection of cognitive markers of dementia is focused on episodic memory and spatio-temporal orientation. However, semantic memory and executive functions may also be impaired in various types of progressive dementias. In this report we describe the distinct clinical features of a case of frontotemporal dementia (FTD), which was falsely been diagnosed and treated for depression. We report a 70-year-old male patient who was admitted to our hospital due to drug resistant depression. The patient was receiving antidepressants for 2 years up to his admission. He showed no clinical improvement of his psychiatric condition and additionally exhibited confusion and marked agitation with incremental drug doses. His neurological examination revealed small-stepped gait, urinary incontinence, pyramidal signs and prominent grasp and suck reflexes. Immediate recall and episodic memory were intact, whereas, he presented with phonemic paraphasias and anosmia. His speech was characterized as syntactically fluent, but empty. Furthermore, he exhibited marked disturbance in all the executive function tasks. Psychiatric manifestations included apathy (emotional indifference) and lack of volution, rather than depression. The brain CT scan pronounced atrophy of the frontal and temporal lobes. Although it is doubtful whether the diagnosis of FTD can be made on pure clinical grounds, the clinical presentation and the course of symptoms in this patient, in conjunction with the brain CT scanning results, directed us towards the diagnosis of a generative type of dementia with frontal symptoms mainly and the exclusion of senile depression. Executive functions and semantic memory tasks should be included in the battery test used in common clinical practice for the evaluation of cognitively impaired patients. These, in conjunction with careful clinical judgment, are of prime importance in order to minimize misdiagnosis of dementia syndromes.

Simultaneously Measuring Gait and Cognitive Performance in Cognitively Healthy and Cognitively Impaired Older Adults: The Basel Motor-Cognition Dual-Task Paradigm

To investigate dual-task performance of gait and cognition in cognitively healthy and cognitively impaired older adults using a motor-cognition dual-task paradigm. Cross-sectional retrospective study. The Basel Memory Clinic and the Basel Study on the Elderly (Project BASEL). Seven hundred eleven older adults (mean age 77.2±6.2, 350 (49.2%) female and 361 (50.8%) male). Gait velocity and cognitive task performance using a working memory (counting backward from 50 by 2s) and a semantic memory (enumerating animal names) task were measured during single- and dual-task conditions. Gait was assessed using the GAITRite electronic walkway system. Cognitive impairment was defined as a score less than 25 on the Mini-Mental State Examination. During dual tasks, participants reduced gait velocity (P<.001) and calculated fewer numbers (P=.03) but did not enumerate fewer animals and did not make more errors or repetitions (P>.10). Cognitively impaired individuals had lower baseline gait velocity and a greater reduction in gait velocity but not cognitive performance during dual tasks than cognitively healthy participants (P<.01). Gait velocity was lower during both dual tasks, whereas decrease in cognitive performance depended on the cognitive ability needed in the dual-task condition. Cognitively impaired individuals generally have poorer baseline performance and greater dual task-related gait velocity reduction than those who are cognitively healthy. Future research should include different conditions for gait to determine adaptive potentials of older adults.

Retraction of “Gaining Control: Training Executive Function and Far Transfer of the Ability to Resolve Interference”

Functional brain-imaging data document overlapping sites of activation in prefrontal cortex across memory tasks, suggesting that these tasks may share common executive components. We leveraged this evidence to develop a training regimen and a set of transfer tasks to examine the trainability of a putative executive-control process: interference resolution. Eight days of training on high-interference versions of three different working memory tasks increased the efficiency with which proactive interference was resolved on those particular tasks. Moreover, an improved ability to resolve interference was also transferred to different working memory, semantic memory, and episodic memory tasks, a demonstration of far-transfer effects from process-specific training. Participants trained with noninterference versions of the tasks did not exhibit transfer. We infer that the transfer we demonstrated resulted from increased efficiency of the interference-resolution process. Therefore, this aspect of executive control is plastic and adaptive, and can be improved by training.

Chronic stress is linked to 5-HT1A receptor changes and functional disintegration of the limbic networks

There are increasing reports about stress related cognitive and psychic declines in subjects who have no psychiatric premorbidity, depression, or major life trauma. Yet, little is known about the underlying neurobiology. Based on the typical symptomatology, fMRI data suggesting that stress activates the limbic circuits, and animal data showing a major involvement of the 5-HT1A receptor in stress regulation, we hypothesized that enduring daily stress causes widespread limbic dysfunctions, and specific changes of the 5-HT1A receptor.To test these hypotheses combined PET studies were carried out in 16 chronically stressed, and 16 non-stressed subjects. Limbic function was tested by measuring cerebral blood flow during rest, and when using an odor activation paradigm. 5-HT1A receptor binding potential (BP) was assessed with [11C]WAY100635. All subjects went through a battery of neuropsychological tests.Stressed subjects showed a functional disconnection between the amygdala and ACC/medial prefrontal cortex (mPFC), and an impaired odor activation of the ACC. They also displayed a reduced 5-HT1A receptor BP in the anterior cingulate (ACC), the insular-cortex, and the hippocampus. Their performance in attention-, odor discrimination-, and semantic memory tasks was impaired, and correlated with the BP-values in the respective region. The degree of reported stress was inversely correlated with activation of ACC, and the 5-HT1A receptor BP in the amygdala and hippocampus.Enduring every day psychosocial stress seems to be associated with a limbic reduction of 5-HT1A receptor binding and functional disintegration of ACC/mPFC. These changes support the notion of an impaired top-down regulation of stress stimuli, and identify potential targets for early treatment.

Prediction of Cognitive Decline in Healthy Older Adults using fMRI

Few studies have examined the extent to which structural and functional MRI, alone and in combination with genetic biomarkers, can predict future cognitive decline in asymptomatic elders. This prospective study evaluated individual and combined contributions of demographic information, genetic risk, hippocampal volume, and fMRI activation for predicting cognitive decline after an 18-month retest interval. Standardized neuropsychological testing, an fMRI semantic memory task (famous name discrimination), and structural MRI (sMRI) were performed on 78 healthy elders (73% female; mean age = 73 years, range = 65 to 88 years). Positive family history of dementia and presence of one or both apolipoprotein E (APOE) ε4 alleles occurred in 51.3% and 33.3% of the sample, respectively. Hippocampal volumes were traced from sMRI scans. At follow-up, all participants underwent a repeat neuropsychological examination. At 18 months, 27 participants (34.6%) declined by at least 1 SD on one of three neuropsychological measures. Using logistic regression, demographic variables (age, years of education, gender) and family history of dementia did not predict future cognitive decline. Greater fMRI activity, absence of an APOE ε4 allele, and larger hippocampal volume were associated with reduced likelihood of cognitive decline. The most effective combination of predictors involved fMRI brain activity and APOE ε4 status. Brain activity measured from task-activated fMRI, in combination with APOE ε4 status, was successful in identifying cognitively intact individuals at greatest risk for developing cognitive decline over a relatively brief time period. These results have implications for enriching prevention clinical trials designed to slow AD progression.

Evidence for similar principles in episodic and semantic memory: The presidential serial position function

When people recall a list of items that they have just experienced (an episodic memory task), the resulting serial position function looks strikingly similar to that observed when people are asked to recall the presidents of the United States (a semantic memory task). Despite the similarity in appearance, there is disagreement about whether the two functions arise from the same processes. A local distinctiveness model of memory, SIMPLE, successfully fit the presidential data using two underlying dimensions: one corresponding to item (or presidential) distinctiveness and the other to order (or positional) distinctiveness. According to the model, presidential primacy and recency are due to the same mechanisms that give rise to primacy and recency effects in both short- and long-term episodic memory. All of these primacy and recency effects reflect the relative distinctiveness principle (Surprenant & Neath, 2009): Items will be well remembered to the extent that they are more distinct than competing items at the time of retrieval.

Effect of combined noise sources on cognitive performance and perceived disturbance.

An experiment was conducted to investigate the differences in cognitive performance and perceptions under road traffic noise and construction noise combined with road traffic noise. Under the conditions with individual noise and combined noise sources, an episodic memory task and semantic task were carried out in the laboratory. The subjects were asked to recall the presented words after the exposure to noises (episodic memory task) and to select the target word when the five words, including the target word and other words, were presented simultaneously (semantic memory task). Subjects also rated perceived annoyance and disturbance to the noise exposure during the experiment. The result showed that the percentage of correct answer significantly decreased with an increase in construction noise in an episodic memory task. In contrast, the semantic memory task was not impaired by the level of construction noise level. This indicates that only the retrieval task with a process of generating the internal cues was affected by the level of combined noise sources. And it was also found that the perceptions of combined noise sources were highly correlated with the result of the episodic memory task.

Dose effects of triazolam and alcohol on cognitive performance in healthy volunteers.

Benzodiazepines and alcohol are widely used psychoactive substances that have performance-impairing effects. Research suggests that the impairment profiles for benzodiazepines and alcohol differ, although few cognitive psychopharmacological studies have directly compared these drugs. This double-blind, double-dummy, placebo-controlled, repeated measures study directly compared the acute dose effects of triazolam (0.125, 0.25 mg/70 kg) and alcohol (0.40, 0.80 g/kg) in 20 social drinkers. At doses that produced comparable psychomotor impairment, triazolam was more likely to impair several objective measures of cognitive performance (e.g., episodic memory, divided attention) and to slow performance across several measures. However, only alcohol impaired accuracy on the digit symbol substitution and semantic memory tasks. In addition to objective measures, both drugs impaired awareness of performance impairments (i.e., metacognition) such that participants overestimated impairment, and the magnitude of this effect was generally larger for alcohol. Only triazolam impaired other measures of metacognition (e.g., error detection on a choice reaction time task). Future research might examine the clinical implications of the performance impairments reported here given the widespread use of benzodiazepines and alcohol.

Dose effects of triazolam and scopolamine on metamemory.

The present study compared the acute dose effects of the benzodiazepine triazolam and the anticholinergic scopolamine on metamemory (knowledge and awareness of one's own memory) in a two-phase paradigm designed to assess effects on both monitoring and control components of metamemory in both semantic (general knowledge) and episodic memory (cued-recall) tasks. Placebo and 2 doses each of triazolam (0.125, 0.25 mg/70 kg, oral) and scopolamine (0.25, 0.50 mg/70 kg, subcutaneous) were administered to 80 healthy volunteers (16 per group) in a double-blind, double-dummy, independent groups design. Both triazolam and scopolamine impaired episodic memory (quantity and accuracy) but not semantic memory. Results suggested that both drugs impaired monitoring as reflected in absolute accuracy measures (impaired calibration in the direction of overconfidence) and control sensitivity (the relationship between confidence and behavior). Overall, the results did not provide evidence for differences between triazolam and scopolamine in memory or metamemory. In addition to the clinical relevance of the observed effects, this study adds to the accumulating body of cognitive psychopharmacological research illustrating the usefulness of drug-induced amnesia as a vehicle to explore memory and metamemory.

When the zebra loses its stripes: Semantic priming in early Alzheimer's disease and semantic dementia

Patients suffering from Alzheimer's disease (AD) or semantic dementia (SD) both exhibit deficits on explicit tasks of semantic memory. Semantic priming (SP) paradigms provide a very pure and precise implicit measurement of semantic memory impairment, and a previous study of AD ( Giffard et al., 2002) using one such paradigm revealed that AD patients in the initial stages of semantic deterioration presented an abnormally large priming effect (hyperpriming) in a category-coordinate condition, compared with controls. This astonishing phenomenon could stem from the specific loss of distinctive attributes that make it possible to distinguish between semantically close concepts, while attributes shared by different concepts belonging to a given category remain intact. To test this hypothesis and compare the degradation of semantic memory in AD and SD, we devised an SP paradigm in which word pairs had either a category-coordinate or an attribute relationship. In accordance with our hypothesis, we distinguished between shared ( duck–feathers) versus distinctive attributes ( zebra–stripes) and close ( tiger–lion) versus distant ( elephant–crocodile) category-coordinate relationships. This paradigm, together with two explicit semantic memory tasks (picture-naming and categorization), was administered to 16 AD and 8 SD patients and 30 elderly control subjects. The AD patients, at the very beginning of semantic deterioration, only displayed impaired SP effects in the distinctive attribute condition, whereas in the SD patients, who had more severe semantic deterioration, we observed an extinction of SP effects in both attribute conditions. In SD patients, we also report hyperpriming effects in both category-coordinate conditions. Our results suggest that semantic memory impairment follows the same course in both AD and SD, affecting distinctive attributes first and then shared ones. In accordance with distributed models of semantic memory, the loss of distinctive attributes leads to a confusion between close concepts and it is this which causes the transient hyperpriming phenomenon.

Musical and verbal semantic memory: Two distinct neural networks?

Semantic memory has been investigated in numerous neuroimaging and clinical studies, most of which have used verbal or visual, but only very seldom, musical material. Clinical studies have suggested that there is a relative neural independence between verbal and musical semantic memory. In the present study, “musical semantic memory” is defined as memory for “well-known” melodies without any knowledge of the spatial or temporal circumstances of learning, while “verbal semantic memory” corresponds to general knowledge about concepts, again without any knowledge of the spatial or temporal circumstances of learning. Our aim was to compare the neural substrates of musical and verbal semantic memory by administering the same type of task in each modality. We used high-resolution PET H2O15 to observe 11 young subjects performing two main tasks: (1) a musical semantic memory task, where the subjects heard the first part of familiar melodies and had to decide whether the second part they heard matched the first, and (2) a verbal semantic memory task with the same design, but where the material consisted of well-known expressions or proverbs. The musical semantic memory condition activated the superior temporal area and inferior and middle frontal areas in the left hemisphere and the inferior frontal area in the right hemisphere. The verbal semantic memory condition activated the middle temporal region in the left hemisphere and the cerebellum in the right hemisphere. We found that the verbal and musical semantic processes activated a common network extending throughout the left temporal neocortex. In addition, there was a material-dependent topographical preference within this network, with predominantly anterior activation during musical tasks and predominantly posterior activation during semantic verbal tasks.

Semantic Markers in the Diagnosis of Neurodegenerative Dementias

Background: The search for early cognitive markers of Alzheimer’s disease (AD) has focused on episodic memory and spatiotemporal orientation. However, recent research suggests that semantic memory is also impaired in the preclinical stages of AD. Methods: Age- and education-matched groups of participants with AD, mild cognitive impairment, and subjective memory complaints and healthy controls were assessed with 16 cognitive tests encompassing attention, orientation, episodic and semantic memory, and language tasks. Results: The battery correctly distinguished AD patients from healthy seniors in 92% of the cases. Three semantic memory-based tasks turned out to be particularly powerful for this purpose. Conclusion: Our results suggest that semantic memory tasks should be included in the battery of tests for the evaluation of cognitively impaired patients.

Semantic memory activation in individuals at risk for developing Alzheimer disease

To determine whether whole-brain, event-related fMRI can distinguish healthy older adults with known Alzheimer disease (AD) risk factors (family history, APOE epsilon4) from controls using a semantic memory task involving discrimination of famous from unfamiliar names. Sixty-nine cognitively asymptomatic adults were divided into 3 groups (n = 23 each) based on AD risk: 1) no family history, no epsilon4 allele (control [CON]); 2) family history, no epsilon4 allele (FH); and 3) family history and epsilon4 allele (FH+epsilon4). Separate hemodynamic response functions were extracted for famous and unfamiliar names using deconvolution analysis (correct trials only). Cognitively intact older adults with AD risk factors (FH and FH+epsilon4) exhibited greater activation in recognizing famous relative to unfamiliar names than a group without risk factors (CON), especially in the bilateral posterior cingulate/precuneus, bilateral temporoparietal junction, and bilateral prefrontal cortex. The increased activation was more apparent in the FH+epsilon4 than in the FH group. Unlike the 2 at-risk groups, the control group demonstrated greater activation for unfamiliar than familiar names, predominately in the supplementary motor area, bilateral precentral, left inferior frontal, right insula, precuneus, and angular gyrus. These results could not be attributed to differences in demographic variables, cerebral atrophy, episodic memory performance, global cognitive functioning, activities of daily living, or depression. Results demonstrate that a low-effort, high-accuracy semantic memory activation task is sensitive to Alzheimer disease risk factors in a dose-related manner. This increased activation in at-risk individuals may reflect a compensatory brain response to support task performance in otherwise asymptomatic older adults.

Semantic memory activation in amnestic mild cognitive impairment

Cognitively intact older individuals at risk for developing Alzheimer's disease frequently show increased functional magnetic resonance imaging (fMRI) brain activation presumably associated with compensatory recruitment, whereas mild cognitive impairment (MCI) patients tend not to show increased activation presumably due to reduced neural reserve. Previous studies, however, have typically used episodic memory activation tasks, placing MCI participants at a performance disadvantage relative to healthy elders. In this event-related fMRI study, we employed a low effort, high accuracy semantic memory task to determine if increased activation of memory circuits is preserved in amnestic MCI when task performance is controlled. Fifty-seven participants, aged 65-85 years, comprised three groups (n = 19 each): amnestic MCI patients; cognitively intact older participants at risk for developing Alzheimer's disease based on having at least one ApoE epsilon4 allele and a positive family history of Alzheimer's disease (At Risk); and cognitively intact participants without Alzheimer's disease risk factors (Control). fMRI was conducted on a 3T MR scanner while participants performed a famous name discrimination task. Participants also underwent neuropsychological testing outside the scanner; whole brain and hippocampal atrophy were assessed from anatomical MRI scans. The three groups did not differ on demographic variables or on fame discrimination performance (>87% correct for all groups). As expected, the amnestic MCI participants demonstrated reduced episodic memory performance. Spatial extent of activation (Fame--Unfamiliar subtraction) differentiated the three groups (Control = 0 ml, At Risk = 9.7 ml, MCI = 34.7 ml). The MCI and At Risk groups showed significantly greater per cent signal change than Control participants in 8 of 14 functionally defined regions, including the medial temporal lobe, temporoparietal junction, and posterior cingulate/precuneus. MCI participants also showed greater activation than Controls in two frontal regions. At Risk, but not MCI, participants showed increased activity in the left hippocampal complex; MCI participants, however, evidenced increased activity in this region when hippocampal atrophy was controlled. When performance is equated, MCI patients demonstrate functional compensation in brain regions subserving semantic memory systems that generally equals or exceeds that observed in cognitively intact individuals at risk for Alzheimer's disease. This hyperactivation profile in MCI is even observed in the left hippocampal complex, but only when the extent of hippocampal atrophy is taken into consideration.

Behaviour of motor disabilities and appearance of visual hallucinations in patients with Parkinson’s disease in a virtual enviroment

We studied 23 Parkinson's disease (PD) non-demented patients and 15 controls in Virtual Reality (VR) environments reproducing usual daily living situations. In VR sessions, PD patients performed their actions worse than controls, in terms of time of execution in exploration and pointing, precision as objects avoiding, and in semantic incidental memory task. We observed clear differences of performances between on and off status medication, with a global worsening during off phase. Moreover, all six patients with motor fluctuations described visual hallucinations during off state, with occurrence of images not included in the virtual environment.