Semantic Clustering Strategy Research Articles

Semantic Clustering during Verbal Episodic Memory Encoding and Retrieval in Older Adults: One Cognitive Mechanism of Superaging.

Normal aging is commonly accompanied by a decline in cognitive abilities, including memory, yet some individuals maintain these abilities as they get older. We hypothesize that semantic clustering, as an effective strategy for improving performance on episodic recall tasks, may contribute to the maintenance of youthful memory in older adults. We investigated the dynamics of spontaneous production and utilization of the semantic clustering strategy in two independent samples of older adults who completed a list learning paradigm (N1 = 40 and N2 = 29, respectively). Specifically, we predicted and observed that older adults who spontaneously used a semantic clustering strategy throughout the encoding process learned more words by the culmination of the encoding trials (Sample 1, R2= 0.53, p < 0.001; Sample 2, R2= 0.51, p < 0.001), and that those who utilized this strategy during retrieval recalled more words, when compared to older adults who did not produce or utilize a semantic clustering strategy during both a short (Sample 1, R2 = 0.81, p < 0.001; Sample 2, R2 = 0.70, p < 0.001) and long delay retrieval (Sample 1, R2 = 0.83, p < 0.001; Sample 2, R2 = 0.77, p < 0.001). We further predicted and observed that older adults who maintained a youthful level of delayed free recall (i.e., "Superagers") produced (Sample 1, F(1, 38) = 17.81, p < 0.0001; Sample 2, F(1, 27) = 14.45, p < 0.0001) and utilized (Sample 1, F(1, 39) = 25.84, p < 0.0001; Sample 2, F(1, 27) = 12.97, p < 0.01) more semantic clustering than did older individuals with normal memory for their age. These results suggest one cognitive mechanism through which Superagers maintain youthful memory function and raise the possibility that older adults may be able to train themselves to use strategies to promote better memory.

Superior verbal learning and memory in pediatric brain tumor survivors treated with proton versus photon radiotherapy.

Radiotherapy for pediatric brain tumor has been associated with late cognitive effects. Compared to conventional photon radiotherapy (XRT), proton radiotherapy (PRT) delivers lower doses of radiation to healthy brain tissue. PRT has been associated with improved long-term cognitive outcomes compared to XRT. However, there is limited research comparing the effects of XRT and PRT on verbal memory. Survivors of pediatric brain tumor treated with either XRT (n = 29) or PRT (n = 51) completed neuropsychological testing > 1 year following radiotherapy. Performance on neuropsychological measures was compared between treatment groups using analysis of covariance. Chi-squared tests of independence were used to compare the frequency of encoding, retrieval, and intact memory profiles between treatment groups. Associations between memory performance and other neurobehavioral measures were examined using Pearson correlation. Overall, patients receiving PRT demonstrated superior verbal learning and recall compared to those treated with XRT. Encoding and retrieval deficits were more common in the XRT group than the PRT group, with encoding problems being most prevalent. The PRT group was more likely to engage in semantic clustering strategies, which predicted better encoding and retrieval. Encoding ability was associated with higher intellectual and adaptive functioning, and fewer parent-reported concerns about day-to-day attention and cognitive regulation. Results suggest that PRT is associated with verbal memory sparing, driven by effective encoding and use of learning strategies. Future work may help to clarify underlying neural mechanisms associated with verbal memory decline, which will better inform treatment approaches. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Targeting Cognitive Control Deficits With Neuroplasticity-Based Computerized Cognitive Remediation in Patients With Geriatric Major Depression: A Randomized, Double-Blind, Controlled Trial

Late life major depression (LLD) is often accompanied by cognitive deficits. When patients have specific deficits in cognitive control functions (CCD), they are not only distressing and debilitating, they often predict poor clinical outcomes such as reduced response to SSRI/SNRI antidepressants, increased disability, suicide and all-cause mortality. We recently reported that in an open label trial, our treatment designed to target these specific CCD with neuroplasticity-based computerized cognitive remediation (nCCR) improved depression and CCD in patients who failed to remit with conventional antidepressant treatment. This study tested the hypothesis that in patients with LLD who have failed at least one trial of an SSRI/SNRI antidepressant at an adequate dose for at least 8 weeks, nCCR will improve both depressive symptoms and the CCD associated with poor antidepressant response (i.e. semantic strategy, inhibition of prepotent responses) more than an active control group. Participants were randomized (1:1) to receive either 30 hours/ 4 weeks of neuroplasticity based computerized cognitive remediation (nCCR) designed to target CCD, or the active control condition matched for duration, engagement, reward, computer presentation, and contact with study staff. All participants and raters were blinded. Mixed effects model analysis the time effect (week) (F(1,71.22)=25.2, p<0.0001) and treatment group X time interaction (F(1,61.8)=11.37, p=.002) reached significance indicating that the slope of decline in MADRS was steeper in the nCCR-GD group. Further, the nCCR group improved their semantic clustering strategy(t(28)=9.5; p=.006), as well as performance on the Stroop interference condition, and cognitive flexibility (Trails B). Further, results transferred to memory performance, which was not a function trained by nCCR. clinicaltrials.gov.

Role of learning potential in cognitive remediation: Construct and predictive validity

BackgroundThe construct, convergent, discriminant, and predictive validity of Learning Potential (LP) was evaluated in a trial of cognitive remediation for adults with schizophrenia-spectrum disorders. LP utilizes a dynamic assessment approach to prospectively estimate an individual's learning capacity if provided the opportunity for specific related learning. MethodsLP was assessed in 75 participants at study entry, of whom 41 completed an eight-week cognitive remediation (CR) intervention, and 22 received treatment-as-usual (TAU). LP was assessed in a “test-train-test” verbal learning paradigm. Incremental predictive validity was assessed as the degree to which LP predicted memory skill acquisition above and beyond prediction by static verbal learning ability. ResultsExamination of construct validity confirmed that LP scores reflected use of trained semantic clustering strategy. LP scores correlated with executive functioning and education history, but not other demographics or symptom severity. Following the eight-week active phase, TAU evidenced little substantial change in skill acquisition outcomes, which related to static baseline verbal learning ability but not LP. For the CR group, LP significantly predicted skill acquisition in domains of verbal and visuospatial memory, but not auditory working memory. Furthermore, LP predicted skill acquisition incrementally beyond relevant background characteristics, symptoms, and neurocognitive abilities. ConclusionsResults suggest that LP assessment can significantly improve prediction of specific skill acquisition with cognitive training, particularly for the domain assessed, and thereby may prove useful in individualization of treatment.

Reduced Prefrontal Activation in Pediatric Patients With Obsessive-Compulsive Disorder During Verbal Episodic Memory Encoding

Patients with obsessive-compulsive disorder (OCD) often present with deficits in episodic memory, and there is evidence that these difficulties may be secondary to executive dysfunction, that is, impaired selection and/or application of memory-encoding strategies (mediation hypothesis). Semantic clustering is an effective strategy to enhance encoding of verbal episodic memory (VEM) when word lists are semantically related. Self-initiated mobilization of this strategy has been associated with increased activity in the prefrontal cortex, particularly the orbitofrontal cortex, a key region in the pathophysiology of OCD. We therefore studied children and adolescents with OCD during uncued semantic clustering strategy application in a VEM functional magnetic resonance imaging (fMRI)-encoding paradigm. A total of 25 pediatric patients with OCD (aged 8.1-17.5 years) and 25 healthy controls (HC, aged 8.1-16.9) matched for age, gender, handedness, and IQ were evaluated using a block design VEM paradigm that manipulated semantically related and unrelated words. The semantic clustering strategy score (SCS) predicted VEM performance in HC (p< .001, R(2)= 0.635), but not in patients (p= .099). Children with OCD also presented hypoactivation in the dorsomedial prefrontal cortex (cluster-corrected p < .001). Within-group analysis revealed a negative correlation between Yale-Brown Obsessive Compulsive Scale scores and activation of orbitofrontal cortex in the group with OCD. Finally, a positive correlation between age and SCS was found in HC (p= .001, r= 0.635), but not in patients with OCD (p= .936, r= 0.017). Children with OCD presented altered brain activation during the VEM paradigm and absence of expected correlation between SCS and age, and between SCS and total words recalled. These results suggest that different neural mechanisms underlie self-initiated semantic clustering in OCD.

Semantic overlay network for large-scale spatial information indexing

The increased demand for online services of spatial information poses new challenges to the combined filed of Computer Science and Geographic Information Science. Amongst others, these include fast indexing of spatial data in distributed networks. In this paper we propose a novel semantic overlay network for large-scale multi-dimensional spatial information indexing, called SON_LSII, which has a hybrid structure integrating a semantic quad-tree and Chord ring. The SON_LSII is a small world overlay network that achieves a very competitive trade-off between indexing efficiency and maintenance overhead. To create SON_LSII, we use an effective semantic clustering strategy that considers two aspects, i.e., the semantic of spatial information that peer holds in overlay network and physical network performances. Based on SON_LSII, a mapping method is used to reduce the multi-dimensional features into a single dimension and an efficient indexing algorithm is presented to support complex range queries of the spatial information with a massive number of concurrent users. The results from extensive experiments demonstrate that SON_LSII is superior to existing overlay networks in various respects, including scalability, maintenance, rate of indexing hits, indexing logical hops, and adaptability. Thus, the proposed SON_LSII can be used for large-scale spatial information indexing.

Verbal Learning Strategy Following Mild Traumatic Brain Injury

That learning and memory deficits persist many years following mild traumatic brain injury (mTBI) is controversial due to inconsistent objective evidence supporting subjective complaints. Our prior work demonstrated significant reductions in performance on the initial trial of a verbal learning task and overall slower rate of learning in well-motivated mTBI participants relative to demographically matched controls. In our previous work, we speculated that differences in strategy use could explain the differences in rate of learning. The current study serves to test this hypothesis by examining strategy use on the California Verbal Learning Test-Second Edition. Our present findings support the primary hypothesis that mTBI participants under-utilize semantic clustering strategies during list-learning relative to control participants. Despite achieving comparable total learning scores, we posit that the persisting learning and memory difficulties reported by some mTBI patients may be related to reduced usage of efficient internally driven strategies that facilitate learning. Given that strategy training has demonstrated improvements in learning and memory in educational and occupational settings, we offer that these findings have translational value in offering an additional approach in remediation of learning and memory complaints reported by some following mTBI.

Learning and memory in amnestic mild cognitive impairment: Contribution of working memory

In addition to deficits in delayed recall, recent research suggests that participants with amnestic mild cognitive impairment (aMCI) demonstrate diminished use of strategic encoding strategies during learning. Few studies have explored the cognitive mechanisms underlying this deficit. The aim of this study was to investigate in aMCI whether components of working memory (executive attention--attention set-shifting, dividing and focusing attention; and episodic buffer functions--strategic retrieval and manipulation of information) predict strategic encoding strategies during learning (semantic clustering). Thirty-three participants with aMCI and 33 healthy older adults (HOA) were administered neuropsychological tests assessing word-list learning and working memory. The aMCI group demonstrated significant impairment in acquisition, retrieval of information, and decreased use of semantic clustering strategies. Use of semantic clustering in the aMCI group was not predicted by measures of executive attention or phonemic verbal fluency, but was predicted by semantic verbal fluency performance. In the HOA group, semantic clustering was strongly related to semantic verbal fluency. These findings suggest that in aMCI, diminished strategic encoding strategies during learning (semantic clustering) is selectively related to the strategic function of the episodic buffer, but only when in interaction with the manipulation and retrieval of semantic associations.

HIV-Associated Episodic Memory Impairment: Evidence of a Possible Differential Deficit in Source Memory for Complex Visual Stimuli

HIV-Associated Episodic Memory Impairment: Evidence of a Possible Differential Deficit in Source Memory for Complex Visual Stimuli

Neurophysiological Alterations During Strategy-Based Verbal Learning in Traumatic Brain Injury

Background. Verbal learning and strategic processing deficits are common sequelae of traumatic brain injury (TBI); however, the neurophysiological mechanisms underlying such deficits remain poorly understood. Methods. We performed functional magnetic resonance imaging (fMRI) in 25 individuals with chronic TBI (>1 year after injury) and 20 matched healthy controls. Subjects were scanned while encoding word lists, with free recall and recognition assessed after each scanning run. To vary the strategic processing load, participants learned semantically unrelated words (Unrelated condition), semantically related words under null instruction conditions (Spontaneous condition), and semantically related words following training on the use of a semantic clustering strategy (Directed condition). Results. Behavioral performance on recall, recognition, and semantic clustering improved significantly as follows: Unrelated < Spontaneous < Directed. Individuals with TBI exhibited impaired yet parallel behavioral performance relative to control participants. The fMRI measures of brain activity during verbal encoding revealed decreased activity in participants with TBI relative to controls in left dorsolateral prefrontal cortex (DLPFC; BA 9) and in a region spanning the left angular and supramarginal gyri (BA 39/40). Functional connectivity analysis revealed evidence of a functional—but not anatomical—breakdown in the connectivity between the DLPFC and other regions specifically when participants with TBI were directed to use the semantic encoding strategy. Conclusion. After TBI, the DLPFC appears to be decoupled from other active brain regions specifically when strategic control is required. We hypothesize that approaches designed to help re-couple DLPFC under such conditions may aid TBI cognitive rehabilitation.

Memory for Verbal and Visual Material in Highly Trained Musicians

INTEREST IN STUDYING THE EFFECTS of extensive music training on nonmusical perceptual and cognitive abilities has grown in recent years. Here, we present evidence that formal music instruction is associated with superior verbal and visual memory. Participants included 15 highly trained pianists and 21 individuals with little or no formal music training. The groups were comparable in terms of age, gender distribution, and socioeconomic status. Musicians showed superior immediate and delayed recall of word lists and greater use of a semantic clustering strategy during initial list-learning than nonmusicians. They also exhibited superior learning, delayed recall, and delayed recognition for visual designs. Group differences in delayed free recall of both words and designs persisted after controlling statistically for estimated Full Scale IQ. These results suggest that extensive music training is associated with a generalized enhancement of auditory and visual memory functions.

Memory performance on the California Verbal Learning Test of children with benign childhood epilepsy with centrotemporal spikes

Verbal learning and retrieval, as well as the use of learning strategies, were assessed in 24 children with benign epilepsy with centrotemporal spikes (BECTS) and 16 controls, using the California Verbal Learning Test-Children's Version. Neuropsychological data were correlated with EEG features. Compared with age-matched controls, the children with BECTS younger than 10 exhibited significant learning difficulties and were less efficient in using a semantic clustering strategy, whereas no such difference emerged for subjects older than 10. This suggests that the capacity for spontaneous use of a more efficient strategy matures later in children with BECTS. Moreover, the majority of those younger than 10 had multifocal anomalies, suggesting that the difficulties encountered might be caused by the presence of additional foci.

Sources of declarative memory impairment in bipolar disorder: Mnemonic processes and clinical features

Background There is mounting evidence that declarative memory processes are impaired in patients with bipolar disorder. However, predictors of the observed impairment are not well understood. This study seeks to: (i) better characterize the nature of declarative memory impairment in bipolar disorder, and (ii) determine the relationship between clinical variables and memory function in bipolar disorder. Methods 49 adult patients with bipolar disorder in varying mood states and 38 demographically matched healthy participants completed a comprehensive neurocognitive battery assessing general cognitive functioning, processing speed, and declarative memory. The California verbal learning test was used to characterize learning and memory functions. Results Although patients with bipolar disorder utilized a similar semantic clustering strategy to healthy controls, they recalled and recognized significantly fewer words than controls, suggesting impaired encoding of verbal information. In contrast, lack of rapid forgetting suggests relative absence of a storage deficit in bipolar patients. While severity of mood symptomatology and illness duration were not associated with task performance, gender and family history significantly affected memory function. Conclusions Results suggest that declarative memory impairments in bipolar patients: (1) are consistent with deficits in learning, but do not appear to be related to different organizational strategies during learning, and (2) do not appear to be secondary to clinical state, but rather may be associated with the underlying pathophysiology of the illness.

Delayed-Onset Deficits in Verbal Encoding Strategies Among Patients With Mild Traumatic Brain Injury.

Knowledge obtained from longitudinal animal models was used to predict the course of verbal memory deficits in 19 concussed patients and 19 control patients who were given versions of the Hopkins Verbal Learning Test--Revised at 2 hr, 48 hr, and 1 week postconcussion. The physiological literature suggests that concussed patients should exhibit a decline in performance from 2 hr to 48 hr postconcussion on a measure of complex memory strategies. Consistent with this hypothesis, mixed-factor analysis of covariance revealed that concussed patients used less semantic clustering strategies than control patients at 48 hr postconcussion, whereas minimal differences were found at 2 hr postinjury. Furthermore, a chi-square analysis showed that a significant number of concussed patients experienced a decline in the number of semantic clusters they used from 2 hr to 48 hr. No differences were found between the groups at the 1-week testing session.

Memory encoding and retrieval in frontotemporal dementia and Alzheimer's disease.

Memory encoding and retrieval strategies were assessed in patients with behavior-executive variant frontotemporal dementia (FTD), language variant FTD, and Alzheimer's disease (AD) using verbal and visuospatial supraspan learning tests. FTD patients obtained higher free recall, cued recall, and recognition scores than AD patients. Comparison of free recall scores with cued recall and recognition scores was similar in the 3 dementia groups. Groups did not differ in semantic clustering strategies during learning, but serial-order recall was more common in FTD patients. These data do not support the idea that FTD patients' poor memory is due to a selective retrieval disorder, though FTD patients may fail to implement sophisticated organizational strategies during learning. FTD patients' retained capacity for encoding new information into long-term declarative memory is likely due to relatively spared medial temporal lobe involvement.

Hypofrontality in unmedicated schizophrenia patients studied with PET during performance of a serial verbal learning task

Previous research indicates that verbal learning and memory deficits are among the most severe cognitive deficits observed in schizophrenia. However, the concomitant patterns of regional brain function associated with these deficits in schizophrenia are not well understood. The present study examined verbal-memory performance and simultaneous relative glucose metabolic rates (rGMR) with FDG PET in 20 unmedicated schizophrenia patients who met stringent memory-performance criteria and 32 age- and sex-matched normal volunteers. On a modified version of the California Verbal Learning Test, patients recalled fewer correct words using a semantic-clustering strategy and exhibited more intrusions compared with normal subjects. However, patients had higher serial-ordering strategy scores, indicating their use of a less efficient organizational strategy. Among patients, greater use of the serial-ordering strategy was associated with decreased rGMR in frontal cortex and increased rGMR in temporal cortex. Patients had lower rGMR primarily in frontal and temporal cortex, but not parietal and occipital lobe regions. Patients also exhibited hypofrontality (lower ratio of frontal to occipital rGMR) compared with normal subjects. Among the patients, more severe hypofrontality was associated with increased perseveration errors.

42. The contribution of orbitofrontal cortex to episodic memory impairment in OCD

Biological studies of obsessive-compulsive disorder (OCD) provide consistent evidence of dysfunction in orbitofrontal cortex (OFC). We have used the California Verbal Learning Test (CVLT) in behavioral studies to examine episodic memory in OCD. In two separate investigations, we found that OCD patients failed to spontaneously apply semantic organizational strategies during encoding and this led to problems in delayed recall. We will present new data from a PET study in normal subjects examining the neural systems underlying semantic organization using a verbal memory paradigm patterned after the CVLT. Eight normal subjects listened to lists of 24 words, in three conditions: 1) Unrelated: words were semantically unrelated; 2) Spontaneous: words were related in four semantic categories, and subjects were not instructed of this beforehand; 3) Directed: same as (2) but subjects were explicitly instructed to notice the relationships and use them to improve memory. Behavioral data included a Semantic Clustering score, measuring active regrouping of words into semantic categories during recall. In a graded PET contrast (Directed . Spontaneous . Unrelated), two distinct activations were found in left inferior prefrontal cortex and left dorsolateral prefrontal cortex. Correlation analyses in the Spontaneous condition indicated that blood flow in OFC during encoding predicted the use of semantic clustering strategies during immediate recall. These results indicate that OFC plays a role in episodic memory by supporting the mobilization of effective strategic processes, mediated in other regions of PFC. Disruptions in learning strategies in OCD are likely related to OFC dysfunction.

The Relationship between Semantic Organization and Memory in Obsessive-Compulsive Disorder

Background: A variety of evidence suggests that frontostriatal dysfunction is involved in obsessive-compulsive disorder (OCD). This evidence includes both neuroimaging findings and results from studies using neuropsychological assessments. Previous studies have documented nonverbal memory deficits in individuals with OCD, whereas verbal learning and memory were less affected. Methods: The present study examined both verbal and nonverbal memory in a sample of 17 untreated outpatients with OCD. We also evaluated the effects of encoding strategies which are believed to be mediated by frontostriatal system functioning. Results: OCD patients were significantly impaired in both verbal and nonverbal memory performance. This deficit was correlated with impairments in organizational and semantic clustering strategies at the time of encoding. Conclusions: Deficits in organizational strategies are consistent with frontostriatal dysfunction models in OCD.

Developmental sex differences in verbal learning.

Although sex differences in verbal learning and memory have been reported in adults, much less is known about when these sex differences emerge and how they develop. In this study, 401 boys and 410 girls between the ages of 5 and 16 years were administered the California Verbal Learning Test--Children's Version. Sex differences were found at all age levels. Girls performed better than boys on all of the immediate and delayed recall trials and on the delayed recognition trial. Girls were also more likely than boys to use a semantic clustering strategy and displayed more effective long-term memory mechanisms. Boys made more intrusion errors and displayed greater vulnerability to interference between the 2 test lists. Because boys had higher mean scores on Wechsler Intelligence Scale for Children--Revised Vocabulary, the observed female superiority in verbal learning could not be attributed to sex differences in overall word knowledge.

Verbal memory performance of patients with human immunodeficiency virus infection: Evidence of subcortical dysfunction

In the present study, the California Verbal Learning Test (CVLT) was administered to symptomatic HIV+ (n = 31), asymptomatic HIV+ (n = 94), and HIV-normal control (HIV-NC) (n = 40) subjects to assess the prevalence and nature of their verbal memory deficits. Symptomatic HIV+ subjects were significantly impaired relative to HIV-control subjects on CVLT measures of acquisition and retention, and were significantly less likely than control subjects to use a semantic clustering strategy to support recall. The performance of the asymptomatic HIV+ subjects fell between those of the symptomatic HIV+ subjects and HIV-controls on almost every CVLT measure. A linear discriminant function analysis (DFA) was used to compare the performances of these three groups to Alzheimer's disease (AD). Huntington's disease (HD), and normal control (NC) subjects on three CVLT measures, including total recall over five learning trials, intrusion errors, and a derived score of delayed recognition discriminability minus the final learning trial. Significant differences were found between the number of symptomatic HIV+ subjects classified as HD (32%), AD (3%), and normal (65%), the number of asymptomatic HIV+ subjects classified as HD (16%), AD (1%), and normal (83%), and the number of HIV-NC subjects classified as HD (2%), AD (0%), and normal (98%). The profile of verbal memory deficits exhibited by the subgroup of impaired HIV+ subjects was similar to that of patients with HD, a prototypical subcortical dementia, and different from that of patients with AD, a prototypical cortical dementia. This finding is consistent with reports of the predominance of subcortical neuropathological changes associated with HIV infection.