Measuring semantic memory using associative and dissociative retrieval tasks.

Recent theoretical advances highlighted the need for novel means of assessing semantic cognition. Here, we introduce the associative-dissociative retrieval task (ADT), positing a novel way to test inhibitory control over semantic memory retrieval by contrasting the efficacy of associative (automatic) and dissociative (controlled) retrieval on a standard set of verbal stimuli. All ADT measures achieved excellent reliability, homogeneity, and short-term temporal stability. Moreover, in-depth stimulus level analyses showed that the associative retrieval is easier for words evoking few but strong associates, yet such propensity hampers the inhibition. Finally, we provided critical support for the construct validity of the ADT measures, demonstrating reliable correlations with domain-specific measures of semantic memory functioning (semantic fluency and associative combination) but negligible correlations with domain-general capacities (processing speed and working memory). Together, we show that ADT provides simple yet potent and psychometrically sound measures of semantic memory retrieval and offers noteworthy advantages over the currently available assessment methods.

BDNF Val66Met polymorphism is associated with consolidation of episodic memory during sleep.

The brain-derived neurotrophic factor (BDNF) is an essential regulator of synaptic plasticity, a candidate neurobiological mechanism underlying learning and memory. A functional polymorphism in the BDNF gene, Val66Met (rs6265), has been linked to memory and cognition in healthy individuals and clinical populations. Sleep contributes to memory consolidation, yet information about the possible role of BDNF in this process is scarce. To address this question, we investigated the relationship between the BDNF Val66Met genotype and consolidation of episodic declarative and procedural (motor) non-declarative memories in healthy adults. The carriers of Met66 allele, as compared with Val66 homozygotes, showed stronger forgetting overnight (24 h after encoding), but not over shorter time (immediately or 20 min after word list presentation). There was no effect of Val66Met genotype on motor learning. These data suggest that BDNF plays a role in neuroplasticity underlying episodic memory consolidation during sleep.

Response modularity moderates how executive control aids fluent semantic memory retrieval.

ABSTRACTEmerging work in semantic cognition has begun to elucidate the interaction between the structure of semantic memory and processes mediating goal-directed memory retrieval. Despite having essential implications for basic and applied research, these objectives remain neglected in both the assessment and interpretation of semantic verbal fluency (SVF) tasks. To test the association between semantic structure and the controlled processes underlying verbal fluency, we assessed how the degree of partitioning (modularity) of SVF responses into semantic clusters moderates the relationship of retrieval fluency with working memory and interference control capacities. We found that working memory capacity predicted retrieval fluency in individuals whose SVF responses were arranged in fine-grained semantic clusters (high modularity), whereas interference control was more predictive of retrieval fluency for individuals who delivered responses of low modularity. Our data support the presumed role of working memory and interference control in SVF and provide novel evidence that relative demands on these capacities are predicted by the organisation of semantic knowledge.

Executive functioning moderates the decline of retrieval fluency in time.

Prevailing theoretical accounts consider that automatic and controlled processes are uniformly engaged in memory retrieval across performance of the semantic verbal fluency (SVF) task. We tested this proposal against the alternative, namely that a rapid automatic retrieval, exploiting stable associative structure in the early stages of the performance, is followed by a slower, more executively demanding, retrieval in later stages. Eighty-five healthy adults completed low- and high-demand SVF tasks that were assessed for retrieval rate, response typicality, and inter-response similarity across the performance. Additional measures of executive functioning were collected to estimate individual differences in executive control. We found that decrease in fluency in time was associated with lower typicality and weaker semantic similarity of the responses. Critically, the time-dependent retrieval slowing was steeper in individuals with less efficient interference control, particularly in high-demand SVF tasks. Steeper retrieval slowing was also associated with poorer working-memory capacity. Our findings show that the relative contribution of automatic and controlled processes to semantic retrieval changes with associative sparsity over time and across task demands, and provide implications for the use of SVF tasks in clinical assessment.

Assessment of Automatic and Controlled Retrieval Using Verbal Fluency Tasks.

Category and letter verbal fluency assessment is widely used in basic and clinical research. Yet, the nature of the processes measured by such means remains a matter of debate. To delineate automatic (free-associative) versus controlled (dissociative) retrieval processes involved in verbal fluency tasks, we carried out a psychometric study combining a novel lexical-semantic retrieval paradigm and structural equation modeling. We show that category fluency primarily engages a free-associative retrieval, whereas letter fluency exerts executive suppression of habitual semantic associates. Importantly, the models demonstrated that this dissociation is parametric rather than absolute, exhibiting a degree of unity as well as diversity among the retrieval measures. These findings and further exploratory analyses validate that category and letter fluency tasks reflect partially distinct forms of memory search and retrieval control, warranting different application in basic research and clinical assessment. Finally, we conclude that the novel associative-dissociative paradigm provides straightforward and useful behavioral measures for the assessment and differentiation of automatic versus controlled retrieval ability.

Network analysis approach for exploring dementia representations in the Slovak media.

OBJECTIVES: The aim of the present study is to test the network analysis method on a corpus of media texts with the aim of systematically analysing media representations of dementia in the Slovak media. METHODS: A word-network was modelled from the corpus of media documents using social network analysis. 244 text-documents (web, print, TV and radio) from 2015 to 2018 (inclusive) were retrieved from the Newton media database using the search words 'dementia' and 'Alzheimer's disease'. RESULTS: Twelve clusters of co-occurring concepts corresponding to individual themes were identified. The results of the analysis provide evidence that biomedical themes such as 'medical diagnosis', 'prevalence of dementia' and 'memory disorders' possess the greatest representational strength and centrality and account for roughly two-thirds of the whole corpus. CONCLUSION: Results of the present study provide valuable insights into the representation of dementia in the Slovak media but also demonstrate how media representations can be studied using the innovative approach of network analysis.

Remote associates test: An empirical proof of concept.

Associative processes play a major role in research on human thinking, especially creativity. One of the most influential models emphasizing associative processes in creative thinking was introduced by Mednick (Psychological Review, 69, 220-232, 1962), who developed the remote associates test (RAT) as a domain-general measure of individual differences in associative hierarchies. Although S. Mednick's theoretical framework has recently regained much attention, the fundamental psychometric assumptions and underlying cognitive processes involved in the RAT remain controversial. We carried out two studies to evaluate these issues. In the first, a confirmatory factor analysis showed that a single latent factor accounted for the ability to solve RAT problems, despite their psycholinguistic heterogeneity. Subsequent regression analyses indicated that cue-solution associative remoteness substantially determined the difficulty of RAT problems, accounting for about 80% of variance. In the second study we used a newly developed associative chain test (ACT), which assesses lexical-semantic and executive measures during associative processing. We found that performance on the RAT was related to lexical-semantic (higher response remoteness and lower response commonness) but not to executive (response inhibition and switching) ACT measures. Overall, our findings indicate that the RAT reflects a coherent ability to access and combine remote elements in lexical-semantic and associative networks without considerably engaging executive attention. Although the validity and utility of the RAT was supported, we propose that the ACT provides a more complex and fine-grained tool for the assessment of associative processing.