Aging is accompanied by a decline in associative memory, whereas item memory remains relatively stable compared to young adults. This age-related associative deficit is well replicated, but its mechanisms and influencing factors during learning are still largely unclear. In the present study, we examined mediators of the age-related associative deficit, including encoding intentionality, strategy instructions, the timing of the memory test and the material being learned in a within-subject design. Older and younger adults performed seven encoding tasks on word pairs (...) and picture pairs on two consecutive days, followed by item and associative recognition tests. The associative deficit was evident after all encoding tasks. We found no evidence for a difference in the magnitude of the associative deficit between incidental vs. intentional learning conditions. However, there was some evidence for a larger associative memory deficit with pictures versus words when the encoding task was held equal. Sentence generation and interactive imagery instructions in which participants generated their own mediators reduced the magnitude of the associative deficit. However, increased encoding guidance through the provision of mediators did not lead to an alleviation of the deficit, potentially because the specified mediators were implausible or difficult for the older adults to reconcile with prior knowledge. Finally, we found some evidence for a reduced age-related associative deficit with a test delay of 24 h. These results contribute to a better understanding of the factors affecting the relative difficulty of older adults with encoding and retrieving novel associations. (shrink)

Background: Walking while performing a secondary task walking) increases cognitive workload in young adults. To date, few studies have used neurophysiological measures in combination to subjective measures to assess cognitive workload during a walking task. This combined approach can provide more insights into the amount of cognitive resources in relation with the perceived mental effort involving in a walking task.Research Question: The objective was to examine cognitive workload in young adults during walking conditions varying in complexity.Methods: Twenty-five (...) young adults performed four conditions: usual walking, simple DT walking, complex DT walking and standing while subtracting. During the walking task, mean speed, cadence, stride time, stride length, and their respective coefficient of variation were recorded. Cognitive workload will be measured through changes in oxy- and deoxy-hemoglobin during walking in the dorsolateral prefrontal cortex and perceived mental demand score from NASA-TLX questionnaire.Results: In young adults, ΔHbO2 in the DLPFC increased from usual walking to both DT walking conditions and standing while subtracting condition. ΔHbO2 did not differ between the simple and complex DT and between the complex DT and standing while subtracting condition. Perceived mental demand gradually increased with walking task complexity. As expected, all mean values of gait parameters were altered according to task complexity. CV of speed, cadence and stride time were significantly higher during DT walking conditions than during usual walking whereas CV of stride length was only higher during complex DT walking than during usual walking.Significance: Young adults had greater cognitive workload in the two DT walking conditions compared to usual walking. However, only the mental demand score from NASA-TLX questionnaire discriminated simple from complex DT walking. Subjective measure provides complementary information to objective one on changes in cognitive workload during challenging walking tasks in young adults. These results may be useful to improve our understanding of cognitive workload during walking. (shrink)

It has been proposed that performance in the think – no think task represents a laboratory analogue of the voluntary form of memory repression. The central prediction of this repression hypothesis is that performance in the TNT task will be influenced by emotional characteristics of the material to be remembered. This prediction was tested in two experiments by asking participants to learn paired associates in which the first item was either emotionally positive or emotionally negative . The (...) second word was always emotionally neutral . Consistent with the repression hypothesis, significant memory suppression was observed in both experiments following ‘no think’ instructions for memories associated with emotionally negative material. No suppression was observed for memories associated with emotionally positive information. Implications of these findings for the relationship between performance in the TNT task and the controversial notion of memory repression are considered. (shrink)

Performance on working memory (WM) tasks may partially be supported by long-term memory (LTM) processing. Hence, brain activation recently being implicated in WM may actually have been driven by (incidental) LTM formation. We examined which brain regions actually support successful WM processing, rather than being confounded by LTM processes, during the maintenance and probe phase of a WM task. We administered a four-pair (faces and houses) associative delayed-match-to-sample (WM) task using event-related fMRI and a subsequent associative recognition LTM (...) task, using the same stimuli. This enabled us to analyze subsequent memory effects for both the WM and the LTM test by contrasting correctly recognized pairs with incorrect pairs for either task. Critically, with respect to the subsequent WM effect, we computed this analysis exclusively for trials that were forgotten in the subsequent LTM recognition task. Hence, brain activity associated with successful WM processing was less likely to be confounded by incidental LTM formation. The subsequent LTM effect, in contrast, was analyzed exclusively for pairs that previously had been correctly recognized in the WM task, disclosing brain regions involved in successful LTM formation after successful WM processing. Results for the subsequent WM effect showed no significantly activated brain areas for WM maintenance, possibly due to an insensitivity of fMRI to mechanisms underlying active WM maintenance. In contrast, a correct decision at WM probe was linked to activation in the “retrieval success network” (anterior and posterior midline brain structures). The subsequent LTM analyses revealed greater activation in left dorsolateral prefrontal cortex and posterior parietal cortex in the early phase of the maintenance stage. No supra-threshold activation was found during the WM probe. Together, we obtained clearer insights in which brain regions support successful WM and LTM without the potential confound of the respective memory system. (shrink)

We performed an EEG graph analysis on data from 31 typical readers and 24 dyslexics, recorded while they were engaged in an audiovisual task and during resting-state. The task simulates reading acquisition as participants learned new letter-sound mappings via feedback. EEG data was filtered for the delta, theta, alpha, and beta bands. We computed the Phase Lag Index to provide an estimate of the functional connectivity between all pairs of electrodes per band. Then, networks were constructed using a (...) Minimum Spanning Tree, a unique sub-graph connecting all nodes without loops, aimed at minimizing bias in between groups and conditions comparisons. Both groups showed a comparable accuracy increase during task blocks, indicating that they correctly learned the new associations. The EEG results revealed lower task-specific theta connectivity, and lower theta degree correlation over both rest and task recordings, indicating less network integration in dyslexics compared to typical readers. This pattern suggests a role of theta oscillations in dyslexia and may reflect differences in task engagement between the groups, although robust correlations between MST metrics and performance indices were lacking. (shrink)