To boost or to CRUNCH? Effect of effortful encoding on episodic memory in older adults is dependent on executive functioning

Why Does Cognitive Training Yield Inconsistent Benefits? A Meta-Analysis of Individual Differences in Baseline Cognitive Abilities and Training Outcomes

Despite growing interest in improving cognitive abilities across the lifespan through training, the benefits of cognitive training are inconsistent. One powerful contributor may be that individuals arrive at interventions with different baseline levels of the cognitive skill being trained. Some evidence suggests poor performers benefit the most from cognitive training, showing compensation for their weak abilities, while other evidence suggests that high performers benefit most, experiencing a magnification of their abilities. Whether training leads to compensation or magnification effects may depend upon the specific cognitive domain being trained (such as executive function or episodic memory) and the training approach implemented (strategy or process). To clarify the association between individual differences in baseline cognitive ability and training gains as well as potential moderators, we conducted a systematic meta-analysis of the correlation between these two variables. We found evidence of a significant meta-correlation demonstrating a compensatory effect, a negative association between initial ability on a trained cognitive process and training gains. Too few papers met our search criteria across the levels of proposed moderators of cognitive domain and training approach to conduct a reliable investigation of their influence over the meta-analytic effect size. We discuss the implications of a compensatory meta-correlation, potential reasons for the paucity of qualifying papers, and important future directions for better understanding how cognitive trainings work and for whom.

The neural basis of individual differences in memory performance in young and older adults: Using the encoding/retrieval flip account as framework

Aging is associated with cognitive decline, specifically in episodic memory. However, there are large individual differences in the extent of this decline and previous research suggests that these are associated with differences in executive functioning (EF). These EF differences, and associated differences in the encoding and retrieval of episodic information, have been linked to differences in the activation of particular brain regions. The "encoding/retrieval flip" (E/R flip) framework assumes deactivation and activation of specific brain regions during successful encoding and retrieval, respectively. The present study assessed whether this framework can be used to explain EF-based individual differences in memory performance of young and older participants. Young adults (N = 19) and older adults (N = 39) performed an incidental semantic encoding and memory recognition task in an fMRI setting, focusing on brain regions that show the E/R flip. The association between an index of EF and fMRI activity in brain regions showing the E/R flip was tested in each age group. EF predicted E/R flip activity in the older, but not young adults. These findings underscore the importance of individual differences in ageing research and provide empirical evidence for the association between EF and the E/R flip.

Narrative Discourse in Young and Older Adults: Behavioral and NIRS Analyses

Discourse comprehension is at the core of communication capabilities, making it an important component of elderly populations' quality of life. The aim of this study is to evaluate changes in discourse comprehension and the underlying brain activity. Thirty-six participants read short stories and answered related probes in three conditions: micropropositions, macropropositions and situation models. Using near-infrared spectroscopy (NIRS), the variation in oxyhemoglobin (HbO₂) and deoxyhemoglobin (HbR) concentrations was assessed throughout the task. The results revealed that the older adults performed with equivalent accuracy to the young ones at the macroproposition level of discourse comprehension, but were less accurate at the microproposition and situation model levels. Similar to what is described in the compensation-related utilization of neural circuits hypothesis (CRUNCH) model, older participants tended to have greater activation in the left dorsolateral prefrontal cortex while reading in all conditions. Although it did not enable them to perform similarly to younger participants in all conditions, this over-activation could be interpreted as a compensation mechanism.