Adult Age Differences in Sensitivity to Semantic Satiation.

OBJECTIVE: In this study, we investigated age differences in sensitivity to semantic satiation.Semantic satiation was conceptualized as occurring within a semantic activation framework. METHOD: A prime or to-be-satiated word (e.g., ANIMAL) was presented repeatedly for an average of 2.5, 12.5, or 22.5 times. Afterward, a word triad comprised of two related words (e.g., PURPLE, YELLOW) and one unrelated word (e.g., DOG) was presented. The two related words were designated as nontargets or context words in the display and the unrelated word was the target. Participants were instructed to indicate as quickly and as accurately as possible which of the words in the triad was the unrelated word by pressing a key which was spatially compatible to the position of the stimulus on the CRt. RESULTS: For young but not older adults, there was an attenuation of priming effects in the response latency data as repetition of the prime increased. CONCLUSION: These results were interpreted as evidence that older adults are less sensitive to the semantic satiation phenomenon than young adults.

Risk for Alzheimer's disease: A review of long-term episodic memory encoding and retrieval fMRI studies.

Many risk factors have been identified that predict future progression to Alzheimer's disease (AD). However, clear links have yet to be made between these risk factors and how they affect brain functioning in early stages of AD. We conducted a narrative review and a quantitative analysis to better understand the relationship between nine categories of AD risk (i.e., brain pathology, genetics/family history, vascular health, head trauma, cognitive decline, engagement in daily life, late-life depression, sex/gender, and ethnoracial group) and task-evoked fMRI activity during episodic memory in cognitively-normal older adults. Our narrative review revealed widespread regional alterations of both greater and lower brain activity with AD risk. Nevertheless, our quantitative analysis revealed that a subset of studies converged on two patterns: AD risk was associated with (1) greater brain activity in frontal and parietal regions, but (2) reduced brain activity in hippocampal and occipital regions. The brain regions affected depended on the assessed memory stage (encoding or retrieval). Although the results clearly indicate that AD risks impact brain activity, we caution against using fMRI as a diagnostic tool for AD at the current time because the above consistencies were present among much variability, even among the same risk factor.

A Review on the Trajectory of Attentional Mechanisms in Aging and the Alzheimer's Disease Continuum through the Attention Network Test.

Multiple domains of cognition are known to decline in both normal aging and in the trajectory towards Alzheimer's disease (AD). While declines in episodic memory are most well-known in both normal aging and AD, some of these memory differences might stem from early deteriorations in attention that have consequences for later memory. Further complicating the matter is that attention is a multifaceted construct that might be differentially affected in normal aging and AD. According to cognitive neuroscience models of attention, three types of attention networks exist: alerting, orienting, and executive. Efficiency of these three networks can be captured using the Attention Network Test (ANT). We reviewed the literature investigating differences in attention networks using the ANT as a function of normal aging and the AD trajectory, which included people at risk for AD, preclinical stages of AD, mild cognitive impairment, and those diagnosed with AD. We found that normal aging and the AD trajectory evidenced different patterns of attentional declines. Whereas normal aging was most consistently associated with impairments in alerting, early phases of the AD trajectory were most consistently associated with impairments in executive attention, and later phases of the AD trajectory were mixed. The mixed results with AD are largely attributed to small sample sizes and confounding effects of general slowing. These findings highlight key gaps in the literature linking different phases of AD while also highlighting the usefulness of the ANT to distinguish normal aging from the AD trajectory, especially in the earliest phases of the disease process.