Hyemi Chong

False recognition of emotional word lists in aging and Alzheimer disease.

ObjectiveTo examine 3 different aspects of the emotional memory effect in aging and Alzheimer disease (AD): item-specific recollection, gist memory, and recognition response bias. MethodYounger adults, older adults, and patients with AD performed a false recognition memory test in which participants were tested on “lure” items that were not seen at study, but were semantically related to the study items. Participants were tested on 5 emotional and 5 non-emotional lists. ResultsIn addition to finding an increase in true recognition for emotional versus non-emotional items in healthy younger and older adults but not in patients with AD, and confirming that emotional items led younger adults to shift their response bias to a more liberal one, 3 novel findings were observed. First, the emotional effect on response bias was also observed in healthy older adults. Second, the opposite emotional effect on response bias was observed in patients with AD. Third, emotional items did not lead to an improvement in item-specific recollection or gist memory. ConclusionsAlthough healthy older adults show the normal amygdala-modulated criterion shift for emotional items—influencing their subjective feeling that information has been previously encountered, the amygdala pathology present in early AD may disrupt this influence.

Mechanisms underlying age-and performance-related differences in working memory

This study took advantage of the subsecond temporal resolution of ERPs to investigate mechanisms underlying age- and performance-related differences in working memory. Young and old subjects participated in a verbal n-back task with three levels of difficulty. Each group was divided into high and low performers based on accuracy under the 2-back condition. Both old subjects and low-performing young subjects exhibited impairments in preliminary mismatch/match detection operations (indexed by the anterior N2 component). This may have undermined the quality of information available for the subsequent decision-making process (indexed by the P3 component), necessitating the appropriation of more resources. Additional anterior and right hemisphere activity was recruited by old subjects. Neural efficiency and the capacity to allocate more resources to decision-making differed between high and low performers in both age groups. Under low demand conditions, high performers executed the task utilizing fewer resources than low performers (indexed by the P3 amplitude). As task requirements increased, high-performing young and old subjects were able to appropriate additional resources to decision-making, whereas their low-performing counterparts allocated fewer resources. Higher task demands increased utilization of processing capacity for operations other than decision-making (e.g., sustained attention) that depend upon a shared pool of limited resources. As demands increased, all groups allocated additional resources to the process of sustaining attention (indexed by the posterior slow wave). Demands appeared to have exceeded capacity in low performers, leading to a reduction of resources available to the decision-making process, which likely contributed to a decline in performance.

Compensatory neural activity distinguishes different patterns of normal cognitive aging

Most cognitive neuroscientific research exploring the nature of age-associated compensatory mechanisms has compared old adults (high vs. average performers) to young adults (not split by performance), leaving ambiguous whether findings are truly age-related or reflect differences between high and average performers throughout the life span. Here, we examined differences in neural activity (as measured by ERPs) that were generated by high vs. average performing old, middle-age, and young adults while processing novel and target events to investigate the following three questions: (1) Are differences between cognitively high and average performing subjects in the allocation of processing resources (as indexed by P3 amplitude) specific to old subjects, or found throughout the adult life span? (2) Are differences between cognitively high and average performing subjects in speed of processing (as indexed by target P3 latency) of similar magnitude throughout the adult life span? (3) Where along the information processing stream does the compensatory neural activity attributed to cognitively high performing old subjects begin to take place? Our results suggest that high performing old adults successfully manage the task by a compensatory neural mechanism associated with the modulation of controlled processing and the allocation of more resources, whereas high performing younger subjects execute the task more efficiently with fewer resources. Differences between cognitively high and average performers in processing speed increase with age. Middle-age seems to be a critical stage in which substantial differences in neural activity between high and average performers emerge. These findings provide strong evidence for different patterns of age-related changes in the processing of salient environmental stimuli, with cognitive status serving as a key mediating variable.

ERP correlates of item recognition memory : Effects of age and performance

Decline in episodic memory is a common feature of healthy aging. Event-related potential (ERP) studies in young adults have consistently reported several modulations thought to index memory retrieval processes, but relatively limited work has explored the impact of aging on them. Further, work with functional imaging has demonstrated differential neural recruitment in elderly subjects depending on their level of cognitive performance which may reflect compensatory or, alternatively, inefficient processing. In the present study we examined the effect of aging and level of performance on both early (FN400, LPC) and later [late frontal effect (LFE)] ERP indices of recognition memory. We found that the FN400 and LPC were absent or attenuated in the older group relative to young adults, but that the LFE was actually increased, analogous to findings in the functional imaging literature. Additionally, the latter effect was most prominent in the poorer performing older participants. These findings suggest that weak memory retrieval supported by earlier ERP modulations, may lead to an enhanced LFE in the service of additional retrieval attempts.

Age-related changes in early novelty processing as measured by ERPs

This study investigated age-related changes in the early processing of novel visual stimuli using ERPs. Well-matched old (n=30), middle-aged (n=30), and young (n=32) subjects were presented standard, target/rare, and perceptually novel visual stimuli under Attend and Ignore conditions. Our results suggest that the anterior P2 component indexes the motivational salience of a stimulus as determined by either task relevance or novelty. Its enhancement by focused attention does not decrease with age. Its responsiveness to novel stimuli is particularly striking in older adults. The age-related increase in the anterior P2 to novel visual stimuli does not appear to be due to impaired inhibitory control associated with aging. Rather, the enhanced anterior P2 to novel stimuli in older adults may be linked to age-related changes in the process of matching unusual visual stimuli to stored representations, which is indexed by the temporally overlapping anterior N2 component whose amplitude substantially decreases with age.

Cognitive status impacts age-related changes in attention to novel and target events in normal adults.

In this study, the authors investigated the relationship between the cognitive status of normal adults and age-related changes in attention to novel and target events. Old, middle-age, and young subjects, divided into cognitively high and cognitively average performing groups, viewed repetitive standard stimuli, infrequent target stimuli, and unique novel visual stimuli. Subjects controlled viewing duration by a button press that led to the onset of the next stimulus. They also responded to targets by pressing a foot pedal. The amount of time spent looking at different kinds of stimuli served as a measure of visual attention and exploratory activity. Cognitively high performers spent more time viewing novel stimuli than cognitively average performers. The magnitude of the difference between cognitively high and cognitively average performing groups was largest among old subjects. Cognitively average performers had slower and less accurate responses to targets than cognitively high performers. The results provide strong evidence that the link between engagement by novelty and higher cognitive performance increases with age. Moreover, the results support the notion of there being different patterns of normal cognitive aging and the need to identify the factors that influence them.

IC-P3-176: What goes up, must come down: Compensatory neural activity among the very old

Background: Understanding factors that contribute to successful cognitive aging has become increasingly important as a growing portion of the population lives to very old age. Our research has focused on different patterns of cognitive aging by using electrophysiologic and behavioral measures. Previously, we demonstrated (e.g., NeuroImage, 2008; 39(1)) that cognitively high-functioning younger-old (y-old) (65-79 y.o.) subjects allocate more neural resources, as measured by the P3 event-related potential, than cognitively high-functioning middle-aged and young subjects and than cognitively average-functioning y-old subjects. Interestingly, although cognitively average-functioning middle-aged subjects appropriate more resources to novel stimuli than cognitively-matched young subjects, cognitively average-functioning y-old subjects exhibit a substantial reduction in novelty P3 amplitude. These findings suggest that age-related compensatory activity may involve increased allocation of capacity-limited controlled resources that persists until capacity limits are exceeded. For cognitively average-functioning adults this may occur by y-old age. We hypothesized that in cognitively high functioning adults this would develop in old-old (o-old) age. Here we have extended our investigations to include o-old individuals (’80 y.o.), and report on preliminary results. Objective: To determine whether cognitively high functioning o-old adults continue to exhibit compensatory neural activity and a preference for attending to novelty. Methods: Electrophysiologic and behavioral responses to standard, target, and novel visual stimuli were recorded while young, middleaged, y-old, and o-old individuals performed a subject-controlled variant of the novelty oddball task. Results: Cognitively high-functioning o-old adults exhibited a large reduction in their novelty P3, but not until their mid to late 80s. Behaviorally, cognitively high-functioning individuals in their 90s continued to spend more time exploring novel than repetitive standard visual stimuli. Conclusions: Our research suggests that age-related compensatory neural activity may not be limited to high-functioning older individuals with substantial cognitive reserve, but also be observed among cognitively average-functioning adults at an earlier stage of the lifespan. Cognitively high-functioning adults appear to have the capacity to appropriate compensatory neural resources at least through their early 80s, and continue to be attracted to novelty, a hallmark of healthy human behavior, at least through their early 90s.

Associative and item memory as outcome measures for Alzheimer’s disease clinical trials: A pilot study

OUTCOME MEASURES FOR ALZHEIMER’S DISEASE CLINICAL TRIALS: A PILOT STUDY Andrew E. Budson, Hyemi Chong, Lisa M. Sardinha, Sibyl Salisbury, Dorene M. Rentz, Reisa A. Sperling; Geriatric Research Education Clinical Center, Edith Nourse Rogers Memorial Veterans Hospital, Bedford, MA, USA; Alzheimer’s Disease Center, Boston University, Boston, MA, USA; Division of Cognitive & Behavioral Neurology, Department of Neurology, Brigham and Women’s Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA