Age differences in brain activity during perceptual versus reflective attention

Cross-situational statistical learning in younger and older adults

Research investigating statistical learning, the process of tracking regularities in the environment, in older adults has been limited; with existing studies suggesting there are age-related declines. We aim to further understand older adults' statistical learning abilities using a cross-situational statistical learning paradigm in which learners map novel words to novel objects. In Experiment 1, we manipulated task difficulty and found an overall age deficit but no interaction between age and difficulty. In Experiment 2, after extended practice with a first set of object-word mappings, learners could remap a subset of previously learned words to novel objects. Based on hyper-binding, older adults might be more willing to remap previously learned words to novel objects. However, despite overall poorer learning, older adults were actually less likely to remap. Even though older adults may have an associative memory deficit, learned associations are not more weakly bound for older relative to younger adults.

Age-related delay in reduced accessibility of refreshed items

Previously, we demonstrated that in young adults, briefly thinking of (i.e., refreshing) a just-seen word impairs immediate (100-ms delay) perceptual processing of the word, relative to words seen but not refreshed. We suggested that such reflective-induced inhibition biases attention toward new information. Here, we investigated whether reduced accessibility of refreshed targets dissipates with a longer delay and whether older adults would show a smaller and/or delayed effect compared with young adults. Young adult and older adult participants saw 2 words, followed by a cue to refresh one of these words. After either a 100-ms or 500-ms delay, participants read a word that was the refreshed word (refreshed probe), the nonrefreshed word (nonrefreshed probe), or a new word (novel probe). Young adults were slower to read refreshed probes than nonrefreshed probes at the 100-ms, but not the 500-ms, delay. Conversely, older adults were slower to read refreshed probes than nonrefreshed probes at the 500-ms, but not the 100-ms, delay. The delayed slowing of responses to refreshed probes was primarily observed in older-old adults (75+ years). A delay in suppressing the target of refreshing may disrupt the fluidity with which attention can be shifted to a new target. Importantly, a long-term memory benefit of refreshing was observed for both ages and delays. These results suggest that a full characterization of age-related memory deficits should consider the time course of effects and how specific component cognitive processes affect both working and long-term memory. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

The Impact of Focusing on Different Features During Encoding on Young and Older Adults’ Source Memory

Age-related source memory deficits result, in part, because young and older adults attend to different information. We asked whether focusing young and older adults‘ attention on specific features at encoding would result in similar subjective experiences of the vividness of the features and how this might affect source memory. Ratings of the vividness of visual detail, emotion, and associations were similar for young and older adults both when they were perceiving pictures and when they were thinking about them after a brief delay. Although young adults had better source memory than older adults, source accuracy did not differ depending on feature attended, and correlations between ratings and source memory showed that focus on the different types of information was equally predictive of source memory accuracy for young and older adults. Although preliminary, the results suggest that when attention is focused on specific information at encoding, young and older adults later use the various categories of source-specifying information similarly in making source attributions. Nevertheless, older adults did worse on the source test, suggesting they had less discriminable source information overall, this information was not well bound, and/or they experienced difficulty in strategic retrieval and monitoring processes.

Age-related changes in the relationship between visual exploration and hippocampal activity

Deciphering the mechanisms underlying age-related memory declines remains an important goal in cognitive neuroscience. Recently, we observed that visual sampling behavior predicted activity within the hippocampus, a region critical for memory. In younger adults, increases in the number of gaze fixations were associated with increases in hippocampal activity (Liu et al., 2017). This finding suggests a close coupling between the oculomotor and memory system. However, the extent to which this coupling is altered with aging has not been investigated. In this study, we gave older adults the same face processing task used in Liu et al. (2017) and compared their visual exploration behavior and neural activation in the hippocampus and the fusiform face area (FFA) to those of younger adults. Compared to younger adults, older adults showed an increase in visual exploration as indexed by the number of gaze fixations. However, the relationship between visual exploration and neural responses in the hippocampus and FFA was weaker than that of younger adults. Older adults also showed weaker responses to novel faces and a smaller repetition suppression effect in the hippocampus and FFA compared to younger adults. All together, this study provides novel evidence that the capacity to bind visually sampled information, in real-time, into coherent representations along the ventral visual stream and the medial temporal lobe declines with aging.

Arousal increases neural gain via the locus coeruleus-norepinephrine system in younger adults but not in older adults

In younger adults, arousal amplifies attentional focus to the most salient or goal-relevant information while suppressing other information. A computational model of how the locus coeruleus-norepinephrine (LC-NE) system can implement this increased selectivity under arousal and an fMRI study comparing how arousal affects younger and older adults' processing indicate that the amplification of salient stimuli and the suppression of non-salient stimuli are separate processes, with aging affecting suppression without impacting amplification under arousal. In the fMRI study, arousal increased processing of salient stimuli and decreased processing of non-salient stimuli for younger adults. In contrast, for older adults, arousal increased processing of both low and high salience stimuli, generally increasing excitatory responses to visual stimuli. Older adults also showed decline in LC functional connectivity with frontoparietal networks that coordinate attentional selectivity. Thus, among older adults, arousal increases the potential for distraction from non-salient stimuli.

What is attentional refreshing in working memory?

Working memory is one of the most important topics of research in cognitive psychology. The cognitive revolution that introduced the computer metaphor to describe human cognitive functioning called for this system in charge of the temporary storage of incoming or retrieved information to permit its processing. In the past decades, one particular mechanism of maintenance, attentional refreshing, has attracted an increasing amount of interest in the field of working memory. However, this mechanism remains rather mysterious, and its functioning is conceived in very different ways across the literature. This article presents an up-to-date review on attentional refreshing through the joint effort of leading researchers in the domain. It highlights points of agreement and delineates future avenues of research.

Age-related differences in the neural basis of the subjective vividness of memories: evidence from multivoxel pattern classification

Although older adults often show reduced episodic memory accuracy, their ratings of the subjective vividness of their memories often equal or even exceed those of young adults. Such findings suggest that young and older adults may differentially access and/or weight different kinds of information in making vividness judgments. We examined this idea using multivoxel pattern classification of fMRI data to measure category representations while participants saw and remembered pictures of objects and scenes. Consistent with our hypothesis, there were age-related differences in how category representations related to the subjective sense of vividness. During remembering, older adults' vividness ratings were more related, relative to young adults', to category representations in prefrontal cortex. In contrast, young adults' vividness ratings were more related, relative to older adults, to category representations in parietal cortex. In addition, category representations were more correlated among posterior regions in young than in older adults, whereas correlations between PFC and posterior regions did not differ between the 2 groups. Together, these results are consistent with the idea that young and older adults differentially weight different types of information in assessing subjective vividness of their memories.

How fMRI Can Inform Cognitive Theories

How can functional magnetic resonance imaging (fMRI) advance cognitive theory? Some have argued that fMRI can do little beyond localizing brain regions that carry out certain cognitive functions (and may not even be able to do that). However, in this article, we argue that fMRI can inform theories of cognition by helping to answer at least four distinct kinds of questions. Which mental functions are performed in brain regions specialized for just that function (and which are performed in more general-purpose brain machinery)? When fMRI markers of a particular Mental Process X are found, is Mental Process X engaged when people perform Task Y? How distinct are the representations of different stimulus classes? Do specific pairs of tasks engage common or distinct processing mechanisms? Thus, fMRI data can be used to address theoretical debates that have nothing to do with where in the brain a particular process is carried out.

A systematic review of type 2 diabetes mellitus and hypertension in imaging studies of cognitive aging: time to establish new norms

The rising prevalence of type 2 diabetes (T2DM) and hypertension in older adults, and the deleterious effect of these conditions on cerebrovascular and brain health, is creating a growing discrepancy between the "typical" cognitive aging trajectory and a "healthy" cognitive aging trajectory. These changing health demographics make T2DM and hypertension important topics of study in their own right, and warrant attention from the perspective of cognitive aging neuroimaging research. Specifically, interpretation of individual or group differences in blood oxygenation level dependent magnetic resonance imaging (BOLD MRI) or positron emission tomography (PET H2O(15)) signals as reflective of differences in neural activation underlying a cognitive operation of interest requires assumptions of intact vascular health amongst the study participants. Without adequate screening, inclusion of individuals with T2DM or hypertension in "healthy" samples may introduce unwanted variability and bias to brain and/or cognitive measures, and increase potential for error. We conducted a systematic review of the cognitive aging neuroimaging literature to document the extent to which researchers account for these conditions. Of the 232 studies selected for review, few explicitly excluded individuals with T2DM (9%) or hypertension (13%). A large portion had exclusion criteria that made it difficult to determine whether T2DM or hypertension were excluded (44 and 37%), and many did not mention any selection criteria related to T2DM or hypertension (34 and 22%). Of all the surveyed studies, only 29% acknowledged or addressed the potential influence of intersubject vascular variability on the measured BOLD or PET signals. To reinforce the notion that individuals with T2DM and hypertension should not be overlooked as a potential source of bias, we also provide an overview of metabolic and vascular changes associated with T2DM and hypertension, as they relate to cerebrovascular and brain health.

Age-related differences in agenda-driven monitoring of format and task information

Age-related source memory deficits may arise, in part, from changes in the agenda-driven processes that control what features of events are relevant during remembering. Using fMRI, we compared young and older adults on tests assessing source memory for format (picture, word) or encoding task (self-, other-referential), as well as on old-new recognition. Behaviorally, relative to old-new recognition, older adults showed disproportionate and equivalent deficits on both source tests compared to young adults. At encoding, both age groups showed expected activation associated with format in posterior visual processing areas, and with task in medial prefrontal cortex. At test, the groups showed similar selective, agenda-related activity in these representational areas. There were, however, marked age differences in the activity of control regions in lateral and medial prefrontal cortex and lateral parietal cortex. Results of correlation analyses were consistent with the idea that young adults had greater trial-by-trial agenda-driven modulation of activity (i.e., greater selectivity) than did older adults in representational regions. Thus, under selective remembering conditions where older adults showed clear differential regional activity in representational areas depending on type of test, they also showed evidence of disrupted frontal and parietal function and reduced item-by-item modulation of test-appropriate features. This pattern of results is consistent with an age-related deficit in the engagement of selective reflective attention.

Lifespan age differences in working memory: a two-component framework

We suggest that working memory (WM) performance can be conceptualized as the interplay of low-level feature binding processes and top-down control, relating to posterior and frontal brain regions and their interaction in a distributed neural network. We propose that due to age-differential trajectories of posterior and frontal brain regions top-down control processes are not fully mature until young adulthood and show marked decline with advancing age, whereas binding processes are relatively mature in children, but show senescent decline in older adults. A review of the literature spanning from middle childhood to old age shows that binding and top-down control processes undergo profound changes across the lifespan. We illustrate commonalities and dissimilarities between children, younger adults, and older adults reflecting the change in the two components' relative contribution to visual WM performance across the lifespan using results from our own lab. We conclude that an integrated account of visual WM lifespan changes combining research from behavioral neuroscience and cognitive psychology of child development as well as aging research opens avenues to advance our understanding of cognition in general.

Memory: enduring traces of perceptual and reflective attention

Attention and memory are typically studied as separate topics, but they are highly intertwined. Here we discuss the relation between memory and two fundamental types of attention: perceptual and reflective. Memory is the persisting consequence of cognitive activities initiated by and/or focused on external information from the environment (perceptual attention) and initiated by and/or focused on internal mental representations (reflective attention). We consider three key questions for advancing a cognitive neuroscience of attention and memory: to what extent do perception and reflection share representational areas? To what extent are the control processes that select, maintain, and manipulate perceptual and reflective information subserved by common areas and networks? During perception and reflection, to what extent are common areas responsible for binding features together to create complex, episodic memories and for reviving them later? Considering similarities and differences in perceptual and reflective attention helps integrate a broad range of findings and raises important unresolved issues.

Deficit in switching between functional brain networks underlies the impact of multitasking on working memory in older adults

Multitasking negatively influences the retention of information over brief periods of time. This impact of interference on working memory is exacerbated with normal aging. We used functional MRI to investigate the neural basis by which an interruption is more disruptive to working memory performance in older individuals. Younger and older adults engaged in delayed recognition tasks both with and without interruption by a secondary task. Behavioral analysis revealed that working memory performance was more impaired by interruptions in older compared with younger adults. Functional connectivity analyses showed that when interrupted, older adults disengaged from a memory maintenance network and reallocated attentional resources toward the interrupting stimulus in a manner consistent with younger adults. However, unlike younger individuals, older adults failed to both disengage from the interruption and reestablish functional connections associated with the disrupted memory network. These results suggest that multitasking leads to more significant working memory disruption in older adults because of an interruption recovery failure, manifest as a deficient ability to dynamically switch between functional brain networks.

Arousal-Biased Competition in Perception and Memory

Our everyday surroundings besiege us with information. The battle is for a share of our limited attention and memory, with the brain selecting the winners and discarding the losers. Previous research shows that both bottom-up and top-down factors bias competition in favor of high priority stimuli. We propose that arousal during an event increases this bias both in perception and in long-term memory of the event. Arousal-biased competition theory provides specific predictions about when arousal will enhance memory for events and when it will impair it, which accounts for some puzzling contradictions in the emotional memory literature.