Social Robots for Evaluating Attention State in Older Adults.

Sustained attention is essential for older adults to maintain an active lifestyle, and the deficiency of this function is often associated with health-related risks such as falling and frailty. The present study examined whether the well-established age-effect on reducing mind-wandering, the drift to internal thoughts that are seen to be detrimental to attentional control, could be replicated by using a robotic experimenter for older adults who are not as familiar with online technologies. A total of 28 younger and 22 older adults performed a Sustained Attention to Response Task (SART) by answering thought probes regarding their attention states and providing confidence ratings for their own task performances. The indices from the modified SART suggested a well-documented conservative response strategy endorsed by older adults, which were represented by slower responses and increased omission errors. Moreover, the slower responses and increased omissions were found to be associated with less self-reported mind-wandering, thus showing consistency with their higher subjective ratings of attentional control. Overall, this study demonstrates the potential of constructing age-related cognitive profiles with attention evaluation instruction based on a social companion robot for older adults at home.

Frontal, Striatal, and Medial Temporal Sensitivity to Value Distinguishes Risk-Taking from Risk-Aversive Older Adults during Decision Making.

Aging compromises the frontal, striatal, and medial temporal areas of the reward system, impeding accurate value representation and feedback processing critical for decision making. However, substantial variability characterizes age-related effects on the brain so that some older individuals evince clear neurocognitive declines whereas others are spared. Moreover, the functional correlates of normative individual differences in older-adult value-based decision making remain unclear. We performed a functional magnetic resonance imaging study in 173 human older adults during a lottery choice task in which costly to more desirable stakes were depicted using low to high expected values (EVs) of points. Across trials that varied in EVs, participants decided to accept or decline the offered stakes to maximize total accumulated points. We found that greater age was associated with less optimal decisions, accepting stakes when losses were likely and declining stakes when gains were likely, and was associated with increased frontal activity for costlier stakes. Critically, risk preferences varied substantially across older adults and neural sensitivity to EVs in the frontal, striatal, and medial temporal areas dissociated risk-aversive from risk-taking individuals. Specifically, risk-averters increased neural responses to increasing EVs as stakes became more desirable, whereas risk-takers increased neural responses with decreasing EV as stakes became more costly. Risk preference also modulated striatal responses during feedback with risk-takers showing more positive responses to gains compared with risk-averters. Our findings highlight the frontal, striatal, and medial temporal areas as key neural loci in which individual differences differentially affect value-based decision-making ability in older adults. SIGNIFICANCE STATEMENT: Frontal, striatal, and medial temporal functions implicated in value-based decision processing of rewards and costs undergo substantial age-related changes. However, age effects on brain function and cognition differ across individuals. How this normative variation relates to older-adult value-based decision making is unclear. We found that although the ability make optimal decisions declines with age, there is still much individual variability in how this deterioration occurs. Critically, whereas risk-averters showed increased neural activity to increasingly valuable stakes in frontal, striatal, and medial temporal areas, risk-takers instead increased activity as stakes became more costly. Such distinct functional decision-making processing in these brain regions across normative older adults may reflect individual differences in susceptibility to age-related brain changes associated with incipient cognitive impairment.

Changes in brain function occur years before the onset of cognitive impairment.

To develop targeted intervention strategies for the treatment of Alzheimer's disease, we first need to identify early markers of brain changes that occur before the onset of cognitive impairment. Here, we examine changes in resting-state brain function in humans from the Baltimore Longitudinal Study of Aging. We compared longitudinal changes in regional cerebral blood flow (rCBF), assessed by (15)O-water PET, over a mean 7 year period between participants who eventually developed cognitive impairment (n = 22) and those who remained cognitively normal (n = 99). Annual PET assessments began an average of 11 years before the onset of cognitive impairment in the subsequently impaired group, so all participants were cognitively normal during the scanning interval. A voxel-based mixed model analysis was used to compare groups with and without subsequent impairment. Participants with subsequent impairment showed significantly greater longitudinal rCBF increases in orbitofrontal, medial frontal, and anterior cingulate regions, and greater longitudinal decreases in parietal, temporal, and thalamic regions compared with those who maintained cognitive health. These changes were linear in nature and were not influenced by longitudinal changes in regional tissue volume. Although all participants were cognitively normal during the scanning interval, most of the accelerated rCBF changes seen in the subsequently impaired group occurred within regions thought to be critical for the maintenance of cognitive function. These changes also occurred within regions that show early accumulation of pathology in Alzheimer's disease, suggesting that there may be a connection between early pathologic change and early changes in brain function.

Frontal function and executive processing in older adults: process and region specific age-related longitudinal functional changes.

Longitudinal studies on aging brain function have shown declines in frontal activity as opposed to the over-recruitment shown in cross-sectional studies. Such mixed findings suggest that age-related changes in frontal activity may be process- and region-specific, having varied associations across different frontal regions involved in distinct cognitive processes, rather than generalized across the frontal cortex. Using data from the Baltimore Longitudinal Study of Aging (BLSA), we examined individual differences through cross-sectional associations at baseline evaluation and longitudinal changes in regional cerebral blood flow (rCBF) in relation to different executive abilities in cognitively normal older adults. We found that, at baseline, greater rCBF in middle frontal regions correlated with better performance in abstraction and chunking, but greater rCBF in the insula and a distinct middle frontal region correlated with poorer inhibition and discrimination, respectively. In addition, increases in frontal rCBF over time were associated with longitudinal declines in abstraction, chunking, inhibition, discrimination, switching, and manipulation. These findings indicate process- and region-specific, rather than uniform, age-related changes in frontal brain-behavior associations, and also suggest that longitudinally high-levels of frontal engagement reflect declining rather than stable cognition.

Identifying Mild Cognitive Impairment by Using Human-Robot Interactions.

BACKGROUND: Mild cognitive impairment (MCI), which is common in older adults, is a risk factor for dementia. Rapidly growing health care demand associated with global population aging has spurred the development of new digital tools for the assessment of cognitive performance in older adults. OBJECTIVE: To overcome methodological drawbacks of previous studies (e.g., use of potentially imprecise screening tools that fail to include patients with MCI), this study investigated the feasibility of assessing multiple cognitive functions in older adults with and without MCI by using a social robot. METHODS: This study included 33 older adults with or without MCI and 33 healthy young adults. We examined the utility of five robotic cognitive tests focused on language, episodic memory, prospective memory, and aspects of executive function to classify age-associated cognitive changes versus MCI. Standardized neuropsychological tests were collected to validate robotic test performance. RESULTS: The assessment was well received by all participants. Robotic tests assessing delayed episodic memory, prospective memory, and aspects of executive function were optimal for differentiating between older adults with and without MCI, whereas the global cognitive test (i.e., Mini-Mental State Examination) failed to capture such subtle cognitive differences among older adults. Furthermore, robot-administered tests demonstrated sound ability to predict the results of standardized cognitive tests, even after adjustment for demographic variables and global cognitive status. CONCLUSION: Overall, our results suggest the human-robot interaction approach is feasible for MCI identification. Incorporating additional cognitive test measures might improve the stability and reliability of such robot-assisted MCI diagnoses.

Age-Related Differences in the Neural Processing of Idioms: A Positive Perspective.

We examined whether older adults benefit from a larger mental-lexicon size and world knowledge to process idioms, one of few abilities that do not stop developing until later adulthood. Participants viewed four-character sequences presented one at a time that combined to form (1) frequent idioms, (2) infrequent idioms, (3) random sequences, or (4) perceptual controls, and judged whether the four-character sequence was an idiom. Compared to their younger counterparts, older adults had higher accuracy for frequent idioms and equivalent accuracy for infrequent idioms. Compared to random sequences, when processing frequent and infrequent idioms, older adults showed higher activations in brain regions related to sematic representation than younger adults, suggesting that older adults devoted more cognitive resources to processing idioms. Also, higher activations in the articulation-related brain regions indicate that older adults adopted the thinking-aloud strategy in the idiom judgment task. These results suggest re-organized neural computational involvement in older adults' language representations due to life-long experiences. The current study provides evidence for the alternative view that aging may not necessarily be solely accompanied by decline.

Hippocampal activation and connectivity in the aging brain.

The hippocampus and underlying cortices are highly susceptible to pathologic change with increasing age. Using an associative face-scene (Face-Place) encoding task designed to target these regions, we investigated activation and connectivity patterns in cognitively normal older adults. Functional MRI scans were collected in 210 older participants (mean age = 76.4 yrs) in the Baltimore Longitudinal Study of Aging (BLSA). Brain activation patterns were examined during encoding of novel Face-Place pairs. Functional connectivity of the hippocampus was also examined during encoding, with seed regions placed along the longitudinal axis in the head, body and tail of the structure. In the temporal lobe, task activation patterns included coverage of the hippocampus and underlying ventral temporal cortices. Extensive activation was also seen in frontal, parietal and occipital lobes of the brain. Functional connectivity analyses during overall encoding showed that the head of the hippocampus was connected to frontal and anterior/middle temporal regions, the body with frontal, widespread temporal and occipital regions, and the tail with posterior temporal and occipital cortical regions. Connectivity limited to encoding of subsequently remembered stimuli showed a similar pattern for the hippocampal body, but differing patterns for the head and tail regions. These results show that the Face-Place task produces activation along the occipitotemporal visual pathway including medial temporal areas. The connectivity results also show that patterns of functional connectivity vary throughout the anterior-posterior extent of the hippocampus during memory encoding. As these patterns include regions vulnerable to pathologic change in early stages of Alzheimer's disease, continued longitudinal assessment of these individuals can provide valuable information regarding changes in brain-behavior relationships that may occur with advancing age and the onset of cognitive decline.

Reduced neural selectivity increases fMRI adaptation with age during face discrimination.

Ventral-visual activity in older adults has been characterized by dedifferentiation, or reduced distinctiveness, of responses to different categories of visual stimuli such as faces and houses, that typically elicit highly specialized responses in the fusiform and parahippocampal brain regions respectively in young adults (Park et al., 2004). In the present study, we demonstrate that age-related neural dedifferentiation applies to within-category stimuli (different types of faces) as well, such that older adults process less distinctive representations for individual faces than young adults. We performed a functional magnetic resonance imaging adaptation experiment while young and older participants made same-different judgments to serially presented face-pairs that were Identical, Moderate in similarity through morphing, or Different. As expected, older adults showed adaptation in the fusiform face area (FFA), during the Identical as well as the Moderate conditions relative to the Different condition. Young adults showed adaptation during the Identical condition, but minimal adaptation to the Moderate condition. These results indicate that older adults' FFA treated the morphed faces as Identical faces, reflecting decreased fidelity of neural representation of faces with age.

Neural responses reveal associations between personal values and value-based decisions.

Personal values are thought to modulate value-based decisions, but the neural mechanisms underlying this influence remain unclear. Using a Lottery Choice Task functional brain imaging experiment, we examined the associations between personal value for hedonism and security (based on the Schwartz Value Survey) and subjective neurocognitive processing of reward and loss probability and magnitude objectively coded in stimuli. Hedonistic individuals accepted more losing stakes and showed increased right dorsolateral prefrontal and striatal and left parietal responses with increasing probability of losing. Individuals prioritizing security rejected more stakes and showed reduced right inferior frontal and amygdala responses with increasing stake magnitude, but increased precuneus responses for high-magnitude high-winning probability. With higher hedonism, task-related functional connectivity with the whole brain was higher in right insula and lower in bilateral habenula. For those with higher security ratings, whole-brain functional connectivity was higher in bilateral insula, supplementary motor areas, right superior frontal gyrus, dorsal anterior cingulate cortex, and lower in right middle occipital gyrus. These findings highlight distinct neural engagement across brain systems involved in reward and affective processing, and cognitive control that subserves how individual differences in personal value for gaining rewards or maintaining status quo modulate value-based decisions.

Integrity of the Prefronto-striato-thalamo-prefrontal Loop Predicts Tai Chi Chuan Training Effects on Cognitive Task-switching in Middle-aged and Older Adults.

Tai Chi Chuan (TCC) exercise has been shown to improve cognitive task-switching performance in older adults, but the extent of this positive effect varies among individuals. Past research also shows that brain white matter integrity could predict behavioral gains of cognitive and motor learning. Therefore, in this randomized controlled trial (NCT02270320), we examined whether baseline integrity of three target white matter tract groups was predictive of task-switching improvement after 12-week TCC training in middle-aged and older adults. Thirty-eight eligible participants were randomly assigned to a TCC group (n = 19) and a control group (n = 19). Cognitive task-switching and physical performances were collected before and after training. Brain diffusion spectrum MR images were acquired before training and the general fractional anisotropy (GFA) of each target white matter tract group was calculated to indicate baseline white matter integrity of that group. Correlation and regression analyses between these GFAs and post-training task-switching improvement were analyzed using adjusted p-values. After 12 weeks, significant task-switching and physical performance improvements were found only in the TCC group. Moreover, higher baseline GFA of the prefronto-striato-thalamo-prefrontal loop fibers (r = -0.63, p = 0.009), but not of the prefronto-parietal/occipital (r = -0.55, p = 0.026) and callosal (r = -0.35, p = 0.189) fiber groups, was associated with greater reductions of task-switching errors after the TCC training. Multiple regression analysis revealed that baseline GFA of the prefronto-striato-thalamo-prefrontal loop fibers was the only independent white matter integrity predictor of task-switching error reductions after TCC training (ß = -0.620, adjusted R2 change = 0.265, p = 0.009). These findings not only highlight the important role of baseline integrity of the prefronto-striatal circuits in influencing the extent of positive cognitive task-switching effects from short-term TCC training, but also implicate that preserving good white matter integrity in the aging process may be crucial in order to gain the best cognitive effects of exercise interventions.

Neuroplasticity and cognitive aging: the scaffolding theory of aging and cognition.

A recent proposal called the Scaffolding Theory of Cognitive Aging (STAC) postulates that functional changes with aging are part of a lifespan process of compensatory cognitive scaffolding that is an attempt to alleviate the cognitive declines associated with aging. Indeed, behavioral studies have shown that aging is associated with both decline as well as preservation of selective cognitive abilities. Similarly, neuroimaging studies have revealed selective changes in the aging brain that reflect neural decline as well as compensatory neural recruitment. While aging is associated with reductions in cortical thickness, white-matter integrity, dopaminergic activity, and functional engagement in posterior brain regions such as the hippocampus and occipital areas, there are compensatory increases in frontal functional engagement that correlate with better behavioral performance in older adults. In this review, we discuss these age-related behavioral and brain findings that support the STAC model of cognitive scaffolding and additionally integrate the findings on neuroplasticity as a compensatory response in the aging brain. As such, we also examine the impact of external experiences in facilitating neuroplasticity in older adults. Finally, having laid the foundation for STAC, we briefly describe a proposed intervention trial (The Synapse Program) designed to evaluate the behavioral and neural impact of engagement in lifestyle activities that facilitates successful cognitive scaffolding using a controlled experiment where older adult participants are randomly assigned to different conditions of engagement.

Financial Incentives Differentially Regulate Neural Processing of Positive and Negative Emotions during Value-Based Decision-Making.

Emotional and economic incentives often conflict in decision environments. To make economically desirable decisions then, deliberative neural processes must be engaged to regulate automatic emotional reactions. In this functional magnetic resonance imaging (fMRI) study, we evaluated how fixed wage (FW) incentives and performance-based (PB) financial incentives, in which pay is proportional to outcome, differentially regulate positive and negative emotional reactions to hypothetical colleagues that conflicted with the economics of available alternatives. Neural activity from FW to PB incentive contexts decreased for positive emotional stimuli but increased for negative stimuli in middle temporal, insula, and medial prefrontal regions. In addition, PB incentives further induced greater responses to negative than positive emotional decisions in the frontal and anterior cingulate regions involved in emotion regulation. Greater response to positive than negative emotional features in these regions also correlated with lower frequencies of economically desirable choices. Our findings suggest that whereas positive emotion regulation involves a reduction of responses in valence representation regions, negative emotion regulation additionally engages brain regions for deliberative processing and signaling of incongruous events.

Task-Switching Performance Improvements After Tai Chi Chuan Training Are Associated With Greater Prefrontal Activation in Older Adults.

Studies have shown that Tai Chi Chuan (TCC) training has benefits on task-switching ability. However, the neural correlates underlying the effects of TCC training on task-switching ability remain unclear. Using task-related functional magnetic resonance imaging (fMRI) with a numerical Stroop paradigm, we investigated changes of prefrontal brain activation and behavioral performance during task-switching before and after TCC training and examined the relationships between changes in brain activation and task-switching behavioral performance. Cognitively normal older adults were randomly assigned to either the TCC or control (CON) group. Over a 12-week period, the TCC group received three 60-min sessions of Yang-style TCC training weekly, whereas the CON group only received one telephone consultation biweekly and did not alter their life style. All participants underwent assessments of physical functions and neuropsychological functions of task-switching, and fMRI scans, before and after the intervention. Twenty-six (TCC, N = 16; CON, N = 10) participants completed the entire experimental procedure. We found significant group by time interaction effects on behavioral and brain activation measures. Specifically, the TCC group showed improved physical function, decreased errors on task-switching performance, and increased left superior frontal activation for Switch > Non-switch contrast from pre- to post-intervention, that were not seen in the CON group. Intriguingly, TCC participants with greater prefrontal activation increases in the switch condition from pre- to post-intervention presented greater reductions in task-switching errors. These findings suggest that TCC training could potentially provide benefits to some, although not all, older adults to enhance the function of their prefrontal activations during task-switching.

Vascular burden and brain aging in a senior volunteer cohort: A pilot study.

OBJECTIVE: To test the feasibility of establishing a senior volunteer cohort and describe vascular risks, cognitive function, and brain aging indices in a pilot study. MATERIALS AND METHODS: We enrolled 40 senior volunteers from the Tzu Chi Foundation and other organizations in Hualien in 2014-2015. We conducted in-person interviews to collect information on demographic features, physical fitness, dietary habits, comorbidities, and narratives of aging. Vascular risks including blood pressure, body mass index (BMI), serum glucose level, and lipid profile were examined. Each participant underwent a comprehensive battery of neuropsychological tests and structural brain magnetic resonance imaging (MRI). Descriptive statistics and tabulation were applied to characterize this pilot cohort. RESULTS: There were more volunteers from the Tzu Chi Foundation (n = 25) than other organizations. The mean age was 66.7 years (standard deviation = 5.1) and there was a female predominance (M:F = 13:27). The mean number of comorbid chronic diseases was 2.1 and the mean BMI was 24.5. Most participants (77.5%) engaged in outdoor walking activities every week. Nutrient intake in vegetarians (n = 18) did not differ from nonvegetarians except for lower Vitamin B12 levels (mean = 0.9 µg). All participants but one scored 26 or above in the Mini-Mental State Examination (mean = 28.4). Among the other cognitive tests, only one task related to inhibition and switching abilities was at the low average level. The mean values of vascular risk markers were within the normal ranges. The most common genotype of apolipoprotein E was ɛ3/ɛ3 (n = 32). The quality of MRI was sufficient for volumetric analysis. CONCLUSION: It is feasible to establish a volunteer-based cohort to study brain aging in Taiwan. The senior volunteers were physically active and cognitively healthy. Vascular risks were well distributed among these participants. Future longitudinal study will allow us to observe changes in these markers over time and provide dynamic evidence about vascular health and cognitive aging.

Distinct and Overlapping Brain Areas Engaged during Value-Based, Mathematical, and Emotional Decision Processing.

When comparing between the values of different choices, human beings can rely on either more cognitive processes, such as using mathematical computation, or more affective processes, such as using emotion. However, the neural correlates of how these two types of processes operate during value-based decision-making remain unclear. In this study, we investigated the extent to which neural regions engaged during value-based decision-making overlap with those engaged during mathematical and emotional processing in a within-subject manner. In a functional magnetic resonance imaging experiment, participants viewed stimuli that always consisted of numbers and emotional faces that depicted two choices. Across tasks, participants decided between the two choices based on the expected value of the numbers, a mathematical result of the numbers, or the emotional face stimuli. We found that all three tasks commonly involved various cortical areas including frontal, parietal, motor, somatosensory, and visual regions. Critically, the mathematical task shared common areas with the value but not emotion task in bilateral striatum. Although the emotion task overlapped with the value task in parietal, motor, and sensory areas, the mathematical task also evoked responses in other areas within these same cortical structures. Minimal areas were uniquely engaged for the value task apart from the other two tasks. The emotion task elicited a more expansive area of neural activity whereas value and mathematical task responses were in more focal regions. Whole-brain spatial correlation analysis showed that valuative processing engaged functional brain responses more similarly to mathematical processing than emotional processing. While decisions on expected value entail both mathematical and emotional processing regions, mathematical processes have a more prominent contribution particularly in subcortical processes.

Cortical areas involved in object, background, and object-background processing revealed with functional magnetic resonance adaptation.

Previous work has suggested that object and place processing are neuroanatomically dissociated in ventral visual areas under conditions of passive viewing. It has also been shown that the hippocampus and parahippocampal gyrus mediate the integration of objects with background scenes in functional imaging studies, but only when encoding or retrieval processes have been directed toward the relevant stimuli. Using functional magnetic resonance adaptation, we demonstrated that object, background scene, and contextual integration of selectively repeated objects and background scenes could be dissociated during the passive viewing of naturalistic pictures involving object-scene pairings. Specifically, bilateral fusiform areas showed adaptation to object repetition, regardless of whether the associated scene was novel or repeated, suggesting sensitivity to object processing. Bilateral parahippocampal regions showed adaptation to background scene repetition, regardless of whether the focal object was novel or repeated, suggesting selectivity for background scene processing. Finally, bilateral parahippocampal regions distinct from those involved in scene processing and the right hippocampus showed adaptation only when the unique pairing of object with background scene was repeated, suggesting that these regions perform binding operations.

Greater cortical thinning in normal older adults predicts later cognitive impairment.

Cross-sectional studies have shown regional differences in cortical thickness between healthy older adults and patients with Alzheimer's disease (AD) or mild cognitive impairment (MCI). We now demonstrate that participants who subsequently develop cognitive impairment leading to a diagnosis of MCI or AD (n = 25) experience greater cortical thinning in specific neuroanatomic regions compared with control participants who remained cognitively normal (n = 96). Based on 8 years of annual magnetic resonance imaging scans beginning an average of 11 years before onset of cognitive impairment, participants who developed cognitive impairment subsequent to the scanning period had greater longitudinal cortical thinning in the temporal poles and left medial temporal lobe compared with controls. No significant regional cortical thickness differences were found at baseline between the 2 study groups indicating that we are capturing a critical time when brain changes occur before behavioral manifestations of impairment are detectable. Our findings suggest that early events of the pathway that leads to cognitive impairment may involve the temporal lobe and that this increased atrophy could be considered an early biomarker of neurodegeneration predictive of cognitive impairment years later.

Imaging-based biomarkers of cognitive performance in older adults constructed via high-dimensional pattern regression applied to MRI and PET.

In this study, we used high-dimensional pattern regression methods based on structural (gray and white matter; GM and WM) and functional (positron emission tomography of regional cerebral blood flow; PET) brain data to identify cross-sectional imaging biomarkers of cognitive performance in cognitively normal older adults from the Baltimore Longitudinal Study of Aging (BLSA). We focused on specific components of executive and memory domains known to decline with aging, including manipulation, semantic retrieval, long-term memory (LTM), and short-term memory (STM). For each imaging modality, brain regions associated with each cognitive domain were generated by adaptive regional clustering. A relevance vector machine was adopted to model the nonlinear continuous relationship between brain regions and cognitive performance, with cross-validation to select the most informative brain regions (using recursive feature elimination) as imaging biomarkers and optimize model parameters. Predicted cognitive scores using our regression algorithm based on the resulting brain regions correlated well with actual performance. Also, regression models obtained using combined GM, WM, and PET imaging modalities outperformed models based on single modalities. Imaging biomarkers related to memory performance included the orbito-frontal and medial temporal cortical regions with LTM showing stronger correlation with the temporal lobe than STM. Brain regions predicting executive performance included orbito-frontal, and occipito-temporal areas. The PET modality had higher contribution to most cognitive domains except manipulation, which had higher WM contribution from the superior longitudinal fasciculus and the genu of the corpus callosum. These findings based on machine-learning methods demonstrate the importance of combining structural and functional imaging data in understanding complex cognitive mechanisms and also their potential usage as biomarkers that predict cognitive status.

Neural correlates of conceptual object priming in young and older adults: an event-related functional magnetic resonance imaging study.

In this event-related functional magnetic resonance imaging study, we investigated age-related differences in brain activity associated with conceptual repetition priming in young and older adults. Participants performed a speeded "living/nonliving" classification task with 3 repetitions of familiar objects. Both young and older adults showed a similar magnitude of behavioral priming to repeated objects and evidenced repetition-related activation reductions in fusiform gyrus, superior occipital, middle, and inferior temporal cortex, and inferior frontal and insula regions. The neural priming effect in young adults was extensive and continued through both the second and third stimulus repetitions, and neural priming in older adults was markedly attenuated and reached floor at the second repetition. In young adults, greater neural priming in multiple brain regions correlated with greater behavioral facilitation and in older adults, only activation reduction in the left inferior frontal correlated with faster behavioral responses. These findings provide evidence for altered neural priming in older adults despite preserved behavioral priming, and suggest the possibility that age-invariant behavioral priming is observed as a result of more sustained neural processing of stimuli in older adults which might be a form of compensatory neural activity.

Culture-related differences in default network activity during visuo-spatial judgments.

Studies on culture-related differences in cognition have shown that Westerners attend more to object-related information, whereas East Asians attend more to contextual information. Neural correlates of these different culture-related visual processing styles have been reported in the ventral-visual and fronto-parietal regions. We conducted an fMRI study of East Asians and Westerners on a visuospatial judgment task that involved relative, contextual judgments, which are typically more challenging for Westerners. Participants judged the relative distances between a dot and a line in visual stimuli during task blocks and alternated finger presses during control blocks. Behaviorally, East Asians responded faster than Westerners, reflecting greater ease of the task for East Asians. In response to the greater task difficulty, Westerners showed greater neural engagement compared to East Asians in frontal, parietal, and occipital areas. Moreover, Westerners also showed greater suppression of the default network-a brain network that is suppressed under condition of high cognitive challenge. This study demonstrates for the first time that cultural differences in visual attention during a cognitive task are manifested both by differences in activation in fronto-parietal regions as well as suppression in default regions.