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Neural correlates of focused attention in patients with mild Alzheimer’s disease  [PDF]
Jennifer R. Bowes, Patrick Stroman, Angeles Garcia
World Journal of Neuroscience (WJNS) , 2012, DOI: 10.4236/wjns.2012.24034
Abstract: Alzheimer’s Disease (AD) is characterized by an early and significant memory impairment, and progresses to affect other cognitive domains. Impairments in Focused Attention (FA) have been observed in patients diagnosed with mild AD. A functional magnetic resonance imaging (fMRI) Stroop paradigm with verbal responses was used to investigate the neural correlates of FA in AD patients. Twenty-one patients diagnosed with mild AD performed a verbal Stroop—fMRI paradigm. Colour words were printed in an incongruent ink colour. Series 1 consisted of four blocks “Read the word” followed by four blocks “Say the colour of the ink”; Series 2 alternated between the two conditions. Functional data were analyzed using SPM5 to detect anatomical areas with significant signal intensity differences between the conditions. Within-group analyses of the colour minus word contrast yielded significant activation in the following left hemisphere regions: precentral gyrus, inferior frontal gyrus, fusiform gyrus and supplementary motor area (p < 0.05, uncorrected). Relative to cognitively normal older adults who underwent the same experimental task, Stroop performance was significantly worse in AD patients. The fMRI task yielded similar activated brain regions between the two groups. The use of verbal responses in this novel fMRI Stroop task avoids the confusion and memorizing of button locations seen with the manual response modality, allowing the neural correlates of FA to be investigated in AD patients.
Neural Correlates Associated with Successful Working Memory Performance in Older Adults as Revealed by Spatial ICA  [PDF]
Emi Saliasi, Linda Geerligs, Monicque M. Lorist, Natasha M. Maurits
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0099250
Abstract: To investigate which neural correlates are associated with successful working memory performance, fMRI was recorded in healthy younger and older adults during performance on an n-back task with varying task demands. To identify functional networks supporting working memory processes, we used independent component analysis (ICA) decomposition of the fMRI data. Compared to younger adults, older adults showed a larger neural (BOLD) response in the more complex (2-back) than in the baseline (0-back) task condition, in the ventral lateral prefrontal cortex (VLPFC) and in the right fronto-parietal network (FPN). Our results indicated that a higher BOLD response in the VLPFC was associated with increased performance accuracy in older adults, in both the baseline and the more complex task condition. This ‘BOLD-performance’ relationship suggests that the neural correlates linked with successful performance in the older adults are not uniquely related to specific working memory processes present in the complex but not in the baseline task condition. Furthermore, the selective presence of this relationship in older but not in younger adults suggests that increased neural activity in the VLPFC serves a compensatory role in the aging brain which benefits task performance in the elderly.
Reduced Sensitivity to Immediate Reward during Decision-Making in Older than Younger Adults  [PDF]
Ben Eppinger, Leigh E. Nystrom, Jonathan D. Cohen
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0036953
Abstract: We examined whether older adults differ from younger adults in the degree to which they favor immediate over delayed rewards during decision-making. To examine the neural correlates of age-related differences in delay discounting we acquired functional MR images while participants made decisions between smaller but sooner and larger but later monetary rewards. The behavioral results show age-related reductions in delay discounting. Less impulsive decision-making in older adults was associated with lower ventral striatal activations to immediate reward. Furthermore, older adults showed an overall higher percentage of delayed choices and reduced activity in the dorsal striatum than younger adults. This points to a reduced reward sensitivity of the dorsal striatum in older adults. Taken together, our findings indicate that less impulsive decision-making in older adults is due to a reduced sensitivity of striatal areas to reward. These age-related changes in reward sensitivity may result from transformations in dopaminergic neuromodulation with age.
Grey Matter Correlates of Three Language Tests in Non-demented Older Adults  [PDF]
Haobo Zhang, Perminder S. Sachdev, Wei Wen, Nicole A. Kochan, John D. Crawford, Henry Brodaty, Melissa J. Slavin, Simone Reppermund, Kristan Kang, Julian N. Trollor
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0080215
Abstract: Language has been extensively investigated by functional neuroimaging studies. However, only a limited number of structural neuroimaging studies have examined the relationship between language performance and brain structure in healthy adults, and the number is even less in older adults. The present study sought to investigate correlations between grey matter volumes and three standardized language tests in late life. The participants were 344 non-demented, community-dwelling adults aged 70-90 years, who were drawn from the population-based Sydney Memory and Ageing Study. The three language tests included the Controlled Oral Word Association Task (COWAT), Category Fluency (CF), and Boston Naming Test (BNT). Correlation analyses between voxel-wise GM volumes and language tests showed distinctive GM correlation patterns for each language test. The GM correlates were located in the right frontal and left temporal lobes for COWAT, in the left frontal and temporal lobes for CF, and in bilateral temporal lobes for BNT. Our findings largely corresponded to the neural substrates of language tasks revealed in fMRI studies, and we also observed a less hemispheric asymmetry in the GM correlates of the language tests. Furthermore, we divided the participants into two age groups (70-79 and 80-90 years old), and then examined the correlations between structural laterality indices and language performance for each group. A trend toward significant difference in the correlations was found between the two age groups, with stronger correlations in the group of 70-79 years old than those in the group of 80-90 years old. This difference might suggest a further decline of language lateralization in different stages of late life.
Indian Streams Research Journal , 2013,
Abstract: Falls are a serious problem among older adults, but there is little knowledge about the prevalence and correlated factors among Thai rural older adults. This crosssectional study was conducted among 386 Thai rural older adults in a province of southern Thailand. The researcher examined the prevalence of falls and association with measures of health conditions, functional impairment, and activities of daily living. Participants were interviewed about sociodemographic data, health conditions, activities of daily living and history of falls. Following this interview, an examination of visual acuity and balance were given. Regarding the falling frequency, 19.4% of the older adults reported having suffered at least one fall during the previous year, and 27.8 % declared recurrent episodes. The fall group contained more visual impairment, mobility impairment, and balance impairment than the non-fall group (p < 0.001). Logistic regression analyses showed that participants who had visual, mobility and balance impairment had more than two times the risk of falling as those without impairment (p < 0.05). In addition, participants who had been using a sedative drug had more than five times the risk of falling of those who were not using a sedative drug (p < 0.05). A better understanding of prevalence and correlates of falls can contribute to the early identification and detection of the risk group among rural older adults.
Electrophysiological correlates of selective attention: A lifespan comparison
Viktor Mueller, Yvonne Brehmer, Timo von Oertzen, Shu-Chen Li, Ulman Lindenberger
BMC Neuroscience , 2008, DOI: 10.1186/1471-2202-9-18
Abstract: Both primary and secondary ERP components showed age-related differences in peak amplitude, peak latency, and topological distribution. The P2 amplitude was higher in adults compared to children, whereas N2 showed the opposite effect. P3 peak amplitude was higher in older children and younger adults than in older adults. The amplitudes of N3, LDN, and LPN were higher in older children compared with both of the adult groups. In addition, both P3 and N3 peak latencies were significantly longer in older than in younger adults. Interestingly, in the young adult sample P3 peak amplitude correlated positively and P3 peak latency correlated negatively with performance in the Identical Picture test, a marker measure of fluid intelligence.The present findings suggest that patterns of event-related brain potentials are highly malleable within individuals and undergo profound reorganization from childhood to adulthood and old age.Scalp-recorded event-related brain potentials (ERPs) derived from electroencephalogram (EEG) play an important role in studies of cortical correlates of cognitive processes, primarily because of their relatively high temporal resolution (see [1,2] for reviews). The non-invasive nature of EEG assessments makes them particularly suitable for studying neurocognitive development in infants and children [3,4]. To date, age-comparative studies compared electrophysiological correlates of cognition either across childhood, adolescence and adulthood (e.g., [4-9]) or across adulthood and old age (e.g., [10-12]. Other than a few studies covering a wide age range of lifespan development [13,14], changes in brain electrophysiological activity have primarily been investigated with respect to either child development or aging. The aim of the present study was to explore changes in brain electrophysiological activity (also attention-related activity) across the lifespan.ERPs reflect invariant changes of ongoing EEG activity evoked by the stimulus. ERP components are
Motor Variability during Sustained Contractions Increases with Cognitive Demand in Older Adults  [PDF]
Marnie L. Vanden Noven,Hugo M. Pereira,Tejin Yoon,Alyssa A. Stevens,Kristy A. Nielson,Sandra K. Hunter
Frontiers in Aging Neuroscience , 2014, DOI: 10.3389/fnagi.2014.00097
Abstract: To expose cortical involvement in age-related changes in motor performance, we compared steadiness (force fluctuations) and fatigability of submaximal isometric contractions with the ankle dorsiflexor muscles in older and young adults and with varying levels of cognitive demand imposed. Sixteen young (20.4 ± 2.1 year: 8 men, 9 women) and 17 older adults (68.8 ± 4.4 years: 9 men, 8 women) attended three sessions and performed a 40 s isometric contraction at 5% maximal voluntary contraction (MVC) force followed by an isometric contraction at 30% MVC until task failure. The cognitive demand required during the submaximal contractions in each session differed as follows: (1) high-cognitive demand session where difficult mental math was imposed (counting backward by 13 from a 4-digit number); (2) low-cognitive demand session which involved simple mental math (counting backward by 1); and (3) control session with no mental math. Anxiety was elevated during the high-cognitive demand session compared with other sessions for both age groups but more so for the older adults than young adults (p < 0.05). Older adults had larger force fluctuations than young adults during: (1) the 5% MVC task as cognitive demand increased (p = 0.007), and (2) the fatiguing contraction for all sessions (p = 0.002). Time to task failure did not differ between sessions or age groups (p > 0.05), but the variability between sessions (standard deviation of three sessions) was greater for older adults than young (2.02 ± 1.05 vs. 1.25 ± 0.51 min, p < 0.05). Thus, variability in lower limb motor performance for low- and moderate-force isometric tasks increased with age and was exacerbated when cognitive demand was imposed, and may be related to modulation of synergist and antagonist muscles and an altered neural strategy with age originating from central sources. These data have significant implications for cognitively demanding low-force motor tasks that are relevant to functional and ergonomic in an aging workforce.
Differences in risk aversion between young and older adults
Albert SM, Duffy J
Neuroscience and Neuroeconomics , 2012, DOI: http://dx.doi.org/10.2147/NAN.S27184
Abstract: ences in risk aversion between young and older adults Original Research (2780) Total Article Views Authors: Albert SM, Duffy J Published Date February 2012 Volume 2012:1 Pages 3 - 9 DOI: http://dx.doi.org/10.2147/NAN.S27184 Received: 10 October 2011 Accepted: 11 January 2012 Published: 15 February 2012 Steven M Albert1, John Duffy2 1Department of Behavioral and Community Health Sciences, 2Department of Economics, University of Pittsburgh, Pittsburgh, PA, USA Abstract: Research on decision-making strategies among younger and older adults suggests that older adults may be more risk averse than younger people in the case of potential losses. These results mostly come from experimental studies involving gambling paradigms. Since these paradigms involve substantial demands on memory and learning, differences in risk aversion or other features of decision making attributed to age may in fact reflect age-related declines in cognitive abilities. In the current study, older and younger adults completed a simpler, paired lottery choice task used in the experimental economics literature to elicit risk aversion. A similar approach was used to elicit participants' discount rates. The older adult group was more risk averse than the younger (P < 0.05) and had a higher discount rate (15.6%–21.0% versus 10.3%–15.5%, P < 0.01), indicating lower expected utility from future income. Risk aversion and implied discount rates were weakly correlated. It may be valuable to investigate developmental changes in neural correlates of decision making across the lifespan.
Faster cognitive decline in the years prior to MR imaging is associated with smaller hippocampal volumes in cognitively healthy older persons  [PDF]
Debra A. Fleischman,Lei Yu,Konstantinos Arfanakis,S. Duke Han,Patricia A. Boyle,David A. Bennett
Frontiers in Aging Neuroscience , 2013, DOI: 10.3389/fnagi.2013.00021
Abstract: Early identification of persons at risk for cognitive decline in aging is critical to optimizing treatment to delay or avoid a clinical diagnosis of mild cognitive impairment (MCI) or dementia due to Alzheimer's disease (AD). To accomplish early identification, it is essential that trajectories of cognitive change be characterized and associations with established biomarkers of MCI and AD be examined during the phase in which older persons are considered cognitively healthy. Here we examined the association of rate of cognitive decline in the years leading up to structural magnetic resonance imaging with an established biomarker, hippocampal volume. The sample comprised 211 participants of the Rush Memory and Aging Project who had an average of 5.5 years of cognitive data prior to structural scanning. Results showed that there was significant variability in the trajectories of cognitive change prior to imaging and that faster cognitive decline was associated with smaller hippocampal volumes. Domain-specific analyses suggested that this association was primarily driven by decline in working memory. The results emphasize the importance of closely examining cognitive change and its association with brain structure during the years in which older persons are considered cognitively healthy.
Action Prediction in Younger versus Older Adults: Neural Correlates of Motor Familiarity  [PDF]
Nadine Diersch, Karsten Mueller, Emily S. Cross, Waltraud Stadler, Martina Rieger, Simone Schütz-Bosbach
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0064195
Abstract: Generating predictions during action observation is essential for efficient navigation through our social environment. With age, the sensitivity in action prediction declines. In younger adults, the action observation network (AON), consisting of premotor, parietal and occipitotemporal cortices, has been implicated in transforming executed and observed actions into a common code. Much less is known about age-related changes in the neural representation of observed actions. Using fMRI, the present study measured brain activity in younger and older adults during the prediction of temporarily occluded actions (figure skating elements and simple movement exercises). All participants were highly familiar with the movement exercises whereas only some participants were experienced figure skaters. With respect to the AON, the results confirm that this network was preferentially engaged for the more familiar movement exercises. Compared to younger adults, older adults recruited visual regions to perform the task and, additionally, the hippocampus and caudate when the observed actions were familiar to them. Thus, instead of effectively exploiting the sensorimotor matching properties of the AON, older adults seemed to rely predominantly on the visual dynamics of the observed actions to perform the task. Our data further suggest that the caudate played an important role during the prediction of the less familiar figure skating elements in better-performing groups. Together, these findings show that action prediction engages a distributed network in the brain, which is modulated by the content of the observed actions and the age and experience of the observer.
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