Brain Activity In Older Adults Research Articles

Enhanced neural activation with blueberry supplementation in mild cognitive impairment

Objectives: Preclinical studies have shown that blueberry supplementation can improve cognitive performance and neural function in aged animals and have identified associations between anthocyanins and such benefits. Preliminary human trials also suggest cognitive improvement in older adults, although direct evidence of enhancement of brain function has not been demonstrated. In this study, we investigated the effect of blueberry supplementation on regional brain activation in older adults at risk for dementia.Methods: In a randomized, double-blind, placebo-controlled trial we performed pre- and post-intervention functional magnetic resonance imaging during a working memory (WM) task to assess the effect of blueberry supplementation on blood oxygen level-dependent (BOLD) signal in older adults with mild cognitive impairment, a risk condition for dementia.Results: Following daily supplementation for 16 weeks, blueberry-treated participants exhibited increased BOLD activation in the left pre-central gyrus, left middle frontal gyrus, and left inferior parietal lobe during WM load conditions (corrected P < 0.01). There was no clear indication of WM enhancement associated with blueberry supplementation. Diet records indicated no between-group difference in anthocyanin consumption external to the intervention.Discussion: These data demonstrate, for the first time, enhanced neural response during WM challenge in blueberry-treated older adults with cognitive decline and are consistent with prior trials showing neurocognitive benefit with blueberry supplementation in this at-risk population.

Relationships between years of education, regional grey matter volumes, and working memory-related brain activity in healthy older adults.

The aim of this study was to examine the relationships between educational attainment, regional grey matter volume, and functional working memory-related brain activation in older adults. The final sample included 32 healthy older adults with 8 to 22years of education. Structural magnetic resonance imaging (MRI) was used to measure regional volume and functional MRI was used to measure activation associated with performing an n-back task. A positive correlation was found between years of education and cortical grey matter volume in the right medial and middle frontal gyri, in the middle and posterior cingulate gyri, and in the right inferior parietal lobule. The education by age interaction was significant for cortical grey matter volume in the left middle frontal gyrus and in the right medial cingulate gyrus. In this region, the volume loss related to age was larger in the low than high-education group. The education by age interaction was also significant for task-related activity in the left superior, middle and medial frontal gyri due to the fact that activation increased with age in those with higher education. No correlation was found between regions that are structurally related with education and those that are functionally related with education and age. The data suggest a protective effect of education on cortical volume. Furthermore, the brain regions involved in the working memory network are getting more activated with age in those with higher educational attainment.

Physical Activity Is Linked to Greater Moment-To-Moment Variability in Spontaneous Brain Activity in Older Adults.

Higher cardiorespiratory fitness (CRF) and physical activity (PA) in old age are associated with greater brain structural and functional integrity, and higher cognitive functioning. However, it is not known how different aspects of lifestyle such as sedentariness, light PA (LI-PA), or moderate-to-vigorous physical activity (MV-PA) relate to neural activity in aging. In addition, it is not known whether the effects of PA on brain function differ or overlap with those of CRF. Here, we objectively measured CRF as oxygen consumption during a maximal exercise test and measured PA with an accelerometer worn for 7 days in 100 healthy but low active older adults (aged 60–80 years). We modeled the relationships between CRF, PA, and brain functional integrity using multivariate partial least squares analysis. As an index of functional brain integrity we used spontaneous moment-to-moment variability in the blood oxygenation level-dependent signal (SDBOLD), known to be associated with better cognitive functioning in aging. We found that older adults who engaged more in LI-PA and MV-PA had greater SDBOLD in brain regions that play a role in integrating segregated functional domains in the brain and benefit from greater CRF or PA, such as precuneus, hippocampus, medial and lateral prefrontal, and temporal cortices. Our results suggest that engaging in higher intensity PA may have protective effects on neural processing in aging. Finally, we demonstrated that older adults with greater overall WM microstructure were those showing more LI-PA and MV-PA and greater SDBOLD. We conclude that SDBOLD is a promising correlate of functional brain health in aging. Future analyses will evaluate whether SDBOLD is modifiable with interventions aimed to increase PA and CRF in older adults.

The APOE ɛ4 allele affects complexity and functional connectivity of resting brain activity in healthy adults

The apolipoprotein E (APOE) gene is associated with structural and functional brain changes. We have used multiscale entropy (MSE) analysis to detect changes in the complexity of resting blood oxygen level-dependent (BOLD) signals associated with aging and cognitive function. In this study, we further hypothesized that the APOE genotype may affect the complexity of spontaneous BOLD activity in younger and older adults, and such altered complexity may be associated with certain changes in functional connectivity. We conducted a resting-state functional magnetic resonance imaging experiment in a cohort of 100 younger adults (aged 20-39 years; mean 27.2 ± 4.3 years; male/female: 53/47) and 112 older adults (aged 60-79 years; mean 68.4 ± 6.5 years; male/female: 54/58), and applied voxelwise MSE analysis to assess the main effect of APOE genotype on resting-state BOLD complexity and connectivity. Although the main effect of APOE genotype on BOLD complexity was not observed in younger group, we observed that older APOE ɛ4 allele carriers had significant reductions in BOLD complexity in precuneus and posterior cingulate regions, relative to noncarriers. We also observed that reduced BOLD complexity in precuneus and posterior cingulate regions was associated with increased functional connectivity to the superior and inferior frontal gyrus in the older group. These results support the compensatory recruitment hypothesis in older APOE ɛ4 carriers, and confer the impact of the APOE genotype on the temporal dynamics of brain activity in older adults.

Acute moderate exercise enhances compensatory brain activation in older adults

A growing number of reports state that regular exercise enhances brain function in older adults. Recently a functional near-infrared spectroscopy (fNIRS) study revealed that an acute bout of moderate exercise enhanced activation of the left dorsolateral prefrontal cortex (L-DLPFC) associated with Stroop interference in young adults. Whether this acute effect is also applicable to older adults was examined. Sixteen older adults performed a color-word matching Stroop task before and after 10 minutes of exercise on a cycle ergometer at a moderate intensity. Cortical hemodynamics of the prefrontal area was monitored with a fNIRS during the Stroop task. We analyzed Stroop interference (incongruent-neutral) as Stroop performance. Though activation for Stroop interference was found in the bilateral prefrontal area before the acute bout of exercise, activation of the right frontopolar area (R-FPA) was enhanced after exercise. In the majority of participants, this coincided with improved performance reflected in Stroop interference results. Thus, an acute bout of moderate exercise improved Stroop performance in older adults, and this was associated with contralateral compensatory activation.

Training-related brain plasticity in subjects at risk of developing Alzheimer’s disease

Subjects with mild cognitive impairment are at risk of developing Alzheimer's disease. Cognitive stimulation is an emerging intervention in the field of neurology and allied sciences, having already been shown to improve cognition in subjects with mild cognitive impairment. Yet no studies have attempted to unravel the brain mechanisms that support such improvement. This study uses functional magnetic resonance imaging to measure the effect of memory training on brain activation in older adults with mild cognitive impairment and to assess whether it can reverse the brain changes associated with mild cognitive impairment. Brain activation associated with verbal encoding and retrieval was recorded twice prior to training and once after training. In subjects with mild cognitive impairment, increased activation was found after training within a large network that included the frontal, temporal and parietal areas. Healthy controls showed mostly areas of decreased activation following training. Comparison with pre-training indicated that subjects with mild cognitive impairment used a combination of specialized areas; that is, areas activated prior to training and new alternative areas activated following training. However, only activation of the right inferior parietal lobule, a new area of activation, correlated with performance. Furthermore, the differences between the brain activation patterns of subjects with mild cognitive impairment and those of healthy controls were attenuated by training in a number of brain regions. These results indicate that memory training can result in significant neural changes that are measurable with brain imaging. They also show that the brains of people with mild cognitive impairment remain highly plastic.

Functional implications of age differences in motor system connectivity

Older adults show less lateralized task-related brain activity than young adults. One potential mechanism of this increased activation is that age-related degeneration of the corpus callosum (CC) may alter the balance of inhibition between the two hemispheres. To determine whether age differences in interhemispheric connectivity affect functional brain activity in older adults, we used magnetic resonance imaging (MRI) to assess resting functional connectivity and functional activation during a simple motor task. We found that older adults had smaller CC area compared to young adults. Older adults exhibited greater recruitment of ipsilateral primary motor cortex (M1), which was associated with longer reaction times. Additionally, recruitment of ipsilateral M1 in older adults was correlated with reduced resting interhemispheric connectivity and a larger CC. We suggest that reduced interhemispheric connectivity reflects a loss of the ability to inhibit the non-dominant hemisphere during motor task performance for older adults, which has a negative impact on performance.

Executive control function, brain activation and white matter hyperintensities in older adults

ContextOlder adults responding to executive control function (ECF) tasks show greater brain activation on functional MRI (fMRI). It is not clear whether greater fMRI activation indicates a strategy to compensate for underlying brain structural abnormalities while maintaining higher performance. ObjectiveTo identify the patterns of fMRI activation in relationship with ECF performance and with brain structural abnormalities. DesignCross-sectional analysis. Main variables of interest: fMRI activation, accuracy while performing an ECF task (Digit Symbol Substitution Test), and volume of white matter hyperintensities and of total brain atrophy. SettingCohort of community-dwelling older adults. ParticipantsData were obtained on 25 older adults (20 women, 81 years mean age). Outcome measureAccuracy (number of correct response/total number of responses) while performing the Digit Symbol Substitution Test. ResultsGreater accuracy was significantly associated with greater peak fMRI activation, from ECF regions, including left middle frontal gyrus and right posterior parietal cortex. Greater WMH was associated with lower activation within accuracy-related regions. The interaction of accuracy by white matter hyperintensity volume was significant within the left posterior parietal region. Specifically, the correlation of white matter hyperintensity volume with fMRI activation varied as a function of accuracy and it was positive for greater accuracy. Associations with brain atrophy were not significant. ConclusionsRecruitment of additional areas and overall greater brain activation in older adults is associated with higher performance. Posterior parietal activation may be particularly important to maintain higher accuracy in the presence of underlying brain connectivity structural abnormalities.

The ageing brain

The ageing brain

Cognitive Control, Goal Maintenance, and Prefrontal Function in Healthy Aging

Cognitive control impairments in healthy older adults may partly reflect disturbances in the ability to actively maintain goal-relevant information, a function that depends on the engagement of lateral prefrontal cortex (PFC). In 2 functional magnetic resonance imaging studies, healthy young and older adults performed versions of a task in which contextual cues provide goal-relevant information used to bias processing of subsequent ambiguous probes. In Study 1, a blocked design and manipulation of the cue-probe delay interval revealed a generalized pattern of enhanced task-related brain activity in older adults but combined with a specific delay-related reduction of activity in lateral PFC regions. In Study 2, a combined blocked/event-related design revealed enhanced sustained (i.e., across-trial) activity but a reduction in transient trial-related activation in lateral PFC among older adults. Further analyses of within-trial activity dynamics indicated that, within these and other lateral PFC regions, older adults showed reduced activation during the cue and delay period but increased activation at the time of the probe, particularly on high-interference trials. These results are consistent with the hypothesis that age-related impairments in goal maintenance abilities cause a compensatory shift in older adults from a proactive (seen in young adults) to a reactive cognitive control strategy.

Increasing Memory Load Modulates Regional Brain Activity in Older Adults as Measured by fMRI

Several recent studies using functional magnetic resonance imaging (fMRI) during recognition memory tests have suggested that the ability to neuromodulate as a function of cognitive demand may be impaired in older adults due to age-related cell loss and neural volume reduction in memory specific regions. In the current study, older adults (ages 59-77) were tested with fMRI during a delayed-recognition task in which memory load for faces was varied across trials. Activity was greater in amplitude for three- versus one-face stimuli within the superior, middle, and inferior frontal gyri, intraparietal sulcus, and fusiform gyrus. It was concluded that the ability to modulate activity with increasing load is preserved in older adults despite reductions in neural volume.

The effects of encoding task on age-related differences in the functional neuroanatomy of face memory.

Age-related differences in brain activity mediating face recognition were examined using positron emission tomography. Participants encoded faces using a pleasant-unpleasant judgment, a right-left orientation task, and intentional learning. Scans also were obtained during recognition. Both young and old groups showed signficant effects of encoding task on recognition accuracy, but older adults showed reduced accuracy overall. Increased brain activity in older adults was similar to that seen in young adults during conditions associated with deeper processing, but was reduced during the shallow encoding and recognition conditions. Left prefrontal activity was less in older adults during encoding, but greater during recognition. Differential correlations of brain activity and behavior were found that suggest older adults use unique neural systems to facilitate face memory.