Neural markers of category-based selective working memory in aging.

Working memory (WM) is essential for normal cognitive function, but shows marked decline in aging. The importance of selective attention in guiding WM performance is increasingly recognized. Studies so far are inconclusive about the ability to use selective attention during WM in aging. To investigate the neural mechanisms supporting selective attention in WM in aging, we tested a large group of older adults using functional magnetic resonance imaging whilst they performed a category-based (faces/houses) selective-WM task. Older adults were able to use attention to encode targets and suppress distractors to reach high levels of task performance. A subsequent, surprise recognition-memory task showed strong consequences of selective attention. Attended items in the relevant category were recognized significantly better than items in the ignored category. Neural measures also showed reliable markers of selective attention during WM. Purported control regions including the dorsolateral and inferior prefrontal and anterior cingulate cortex were reliably recruited for attention to both categories. Activation levels in category-sensitive visual cortex showed reliable modulation according to attentional demands, and positively correlated with subsequent memory measures of attention and WM span. Psychophysiological interaction analyses showed that activity in category-sensitive areas were coupled with non-sensory cortex known to be involved in cognitive control and memory processing, including regions in the prefrontal cortex and hippocampus. In summary, we found that older adults were able to recruit a network of brain regions involved in top-down attention during selective WM, and individual differences in attentional control corresponded to the degree of attention-related modulation in the brain.

White-coat hypertension/effect is associated with higher arterial stiffness and stroke events.

OBJECTIVES: The risk profile of white-coat hypertension/effect (WCH/E) remains unclear. This study aimed to investigate the relationship between WCH/E, markers of cardiovascular risk and cerebrovascular events. METHODS: This is a sub-group analysis of The Arterial Stiffness In lacunar Stroke and Transient ischemic attack (ASIST) study, which recruited 96 patients aged at least 40 years old with a diagnosis of transient ischemic attack or lacunar stroke in the preceding 14 days. Thirty-two patients with target blood pressure (clinic blood pressure <140/90 mmHg and daytime ambulatory blood pressure <135/85 mmHg) and 30 patients with WCH/E (clinic blood pressure ≥140/90 mmHg and daytime ambulatory blood pressure <135/85 mmHg) were included in the analysis. RESULTS: Patients with WCH/E were older and had a higher BMI. Central SBP (145 ±â€Š13 vs. 118 ±â€Š8 mmHg, P < 0.001) and DBP (82 ±â€Š8 vs. 76 ±â€Š7 mmHg, P = 0.004) were higher in those with WCH/E. They also had higher arterial stiffness measured by carotid-femoral pulse wave velocity (11.9 ±â€Š3.0 vs. 9.6 ±â€Š2.3 m/s, P = 0.002) and cardio-ankle vascular index (10.3 ±â€Š1.3 vs. 9.4 ±â€Š1.7, P = 0.027). Regression analysis showed an independent relationship between WCH/E and both measures of arterial stiffness. Lacunar strokes were more prevalent in those with WCH/E (47 vs. 22%, P = 0.039) and individuals in this group were more likely to have had a lacunar stroke than a transient ischemic attack (odds ratio 9.6, 95% CI 1.5-62.6, P = 0.02). CONCLUSION: In this cohort of patients with lacunar stroke and transient ischemic attack, WCH/E was associated with elevated markers of cardiovascular risk and a higher prevalence of lacunar stroke. These results suggest that WCH/E is associated with adverse cardiovascular risk.

C-Reactive Protein Predicts Further Ischemic Events in Patients With Transient Ischemic Attack or Lacunar Stroke.

Patients who have experienced a first cerebral ischemic event are at increased risk of recurrent stroke. There is strong evidence that low-level inflammation as measured by high sensitivity C-reactive protein (hs-CRP) is a predictor of further ischemic events. Other mechanisms implicated in the pathogenesis of stroke may play a role in determining the risk of secondary events, including oxidative stress and the adaptive response to it and activation of neuroprotective pathways by hypoxia, for instance through induction of erythropoietin (EPO). This study investigated the association of the levels of CRP, peroxiredoxin 1 (PRDX1, an indicator of the physiological response to oxidative stress) and EPO (a neuroprotective factor produced in response to hypoxia) with the risk of a second ischemic event. Eighty patients with a diagnosis of lacunar stroke or transient ischemic attack (TIA) were included in the study and a blood sample was collected within 14 days from the initial event. Hs-CRP, PRDX1, and EPO were measured by ELISA. Further ischemic events were recorded with a mean follow-up of 42 months (min 24, max 64). Multivariate analysis showed that only CRP was an independent predictor of further events with an observed risk (OR) of 1.14 (P = 0.034, 95% CI 1.01-1.29). No association was observed with the levels of PRDX1 or EPO. A receiver operating curve (ROC) determined a cut-off CRP level of 3.25 µg/ml, with a 46% sensitivity and 81% specificity. Low-level inflammation as detected by hs-CRP is an independent predictor of recurrent cerebrovascular ischemic events.

Imagining a brighter future: the effect of positive imagery training on mood, prospective mental imagery and emotional bias in older adults.

Positive affect and optimism play an important role in healthy ageing and are associated with improved physical and cognitive health outcomes. This study investigated whether it is possible to boost positive affect and associated positive biases in this age group using cognitive training. The effect of computerised imagery-based cognitive bias modification on positive affect, vividness of positive prospective imagery and interpretation biases in older adults was measured. 77 older adults received 4 weeks (12 sessions) of imagery cognitive bias modification or a control condition. They were assessed at baseline, post-training and at a one-month follow-up. Both groups reported decreased negative affect and trait anxiety, and increased optimism across the three assessments. Imagery cognitive bias modification significantly increased the vividness of positive prospective imagery post-training, compared with the control training. Contrary to our hypothesis, there was no difference between the training groups in negative interpretation bias. This is a useful demonstration that it is possible to successfully engage older adults in computer-based cognitive training and to enhance the vividness of positive imagery about the future in this group. Future studies are needed to assess the longer-term consequences of such training and the impact on affect and wellbeing in more vulnerable groups.

Structural and functional bases of visuospatial associative memory in older adults.

Impaired visuospatial associative memory may be one of the earliest changes predicting cognitive impairment and Alzheimer's disease. We explored the relationship between performance on a visuospatial associative memory task (the Placing Test) and brain structure and function in cognitively healthy older adults. First, we performed a voxel-based morphometry correlational analysis on structural magnetic resonance imaging (MRI) data from 144 healthy older adults with their scores on the Placing Test. Second, we carried out a functional MRI study on another group of 28 healthy older adults who performed a similar task during functional MRI. Decreased performance on the Placing Test was associated with increased atrophy in medial-temporal regions. Functional activation of the same regions-controlling for the effect of atrophy-occurred during successful performance of the same task. The colocalization of structural and functional MRI correspondents of visuospatial associative test performance within medial-temporal regions validates multimodal imaging in describing behaviorally relevant variability in the aging brain and suggests that the Placing Test has the potential for detecting early cognitive changes occurring in preclinical phases of Alzheimer's disease.

Neuroanatomy of impaired self-awareness in Alzheimer's disease and mild cognitive impairment.

INTRODUCTION: Patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI) may be unaware of their cognitive impairment. The neuroanatomical mechanisms underlying this symptom, termed anosognosia or impaired self-awareness, are still poorly understood. In the present study we aimed to explore the functional correlates of self-awareness in patients with MCI and AD. METHODS: Fifty-one participants (17 healthy elderly, 17 patients with MCI, and 17 patients with AD), each accompanied by a study partner, took part in a functional magnetic resonance imaging (fMRI) study, in which they were presented with questions regarding themselves (Self condition) or their study partner (Other condition). The study partner was asked to complete a paper questionnaire answering the same questions so the responses of participant and study partner could be compared and "discrepancy" scores calculated for each of the 2 conditions (Self and Other). RESULTS: Behavioural results showed that AD patients had significantly higher "Self discrepancy scores" than controls and MCI patients, whereas there were no significant differences between groups for "Other discrepancy scores". Imaging results showed a significant group-by-condition interaction in brain activation in medial prefrontal and anterior temporal regions, with AD patients showing significantly decreased activation in these regions only for the Self condition. There were no significant differences between Self and Other conditions in either control or MCI groups, suggesting that, in these groups, Self- and Other-appraisal share similar neuroanatomical substrates. CONCLUSIONS: Decreased functional activation of medial prefrontal and anterior temporal cortices is associated with impaired self-awareness in AD patients. This dysfunction, which is specific for Self- but not for Other-appraisal, may be a contributing factor to anosognosia in AD.

Resting functional connectivity reveals residual functional activity in Alzheimer's disease.

BACKGROUND: Functional magnetic resonance imaging (fMRI) has great potential for measuring mechanisms of functional changes in Alzheimer's disease (AD) and mild cognitive impairment, but task fMRI studies have produced conflicting results, partly due to failure to account for underlying morphological changes and to variations in patients' ability to perform the tasks. Resting fMRI has potential for assessing brain function independently from a task, but greater understanding of how networks of resting functional connectivity relate to the functioning of the brain is needed. We combined resting fMRI and task fMRI to examine the correspondence between these methods in individuals with cognitive impairment. METHODS: Eighty elderly (25 control subjects, 25 mild cognitive impairment, 30 AD) underwent a combined multimodal magnetic resonance imaging protocol including task fMRI and resting fMRI. Task fMRI data were acquired during the execution of a memory paradigm designed to account for differences in task performance. Structural and physiological confounds were modeled for both fMRI modalities. RESULTS: Successful recognition was associated with increased task fMRI activation in lateral prefrontal regions in AD relative to control subjects; this overlapped with increased resting fMRI functional connectivity in the same regions. CONCLUSIONS: Our results show that task fMRI and resting fMRI are sensitive markers of residual ability over the known changes in brain morphology and cognition occurring in AD and suggest that resting fMRI has a potential to measure the effect of new treatments.