Cognitive function by brain event-related potentials (ERP) in elderly with borderline isolated systolic hypertension (BISH)

Evaluation of Event-Related Potentials in Somatic Diseases - Systematic Review

Many somatic illnesses (e.g. hypertension, diabetes, pulmonary and cardiac diseases, hepatitis C, kidney and heart failure, HIV infection, Sjogren's disease) may impact central nervous system functions resulting in emotional, sensory, cognitive or even personality impairments. Event-related potential (ERP) methodology allows for monitoring neurocognitive processes and thus can provide a valuable window into these cognitive processes that are influenced, or brought about, by somatic disorders. The current review aims to present published studies on the relationships between somatic illness and brain function as assessed with ERP methodology, with the goal to discuss where this field of study is right now and suggest future directions.

Assessment of Cognition in Hypertensives and Normotensives: A Comparative P300 Study

Background: Hypertension is an established risk factor for dementia, and the prevalence of hypertension and dementia is rising. Current tests to diagnose cognitive dysfunction at an early stage lack sensitivity and specificity. Recently event-related potentials (ERPs) have gained much attention in diagnosing cognitive dysfunction and are independent of the education status of the subject. This study was done to find any cognitive deficits in the hypertensive population with electrophysiological evidence, which might open the doors for the need to screen the population at an earlier stage so that the population can be prevented from dementia.

Methods: Some 31 middle-aged (18-65 years) hypertensives were compared with 31 age, sex, education, and handedness matched normotensives about cognition by neuropsychometric test battery including Hindi Mini-mental Status Examination (HMSE), Hindi Montreal Cognitive Assessment (MoCA), choice reaction time (CRT), and auditory event-related potentials.

Results: Hypertensives and normotensives differed significantly concerning P300 potentials’ latency (Fz and Cz P300 latencies: p-value: 0.001), and this change was correlated well with the duration of diastolic blood pressure (BP) (r-value: 0.670). The remaining tests, HMSE, Hindi MoCA, and CRT, were dependent on the education status of the patient.

Conclusions: The effect of hypertension on cognitive impairment is evident and can be proved early in its pre-clinical stage using ERPs. Early identification can help in specifying high-risk individuals. ERPs have great potential in screening and diagnosing and can also help in assessing cognition as a reliable tool to show the effect of treatments/interventions on cognitive defects.

Cognitive and neuroimaging markers for preclinical vascular cognitive impairment

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Explores the cognitive correlates of midlife risk factors of pre-clinical vascular cognitive impairment.

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Midlife cardiovascular risks associated with reduces neural integrity in parietal to anterior structures and may identify at-risk individuals.

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Novel experimental investigation testing fronto-parietal structures is required to increase specificity and sensitivity to pre-clinical VCI and inform clinical testing and diagnostic pathways of at-risk individuals.

Detection of incipient cognitive impairment and dementia pathophysiology is critical to identify preclinical populations and target potentially disease modifying interventions towards them. There are currently concerted efforts for such detection for Alzheimer's disease (AD). By contrast, the examination of cognitive markers and their relationship to biomarkers for Vascular Cognitive Impairment (VCI) is far less established, despite VCI being highly prevalent and often concomitantly presenting with AD. Critically, vascular risk factors are currently associated with the most viable treatment options via pharmacological and non-pharmacological intervention, hence early identification of vascular factors have important implications for modifying dementia disease trajectories. The aim of this review is to examine the current evidence of cognitive marker correlates to VCI pathology. We begin by examining midlife risk factors that predict VCI. Next, discuss preclinical cognitive hallmarks of VCI informed by insights from neuropsychological assessment, network connectivity and ERP/EEG experimental findings. Finally, we discuss limitations of current cognitive assessments and the need for future cognitive test development to inform diagnostic assessment. As well as, intervention outcome measures for preclinical VCI. In turn, these tests will inform earlier detection of vascular changes and allow implementation of disease intervention approaches.

Age Differences in Memory-Based Task Switching With and Without Cues

The study investigated the neuronal mechanisms of age-related changes in mixing costs during memory-based task switching with two levels of working memory (WM) load. Forty-eight healthy younger and 45 healthy older participants performed a memory based (high WM load) and a memory plus cue based (low WM load) switching task while event-related brain potentials (ERPs) were registered. Older adults revealed larger mixing costs in both reaction time (RT) and accuracy at higher WM loads than younger adults. The presence of explicit cues substantially reduced age differences in mixing costs for accuracy but not for RT. Similarly, no age differences regarding local switch costs were found at lower WM load. Surprisingly, larger RT local costs in younger adults than in older adults were found in the memory-based block. The CNV was reduced under high WM load and positively correlated with accuracy mixing costs in older adults. The target-locked occipital N1 and fronto-central P2 were larger in older adults relative to younger adults irrespective of WM load. The P2 latency reflected the pattern of switch costs observed in behavioral data. Moreover, P2 latency positively correlated with RT mixing costs in older adults. Elderly also showed a delayed N2 and a delayed and reduced P3b. The results suggest that age-related differences in mixing costs may be partially due to a less efficient task preparation and task set maintenance (CNV) in elderly. However, elderly attempted to compensate for these deficits by permanent activation of mechanisms relating to stimulus encoding (N1) and task-set retrieval (P2). Finally, the delayed fronto-central N2 as well as the delayed and reduced parietal P3b strongly suggest delays of response selection and working memory updating in elderly due to an increase in selection threshold or in response selection variability constituting the performance decline.

Impairment in preattentive processing among patients with hypertension revealed by visual mismatch negativity

Objective. Patients with hypertension show deficits in cognitive function. However, the neural mechanisms underlying the preattentive information processing in hypertensive patients are poorly understood. We seek to investigate whether hypertensive patients have impairments in preattentive information processing. Methods. We compared visual mismatch negativity (vMMN) between 15 hypertensive patients and 15 age-matched healthy controls, which was elicited by the change of visual duration randomly presented in both peripheral visual fields. In addition, the global cognitive function for all participants was assessed with Mini-Mental State Examination (MMSE). Results. The vMMN in deviant-standard comparison was observed at occipital-temporal regions. Compared with normal healthy controls, the amplitude of vMMN was significantly decreased in hypertensive patients (P < 0.05). Meanwhile, the vMMN peak latency was delayed in the hypertensive group (P < 0.05). However, the MMSE scores of patients with hypertension were not significantly different from those of controls (P > 0.05), and there was no significant correlation between the mean amplitude of vMMN and SBP, DBP, and MMSE in hypertensive individuals, respectively. Conclusions. These data indicate dysfunction of automatically change detection processing in patients with hypertension. Moreover, the changes of vMMN provide a more objective and reliable assessment for cognitive impairment in hypertensive patients.

Low ambulatory blood pressure is associated with lower cognitive function in healthy elderly men

INTRODUCTION

Low blood pressure (BP) has been found to be associated with cerebrovascular damage in the elderly. Studies of the relation of ambulatory BP to cognitive function in elderly persons aged 80 years or above is lacking, however.

METHODS

Ninety-seven 81-year-old men from the population study 'Men born in 1914' underwent ambulatory BP monitoring and were given a cognitive test battery, 79 subjects completing all six tests. Low ambulatory systolic blood pressure (SBP) was defined as <130 mmHg and low ambulatory diastolic blood pressure (DBP) as <80 mmHg (corresponding in terms of office BP to approximately <140 and <90 mmHg, respectively). Odds ratios (OR) for lower cognitive function were calculated using a forward stepwise logistic regression model, controlling for confounding factors.

RESULTS

Subjects with ambulatory SBP <130 mmHg had higher OR values for daytime (OR 2.6; P=0.037), nighttime (OR 3.6; P=0.032) and 24h (OR 2.6; P=0.038) BP measurements. A lower cognitive function was associated with lower nighttime SBP and DBP levels and lower 24-h mean SBP compared to subjects with higher cognitive function. OR values connected to low nocturnal SBP, had a tendency to be particularly high among subjects on anti-hypertensive drugs (OR 9.1; P=0.067, n.s.).

CONCLUSION

Ambulatory SBP levels <130 mmHg and lower nighttime SBP and DBP were associated with lower cognitive function in healthy elderly men. Further investigation is needed to ascertain the effects of the presently recommended treatment goal of <140 mmHg for office SBP also on elderly over 80 years of age.