The locus coeruleus (LC) is a nucleus in the brainstem, and projects widely to the forebrain where it releases norepinephrine (NE). Catecholamines such as NE do not have a unitary effect on their... Show moreThe locus coeruleus (LC) is a nucleus in the brainstem, and projects widely to the forebrain where it releases norepinephrine (NE). Catecholamines such as NE do not have a unitary effect on their target neurons, but instead influence the function of other neurotransmitters, a process that is known known as neuromodulation. By virtue of the LC’s wide projection profile and the neuromodulatory properties of NE, the LC-NE system profoundly influences neural firing characteristics and associated cognitive processes. The work presented in this thesis addresses the role of the LC-NE system in various aspects of human cognition, and the modulation of brain state. Show less
The overriding aim of my thesis was to study the relationship between blood pressure (BP) and cognitive and psychological functioning in older persons. Observational studies indicate that lower BP... Show moreThe overriding aim of my thesis was to study the relationship between blood pressure (BP) and cognitive and psychological functioning in older persons. Observational studies indicate that lower BP increases risk for cognitive decline in older persons. Older persons are at risk for impaired cerebral autoregulation, and lowering their BP may compromise cerebral blood flow and cognitive function. Contradictory to our hypothesis, the Discontinuation of Antihypertensive Treatment in Elderly people (DANTE) Study Leiden, a community-based randomized clinical trial in older persons (aged ≥75 years) with mild cognitive deficits, did not show that discontinuation of antihypertensive treatment improves cognitive functioning. The lack of the effect of this trial may be due to the unintentional inclusion of persons with a relatively intact cerebral autoregulation. Furthermore, we demonstrated that older persons with mild cognitive deficits and with orthostatic hypotension, who discontinued all their antihypertensive medication had an increased probability of being free from orthostatic hypotension 4 months later, compared to persons who continued their medication. Finally, in the DANTE MRI sub study, the relationship between BP and both conventional features of small vessel disease (SVD) and microstructural damage was explored, as well as the relation between microstructural damage and cognitive and psychological dysfunction. Show less
With increasing age the prevalence of hypertension rises. High blood pressure at midlife is associated with cognitive impairment. Nevertheless, in older persons a lower rather than a higher... Show more With increasing age the prevalence of hypertension rises. High blood pressure at midlife is associated with cognitive impairment. Nevertheless, in older persons a lower rather than a higher blood pressure is associated with incident dementia. The main purpose of the work in this thesis was to explore the role of blood pressure in relation to cerebral structure, neurocognitive functioning and hemodynamics of the brain in old age. Therefore, we sought to determine whether discontinuation of antihypertensive therapy in persons aged 75 years and over with mild cognitive deficits and using antihypertensive medication (the Discontinuation of ANtihypertensive Treatment in Elderly people [DANTE] population) would improve their cognitive and psychological functioning. The assumption was that the increase in blood pressure after the discontinuation of antihypertensives would lead to a direct increase in cerebral blood flow and, as a consequence, to an improvement in cerebral functioning. An additional objective was to investigate possible underlying mechanisms in the relation between blood pressure and neurocognitive functioning. To enable this, brain MRI was used to determine whether (lower) blood pressure was associated with (micro)structural damage, cerebral small vessel disease and blood flow in the brain, and also whether the presence of cerebral (micro)structural damage was related to neurocognitive functioning. Show less
In this dissertation, we aimed to identify the influence of cortisol exposure and cognitive performance on the clinical course of bipolar disorder. Data regarding sociodemographics, disease... Show moreIn this dissertation, we aimed to identify the influence of cortisol exposure and cognitive performance on the clinical course of bipolar disorder. Data regarding sociodemographics, disease characteristics and genetic analysis of the cortisol receptors, were collected of 366 patients with bipolar disorder (BD). Part of this cohort participated in the longitudinal study, including the Test for Attentional Performance, prospectively registration of mood, and the collection of hair samples to assess long term cortisol. The main findings are as follows: 1) Several Glucocorticoid Receptor (GR) gene polymorphisms, in particular the 9β polymorphism (rs6198), relate with clinical characteristics of BD. The most important relations were with the number of (hypo)manic episodes, and second, with seasonal patterns of mood episodes, especially hypomania. 2) Higher long term cortisol exposure is associated with more psychiatric co morbidity in BD patients., and with an older age at onset, indicating a subgroup of patients. 3) Medication as potential confounder on cognitive performance, appeared to relate with the type (mainly antipsychotics) and the number of different types of medication used. Summarizing, cortisol exposure is associated with several clinically relevant phenomena defining course of BD and give insight in possible subgroups of patients with higher cortisol exposure. Show less
This thesis explores cognitive vulnerability to depression and the interplay between genetic and environmental influences. Cognitive vulnerability to depression is characterized by negative... Show moreThis thesis explores cognitive vulnerability to depression and the interplay between genetic and environmental influences. Cognitive vulnerability to depression is characterized by negative patterns of information processing. One aspect is cognitive reactivity - the tendency to respond with maladaptive thoughts when mood is challenged. Vulnerable individuals also show negative cognitive biases in emotion perception and attention, and impaired decision-making. How one processes personal and socially relevant information plays an important role in the development and maintenance of depression. The first part of the thesis reports how the interplay between genes and environment affects cognitive reactivity and emotional information processing. We observed that genes and environmental stressors interact to determine a person’s vulnerability to depression or resilience. Cognitive reactivity was also found to be a residual vulnerability factor in individuals with history of suicidal tendencies. The second part of the thesis is comprised of two experimental manipulations on emotional cognition. Effects of omega-3 fatty acid supplementation were examined on mood and cognition of healthy participants and recovered depressed individuals. Omega-3 fatty acids can have selective effects on mood and cognition of individuals, but the pathways through which this happens remain to be investigated. Show less
Early dementias are difficult to distinguish from normal age-related memory decline. In the preclinical stages of Alzheimer’s disease and Huntington’s disease, brain functions are already changing... Show moreEarly dementias are difficult to distinguish from normal age-related memory decline. In the preclinical stages of Alzheimer’s disease and Huntington’s disease, brain functions are already changing, but this is not directly visible from the outside. Many research is aimed at discovering early disease markers. However, research using EEG registration during conventional eyes closed conditions revealed little additional information. The yield of EEG research can be improved by probing the weakest spot, which, in case of dementia, is memory. Karin van der Hiele introduced memory tests during EEG registration and found that early abnormalities in brain functioning can then be observed in Alzheimer’s disease and Huntington’s disease. An interesting finding came to light: the EEG in dementia displays a lot of muscle activity which is normally filtered out. However, the researchers decided not to throw this activity away but to measure it. Interestingly, they found that the amount of muscle activity was related to cognition and to the number of depressive complaints. It may pay to keep an open mind regarding the nature of the parameter to be measured. Show less
