Neuroimaging in (mild) cognitive impairment

The main aim of this thesis was to extend our understanding of mild cognitive impairment, an age-related decline in cognition that is more severe than expected for age, but not severe enough to warrant a diagnosis of dementia. In Chapters 2 and 3 we report the results of two studies where we investigated how brain structure and function relate to cognition in people with mild cognitive impairment. In Chapter 2 we found that the speed with which people with mild cognitive impairment processed information was related to the integrity of the white matter across the brain. In Chapter 3 we found that compared to healthy older adults, people with mild cognitive impairment had lower performance and brain activity during a planning task. In Chapter 4 we synthesized the findings of studies that investigated alpha oscillations in mild cognitive impairment, and found that power and synchronization of alpha oscillations decrease from healthy ageing to mild cognitive impairment to dementia. In Chapter 5 we investigated whether transcranial alternating current stimulation, a form of non-invasive electric brain stimulation, can be used to synchronize oscillations and improve processing speed in people with cognitive impairment due to multiple sclerosis. We did not find evidence that the stimulation led to improvements in synchronization or cognition, but there was some evidence to suggest that improvement in processing speed may depend on the integrity of white matter.