Revealing the differences between normal and pathological ageing using functional magnetic resonance imaging (fMRI)

The aim of the present study was to use fMRI to examine the brain activation patterns found in normal and pathological ageing on specific cognitive tasks. The cognitive paradigms that were chosen, consisted of an n-back working memory task and a semantic memory and processing task. Manipulation of the n-back task enabled vigilance and working memory load to be investigated. Patients with Alzheimer's Disease (AD) and individuals with amnestic Mild Cognitive Impairment (MCI) were compared to normal elderly and young controls. The experiments showed that the patterns of brain activation found in normal and pathological ageing do not appear to fall along the same continuum. When comparing the elderly group to the young group, areas of under-activation could be seen, in addition to other regions of activation which were thought to be due to compensation. The comparison of the normal to the pathological groups revealed distinct differences in the levels and locations of the significant activations. On the vigilance and working memory tasks, the behavioural scores and reaction times of the pathological groups were not significantly different from the normal elderly, yet substantial differences could be identified in the brain activation patterns. The semantic memory task, contrary to expectation, revealed a significant difference in behavioural performance between the young group and the elderly group. Both the reaction times and the performance scores of the AD group were significantly different compared to the elderly, however. Significant differences also occurred in the brain activation patterns of both pathological groups (AD and MCI) compared to the elderly. The differences that were present between the normal and pathological groups on each of the tasks, suggest that sensitive cognitive fMRI paradigms might be very useful in resolving diagnostic ambiguity in people at increased risk of developing AD

Brain Activation Patterns Characterizing Different Phases of Motor Action: Execution, Choice and Ideation.

Motor behaviour is controlled by a large set of interacting neural structures, subserving the different components involved in hierarchical motor processes. Few studies have investigated the neural substrate of higher-order motor ideation, i.e. the mental operation of conceiving a movement. The aim of this functional magnetic resonance imaging study was to segregate the neural structures involved in motor ideation from those involved in movement choice and execution. An index finger movement paradigm was adopted, including three different conditions: performing a pre-specified movement, choosing and executing a movement and ideating a movement of choice. The tasks involved either the right or left hand, in separate runs. Neuroimaging results were obtained by comparing the different experimental conditions and computing conjunction maps of the right and left hands for each contrast. Pre-specified movement execution was supported by bilateral fronto-parietal motor regions, the cerebellum and putamen. Choosing and executing finger movement involved mainly left fronto-temporal areas and the anterior cingulate. Motor ideation activated almost exclusively left hemisphere regions, including the inferior, middle and superior frontal regions, middle temporal and middle occipital gyri. These findings show that motor ideation is controlled by a cortical network mainly involved in abstract thinking, cognitive and motor control, semantic and visual imagery processes