Patients with Alzheimer's disease have an impairment of inhibitory control for reasons that are currently unclear. Using an eye-tracking task (the gapoverlap paradigm), we examined whether the uncorrected errors relate to the task of attentional disengagement in preparation for action. Alternatively, the difficulty in correcting for errors may be caused by the working memory representation of the task. A major aim of this study was to distinguish between the effects of healthy aging and neurodegenerative disease on the voluntary control of saccadic eye movements. Using the antisaccade task (AST) and pro-saccade task (PST) with the 'gap' and 'overlap' procedures, we obtained detailed eye-tracking measures in patients, with 18 patients with probable Alzheimer's disease, 25 patients with Parkinson's disease and 17 healthy young and 18 old participants. Uncorrected errors in the AST were selectively increased in Alzheimer's disease, but not in Parkinson's disease compared to the control groups. These uncorrected errors were strongly correlated with spatial working memory. There was an increase in the saccade reaction times to targets that were presented simultaneously with the fixation stimulus, compared to the removal of fixation. This 'gap' effect (i.e. overlap-gap) saccade reaction time was elevated in the older groups compared to young group, which yielded a strong effect of aging and no specific effect of neurodegenerative disease. Healthy aging, rather than neurodegenerative disease, accounted for the increase in the saccade reaction times to the target that are presented simultaneously with a fixation stimulus. These results suggest that the impairment of inhibitory control in the AST may provide a convenient and putative mark of working memory dysfunction in Alzheimer's disease.
The relationship between social support and psychological outcome in people with PD is complex. Furthermore, the complexity of this relationship should be addressed in any therapeutic attempts to relieve psychological distress and promote happiness.
The contribution of a multi-disciplinary approach is crucial given the many variables which affect HrQoL; in particular, significant overall improvements on HrQoL are unlikely if only physical rehabilitation is offered. Rehabilitation is likely to be beneficial in terms of HrQoL only if it is planned and delivered holistically. Implications for Rehabilitation Interventions to improve physical function may have only limited impact on quality of life and might be limited to more physical HrQoL domains. Psychological interventions have the potential to improve quality of life over a wider range of both emotional and physical HrQoL domains. Clinician-measured level of functioning does not necessarily translate into patient-perceived levels of functional ability and relatively small objective decreases in ability can be appraised much more significantly disabling by people with PD.
Illness beliefs are important predictors of psychological outcome in people with chronic illness and evidence suggests these could also be significant in furthering our understanding of psychological functioning in people with Parkinson's disease. Illness beliefs are specific, dynamic representations of an illness and cover dimensions such as cause, identity, consequences and controllability. Eighty-one people with Parkinson's disease completed a series of questionnaires to provide demographic, clinical and psychosocial data, which were then used to assess the relative impact of illness beliefs on their psychological functioning. Psychological functioning was assessed by measuring levels of depression, anxiety, stress, positive affect and emotional well-being. Hierarchical block regression indicated that illness beliefs were important independent predictors across some but not all outcomes and the results emphasised the importance of testing new predictors against more established predictors of outcome such as physical functioning and self-esteem. The illness beliefs most important in psychological outcome in people with PD were causal beliefs (particularly in psychosocial causes) and illness coherence (the level of understanding of the illness). The therapeutic potential of psychosocial variables was discussed given that these can be modified during therapy and this change can positively influence psychological outcome.
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