Computer-based dual-task and visuospatial processing in Parkinson's disease

The present study aims to measure the efficiency and symmetry of visuo-spatial functions in Parkinson’s Disease (PD) through a multitasking paradigm. Indeed, PD is a condition that affects not only motor functions, but also visuospatial and attentive ones. Such deficits have been extensively explored alone, however this paper aims to investigate the connection between the asymmetry in motor symptoms and a possible reflected asymmetry in visuo-spatial functions. The efficiency and symmetry of visuo-spatial functions can be assessed using traditional paper-and-pencil neuropsychological tests, although these have limited sensitivity for detecting mild visuospatial deficits. For this reason, the present study will also be using a computerised dual-task assessing visual-spatial processing. This task results more sensitive to detect milder forms of visuospatial asymmetries and is designed to enhance attentional load and decrease compensatory strategies. The performance in such tasks is examined with a focus on the effects of task difficulty and spatial configuration of the stimuli on accuracy and error pattern. Both for the paper-and-pencil and the computerised tasks, the stimuli were presented either in the left or the right side of PD patients’ space. The location of the stimuli were then coded as ipsilateral or contralateral to the opposite side of Parkinson’s Disease motor symptoms in order to reflect the underlying hemispheric pathology. Spefically, in the computerised task, participants performed a primary detection task requiring them to report the location of lateralised dots appearing on the screen. In the dual-task conditions they must also perform a secondary visual or auditory task, that is, to recognize a geometric figure or sound respectively presented immediately after the dots. In the single-task condition, participants only perform the primary detection task ignoring the figures and the sounds. The study sample comprises 16 patients with Parkinson’s disease, with years of illness that range from 1 to 15, who were participating in cognitive stimulation therapy at “Parkinson Cafe” in Arzignano (VI). Among the patients 10 report having left onset of motor symptoms and 6 a right one. As the control group, data from 16 healthy older individuals was collected as well. Results reveal condition-dependent spatial asymmetries, especially under dual-task conditions, for Parkinson’s patients. Such asymmetries result more evident in patients during the first years of their diagnosis, consistently with the fact that PD start as a unilateral pathology and then progresses as a bilateral one. In addition, PD patients showed higher accuracy in the single task conditions compared to the dual-task conditions. They made more errors when the dots were presented bilaterally. Further analysis indicates that bilateral stimulation is linked to capacity limitations when processing spatial competing stimuli; in those trials, PD patients tend to report only one side of the space being stimulated, in line with findings that show that Parkinson’s patients' cognitive deficits increase under high attentional load. For the control group, no asymmetry in visual-spatial functions under conditions of multitasking emerge and the group shows high accuracy even under conditions of cognitive load. Clinical implications of this study suggest that Parkinson’s patients in the early stage of their diagnosis tend to show more evident visual-spatial processing asymmetries, whereas those with more years of illness tend to be more sensitive to cognitive load overall. The use of this assessment tool is therefore valuable for achieving a more accurate neuropsychological evaluation of PD patients, especially at different times of their diagnosis. Consequently, a more precise clinical characterisation allows for the personalisation of rehabilitation programs and cognitive stimulation activities, according to each patient’s needs.