Ocular and visual disorders has been reported in Parkinson’s Disease (PD). BOLD activation was mapped during visual color hue discrimination stimuli in PD (n=10, mean age=59 years, SD=6.8) and healthy control (HC) (n=6, mean age=53.67 years, SD=2.6) participants at 3 T MR scanner. Comparison between the two groups revealed lower activation in secondary visual areas (BA 18/19) and fusiform gyrus (BA 37), more dependence on memory areas and increased cluster size in PD (in comparison with HC) suggesting impairment in colour hue processing.
Introduction
Ocular (affecting the eyes or eyelids) and visual disorders (including central visual perception) are associated with Parkinson’s Disease (PD), which include dry eye disease, oculomotor disturbances and diplopia, Glaucoma and glaucoma simulating optic neuropathy, diminished contrast sensitivity and colour discrimination, visuospatial and visuoperceptual impairments, visual hallucinations, etc.1,2 Colour vision processing is performed by a variety of cortical structures, including primary and secondary visual areas and regions of the inferior temporal cortex. The pathophysiology of the dysfunction has been associated with dopaminergic deficiency in retina and dysfunctional cortical areas, and remains poorly understood. This study focuses on colour discrimination ability in PD patients.3Methodology
After the ethics approval, 10 PD patients (8M/2F, mean age=59 years, SD=6.8) and 6 healthy controls (HC) (4M/2F, mean age=53.67 years, SD=2.6) were recruited for the study. Colour discrimination task with four hues of a colour in a slide displayed for 4 s (followed by 2 s of blank screen for removal of habituation), and 30 stimuli in a session, with 3 blocks of active and baseline (black screen) was developed using SuperLab software (ver 4.5, Cedrus Inc, USA) and was presented to the participants using MR compatible LCD goggles visual system (NNL, Norway) mounted over the 32 channel head coil in 3T MRI (Achieva, Philips). EPI sequence (TR/TE=2000/30ms, slices=40; gap: 0, slice thickness=3.6 mm, 137 dynamics) was used to observe the BOLD effects. Data was processed using SPM12. One sample t-test (p<0.001(uncorrected), k=10) for within group activation and two sample t-test (p<0.005(uncorrected), k=5) was used to see the differential activation between PD and HC groups.Results
On group analysis, activation in the control group was observed in primary and secondary visual cortex (Brodmann area (BA) 17/18), inferior temporal cortex (BA 37) and middle frontal gyrus (BA 6). In PD group, activation was seen in primary visual cortex (BA 17), precuneus (BA 7) and frontal regions (BA 9, 6, 32, 47). On comparing HC versus PD, no higher activation region was found. On comparing PD with HC, right hemispheric limbic lobe (BA 28) and temporal lobe (BA 21) were activated.1) Armstrong RA. Oculo-Visual Dysfunction in Parkinson's Disease. J Parkinsons Dis. 2015; 5:715-26.
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