Color discrimination deficits in Parkinson's disease are related to cognitive impairment and white‐matter alterations

Abstract

Color discrimination deficit is a common nonmotor manifestation of Parkinson's disease (PD). However, the pathophysiology of this dysfunction remains poorly understood. Although retinal structure changes found in PD have been suggested to cause color discrimination deficits, the impact of cognitive impairment and cortical alterations remains to be determined. We investigated the contribution of cognitive impairment to color discrimination deficits in PD and correlated them with cortical anomalies. Sixty-six PD patients without dementia and 20 healthy controls performed the Farnsworth-Munsell 100 hue test and underwent a comprehensive neuropsychological assessment for mild cognitive impairment diagnosis. In a subgroup of 26 PD patients, we also used high-definition neuroanatomical magnetic resonance imaging for cortical thickness and diffusion tensor analysis. PD patients with mild cognitive impairment performed poorly on the Farnsworth-Munsell 100 hue test compared with PD patients without mild cognitive impairment and controls. In PD patients, performance on the Farnsworth-Munsell 100 hue test was correlated with measures of visuospatial abilities and executive functions. Neuroimaging analysis revealed higher mean and radial diffusivity values in right posterior white-matter structures that correlated with poor performance on the Farnsworth-Munsell 100 hue test. No cortical thickness correlation reached significance. This study showed that cognitive impairment makes a major contribution to the color discrimination deficits reported in PD. Thus, performance on the Farnsworth-Munsell 100 hue test may reflect cognitive impairment more than color discrimination deficits in PD. Poor performance on the Farnsworth-Munsell 100 hue test was also associated with white-matter alterations in right posterior brain regions.

Stereopsis impairment is associated with decreased color perception and worse motor performance in Parkinson’s disease

“…These results are in line with those reported in previous studies showing that blue cone deficiency is predominant in older PD patients [20] and that nonmotor impairments, including color discrimination deficits, are highly associated with PD [2,4]. Interestingly, our study demonstrates that color discrimination deficits were independent of the progression of PD, suggesting that the factor of age might be the sole independent risk factor to consider in determining the severity of retinal impairment in PD patients [16].…”

Electroencephalogram slowing in rapid eye movement sleep behavior disorder is associated with mild cognitive impairment

“…Moreover, the absence of these associations in the controls suggests that the associations between EEG measures and cognitive performance found in our study are specific to iRBD patients. Poor performance on the Trail Making Test Part B and the Block Design subtest has been reported in DLB and PD with cognitive impairment [6,29,30]. This observation suggests that both EEG slowing and impaired performance on these tasks could be early manifestations of cognitive decline in iRBD patients.…”

Non-motor features of Parkinson’s disease in a nested case–control study of US men

“…In a cohort of 62 patients with RBD, the 21 patients who developed PD during the 5-year follow-up period had significantly worse colour discrimination at baseline compared with those who remained PD free, with only minimal worsening closer to the time of disease onset 30. However, impaired colour discrimination in PD is also associated with cognitive impairment and posterior white-matter alterations 31. Performance on the Farnsworth-Munsell 100 hue test may therefore at least partly reflect cognitive impairment, which itself appears to be a sign of prodromal PD 31 32…”