Abstract
Purpose: :
Duchenne Muscular Dystrophy (DMD) has been associated with color vision losses and cognitive decrements in independent assessments. We examined the possibility of association between color vision impairment and cognitive deficits in patients with DMD.
Methods: :
20 DMD patients and 20 controls (age range: 11 to 26 years old) were tested. Color vision was evaluated with Trivector protocol of the Cambridge Colour Test (CCT) to measure discrimination thresholds in the protan, deutan and tritan color confusion axes (0.1977, 0.4689 u’v’ coordinates of the CIE 1976 color space). Cognitive performance was assessed using tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB), including immediate atention and working memory examination (Spatial Span, SSP), spatial short term memory (Spatial Recognition Memory, SRM), short and long term visual memory (Pattern Recognition Memory, PRM), and perception and memory for complex stimuli presented simultaneously or after short interval (Delayed Matching to Sample, DMS). The participants had intellectual scores in the normal range according to the Wechsler Intelligence Scale or the Raven Matrices Test.
Results: :
Ten patients (50% of the sample) had color vision deficits: 4 patients had losses in the protan axis and 6 had impairment along protan and deutan axes. The patients with combined losses (protan/deutan) performed significantly worse on SSP forward and on PRM delayed recall (Kruskal-Wallis ANOVA, p<0.05).
Conclusions: :
Immediate visuospatial attention (SSP forward) and long term visual memory (PRM) deficits were more frequent in patients with combined (protan/deutan) defects. Red-green color vision impairment in DMD reflects selective parvocellular dysfunction. In agreement with this, the visual memory losses detected were for detailed shapes with chromatic information (PRM), which are processed in ventral stream sites and receive parvocellular input. However, SSP stimuli (white squares) activate mainly the magnocellular pathway. There seems to be an association between visual memory and damage in parvocellular pathways, but the relation between attention deficit and alterations in the magnocellular pathway is not clear. Further analysis should clarify if these associations are found in non DMD individuals. The findings raise the question of the importance of psychophysical function on cognitive assessment.
Keywords: color vision • memory • perception