Spatio-temporal selectivity of loss of colour and luminance contrast sensitivity with multiple sclerosis and optic neuritis.
Colour and luminance-contrast thresholds were measured in the presence of dynamic Random Luminance-contrast Masking (RLM) in individuals who had had past diagnoses of optic neuritis (ON) some of whom have progressed to a diagnosis of multiple sclerosis (MS). To explore the spatio-temporal selectivity of chromatic and luminance losses in MS/ON, thresholds were measured using three different sizes and modulation rates of the RLM displays: small checks modulating slowly, medium-sized checks with moderate modulation and large checks modulating rapidly. The colour of the chromatic stimuli used were specified in a cone-excitation space to measure relative impairments in red-green and blue-yellow chromatic channels. These observers showed chromatic thresholds along the L/(L+M) axis that were higher than those along the S-cone axis for all display sizes/modulation rates and both red-green and blue-yellow colour thresholds were higher than luminance-contrast thresholds. The principal change in thresholds with spatio-temporal changes in the display was a reduction in thresholds for L/(L+M) and S-cones with increasing check size and modulation rate. However, luminance contrast thresholds did not change with display size/rate. These results are consistent with MS/ON selectively affecting processing in colour pathways rather than in the magnocellular pathway, and that within the colour pathways neurones with opposed L- and M-cone inputs are more damaged than colour-opponent neurons with input from S-cones.
Flanagan
Patrick
P
School of Psychology, Deakin University, Victoria, 3217, Australia. flanagan@deakin.edu.au
Markulev
Connie
C
D000328:Adult; D003119:Color Perception Tests / Q000379:methods; D003117:Color Vision Defects / Q000175:diagnosis / Q000209:etiology*; D015350:Contrast Sensitivity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000150:complications* / Q000523:psychology; D009434:Neural Pathways / Q000503:physiopathology; D009902:Optic Neuritis / Q000150:complications* / Q000523:psychology; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D012684:Sensory Thresholds