Delayed access to conscious processing in multiple sclerosis: Reduced cortical activation and impaired structural...

Area of Science:

• Neuroscience
• Cognitive Science
• Medical Imaging

Background:

• Multiple sclerosis (MS) often causes visuo-cognitive impairment, but the underlying brain mechanisms are not fully understood.
• Visual information processing, differentiating unconscious and conscious perception, is crucial for understanding these impairments.

Purpose of the Study:

• To investigate the functional brain mechanisms of visual information processing in MS using a backward masking task.
• To correlate psychophysical and functional MRI (fMRI) findings with structural brain integrity markers.

Main Methods:

• fMRI backward masking task with 30 persons with MS (pwMS) and 34 healthy controls (HC).
• Assessment of retinal and optic tract integrity (OCT, VEP) and structural brain connectivity (probabilistic tractography).
• Analysis of brain activation during unconscious and conscious visual processing.

Main Results:

• pwMS showed delayed conscious access to visual stimuli (50 ms vs. 16 ms in HC), increasing with disease duration and disability.
• pwMS exhibited decreased brain activation during unconscious processing, with no group differences in conscious processing.
• Reduced fractional anisotropy in the corpus callosum and impaired insula-visual cortex connectivity correlated with delayed conscious access.

Conclusions:

• Conscious access to visual stimuli is significantly slowed in MS.
• Functional and structural brain alterations, particularly in connectivity, underlie impaired visual processing and delayed conscious access in MS.
• Retinal and optic nerve integrity markers did not correlate with the observed processing delays.