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

• Main Authors: Audoin, B. (Author), Gold, S.M (Author), Has Silemek, A.C (Author), Heesen, C. (Author), Kühn, S. (Author), Ranjeva, J.-P (Author), Stellmann, J.-P (Author), Weygandt, M. (Author)
• Format: Article
• Language: English
• Published: John Wiley and Sons Inc 2021
• Subjects: (un)consciousness; adult; Adult; alemtuzumab; anterior cingulate; anterior visual system; antidepressant agent; Article; backward masking; beta interferon; brain; Brain; brain cortex; Cerebral Cortex; cingulate gyrus; clinical article; clinical assessment; cognitive defect; Cognitive Dysfunction; comparative study; complication; consciousness; Consciousness; controlled study; corpus callosum; diagnostic imaging; diffusion tensor imaging; Diffusion Tensor Imaging; disease duration; ego development; Evoked Potentials, Visual; Expanded Disability Status Scale; female; Female; fingolimod; fractional anisotropy; fumaric acid; functional connectivity; functional magnetic resonance imaging; glatiramer; gray matter; health care access; human; Humans; information processing; insula; macular volume; Magnetic Resonance Imaging; male; Male; masking; middle aged; Middle Aged; middle frontal gyrus; mild cognitive impairment; multiple sclerosis; Multiple Sclerosis; natalizumab; nerve cell network; Nerve Net; nuclear magnetic resonance imaging; occipital cortex; occipital lobe; ocrelizumab; optic neuritis; optic tract; optical coherence tomography; pathology; pathophysiology; pattern recognition; Pattern Recognition, Visual; Perceptual Masking; physiology; posterior cingulate; precuneus; primary motor cortex; retina; Retina; rituximab; striate cortex; structural connectivity; superior frontal gyrus; symbol digit modalities test; teriflunomide; thalamus; time factor; Time Factors; tractography; unconsciousness; visual acuity; visual backward masking paradigm; visual evoked potential; visual information; visual stimulation; visual system
• Online Access: View Fulltext in Publisher

 Although multiple sclerosis (MS) is frequently accompanied by visuo-cognitive impairment, especially functional brain mechanisms underlying this impairment are still not well understood. Consequently, we used a functional MRI (fMRI) backward masking task to study visual information processing stratifying unconscious and conscious in MS. Specifically, 30 persons with MS (pwMS) and 34 healthy controls (HC) were shown target stimuli followed by a mask presented 8–150 ms later and had to compare the target to a reference stimulus. Retinal integrity (via optical coherence tomography), optic tract integrity (visual evoked potential; VEP) and whole brain structural connectivity (probabilistic tractography) were assessed as complementary structural brain integrity markers. On a psychophysical level, pwMS reached conscious access later than HC (50 vs. 16 ms, p <.001). The delay increased with disease duration (p <.001, β =.37) and disability (p <.001, β =.24), but did not correlate with conscious information processing speed (Symbol digit modality test, β =.07, p =.817). No association was found for VEP and retinal integrity markers. Moreover, pwMS were characterized by decreased brain activation during unconscious processing compared with HC. No group differences were found during conscious processing. Finally, a complementary structural brain integrity analysis showed that a reduced fractional anisotropy in corpus callosum and an impaired connection between right insula and primary visual areas was related to delayed conscious access in pwMS. Our study revealed slowed conscious access to visual stimulus material in MS and a complex pattern of functional and structural alterations coupled to unconscious processing of/delayed conscious access to visual stimulus material in MS. © 2021 The Authors. Human Brain Mapping published by Wiley Periodicals LLC.