White matter damage impairs access to consciousness in multiple sclerosis

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neurology

Background:

• Global neuronal workspace theory posits that white matter (WM) integrity is crucial for conscious access.
• Multiple sclerosis (MS) is a demyelinating disease causing widespread WM damage.
• The impact of early MS-related WM damage on conscious perception remains under-investigated.

Purpose of the Study:

• To investigate the relationship between WM integrity and conscious perception in early MS.
• To test predictions of the global neuronal workspace theory in a clinical population.
• To quantitatively assess conscious access using visual backward masking.

Main Methods:

• Visual backward masking paradigm used in 18 early MS patients and 18 controls.
• Non-linear regression fitted sigmoid curves to performance and visibility data.
• Identified 'non-linear transition threshold' as a measure of masking efficiency.
• Correlated transition thresholds with Magnetization Transfer Ratio (MTR) in WM tracts.

Main Results:

• MS patients exhibited higher non-linear transition thresholds than controls, indicating impaired conscious access.
• Objective and subjective thresholds were highly correlated.
• Impaired conscious access in MS patients correlated inversely with MTR in prefrontal and cerebellar WM tracts.

Conclusions:

• Clinical evidence supports the link between WM integrity and conscious perception, particularly involving prefrontal cortex.
• Findings align with global neuronal workspace theory predictions.
• Early MS provides a model for studying the neural basis of consciousness and WM function.