Deficient processing of regularity violations during visuospatial neglect: a visual mismatch negativity study.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Clinical Neurology

Background:

• Visuospatial neglect (VSN) following right-hemisphere stroke impacts engagement with left-sided stimuli.
• The effect of VSN on automatic processes like regularity detection remains unclear.

Purpose of the Study:

• To investigate automatic regularity and violation detection in VSN using event-related potentials (ERPs).
• To compare VSN patients with stroke controls and healthy individuals.
• To examine changes in these processes over time and with rehabilitation.

Main Methods:

• A passive oddball paradigm with simultaneous left and right visual sequences was used.
• Event-related potential components (C1, C2/N1, visual mismatch negativity - vMMN) were recorded.
• Participants included VSN patients, stroke controls, and healthy controls, with VSN patients assessed pre/post-rehabilitation and at follow-up.

Main Results:

• The early visual processing component C1 was absent in VSN patients across all measurements.
• The C2/N1 component showed no group differences.
• Visual mismatch negativity (vMMN), indicative of regularity violation detection, was absent in VSN patients but present in stroke controls and healthy participants, particularly for left-sided events.

Conclusions:

• Both stroke and VSN impair automatic detection of regularity violations.
• VSN presents a more substantial deficit in this automatic processing.
• The observed deficits in VSN do not improve with time or rehabilitation, and the absence of C1 suggests early visual processing impairments.