Deficits of hierarchical predictive coding in left spatial neglect.

Area of Science:

• Neuroscience
• Cognitive Psychology
• Auditory Perception

Background:

• Unilateral spatial neglect, often resulting from right brain damage, impairs left-sided spatial exploration.
• Evidence suggests neglect patients have deficits in predictive coding, crucial for identifying environmental probabilistic associations.
• Predictive coding involves hierarchical processing of prediction errors at local and global levels.

Purpose of the Study:

• To investigate hierarchical predictive coding deficits in patients with spatial neglect.
• To examine how auditory prediction errors are processed in neglect patients under different statistical regularities.

Main Methods:

• Electroencephalography (EEG) was used to record brain responses to auditory stimuli.
• Participants heard sequences of tones with deviant tones presented on the left or right side.
• Mismatch Negativity (MMN) and P300 responses were analyzed to assess local and global prediction errors.

Main Results:

• When left-sided tones were frequent, neglect patients showed no Mismatch Negativity for left-sided deviations or omissions, and no P300 for global errors.
• When right-sided tones were frequent, patients showed Mismatch Negativity for right-sided deviations but not left-sided ones.
• Despite lacking Mismatch Negativity, patients showed enhanced P300 for infrequent left-sided tones when right-sided tones were predominant, indicating independent global prediction.

Conclusions:

• Spatial neglect is associated with significant deficits in hierarchical predictive coding, particularly for left-sided stimuli.
• Global prediction processing can occur independently of local prediction error signals (Mismatch Negativity).
• Neglect patients' predictive behavior is biased towards statistical regularities associated with the right side of space.