Dichotic listening and interhemispheric integration after callosotomy: A systematic review

Area of Science:

• Neuroscience
• Cognitive Psychology
• Speech Processing

Background:

• The right-ear advantage (REA) in auditory-verbal dichotic listening is traditionally attributed to left-hemisphere speech dominance.
• Split-brain studies initially suggested corpus callosum integrity is crucial for left-ear stimulus recall.
• Contradictory findings in callosotomy patients necessitate re-evaluation of REA models.

Approach:

• Systematic literature review of 32 publications on split-brain patients and dichotic listening.
• Analysis of experimental and patient variables influencing left-ear suppression, extinction, and right-ear enhancement.
• Comparison of case-level data considering surgery extent, stimulus type, and response format.

Key Points:

• Rhyming stimuli significantly increased left-ear suppression and right-ear enhancement.
• Allowing right-hemisphere responses (left-hand) also increased left-ear reports.
• Findings suggest callosal axons are not solely responsible for REA.

Conclusions:

• Classical dichotic listening models require adjustment to include right-hemispheric processing.
• Perceptual competition between hemispheres for attention plays a role in REA.
• Future research should incorporate these factors and utilize appropriate control groups.