Neural resources for processing language and environmental sounds: evidence from aphasia

Area of Science:

• Neuroscience
• Psycholinguistics
• Auditory Processing

Background:

• Aphasia is typically viewed as a language-specific deficit.
• Left hemisphere lesions can affect semantic processing in both verbal and nonverbal auditory domains.
• The relationship between verbal and nonverbal auditory processing in aphasia requires further investigation.

Purpose of the Study:

• To investigate the 'online' relationship between verbal and nonverbal auditory processing in patients with left hemisphere damage.
• To determine if impairments in processing environmental sounds correlate with deficits in processing linguistic phrases.
• To identify specific brain regions associated with shared deficits in auditory processing.

Main Methods:

• Assessed 30 left hemisphere-damaged aphasic patients matching environmental sounds and linguistic phrases to pictures.
• Included 21 age-matched controls and five right hemisphere-damaged patients for comparison.
• Utilized lesion overlay analysis to correlate brain damage with processing deficits.

Main Results:

• Aphasic patients showed similar impairment levels in both verbal and nonverbal auditory processing tasks.
• High correlations were found between accuracy (r = 0.74) and reaction time (r = 0.95) for verbal and nonverbal trials.
• Damage to posterior left temporal and inferior parietal regions predicted deficits in both speech and environmental sound processing.

Conclusions:

• Processing of meaningful verbal and nonverbal auditory information often breaks down concurrently after stroke.
• Recovery of function in auditory processing appears to apply to both verbal and nonverbal domains.
• Language processing may share neural resources with non-linguistic auditory information processing.