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

Ayşe Pinar Saygin, Frederic Dick, Stephen W. Wilson, Nina Dronkers, Elizabeth Bates

Research output: Contribution to journalArticle

150 Scopus citations

Abstract

Although aphasia is often characterized as a selective impairment in language function, left hemisphere lesions may cause impairments in semantic processing of auditory information, not only in verbal but also in nonverbal domains. We assessed the 'online' relationship between verbal and nonverbal auditory processing by examining the ability of 30 left hemisphere-damaged aphasic patients to match environmental sounds and linguistic phrases to corresponding pictures. The verbal and nonverbal task components were matched carefully through a norming study; 21 age-matched controls and five right hemisphere-damaged patients were also tested to provide further reference points. We found that, while the aphasic groups were impaired relative to normal controls, they were impaired to the same extent in both domains, with accuracy and reaction time for verbal and nonverbal trials revealing unusually high correlations (r = 0.74 for accuracy, r = 0.95 for reaction time). Severely aphasic patients tended to perform worse in both domains, but lesion size did not correlate with performance. Lesion overlay analysis indicated that damage to posterior regions in the left middle and superior temporal gyri and to the inferior parietal lobe was a predictor of deficits in processing for both speech and environmental sounds. The lesion mapping and further statistical assessments reliably revealed a posterior superior temporal region (Wernicke's area, traditionally considered a language-specific region) as being differentially more important for processing nonverbal sounds compared with verbal sounds. These results suggest that, in most cases, processing of meaningful verbal and nonverbal auditory information break down together in stroke and that subsequent recovery of function applies to both domains. This suggests that language shares neural resources with those used for processing information in other domains.

Original languageEnglish (US)
Pages (from-to)928-945
Number of pages18
JournalBrain
Volume126
Issue number4
DOIs
StatePublished - Apr 1 2003
Externally publishedYes

Keywords

  • Aphasia
  • Auditory agnosia
  • Environmental sounds
  • Lesion mapping
  • Wernicke's area

ASJC Scopus subject areas

  • Neuroscience(all)

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