Article

Wernicke's aphasia is a condition which results in severely disrupted language
comprehension following a lesion to the left temporo-parietal region. A
phonological analysis deficit has traditionally been held to be at the root of
the comprehension impairment in Wernicke's aphasia, a view consistent with
current functional neuroimaging which finds areas in the superior temporal cortex
responsive to phonological stimuli. However behavioural evidence to support the
link between a phonological analysis deficit and auditory comprehension has not
been yet shown. This study extends seminal work by Blumstein, Baker, and
Goodglass (1977) to investigate the relationship between acoustic-phonological
perception, measured through phonological discrimination, and auditory
comprehension in a case series of Wernicke's aphasia participants. A novel
adaptive phonological discrimination task was used to obtain reliable thresholds
of the phonological perceptual distance required between nonwords before they
could be discriminated. Wernicke's aphasia participants showed significantly
elevated thresholds compared to age and hearing matched control participants.
Acoustic-phonological thresholds correlated strongly with auditory comprehension
abilities in Wernicke's aphasia. In contrast, nonverbal semantic skills showed no
relationship with auditory comprehension. The results are evaluated in the
context of recent neurobiological models of language and suggest that impaired
acoustic-phonological perception underlies the comprehension impairment in
Wernicke's aphasia and favour models of language which propose a leftward
asymmetry in phonological analysis.
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