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Abstract:
Recent behavioural and neuropsychological studies have raised
the possibility that the phonological distinction between vowels
and consonants is reflected in their independent status in language
processing. We used PET scanning to investigate processing of
vowels and consonants in the context of lexical access. Normal
volunteers performed a word reconstruction task involving auditory
presentation of non-words and generation of real words by
replacement of either vowel or consonant sounds. Behavioural data
confirmed previous reports of increased reaction times and error
rates for the replacement of consonants. When word reconstruction
as a whole was compared with word repetition (control test) a left
lateralised system was activated which included Brodmann's areas
44/45 and 9. Vowel versus consonant replacement yielded no
significant difference in activation's: however areas within the
prefrontal cortex were activated more with the more difficult
consonant task. We interpret this data as evidence against
anatomically separable cortical systems for the processing of
consonants or vowels. A conjunction analysis between word
reconstruction and semantic verbal fluency was also performed.
Despite the different phonological or semantic criteria governing
word generation a common system including anterior cingulate,
posterior parietal and Brodmann's areas 44/45 and 9 was observed.
Both these tasks require accurate lexical access from multiple
competing alternatives. We interpret this result in terms of the
general processing and representational demands required for
lexical access.
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