Enhanced activation of the left inferior frontal gyrus in deaf and dyslexic adults during rhyming
MacSweeney M et al. – The finding of greater inferior frontal gyrus activation in both pt groups with phonologic processing difficulties vs controls suggests greater reliance on the articulatory component of speech during phonologic processing when auditory processes are absent (deaf group) or impaired (dyslexic group). Thus, the brain appears to develop a similar solution to a processing problem that has different antecedents in these 2 populations. Methods- Use of a rhyme-judgement task to compare adult hearing developmental dyslexic pts and congenitally profoundly deaf pts vs hearing non-dyslexic controls
- All groups matched on non-verbal intelligence quotient, reading age, and rhyme performance
- Picture stimuli used for pts to self-generate phonologic representations
- Testing of well-matched pt groups on same task elucidates whether previous literature reporting differences between pts with vs without phonologic processing difficulties show same regions of differential activation in these 2 distinct populations
Results- Data show greater activation in deaf and dyslexic pts vs hearing non-dyslexic pts across a large portion of left inferior frontal gyrus
- Area includes pars triangularis, superiorly into middle frontal gyrus and posteriorly to include the pars opercularis, and the ventral precentral gyrus junction
- Variability between the 2 groups with phonological processing difficulties within left inferior frontal gyrus
- More activatation of superior posterior tip of left pars opercularis, extending into precentral gyrus, for deaf vs dyslexic pts
- More activatation of superior posterior portion of pars triangularis, extending into ventral pars opercularis, for dyslexic vs deaf pts
- Whether these regions play differing roles in compensating for poor phonologic processing remains unclear
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