A metaphonological but not an epiphonological disturbance: Evidence that Parkinson’s disease and Normal Ageing Affect the Ability to Manipulate Phonemes but Not the Ability to Rhyme.

We show that Parkinson’s disease (PD) and, to a lesser extent, normal ageing affect the ability to identify and manipulate phonemes. Using a series of phonological awareness tasks – including rhyme detection, rhyme production, phoneme deletion, phoneme exchange and common-unit identification - we show that a group of older adults diagnosed with PD perform significantly worse than a group of healthy older adults (HOA). We also show that normal ageing has an affect on phonological awareness such that the HOA participants performed at a significantly lower level than healthy younger adult participants on some of the
tasks. We also concluded that epiphonological awareness (the awareness of phonological units that develops earlier in childhood) is relatively spared compared to metaphonological awareness (the more high-level awareness of phonemes that develops later in childhood, usually when schooling begins).
These findings suggest that there is an inverse relationship between the development of phonological awareness in childhood and the degeneration of phonological awareness in old age. In general we found that as the level of difficulty of the tasks increases (i.e. from the epiphonological to the metaphonological level) both people with PD and people ageing normally make more errors, make more omissions and respond less quickly. We argue that high-level language functions such as metaphonological awareness rely heavily on the integrity of the frontal-striate systems for working memory; these are often disturbed in normal ageing and to an even greater extent in PD.