Letter Fluency in Motor Neurone Disease: Is there a specific action word deficit?
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Recent studies have demonstrated that there is a specific verb, or action word, deficit in patients with a comorbid diagnosis of Motor Neurone Disease (MND) and dementia of the frontotemporal type. However, there has been less research examining this deficit in patients with non-demented MND. Using a test of letter fluency, this study examined if there was a specific deficit in producing verbs and action words in patients with non-demented MND compared to controls. MND patients and controls produced a similar percentage of verbs, however, MND patients produced a significantly smaller percentage of action words than controls, suggesting that MND patients do not have a deficit producing verbs per sé, but that the deficit is specific to verbs involving movement. This result further advances the idea of a continuum from MND to frontotemporal dementia, as previous research has shown an action word impairment in both demented MND patients and patients with frontotemporal dementia. Now there is growing evidence to suggest that this impairment is also present in patients with non-demented MND. The current study also examined if physical disability in MND patients had an effect on the types of action words produced. Action words were categorised into which part of the body the movement involves. MND patients with impairment to specific body regions were examined to see if they produced fewer verbs involving movement of that body part. They were compared to MND patients without impairment to this body region and controls. However, it was found that although MND patients produced fewer action words overall, physical disability did not interact with the types of action words produced. The findings of this study offer support that knowledge of actions are impairment in MND.