Apraxia of Speech (AOS) is a motor speech disorder (MSD) affecting an individual's ability to translate conscious speech plans into motor plans. Like other apraxias, it only affects volitional movement patterns. Dyspraxia of speech, verbal dyspraxia, and other terms, usually refer to variants of AOS, or a less severe version of the disorder.
Sufferers of AOS have impaired prosody, which causes their speech to be slow, highly segmented (at the syllable or word level), and is often described as 'robotic'. Because of this, they also exhibit equal syllabic stress (tec-ton-ic as opposed to tec-TON-ic), and have trouble consciously producing correct stress patterns, even though they are aware of prosodic patterns required.
Symptoms are evident only in connected speech.
AOS is often associated with Broca's Aphasia. It is actually characterised by damage to the posterior portion of Broca's area; the insula, an area underneath the inferior-anterior portion of the temporal lobe, concealed by the fissure separating the frontal and temporal lobes; and the lentiform nucleus (Dronkers, 1996). However, some studies have shown that only a percentage of patients with AOS have these lesions (Hillis, 2004).
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