Published online by Cambridge University Press: 13 June 2014
Stammering (or stuttering) may be defined as an impairment of continuous utterance. Developmental stammering, regardless of country or language, affects one per cent of adult populations. Exacerbation by the stress of adult conversation or public speaking contrasts sharply with normal flow during singing, acting or conversation with children. Alterations in regional cerebral blood flow suggest that there are underlying differences in sensorimotor function in developmental stammerers whose symptoms commonly appear during the period of intensive language acquisition around the third and fourth year. Emotional tensions may exacerbate the disturbance, but equally psychological growth is adversely affected by the handicap. Abnormal motor control is confirmed by the exaggerated activity in the right hemisphere. The normal sequence of articulatory programming and motor preparation for single word reading is reversed. Absence of activation over the left auditory cortex supports the notion of impaired or diminished auditory feedback in the self-monitoring of speech seen in normal brains. Subcortical abnormalities are a feature of both developmental and acquired stammering.